text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91
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value | word_count int64 101 114k | flesch_reading_ease float64 50 104 |
|---|---|---|---|---|---|
- NAME
- DESCRIPTION
- SYNOPSIS
- FUNCTIONS
- COMPATIBILITY
- PHILOSOPHY and JUSTIFICATION
- BUGS and FEEDBACK
- SEE ALSO
- AUTHOR, COPYRIGHT and LICENCE
- CONSPIRACY
NAME
XML::Tiny - simple lightweight parser for a subset of XML
DESCRIPTION
XML::Tiny is a simple lightweight parser for a subset of XML
SYNOPSIS
use XML::Tiny qw(parsefile); open($xmlfile, 'something.xml); my $document = parsefile($xmlfile);
This will leave
$document looking something like this:
[ { type => 'e', attrib => { ... }, name => 'rootelementname', content => [ ... more elements and text content ... ] } ]
FUNCTIONS
The
parsefile function is optionally exported. By default nothing is exported. There is no objecty interface.
parsefile
This takes at least one parameter, optionally more. The compulsory parameter may be:
- a filename
in which case the file is read and parsed;
- a string of XML.
- a glob-ref or IO::Handle object:
- fatal_declarations
If set to true, <!ENTITY...> and <!DOCTYPE...> declarations in the document are fatal errors - otherwise they are *ignored*.
- no_entity_parsing
If set to true, the five built-in entities are passed through unparsed. Note that special characters in CDATA and attributes may have been turned into
&,
<and friends.
- strict_entity_parsing:
- type
The node's type, represented by the letter 'e'.
- name
The element's name.
- attrib
A hashref containing the element's attributes, as key/value pairs where the key is the attribute name.
- content
An arrayref of the element's contents. The array's contents is a list of nodes, in the order they were encountered in the document.
Text nodes are hashrefs with the following keys:
- type
The node's type, represented by the letter 't'.
- content
A scalar piece of text.
If you prefer a DOMmish interface, then look at XML::Tiny::DOM on the CPAN.
COMPATIBILITY
With other modules XML::Tiny; my $tree = XML::Tiny::parsefile('something.xml');
Any valid document that can be parsed like that using XML::Tiny should produce identical results if you use the above example of how to use XML::Parser::EasyTree.
If you find a document where that is not the case, please report it as a bug.
With perl 5.004
The module is intended to be fully compatible with every version of perl back to and including 5.004, and may be compatible with even older versions of perl 5.
The lack of Unicode and friends in older perls means that XML::Tiny does nothing with character sets. If you have a document with a funny character set, then you will need to open the file in an appropriate mode using a character-set-friendly perl and pass the resulting file handle to the module. BOMs are ignored.
The subset of XML that we understand
Including "self-closing" tags like <pie type = 'steak n kidney' />;
Which are ignored;
- The five "core" entities
ie
&,
<,
>,
'and
";
- Numeric entities
eg
Aand
A;
- CDATA
This is simply turned into PCDATA before parsing. Note how this may interact with the various entity-handling options;
The following parts of the XML standard are handled incorrectly or not at all - this is not an exhaustive list:
- Namespaces
While documents that use namespaces will be parsed just fine, there's no special treatment of them. Their names are preserved in element and attribute names like 'rdf:RDF'.
- DTDs and Schemas
This is not a validating parser. <!DOCTYPE...> declarations are ignored if you've not made them fatal.
- Entities and references
<option, and then use something like HTML::Entities.
- Processing instructions
These are ignored.
- Whitespace
We do not guarantee to correctly handle leading and trailing whitespace.
- Character sets
This is not practical with older versions of perl
PHILOSOPHY and JUSTIFICATION. XML::Tiny exists for those people.
BUGS and FEEDBACK.
SEE ALSO
- For more capable XML parsers:
-
- The requirements for a module to be Tiny
AUTHOR, COPYRIGHT and LICENCE, for reporting another bug that I introduced when fixing the first one, and for providing a patch to improve error reporting;
to 'Corion' for finding a bug with localised filehandles and providing a fix;
to Diab Jerius for spotting that element and attribute names can begin with an underscore;
to Nick Dumas for finding a bug when attribs have their quoting character in CDATA, and providing a patch;
to Mathieu Longtin for pointing out that BOMs exist.. | https://metacpan.org/pod/release/DCANTRELL/XML-Tiny-2.06/lib/XML/Tiny.pm | CC-MAIN-2017-13 | refinedweb | 695 | 55.64 |
31 March 2011 15:52 [Source: ICIS news]
TORONTO (ICIS)--Braskem and Idesa have selected petrochemicals engineering firm Technip to work on their planned 1.05m tonne/year Ethylene XXI joint venture in ?xml:namespace>
Paris-based Technip would provide its technology for the joint venture cracker project between
In addition, the French petrochemicals engineering major would be in charge of front-end engineering design (FEED) for the cracker and two planned high-density polyethylene plants at the complex, they said.
Ethylene XXI, which will also include a low-density polyethylene plant, is expected to start up by the end of 2014, they said.
ICIS reported earlier that the project is expected to cost $2.5bn (€1.8bn), with about 70% of the cost financed with debt.
($1 = €0.71)
For more on | http://www.icis.com/Articles/2011/03/31/9448951/braskem-idesa-picks-technip-for-mexicos-ethylene-xxi-petchem.html | CC-MAIN-2015-22 | refinedweb | 133 | 53.92 |
Python GetNearestEdge returns hidden edges
On 24/06/2016 at 03:54, xxxxxxxx wrote:
User Information:
Cinema 4D Version: R17
Platform: Windows ;
Language(s) :
---------
Hi,
I have a tooldata plugin which uses the viewport utility to check for edges under the mouse cursor.
viewportSelect.Init(width, height, bd, objlist, c4d.Medges, True, c4d.VIEWPORTSELECTFLAGS_IGNORE_HIDDEN_SEL)
edges = viewportSelect.GetNearestEdge(obj, x, y, radius)
With hidden polygons, I still get edges belonging to these polygons, although the flag VIEWPORTSELECTFLAGS_IGNORE_HIDDEN_SEL is used during initialization. So maybe this does not work for hidden polygons.
But even when I select some edges and hide these, the function GetNearestEdge still returns me these hidden edges.
On 27/06/2016 at 01:34, xxxxxxxx wrote:
Hello,
could you please post some more complete code showing what you are doing? Providing a more complete example would help us the reproduce the issue more easily.
Best wishes,
Sebastian
On 28/06/2016 at 13:21, xxxxxxxx wrote:
Hi Sebastian,
Below is the simplified implementation. I removed all non-necessary items to reproduce the problem (note that I also removed the 'out-of-range' checking).
To reproduce the problem, create a cube, make it editable. Open the console, select the plugin (in edge mode) and hover over the edges. The number of the edge is displayed in the console. Now select some edges and hide them and use the plugin again. Hovering over the hidden edges will still print out the found edge number in the console. Which means edges were found, although the flag passed to GetNearestEdge indicates to ignore hidden edges.
Maybe I am just doing something wrong?
import c4d import os from c4d import gui, plugins, bitmaps, utils PLUGIN_ID = 1031001 # dummy ID class GetNearestEdgeBug(plugins.ToolData) : def GetState(self, doc) : docmode = doc.GetMode() # only allow tool if in edge mode or uv polygon if docmode!=c4d.Medges: return 0 # only allow tool if single polygon object selected if len(doc.GetActiveObjects(c4d.GETACTIVEOBJECTFLAGS_0))!=1: return 0 return c4d.CMD_ENABLED def GetCursorInfo(self, doc, data, bd, x, y, bc) : # prepare for viewportselect frame = bd.GetFrame() left = frame["cl"] right = frame["cr"] top = frame["ct"] bottom = frame["cb"] width = right - left + 1 height = bottom - top +1 # get the edge under the mouse cursor viewportSelect = utils.ViewportSelect() obj = doc.GetActiveObject() objlist = [obj] viewportSelect.Init(width, height, bd, objlist, c4d.Medges, True, c4d.VIEWPORTSELECTFLAGS_IGNORE_HIDDEN_SEL) edges = viewportSelect.GetNearestEdge(obj, x, y, 10) if edges: print 'Edge number:', edges["i"] else: print 'No edge under cursor' return True # =============== Main ============= def PluginMain() : try: bmp = bitmaps.BaseBitmap() dir, file = os.path.split(__file__) fn = os.path.join(dir, "res", "GetNearestEdgeBug.tif") bmp.InitWith(fn) plugins.RegisterToolPlugin(id=PLUGIN_ID, str="GetNearestEdgeBug", info=0, icon=bmp, help="GetNearestEdgeBug", dat=GetNearestEdgeBug()) except TypeError: # when performing a 'reload plugin' without the plugin being registered to the system yet # -> user should restart Cinema 4D print "Unable to load plugin (GetNearestEdgeBug)" if __name__ == "__main__": PluginMain()
On 29/06/2016 at 01:43, xxxxxxxx wrote:
Hello,
it looks like the ViewportSelect by default does ignores hidden polygons and edges of the given objects. So the flag VIEWPORTSELECTFLAGS_IGNORE_HIDDEN_SEL does not tell the ViewportSelect to ignore hidden elements but to do the opposite: to ignore the BaseSelect that stores the status if polygons or edges are hidden or not. So just write:
viewportSelect.Init(width, height, bd, objlist, c4d.Medges, True, c4d.VIEWPORTSELECTFLAGS_0)
best wishes,
Sebastian
On 29/06/2016 at 12:33, xxxxxxxx wrote:
Thanks for the reply Sebastian.
I can confirm your suggestion does work.
Will the current behaviour be changed in future, so that the flag is doing what it is supposed to? Or will it be left untouched?
I'd like to know for current and future plugins, as to me, it makes not much sense to change my code to make it work now, and change it back after the behaviour is fixed.
Thanks again.
Daniel
On 01/07/2016 at 01:16, xxxxxxxx wrote:
Hello,
sorry, maybe I wasn't clear enough. The flag behaves as it should, there is no bug and there will be no fix. See the description above.
Best wishes,
Sebastian
On 01/07/2016 at 04:31, xxxxxxxx wrote:
Oh, I see.
I never was very good in reverse logic.
Thanks for the clarification. | https://plugincafe.maxon.net/topic/9563/12838_python-getnearestedge-returns-hidden-edges | CC-MAIN-2020-40 | refinedweb | 710 | 58.69 |
Your answer is one click away!
The goal is to pre-populate the form with seed data:
The relevant code for iterating over stall numbers is in
garages_controller.rb:
def new @garage = Garage.new for i in 1..5 @garage.cars.build :stall_number => i end end
This will give 5 stall_number string values of 1, 2, 3, 4, and 5. Instead of that, how would I iterate over the values in the
seeds.rb file?
Car.create(stall_number: "stall1") Car.create(stall_number: "stall2") Car.create(stall_number: "stall3") Car.create(stall_number: "stall4") Car.create(stall_number: "stall5")
So instead of the stall_numbers having values of 1, 2, 3, 4, and 5. They would have the string values listed in the seeds.rb file.
Here is the
fields_for block in the garage
_form.html.erb:
<%= f.fields_for :cars do |builder| %> <p>Enter license for car parked in stall: <%= builder.object.stall_number %></p> <%= builder.label :license, "License #:" %><br /> <%= builder.text_field :license %> <% end %>
Any input on the matter is greatly appreciated.
Just do the same loop in the seed file.
for i in 1..5 Car.create(stall_number: "stall" + i.to_s) end
If they are static, just create them in an array and call them.
array = ["stallA", "stallDC", "stall874", "stallNN", "stallPO", "stalSF", "stallRE", "stall456", "stall39", "stall99"] array.each {|x| Car.create(stall_number: x)} | http://www.devsplanet.com/question/35274584 | CC-MAIN-2017-30 | refinedweb | 218 | 63.36 |
Opened 6 years ago
Closed 6 years ago
Last modified 6 years ago
#19555 closed Cleanup/optimization (fixed)
tutorial pt 1 - update year for examples to work
Description
last part executes:
Choice.objects.filter(pollpub_dateyear=2012)
and now we're in 2013 :)
happy new year!
salú
rela.
Attachments (1)
Change History (11)
comment:1 Changed 6 years ago by
comment:2 Changed 6 years ago by
As discussed on IRC:
mYk: claudep: mmmm, yeah, we should use a different example then mYk: filter on a field other than the date
comment:3 Changed 6 years ago by
I hadn't noticed that the tutorial created objects with the date set to "now", and then proceeded to filter on the year.
comment:4 Changed 6 years ago by
I think this should solve the problem:
Instead of:
from django.utils import timezone
p = Poll(question="What's new?", pub_date=timezone.now())
You make a fix date doing:
from django.utils import timezone
from datetime import datetime
timezone = timezone.get_current_timezone()
p = Poll(question="What's new?", pub_date=datetime(year=2013, month=10, day=10, tzinfo=timezone))
Then the date will be 2013/10/10 forever, no need to change it in 2014 =)
comment:5 Changed 6 years ago by
Another much simpler solution is to filter by a not hardcoded year:
# Get the poll whose year is current year.
from datetime import datetime
Choice.objects.filter(pollpub_dateyear=datetime.now().year)
<Poll: What's up?>
...
# Find all Choices for any poll whose pub_date is in current year.
Choice.objects.filter(pollpub_dateyear=datetime.now().year)
---
I would also recommend editing the 2012 to 2013, as the 1.5 version is going to be released this year.
Changed 6 years ago by
comment:6 Changed 6 years ago by
I am in favor of keeping the date lookups, since I think it's useful to demo them (plus there aren't really any other fields on Poll to filter by).
The alternative of creating the poll with a specific date or assigning a specific pub_date later as was done before [e0d78f898f] so that the queries aren't dependent on timezone.now() would make the part later in the tutorial that says "If the value of "Date published" doesn't match the time when you created the poll in Tutorial 1, it probably means you forgot to set the correct value for the TIME_ZONE setting" invalid.
Since the images later in the tutorial use 2012, I don't think we should update the shell output for p.pub_date.
Thanks for the report, but docs use various dates between 2005 and now as examples, and it doesn't add much value to change them every year. | https://code.djangoproject.com/ticket/19555 | CC-MAIN-2019-22 | refinedweb | 449 | 58.82 |
Swap 2 number without using third variable
code do not use temp variable for swapping
if the code was useful please let me know
#include <stdio.h>); }
how bout this.
a=a+b;
b=a-b;
a=((a-b)/(-1));
just a tricky way
#define SWAP(a, b) do { a ^= b; b ^= a; a ^= b; } while ( 0 )
You would not even be able to compile the first code sample.
You would not even be able to compile the first code sample.
logic is imp
this can be done using stack...........put the value of a and b in stack....then store first in b then in a.... as stack is first in last out....
For a newbie Zamansiz, you certainly have my vote of confidence.
-
Using 'tricks' and 'trickly subrt'ns is exactly what got Microsoft into so many buggy problems at the beginning.
- You are spot-on by laying this out in the beginning
and allowing the debugger see it right away.
- - Easy to spot - Easy to understand.
Shift-Stop
* by Newbie I am assuming that you're
New to coding
and not Ken Thompson, or D. Ritchie, or K. Knowlton.
^=b; b^=a; a^=b; printf("\nVariables after swap\nA= %d \nB= %d\n",a,b); }
Method1
(The XOR trick) a ^= b ^= a ^= b;
Although the code above works fine for most of the cases, it tries to modify variable 'a' two times between sequence points, so the behavior is undefined. What this means is it wont work in all the cases. This will also not work for floating-point values. Also, think of a scenario where you have written your code like this
swap(int *a, int *b)
{
*a ^= *b ^= *a ^= *b;
}
Now, if suppose, by mistake, your code passes the pointer to the same variable to this function. Guess what happens? Since Xor'ing an element with itself sets the variable to zero, this routine will end up setting the variable to zero (ideally it should have swapped the variable with itself). This scenario is quite possible in sorting algorithms which sometimes try to swap a variable with itself (maybe due to some small, but not so fatal coding error). One solution to this problem is to check if the numbers to be swapped are already equal to each other. swap(int *a, int *b) {
if(*a!=*b) { *a ^= *b ^= *a ^= *b; } }
Method2 This method is also quite popular a=a+b; b=a-b; a=a-b; But, note that here also, if a and b are big and their addition is bigger than the size of an int, even this might end up giving you wrong results. Method3 One can also swap two variables using a macro. However, it would be required to pass the type of the variable to the macro. Also, there is an interesting problem using macros. Suppose you have a swap macro which looks something like this
#define swap(type,a,b) type temp;temp=a;a=b;b=temp;
Now, think what happens if you pass in something like this swap(int,temp,a) //You have a variable called "temp" (which is quite possible). This is how it gets replaced by the macro
int temp;
temp=temp;
temp=b;
b=temp;
Which means it sets the value of "b" to both the variables!. It never swapped them! Scary, isn't it? So the moral of the story is, dont try to be smart when writing code to swap variables. Use a temporary variable. Its not only fool proof, but also easier to understand and maintain.
haii this code also works to swap two numbers
if a=5,b=4
then a=(a+b)-(b=a);
also works
it can be like this
#include<stdio.h> #include<conio.h> int main() { int i,j; printf("enter the two variables:"); scanf("%d%d",&i,&j); printf("before swap:First Var.=%d\tSecond Var.=%d\n",i,j); i=i+j; j=-(j-i); i=-(i-j); printf("After Swap: First Var.=%d\tSecond Var,=%d\n",i,j); getch(); return 0; }
, why in the world would anyone want the use additions, subtraction, multiplications and divisions (inefficient) rather than a simple MOVE instruction (very efficient) and suffer all the ills of truncation and round-off error? It's slower, uses more memory and is failure prone. On the other hand, creating a temp is either a Zero time operation (created at compile time) or a very fast creation on the Stack (one assembly instruction). Iven if the Temp needs to be created on the heap or in thread local storage, it's still probably faster. If you really need to optimize, the only guaranteed method is to use assembly - and even that may have issues of transportability. The only time I would ever consider this would be when swapping giant structures (or perhaps millions of small ones), and even then I would probably re-write the code model to use pointer swaps instead. Why move big chunks of data when you can simply swap a pointer?
Want a simple assembly language example?
Mov ECX, SizeOfVariableInBytes Mov SI, AddressOfOneObject Mov DI, AddressOfOtherObject MLP: Mov AL,[ESI] Mov AH,[EDI] Mov [ESI],AH Mov [EDI],AL Inc ESI INC EDI Loop MLP
This is an untested skeleton, just showing the essentials. It is written in terms of bytes simply because it is bad technique to write an generic example for a certain data type in particular. It also assumes the use of 32 bit registers, and that the data is in the (default) Data Segment. It will only work with simple data types and structure, but will fail miserably on things like Class Instances.
If you are really a Hog for optimization, you could shorten it to this:
Mov ECX, SizeOfVariableInBytes Mov SI, AddressOfOneObject Mov DI, AddressOfOtherObject MLP: Mov AL,[ESI] XCHG AL,[EDI] Mov [ESI],AL Inc ESI INC EDI Loop MLP
Which uses the EXCH instruction to replace a pair of Mov Instructions. My opinion is that no optimizing compiler can do better than this, except perhaps when possible by moving words or double words and therefore fewer loop iterations. In fact, something like this is probably what the compiler would construct anyway.
#include<conio.h> #include<stdio.h> void Change_Address( int *&p, int *&pt) { int *pp; pp = p; p = pt; pt= pp; } int main(void) { int a =3, b = 4, *p, *p1; p = &a; p1 = &b; printf("%d %d\n", *p, *p1); Change_Address(p, p1); printf("%d %d", *p, *p1); getch(); return 0; }
void Change_Address( int *&p, int *&pt)
That's C++, not C. | http://www.daniweb.com/software-development/c/threads/320787/swap-2-number-without-using-third-variable | CC-MAIN-2014-10 | refinedweb | 1,103 | 69.31 |
How To Contribute¶
First off, thank you for considering contributing to
structlog!
It’s people like you who make it is such a great tool for everyone.
This document is mainly to help you to get started by codifying tribal knowledge and expectations and make it more accessible to everyone. But
structlog and helping out in support frees us up to improve
structlog instead!
Workflow¶
- No contribution is too small! Please submit as many fixes for typos and grammar bloopers as you can!
- Try to limit each pull request to one change only.
-:: 17 and leave an empty line before them: make it a non-failure using
tox --skip-missing-interpreters(in that case you may want to look into pyenv that makes it very easy to install many different Python versions in parallel).
Write good test docstrings. your change is noteworthy, add an entry to the changelog. Use semantic newlines, and add a link to your pull request:
- Added ``structlog.func()`` that does foo. It's pretty cool. [`#1 <>`_] - ``structlog.func()`` now doesn't crash the Large Hadron Collider anymore. That was a nasty bug! [`#2 <>`_]
Local Development Environment¶
You can (and should) run our test suite using tox. However, you’ll probably want a more traditional environment as well. We highly recommend to develop using the latest Python 3 release because you’re more likely to catch certain bugs earlier.
First create a virtual environment. It’s out of scope for this document to list all the ways to manage virtual environments in Python but if you don’t have already a pet way, take some time to look at tools like pew, virtualfish, and virtualenvwrapper.
Next get an up to date checkout of the
structlog repository:
$ git checkout [email protected]:hynek/structlog.git
Change into the newly created directory and after activating your virtual environment install an editable version of
structlog along with its test and docs dependencies:
$ cd structlog $ pip install -e .[dev]
If you run the virtual environment’s Python and try to
import structlog it should work!
At this point
$ python -m pytest
should work and pass
and
$ cd docs $ make html
should build docs in
docs/_build/html.
To avoid committing code that violates our style guide, we strongly advise you to install pre-commit [1] hooks:
$ pre-commit install
You can also run them anytime using:
$ pre-commit run --all-files
Again, this list is mainly to help you to get started by codifying tribal knowledge and expectations. If something is unclear, feel free to ask for help!
Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. Please report any harm to Hynek Schlawack in any way you find appropriate.
Thank you for considering contributing to
structlog! | http://www.structlog.org/en/latest/contributing.html | CC-MAIN-2019-13 | refinedweb | 473 | 65.22 |
Opened 3 years ago
Closed 3 years ago
Last modified 8 months ago
#4461 closed defect (fixed)
ST_AsTWKB doesn't always remove duplicate points
Description
In this tweet gabrielroldan says that ST_AsTWKB doesn't remove repeated points
and he is right for some cases. If the writer haven't yet collected enough points for what is needed for that geometry type it doesn't remove the point even if there is many more points after.
The function actually needs one extra before it starts removing.
Example
select st_astwkb('linestring(1 1, 2 2, 2 2, 3 1)'::geometry);
The fix is very small, but might be a braking change for someone.
The proposed svn diff:
svn diff Index: liblwgeom/lwout_twkb.c =================================================================== --- liblwgeom/lwout_twkb.c (revision 17618) +++ liblwgeom/lwout_twkb.c (working copy) @@ -112,7 +112,8 @@ int64_t nextdelta[MAX_N_DIMS]; int npoints = 0; size_t npoints_offset = 0; - + int max_points_left = pa->npoints; + LWDEBUGF(2, "Entered %s", __func__); /* Dispense with the empty case right away */ @@ -173,8 +174,11 @@ /* Skipping the first point is not allowed */ /* If the sum(abs()) of all the deltas was zero, */ /* then this was a duplicate point, so we can ignore it */ - if ( i > minpoints && diff == 0 ) + if ( diff == 0 && max_points_left > minpoints ) + { + max_points_left--; continue; + } /* We really added a point, so... */ npoints++; Index: liblwgeom/measures3d.c =================================================================== --- liblwgeom/measures3d.c (revision 17618) +++ liblwgeom/measures3d.c (working copy) @@ -1508,7 +1508,6 @@ pl->pv.z += vp.z / vl; } } - return (!FP_IS_ZERO(pl->pv.x) || !FP_IS_ZERO(pl->pv.y) || !FP_IS_ZERO(pl->pv.z)); }
Any thoughts before I commit?
Change History (7)
comment:1 by , 3 years ago
comment:2 by , 3 years ago
comment:3 by , 3 years ago
comment:4 by , 3 years ago
Thanks @Algunenano. A 4 row patch and I miss the correct type
comment:5 by , 3 years ago
comment:6 by , 3 years ago
comment:7 by , 8 months ago
From my understanding of the patch, the duplicated point is removed for any linestring. However the TWKB specification only talks about this optimization for linearring of polygons.
EDIT: I was wrong, I misunderstood the optimization done in postgis (removing duplicated consecutive points). I thought the optimization was to remove last point of a linear ring.
This should use the same type as pa→npoints (uint32_t).
This part of the patch is unrelated.
Can you also add tests around this, please? | https://trac.osgeo.org/postgis/ticket/4461 | CC-MAIN-2022-40 | refinedweb | 390 | 62.58 |
Web Scraping in Python
In some cases we may want to get some data from websites to use in our apps or software we are working on. Let’s say you are following new ‘Upcoming Events’ on the Python website but you don’t want to go to the website every time to see whether there is a new upcoming event on the website. In order to handle this problem image that you are working on a python bot which sends an email to your mail address when a new upcoming event is published on the Python website. In this case we usually use APIs and send GET request to the websites and URLs. But what if they don’t have a public API that we can make GET request. This is where web scraping comes in.
Using web scraping techniques we can get the html source code of a web site. And if there is some valuable data in the source code like some texts or links, it is easy to parse the html source using a few line of code.
Let’s scrap and parse some certain data from the original Python website as I mentioned in the first paragraph.
First things first I am sharing the full code and then I will explain how lines work step by step.
In python there are different libraries for web scraping called ‘lxml’ and ‘BeautifulSoup’. I prefered to use lxml in my project. If you wonder about ‘BeautifulSoup’, just check it out its documentation for more details.
def get_data(url, title_selector)
In the function definition we are passing two parameters.
url: This is the website URL we want to scrap.
title_selector: We use a css selector to select some specific tags.
response = requests.get(url)
We make a GET request to the website and get a response object.
if status_code == 200
In this line we check if the request has succeeded.
content = str(response.content, ‘utf-8’)
Content is the html source. We’ll parse this content.
Note: Some of websites are not using utf-8 or unicode encoding. In this case we may have some strange characters in our result. That’s why we are passing a parameter called ‘utf-8’.
tree = html.fromstring(content)
html.fromstring function parses the html, returns a single element/document.
titles = tree.cssselect(title_selector)
Using a css selector we are parsing the tree and getting the upcoming event titles. After you see the output, I’ll make this parameter clearer.
for title in titles:
print(title.text_content())
Here we are iterating all the upcoming event titles using a for loop. text_content () function gives us the text inside a tag. We would might get an attribiute(like ‘href’) using attrib[“href”] function. For more information you can check it out from here.
Now, it’s time to invoke our method.
get_data(
'',
'div.event-widget > div.shrubbery > ul.menu > li > a'
)
Output will be like;
We got the result correctly.
Now let’s make css selectors clearer. Firstly go to the original Python website. On the page when you scroll down a little you’ll see a part called ‘Upcoming Events’.
These were the titles for upcoming events in our output. So just right-click on the title and then click ‘Inspect’.
As you can see here we have some nested html elements. So in our selector we didn’t only use <a> tag to select. Because there can be a lot of different text in different <a> tags. Therefore we used more specific selector to select only ‘Upcoming Events’ part.
Let’s remeber the selector we passed in our function before. It was like given below;
‘div.event-widget > div.shrubbery > ul.menu > li > a’
In general css selectors are used by web developers and designers to style the elements. If you are confused about how css selectors work you can learn them from here in more details.
Note: Web scraping has a disadvantage. When the website owner rebuilds the website or changes its style, we won’t be able to use our selector like before. In this case we need to change our css selector. Even though web scraping has a disadvantage like that, it’s still a good option when we don’t have an API to get data from websites.
I hope the article was useful for you, thanks for reading. | https://a-gorkemunuvar.medium.com/web-scraping-in-python-9f75dfb84dc1?source=post_internal_links---------7---------------------------- | CC-MAIN-2021-10 | refinedweb | 730 | 74.69 |
New in version 2.6.8September 27th,.7 (June 28th, 2015)
- Between 2.6.6 and 2.6.7, the following bugfixes were accomplished:
- Bug #681225 - income statement displays blank base currency entries when trading account transactions are present during the report period.
- Bug # 734183 - Set value to zero before calling gnc_exp_parser_parse.
- Bug #739271 - pt_BR translation wrong word "limpesa". Should be "limpeza".
- Bug #740955 - Correct general journal and general ledger reports to properly handle Use-Split-Action-For-Num option in File->Properties.
- Bug #744858 - Update exchange rate on bill only possible once per session (after unpost/repost).
- Bug #746163 - Custom register colors (table rows) not recognized from .gtkrc-2.0.gnucash file.
- Bug #746792 - process payment in foreign currency leads to broken equation.
- Bug #746873 - Gnucash asks sql passwords before wallet password.
- Bug #746977 - scm ccache files should be in pkglibdir not pkgdatadir.
- Bug # 747300 - SQL backend missing from most recent DMG?
- Bug #747377 - Fix overly restrictive input validation for IBAN of SEPA transfer.
- Bug #747812 - unset LDFLAGS when unsetting CFLAGS.
- Some other fixes not associated with reported bugs:
- Fix hidden panes in lot viewer.
- Fix some abs() errors from new clang and gcc versions.
- Fix dbi driver detection on linux and similar.
- Improve "Auto pay on posting" message.
- Enable travis continuous integration tests on the gnucash repository.
- Translations Updated: Azerbaijani, Basque, Catalan, Chinese (Simplified), Czech, Danish, Dutch, German, Kinyarwanda, Persian (Farsi), Portuguese, Slovak, Swedish, Turkish, Ukrainian.
- New Translations: Serbian
New in version 2.6.6 (March 31st, 2015)
- Bug #619899 - Use normal gettext or intltool toolchain also for scm files
- Bug #649933 - Creating cash flow report takes a long time
- Bug #672760 - Postponed transaction applied invalid date
- Bug #721196 - CSV. Cannot import lines with empty fields for deposit or withdrawal in bank transaction download.
- Bug #723409 - Incorrect symbol for Turkish lira
- Bug #727466 - The symbol of CNY changed to 元
- Bug #727647 - "gncInvoiceGetTotal" is not read-only function?
- Bug #731889 - guile 2 exports different autoconf macros than what is expected
- Bug #733685 - Fancy Date Format doesn't stick
- Bug #738749 - Broken account template en_GB/uk-vat.gnucash-xea.
- Bug #739228 - Advanced Portfolio report: wrong calculation of Value Correctly convert the value into the report's currency.
- Bug #739584 - gnucash-2.6.4 segfaults regularly on transfer .
- Bug #740471 - Applying payment to invoice Segmentation fault
- Bug #741228 - "Red line" threshold applies to Template scheduled transactions
- Bug - Compilation fails because of creating .gnucash
- Bug #742089 - Decimal places. Set the debit and credit cells' print_info to the account so that the decimal places are correct for the commodity.
- Bug #742332 - German tax report uses US tax quarters and not real quarters.
- Bug #742624 - Scheduled Transaction Editor results in immediate segfault
- Bug #743609 - Add configure options to disable libsecret detection
- Bug #743807 - Stops critical error messages.
- Bug #745265 - Segfault in generate_statusbar_lastmodified_message on Windows. Actually change the default date format without AM/PM
- Bug #745354 - Enhance the Find Transactions dialog. Make it possible to define search criteria that consist of multiple terms anded or ored together. Use this to define a new criterion to look for specified text in any of the Description, Notes, or Memo fields
- Bug #746517 - gnc-sql-backend.c compile fails with -Werror=format-nonliteral. Use GCC pragma to disable the warning in the one place that trips it
- Bug #746977 - scm ccache files should be in pkglibdir not pkgdatadir.
New in version 2.6.5 (December 20th, 2014)
- Between 2.6.4 and 2.6.5, the following bugfixes were accomplished:
- Bug #736359 - Date of 0000-00-00 in MySQL backend crashes GnuCash.
- Bug #737815 - Graphs Cannot Be Generated Correctly.
- Bug #738113 - Crash on reload budget report.
- Bug #738477 - WebKit is broken on Win32.
- Bug #741418 - Freeze unposting bill, 100% cpu usage.
- Some other fixes not associated with reported bugs were accomplished:
- Pre-compile scm files when building with guile 2.
- Fix build-time hard-coded path introduced by the guile2 compile changes.
- Prevent crash when standards-report dir doesn't exist.
- QIF Import crashes when closing via the 'X' button on the last page.
- Omit file.
- Translations Updated: Danish, German, Italian
- New Translations: Assamese, Gujarati, Kannada, Konkani (Latin). Thanks to The Centre for Development of Advanced Computing (C-DAC), Pune, India. Translation Team Leader: Chandrakant Dhutadmal
New in version 2.6.4 (September 29th, 2014)
- Between 2.6.3 and 2.6.4, the following bugfixes were accomplished:
- Bug #120199 - Incorrect sort order in "Sort by Statement Date".
- Bug #434462 - register color don't work correct with system theme color.
- Bug #509263 - Since Last Run dialog won't allow resizing of Status column.
- Bug #610202 - gnucash silently closes when no X11/$DISPLAY is present.
- Bug #630638 - 'Process payment' should allow to select equity accounts for payment
- Bug #671615 - French: 'New Customer' button in Find Customer dialog is translated to 'Nouvel onglet'
- Bug #688965 - Page Up, Page Down keys cause GnuCash to hang.
- Bug #692249 - Add Help button in Custom Reports dialog box,
- Bug #695240 - mortgage wizard empty table.
- Bug #707243 - Hard-coded font colors in account tree?
- Bug #711440 - Tab labels have different background colour than containing gui element.
- Bug #711567 - Cannot save a custom report if a path contain diacritic chars
- Bug #719457 - Template for Home Mortgage Loan isn't properly nested.
- Bug #719457 - Template for Home Mortgage Loan isn't properly nested.
- Bug #720427 - Review of french account templates
- Bug #720934 - Barcharts with many data points have overlapping x-axis labels.
- Bug #722140 - Add option to control inclusion of trading accounts in cash flow report.
- Bug #722200 - configure script does not pick the correct am_cv_scanf version.
- Bug #723145 - Currency display does not respect locale.
- Bug #723442 - Report Options - Report Name too short.
- Bug #725054 - Re-numbering sub accounts crashes the program.
- Bug #725366 - Formula Parsing Error with Scheduled Mortgage Transactions
- Bug #726449 - Budget Barchart does not show up if running sum is selected.
- Bug #726888 - cancel button is available on all pages of assistant.
- Bug #727130 - Crash when newline in Report Title
- Bug #727338 - Translation and Account file updates for Latvian.
- Bug #728103 - Invoice opened does not contain the Job under circumstances.
- Bug #728717 - Ubuntu 14.04 - GNUcash crashes on close.
- Bug #728841 - XML backend does not always store KVP slots.
- Bug #729157 - Bill Term discount days are allowed to be more than due days.
- Bug #729497 - Saved Report Configuration selection window resize.
- Bug #730255 - Python bindings: Assigns bill entries to non-existant invoice.
- Bug #731519 - The fix sets the upper limit before it sets the value of the end row spin button.
- Bug #733107 - Search for reconcile status doesn't work right.
- Bug #733283 - [PATCH] Loss of fractions when importing OFX investment transactions.
- Bug #733506 - (ForwadDisableQIF) The forward button is not active even though a file is selected.
- Bug #734183 - Set all of the denominators correctly on the currency values.
- Bug #736703 - Scheduled transaction are registered without credit/debit.
- Bug Jér
New in version 2.6.3 (April 2nd,.2 (March 11th, 2014)
- Bug #497831: Can't change the date of a transaction with certain locales
- Bug #721472: Fix Reconcile description column.
- Bug #721677: Customer Summary does not include inactive customers
- Bug #722123: Zero price entry added to price database on stock purchase
- Bug #722903: Poor performance of account hierarchy, budgets, reconcile window,...
- Bug #723051: Implement gncCustomerNextID in Python bindings.
- Bug #723373: Don't create any sx in the since-last-run dialog if this is a read-only file
- Bug #723644: Make sure that gnc_search_invoice_on_id() returns the correct type of object.
- Bug #724211: Can't select march 6 date on register
- Bug #724426: Errors in account plan
- Bug #724578: Problems clearing incompletely paid invoices
- Bug #724753: Saved Multicolumn Report Error
- Bug #725131: Adding Payments to Fancy Invoice
New in version 2.4.15 (January 13th, 2014)
- Bug #721434: OFX import broken in release 2.4.14
- Bug #721436: Account Report fails in release 2.4.14
New in version 2.4.14 (January 4th, 2014)
- Bug #584869: Net change line in general journal report broken
- Bug #589685: In the report "Budget flow" period it doesn't work ok change the report head line to show the period date for (- period 1). Author : Carsten Rinke
- Bug #627575: Stylesheet names with non-alphanumeric characters and saved-reports -- addendum
- Bug #632362: Unable to create "reversing transaction" again after it is removed
- Bug #632588: Scrub doesn't fix missing currency
- Bug #644044: Lots: SQL backend loses link to Gain/Loss Txn
- Bug #653594: related to check printing.
- Bug #674862: 2038 bug in libdbi
- Bug #684670: Interest amount calculation is wrong in Sqlite3 format
- Bug #699686: Startup dialog windows should be top level windows Author: Simon Arlott
- Bug #701670: Command-V in reconcile window pastes data in register
- Bug #704183: OFX file import tries to match online_id against ACCTID[space]ACCTKEY even when ACCTKEY is empty.
- Bug #705123: qofbookmerge.c: bad if statement
- Bug #710055: advanced portfolio report counts capital gains split as dividend
- Bug #710311: Missing ChangeLogs
- Bug #711317: Indian Rupee Symbol appears as "?" marks
- Bug #712528: Decompress zipped XML files ourself instead of letting libxml2 do it. As of version 2.9.1 it has a bug that causes it to fail to decompress certain files.
New in version 2.5.10 (December 16th, 2013)
- Bug #336843: Attach images/files/urls to transactions: Disable the "show attachment" menu item if the transaction has no attached file.
- Bug #619478:Build warning in html/gnc-html-webkit.c
- Bug #627575: Stylesheet names with non-alphanumeric characters and saved-reports
- Bug #630578: current date instead of posting date in exchange rate, when posting a bill
- Bug #632588: Scrub doesn't fix missing currency
- Bug #639371: Welcome Sample Report reports wrong version and has a broken report
- Bug #653594: wrong amount printed on checks
- Bug #705714: QIF Import - File selection pop-up is not on top during qif import.
- Bug #708526: GnuCash Crashes when opening About page: Downgrade the error to a critical warning.
- Bug #711317: Indian Rupee Symbol appears as "?" marks
- Bug #715123: Post invoice problem, cannot unpost
- Bug #719481: GnuCash report crashes with Guile2
- Bug #719521: Missing radio button in "Edit security" dialog
- Bug #719726: Click on File -> Open seg-faults
- Bug #720235: Python bindings should load environment file just like gnucash does
- Fix Python tests to no longer require gsettings schemas installed.
- Fix the CuteCash (Qt GUI based) build
- Multi-currency "Post invoice" improvements
- Protect gnc_mktime against bad dates.
- Protect against null account pointers in a couple of place to avoid asserts.
- Qif Import Assistant: Don't disable the whole dialog, just the Forward button.
- QifImport: Fix crash from attempting to import an empty file.
- Add the ability to search for transactions that are, or are not, book closing entries.
- Move customer, bill, and invoice importers form the business menu to the file menu.
- Rename some directories in src/import-export so that the gschema.xml.in.in files within them don't have pathnames that are too long for tar when the GnuCash version exceeds 5 digits (e.g., 2.5.10).
- Translations updated: German, Italian, French
- New Translation: Arabic
New in version 2.5.9 (December 2nd, 2013)
- Bug #644044: Lots: SQL backend loses link to Gain/Loss Txn
- Bug #704506: Connection loss to mysql after resume from hibernation
- Bug #707311: Tax Invoice fails to open when using guile 2
- Bug #710871: Python site-packages not found when not installed to default location using --prefix
- Bug #710905: Column withs, visibility, order and sort order not saved and restored
- Bug #711289: Win32 time zone handling is inconsistent between 2.4 and 2.5
- Bug #712299: Tax Invoice with guile 2 doesn't display currency symbols
- Bug #715041: Crash opening a file when a file is already open.
- Bug #715184: Bill or Invoice; a new Bill gives a new Invoice
- Bug #719471: Unused commodities saved to XML file
- No Bug Report: Work around libxml2 gzip archive alignment bug which occasionally prevented compressed XML files from opening.
- Translations updated: German, Italian
New in version 2.5.8 (November 19th, 2013)
- Bug #707311:Tax Invoice fails to open when using guile 2
- Bug #709589: make check fails with guile 2
- Bug #711289: Time Zone Handling is Inconsistent between 2.4 and 2.5
- Partial fix that may also correct 699997
- Bug #711294: Gnucash repeatedly asks for associated income account when importing QFX file. Patch by Kuang-che Wu
- Bug #711493: Fix unselected account that is NULL
- Translations updated: German
New in version 2.5.7 (November 4th, 2013)
- Register2 is now a configure option. Default builds, including the Windows and Mac All-in-one packages, will use only the old register. We've decided that it isn't ready for
- general use and the principal author doesn't have time to make it ready in time for a 2.6 release.
- Frédéric Perrin has contributed a change to display currency symbols whenever they are known and unambiguous.
- Geert Janssens has cleaned up most of the issues from the Initial GSettings preference changes. There's a new configure option, --with-xdg-data-dirs to overide the environment and defaults if necessary.
- Building Gnucash now requires Automake version 1.11 or later.
- Configure will abort if --enable-ofx is set but no libofx configuration files are found. Budget periods may no longer set to values greater than the budget's num_periods, and the budget options descriptions will wrap.
New in version 2.3.11 (March 22nd, 2010)
- Bugs fixed:
- Partial fix for #611014 - CSV import crashes Bug #611014 mentions a problem where after setting the columns, clicking OK and selecting a target account, the Date column is lost. This is because of a difference in behaviour on windows and linux. The code attaches to the "edited" signal of the renderer. On linux, this signal is emitted when a new combo box item is selected. On windows, the combo box needs to be selected and focus lost before the signal is emitted. This is changed to the "changed" signal of the renderer which acts as expected on both platforms.
- Bug #140400 - Crash when deleting an account that is still in use by the business features Add a dialog which contains a list of objects referring to the account and an explanation that these need to be deleted or have the account reference modified. Note: I'm no UI designer. This is functional, but if anybody wants to pretty it up, go ahead.
- Bug #536108 - After cancelling "save as", user is not prompted 2nd time
- Bug #507351 Terms not defined prior to use This commit changes the text in the accounts druid to explain what a placeholder account is, together with some additional improvements in the wording of that page. Since this increases the amount of text, the width of the label has been modified as well.
- Fix Bug 590570 - When deleting more than one report in sequence the program crashes Delete the custom report backup file before renaming the current custom report file.
- Fix Bug 611346 - Crash in Saved Reports dialog if you select Delete button with no report selected Test for no report selected before trying to use the selected report guid.
- Bug #364358 - Import dialog unreadable with dark colored gtk theme (with solution)
- Bug #525821 new or edited account names should be checked for reserved chars like ":"
- Bug #610675 Register Tabs Do Not Display Since Nightly Build r18685 Apply Bob's patch after fixing the whitespace. This patch may cause issues on Windows (a previous version of the patch did). If the next Windows nightly build exhibits the missing register tab names again, it will have to be reverted again and improved upon.
- Bug #611645 gnc-svnversion returns "too long" a string for git users, patch by Jeff Kletsky
- Bug#325436 creating income account for invoice doesn't restrict account type
- Fix Bug 611810 - GC crashes when I click on File -> Properties SCM files still refered to gnc-book-get-slots which had been removed. gnc-book-get-slots was replaced everywhere by qof-book-get-slots.
- Fix bug 611885 - Crash when opening postgresql file Previous work setting Timespec values via gobject properties missed the case where the timespec loaded from the database was NULL.
- Bug #611140: Fix crash on Open Subaccounts (hopefully).
- Bug #610321 - Compile errors with gtk-2.10.4: GTK_BUTTONBOX_CENTER undeclared This commit applies a reworked version of the patch to remove the use of GHashTableIter by Cristian Klein. Cristian's patch didn't apply cleanly to the current trunk. I have made the necessary changes to make it apply (and hopefully do what Cristian intended).
- Bug #611470 Add Japanese concepts guide into GnuCash installer, patch by Yasuaki Taniguchi
- Bug 605802: Can't input Japanese characters at an account register window on windows with SCIM, IIIMF and XIM Latest patch by Yasuaki Taniguchi to fix two problems 1) Can't use account separator char when entering account name in a split, and 2) Can't use + and - to go forward/backward a week.
- Fix bug 591177: Printer font is too small to read with webkit as html renderer. From comment 23: "The PDF in comment 2 is about 8 times smaller than it should be. One possible cause of this bug is if gtk_print_operation_set_unit (op, GTK_UNIT_POINTS) is not called. gtkprint defaults to GTK_UNIT_PIXEL - a useless unit to be using with printers. On Linux GTK_UNIT_PIXEL units are 1 unit = 1/72 inch (the same as GTK_UNIT_POINTS as well as PostScript and PDF units). On Windows GTK_UNIT_PIXEL units are the GDI device units which for printers is the dpi resolution. So for a 600dpi printer 1 unit is 1/600". If the application was developed on Linux and assumes the default gtkprint units are always 1/72" inch the output on Windows using a 600dpi printer will be 72/600 = 0.12 of the size (or approximately 1/8 of the size)." Solution was to use webkit_web_frame_print_full() which allows us to provide our own GtkPrintOperation object with units set to GTK_UNIT_POINTS. Tested on both Linux and Windows.
- Bug #610675: Revert the gnc-main-window parts of r18637 because it makes the tab names disappear under Windows. This disables the enhancement of bug#608329 again, but the disappearing of the tab names is a rather major bug. Note that we either need to fix the enhancement again, or revert the rest of r18637 as well so that the account properties don't show the color chooser without any effects.
- Bug #605802: Fix input of Japanese characters in register with SCIM, IIIMF and XIM Patch by Yasuaki Taniguchi. Revised and extended version of r18638. The main functions are as follows: (1) synchronization of preedit string between the register window and sheet->entry, (2) application to pango attributes to preedit string in the register window, (3) include scroll offset patch (id=153514), (4) include preedit string rollback patch (id=153518), (5) fix formula and account cells input problem which Christian pointed out, (6) surpress quick-fill when preedit string exists, (7) fix Windows IME problem. (8) Fix quick-fill problem.
- Redo of the dot-gnucash fix (so that GNC_DOT_DIR actually works) fixing bug 610707, adding Doxygen comments for all functions in gnc-filepath-utils, and adding testing for xaccResolveURI and more tests for xaccResolveFilePath.
- Revert r18713 (reopen 605802 "Input of Japanese characters". This commit had 2 problems: 1) when entering an account name, the account separator would no longer accept at the current level of the account tree and move to the next level 2) + and - in a date field would not change the field by 1 week.
- Bug #610348: Add compiling our own binary of libbonoboui because the binary still depends on the obsolete libxml2.dll. However, we still download the erroneous binary and unpack it into $GNOME_DIR because libgnomeui depends on libbonoboui which in turn depends on libgnome. Hence, libbonoboui cannot be compiled before libgnome-dev is unpacked, but libgnomeui won't report to be installed correctly before libbonoboui is available as well. Theoretically, we would have to split the inst_gnome step so that it first unpacks libgnome et al., then we run the inst_libbonoboui step, then we run the second part of inst_gnome which would be something like inst_gnomeui. I'm lazy, so I silently overwrite the libbonoboui DLL with our hand-compiled version and that's it.
- Bug #608032 - MySQL timeout and no attempt reconnect, second version This version builds on Phil's implementation of the dbi error callback functions to test for a timeout and to do the reconnect. The same error handling is equally implemented for postgres and sqlite. Unlike MySQL these two database types don't actually generate timeouts, but the functionality can be used later on for other error types as well.
- Bug #610051 - Crash when using GktHtml whenever a report is opened
- Bug #610348 missing dependencies in windows build Update gnome-vfs to 2.24.1 Note that this means Windows 2000 is no longer supported.
- Partial fix for bug #610321 Compile errors with gtk-2.10.4: GTK_BUTTONBOX_CENTER undeclared GTK_BUTTONBOX_CENTER is replaced with GTK_BUTTONBOX_START
- Fix bug #564380 additionally for easy invoice and fancy invoice. Patch by Mike Evans.
- Bug #610047 - Dutch accounts template doesn't work Add missing closing brackets
- Bug #609044: Improve UI strings for tax report options Patch by Frank H. Ellenberger: As we currently have a nice US income and a partial german VAT tax report, I feel uncomfortable with the change of r18413, which renamed Edit->Tax options to Income Tax options. So here is another approach, to clarify the tax report and business tax menu points.
- Bug #609043: Improve (mostly german) translation of txf Patch by Frank H. Ellenberger: This patch is a first extract of so an approach, which I have here, which will probably lead to a german income tax declaration ESt-A1. But this extract is more general and based on r18413 changes. Changes: 1. Header Comments: adding Contributors 2. Most strings in de_DE translated to german.
- Bug #608032: Handle MySQL connection timeouts with reconnect Patch by Tom van Braeckel: For the full discussion, see the mailing list: Rationale: When we try to open a database transaction, and the database reports that the "server has gone away", we try to reconnect before failing hard.
- Bug #609005: Add recipient name on invoices Patch by Mike E: Having set up a client/customer including the name of a recipient when I print an invoice the recipients name ("Account Dept" say) is not printed in the invoice. I think this is a bug rather than a feature. I have attached a patch to fix. It still prints the company name above the recipient name however. I could submit an additional patch to provide an invoice option to toggle printing of the company name if users/developers feel they want this option, as I do.
- Bug #609603: Windows packing/win32/install.sh PATH fix Patch by Yasuaki Taniguchi: When I run /c/soft/gnucash/inst/bin/gnucash or gnucash.cmd after I finish building win32 binary, DLL missing dialog boxes pop up. Missing DLLs are - libgcrypto.dll, - libPQ.dll, - mysql.dll, and - ssleay32.dll. This patch add search path to them to fix this problem.
- Bug #564380 Payment on bills doubles bill Patch by Mike Evans
- Updated translations or translation-related changes:
- Updated Japanese translation, copied from the Translation Project.
- Updated Persian (Farsi) translation by Mehdi Alidoost.
- Add dutch translation to the Windows installer.
- Updated Slovak translation, copied from the Translation Project.
- Updated Dutch translation, copied from the Translation Project.
- Update German translation.
- Add implementation of Gregorian - Jalali converter code. Copied from
- Other user-visible changes:
- Change file loading message to "Loading user data..." Reading file is technically only correct for files not for databases.
- Display the SX variables in the "Since Last Run..." dialog in ASCII order rather than ordering by hashvalue (i.e. no order at all) as was done previously. Patch by Jesse Weinstein.
- Add bzr support to gnc-svnversion. Patch by Jesse Weinstein
- Fix crash on opening the tax report, introduced by r18673. Patch by Alex Aycinena.
- Revert r18881/18884/18885 (bug #610675 - Register Tabs Do Not Display Since Nightly Build r18685)
- Fix missing color in qif-import account copy, patch by Tom Van Braeckel
- Replace Income Tax Options with Tax Report Options. Patch by J. Alex Aycinena.
- Patch my patch in r18884. Spotted by Herbert Thoma.
- Regression fix: patch for colored tabs segfault in trunk, patch by Tom Van Braeckel
- Other code/build changes:
- Remove test-load-module from tests
- Fix Makefile.am handling of gncla-dir.h so that it will be removed so that 'make distcheck' will pass
- Fix guint32 vs gint32 in gnc-uri-utils test.
- Update POTFILES.in based on new source files
- Complete unit tests for gnc-uri-utils api and fix bug found by running the tests.
- More doxygen.log-prompted typo fixes, patch by Jesse Weinstein
- Fix typo in previous commit
- Add first test for the gnc-uri-utils api. This test verifies gnc_uri_get_components.
- Implement the object reference infrastructure routines to allow a list of business objects referring to a specific other object (e.g. an account) to be determined. This will help fix bug 140400 because the account delete code can now determine a list of business (or other) objects which have references to that account, and prevent the account from being deleted while references still exist.
- Add some new gobject-related infrastructure so that when deleting an object, it can be determined if there are other objects with references to that object (bug 140400). Some routines are normal routines, and some routines use the gobject structure to allow different implementations by different object types. Per-instance routine: gboolean qof_instance_refers_to_object(QofInstance* A, QofInstance* B) - returns TRUE/FALSE whether object A contains a reference to object B. Normal routine: GList* qof_instance_get_referring_object_list_from_collection(QofCollection* c, QofInstance* B) - Calls qof_instance_refers_to_object() for each object in the collection, and returns a list of the objects which contain a reference to B. Per-instance routine: GList* qof_instance_get_typed_referring_object_list(QofInstance* A, QofInstance* B) - returns a list of all objects of the same type as A which contain a reference to B. Being per-instance allows an object to use knowledge to avoid scanning cases where there are no references (e.g. billterms do not contain references to splits), or a scan is not needed (references from splits to an account can be determined using xaccAccountGetSplitList()). This routine can do a scan by calling qof_instnace_get_referring_object_list_from_collection(). Normal routine: qof_instance_get_referring_object_list(QofInstance* A) - For all collections in the book, gets an instance and calls its qof_instance_get_typed_referring_object_list() routine, concatenating all of the returned lists. This is the routine that external code can call to get a list of all objects with references to an object A. The list must be freed by the caller but the contents must not. Per-instance routine: gchar* qof_instance_get_display_name(QofInstance* A) - returns a string which can identify object A to the user. This could be used to display a list of the objects returned by qof_instance_get_referring_object_list() ("Invoice 0004 for customer C") so that the user can modify those objects to remove the references. Note that this is going to require internationalization, which has not been implemented yet. If not overridden by the object class, the default string is "Object " e.g. "Object gncCustomer 0x12345678".
- Add event registration and handling from the qof_event_handlers. This way, the split view is updated correctly even on undo/redo.
- Revert r18869, "Move gnc-ui-util.[hc] and gnc-euro.[hc] from app-utils to engine" Those files indeed belong better into app-utils; the app-utils defines several not-yet-GUI parts of gnucash, like many conversions from and to strings (more than those in these two files), so these files are well suited in here.
- MSVC compatiblity: Fix include files in MSVC. Replace QSTRCMP by g_strcmp0 on MSVC.
- Improve non-gnome UI compatiblity: app-utils can compile without gtk as well.
- Add src/calculation and src/app-utils to cmake build system. app-utils is needed for the conversion from and to string for gnc_numeric, date, and other values.
- Fix failing core-utils tests I simply removed the obsolete test cases. More work is still needed to add new valid tests.
- Remove some unused variables.
- Win32/MSVC compatiblity - Replace trunc() by floor() - Provide a round() workaround implementation for MSVC - Use g_strcasecmp instead of the libc one - Add include for libc replacements
- Some more const-correctness in engine functions.
- Update POTFILES.in for the moved dialog-userpass.c and the newely added gnc-jalali.c
- Move gnc-ui-util.[hc] and gnc-euro.[hc] from app-utils to engine because they don't depend on gtk but are important additions for the engine types. In particular, the formatting of a gnc_numeric is defined there.
- Fix circular dependency between gnome and gnome-utils introduced in r18842
- MSVC compatiblity: snprintf is required to have a prefixing underscore. Also, more symbols of libguile/gc.h need explicit declspec on MSVC.
- Add variant of gnc_engine_init which is suitable for statically the linked-in library.
- Only use long long format specifiers if available - avoids error message when compiler thinks they're not available.
- Fix parent/child relationships in billterms in case the parent hasn't been loaded yet. Remove child column from billterm table because it duplicates info in the parent column and just complicates loading objects.
- Fix parent/child links for tax tables. If a tax table's parent table has not been loaded yet, remember the relationship, and after all tables have been loaded, fix up the rest of the parent/child links.
- Handle NULL string pointer as a NULL guid
- Add a mechanism so that the business sql backend module can provide the main sql backend with the order in which objects should be loaded. This will allow billterms and taxtables to be loaded before objects which contain references to those objects.
- MSVC compatiblity: Replace QOF_BOOK_LOOKUP_ENTITY macro by a RETURN_ENTITY macro and add inline functions for lookup. MSVC doesn't accept the syntax with an inlined block, x = ({ foo; bar; value;}). Hence, this is being replaced by actual function definitions, and the body of those functions is defined by the new macro.
- Delete unused variables.
- Use a normalized uri format internally to refer to data stores. Data stores for GC can be a file (xml or sqlite3) or a database one some server (mysql or postgres). Wherever it makes sense internally, data stores will be referred to via a normalized uri: protocol://user:password@host:port/path Depending on the context and story type some of these parts are optional or unused. To achieve this, a new utility interface has been setup: gnc_uri__ that can be used to manipulate the uris or convert from non-normalized formats to normalized and back. For example, when the user selects a file in the Open or Save As dialog, gnc_uri_get_normalized_uri will convert the file into a normalized uri. Or when the actual filename is needed this can be extracted with gnc_uri_get_path. You can also test if a uri defines a file or something else with gnc_uri_is_file_uri. For the complete documentation, see src/core-utils/gnc-uri-uitls.h This commit installs gnc-uri-utils and modifies the source where it makes sense to use its convenience functions. This concerns all functions that had to deal with file access in some way or another, the history module and the functions that generate the history menu list and the window titles. Note that gnc-uri-utils replaces xaccResolveFilePath and xaccResolveUrl in all cases. xaccResolveUrl has been removed, because gnc-uri-utils fully replaces its functionality. xaccResolveFilePath is used internally in gnc-uri-utils to ensure an absolute path is always returned (in case of a file uri, not for db uris). But it has been renamed to gnc_resolve_file_path to be more consistent with the other functions. Lastly, this commit also adds a first implementation to work with a keyring to store and retrieve passwords, althoug
- Make business backend initialization functions accessible when statically linking
- MSVC compatibility: Disable "C99 designated initializers" by a compiler-dependent macro Same as r18755.
- Make the backend initialization functions accessible when statically linking
- Change the definition of QOF_STDOUT The old definition file: conflicts with normal uris that can start with file: as well. I have chosen > instead, which is never a valid filename and on unixlike systems associated with standard out operations.
- Use proper qof CFLAGS/LDFLAGS since core-utils now uses qof
- The webkit used on win32 has webkit_web_frame_print_full() defined in include files, so we don't need a potentially conflicting extern declaration.
- If gmtime_r is defined as a macro, undef it
- Add svn:ignore to src/core-utils/test
- Remove invalid target (got copied from src/engine/test)
- Build test-core before core-utils
- Add the core-utils tests in the automake system
- Move filepath related tests to core-utils/test
- Undefine localtime_r as a macro (new mingw pthreads package defines it)
- Add braces to make if-if-then-else structure clear and avoid GCC 4.4.0 error message
- Remove gncmod-test from test-core It's not used and prevents test-core from being included in core-utils tests
- Add missing NULL sentinel at end of g_strconcat() function call
- Removed erroneously re-created src/engine/gnc-filepath-utils.c
- Move binreloc library include
- Note the moved files in POTFILES.in.
- Remove C executable from cmake as it is no longer necessary.
- Add missing link library after r18811.
- Adapt cmake to the file move in r18811.
- Add src/engine/test/test-resolve-url
- Win32: Add download of cmake, disabled by default.
- MSVC compatibility: strftime() doesn't know "%T" here. Also, g_fopen doesn't work, but fopen does.
- Move gnc-filepath-utils and dependencies from engine to core-utils
- Typo fixes, as found by doxygen.log, patch by Jesse Weinstein
- Tweak to gnc-svnversion's bzr section, patch by Jesse Weinstein
- Use "template-account" property to get/set template account.
- Add "template-account" to schedxaction as a gobject property.
- Simplify handling of sx template_acct column.
- Rename GNCBook into QofBook everywhere and remove separate header gnc-book.h. The former was already #define'd on the latter, so its removal gets rid of one level of indirection which makes function lookup easier. Also, the macro (!) qof_book_get_slots was turned into a normal function again because that's what functions are for (and otherwise the additional declaration in engine.i would break).
- Decrease compiler warnings by removing unused variables.
- Reduce compiler warnings by replacing strerror() with g_strerror() and similar glib replacements.
- Win32: Add more header includes where necessary to avoid using undeclared functions.
- Comment out unimplemented function. Improve const-correctness.
- Include gtk/gtk.h instead of gtk/gtkclist.h as recommended by Gtk
- Fix make dist r18765 introduced test target test-resolve-url, but no source file test-resolve-url.c Removed the target.
- Re-indentation of source code, next batch: src/gnome-utils/* This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header --suffix=none
- Re-indentation of source code, next batch: src/register/* This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header --suffix=none
- Re-indentation of source code, next batch: src/business/* This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header --suffix=none
- Re-indentation of source code, next batch: src/engine/* This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header --suffix=none
- Re-indentation of source code, next batch. This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header --suffix=none
- Replace and-let* in scheme script so that srfi-2 isn't needed.
- Replace one more g_list_append by g_list_prepend.
- MSVC compatibility: Somehow fdopen() doesn't work during the trace file initialization. Use fopen() instead.
- Win32 build: libguile needs minor tweaking for MSVC compatibility.
- MSVC compatibility: Fix r18748, r18761 by replacing strncasecmp() with strnicmp().
- MSVC C++ compatibility: Rename the internal name of union _GUID because _GUID is a builtin keyword here. This does not concern the typedef name, only the internal union name, so it doesn't harm us.
- C++ compatibility: namespace is a keyword, so don't use it as variable name.
- C++ compatibility: export is a keyword, so don't use it as a member name.
- Add support for passing a Timespec as a boxed GValue
- Fix test makefiles. Many tests now need to include other libraries because files have changed directories.
- Add more gobject property definitions to GNCPrice, Transaction, SchedXaction and Split.
- Win32: Create the MSVC import library for libguile during install.sh.
- Remove static current_session variable of libqof - we keep one in gnc-session.c already.
- Doxygen improvements, patch by Jesse Weinstein
- More changes where SQL backend uses gobject properties to load/save objects.
- More conversion to read/write objects from sql backend using gobject parameters
- Start to add properties to business objects. Currently only 1 property per object, but this infrastructure will allow more generic importing of objects.
- Take advantage of the initial property definition for Transaction, Split, GNCPrice and SchedXaction by replacing custom access routines with gobject properties.
- Add a few gobject properties to some engine object types. This adds more of the gobject infrastructure to Transaction, Split, SchedXaction and GNCPrice. Gobject properties provides a standardized interface to the engine objects which should allow standard and simplified read/write mechanisms. For the sql backend, for example, db columns can be mapped to properties. In a generalized csv importer, csv columns can be mapped to properties.
- Partly revert r18748, "Win32 compatibility": lib/libc directory doesn't have glib available.
- Add a "make indent" target, but watch out with using its result. The "astyle" indent tool unfortunately behaves significantly different in its different versions (1.22, 1.23, 1.24) even with identical options. That is, the basic indentation is the same, but in a large project such as ours, there are just too many special cases which astyle doesn't get identical due to its bugfixes and new features. Hence, please use the result of this target with great care, and if in doubt, just use it for your own amusement but don't commit the resulting changes. Thanks!
- Fix up some doxygen comments
- Don't include gnc-lot-p.h where not needed
- Win32: Fix libbonoboui compiling.
- MSVC compatibility: Microsoft doesn't have C99 "designated initializers". Those were introduced in r17724, bug#539957, but apparently this C99 is not supported by MSVC and won't be for some time to come. Hence, for MSVC we need the workaround to define a macro that will shadow the member names. However, the initialization itself works fine and non-MSVC code is unchanged, so I think we can live with that.
- MSVC compatiblity: Struct initialization doesn't work as expected. Somehow, the struct initialization containing a gnc_numeric doesn't work. As an exception, we hand-initialize that member afterwards.
- MSVC compatiblity: open() flags and S_ISDIR doesn't exist on MSVC.
- MSVC compatiblity: Use a char* pointer for the memcpy() input argument. This is required by MSVC because we do some pointer arithmetic in the memcpy() argument, but in order to do this, MSVC wants to know the pointed-to type of the pointer because pointer arithmetic increases the pointer not by a number a bytes but a number of sizeof(type). MSVC thinks for void* it doesn't count bytes. We achieve the desired effect by using a char* pointer so that bytes are counted.
- MSVC compatiblity: Add defines for functions/types which are available under different names in MSVC.
- MSVC compatiblity: Array initialization in MSVC requires a constant, not a variable. That is, gcc accepts a constant variable in many cases now, but MSVC doesn't accept it. So it must be turned into an old preprocessor define.
- MSVC compatibility: Remove forward declaration of static array by reordering the function that uses it.
- Win32 compatibility: Use glib wrappers of non-usual POSIX functions.
- More header include compatibility: Watch out for HAVE_UNISTD_H.
- Re-indentation of source code, next batch. This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header --suffix=none
- Convert GNCLot to use more gobject features. Removes all direct access to lot object fields, which are now accessed through functions or property names (for backend sql load).
- Modify POTFILES.in to handle source files moved to a new directory
- Also build backend/xml in cmake.
- Reverted 18699
- Clarify required steps to setup windows build environment. The mingw website has changed quite a lot since the README was written and some of the url's used in it were confusing. I have changed the url's to point to the actual packages on sourceforge (current at the time of this writing) and added some extra details where I had trouble understanding the actions to perform.
- Doxygen fixes - Have this file show up under module "Utility Functions" - Normalize the function descriptions (some were not in doxygen format) - Add a global file description - rename parameter 'file' to 'filename' for better consistency (note this required an internal parameter to be renamed from filename to new_filename)
- More minor MSVC code fixes. However, this code doesn't compile with MSVC9.0 for a few reasons: 1. libguile.h comes with its own scmconfig.h which contains HAVE_STDINT_H whereas MSVC doesn't have that. This is stupid guile which doesn't accept the fact that the user uses a different compiler than how they compiled guile. 2. Some initializations are not supported: Account.c:3312 etc. 3. The C99 "designated initializers" of e.g. Account.c:4661 ff. (r17724, bug#539957) are not supported by MSVC9.0 - this is the hardest problem of these all.
- Make CMake system more complete so that it builds on win32/mingw. Also, add a test executable to check that we got all the library dependencies.
- More CMake work: Build swig wrappers correctly. Build gnc-module.
- Cosmetic: Remove duplicate include of gnc-engine.h
- Remove trailing whitespace
- Minor doxygen change and lots or trailing whitespace removed
- Remove GNOME_PRINT_{CFLAGS,LIBS} from the Makefile templates
- Spelling errors and trailing whitespace removal
- Remove reference to gnome print in the comments GnuCash no longer uses gnome print. It has been replaced with gtk print.
- Remove two more popt references in support files.
- Remove popt requirement from configure GnuCash doesn't use it. At the same time, I removed a check that has been commented out since the beginning of the revision history (somewhere in 2007). This check tested for the presence of popt.h to then run some libtool changes. As I said this whole block has been commented out since the beginning of time, so I considered it to be obsolete, more even so now that the popt requirement has been removed.
- Remove popt references - popt has been replaced with the GOption infrastructure. So there's no need to include the popt.h file. - Also rewritten the comment that was elaborating on popt vs GOption - Finally removed the loglevel option (which was excluded from the compile anyway) that still referred to popt.
- Fix minor spelling errors
- When creating lists of database objects, use g_list_prepend() rather than g_list_append(). There may be cases where the list order is significant and thus needs to be reversed, but that is not true in these cases. This provides a large improvement in database loading performance. Analysis and basis patch supplied by Donald Allen.
- Update documentation references to Active Perl (5.8->5.10)
- Remove redundant entries in EXTRA_DIST
- More experimental cmake building. Except for the scheme wrappers this seems to work until at least the engine module. However, I didn't tackle the issue with the generated headers which contain some installation paths - but those we should get rid of anyway.
- Move two gtk-dependent files from src/core-utils to src/gnome-utils. core-utils depends on glib and additionally guile and gconf, but not (yet) gtk. Those two files which do are moved to the next module which already depends on gtk, which is gnome-utils.
- Add some experimental CMakeLists.txt which can compile the libqof part, on Linux, Windows/mingw and (no joke) Windows/MSVC. I'm interested in some tests with the cmake build system, but if it doesn't prove useful I will remove it again within a few weeks.
- Make libqof compatible for MSVC9.0 compiler (no joke). The main change is that the syntax for variadic macros is slightly different in MSVC compared to gcc. But they exist, so offering the log macros in the different syntax is sufficient.
- Make more header inclusions conditional on whether they exist.
- Update .gitignore, proposed by Jeff Kletsky
- Make sure file urls actually contain path information or are NULL
- Remove redundant GLIB check.
- Bump minimum required versions of gtk+, goffice and gtkhtml gtk+: 2.10 goffice: 0.5.1 gtkhtml: 3.14
- Add a starter script for gnucash under ddd (a gui frontend for gdb)
- Build fixes for EL5 after glib 2.12 requirement
- Ensure that GNC_DOT_PATH and other gnc_dotgnucash_dir() logic is used for all cases, remove hard-coded references to /usr/etc, /usr/share, /usr/local/etc, and /usr/local/share while providing for xaccResolveFilePath to actually search the data and sysconfdir directories used in the build. (gnc_build_data_path): New function, just a copy of gnc_build_book_path. Needed for rewrite of xaccResolveFilePath. (xaccResolveFilePath): Cleaned out the hard-coded paths and weird file path contruction functions and rewrote the function to use gnc_path_get_foo and gnc_build_data_path without all of the silly indirection. Removed superfluous URI checks (which are correctly perfomed by xaccResolveURL()). (MakeHomeDir, xaccPathGenerator, xaccDataPathGenerator) (xaccUserPathGenerator): Deleted; their functionality is replaced as noted above. (check_file_return_if_true): Renamed check_file_return_if_valid, a more descriptive name.
- Bump glib2 minimum requirement to 2.12. At the same time, remove all the conditional code and workarounds that were in the code to cater for glib < 2.12. Note: this commit will require a rerun of autogen.sh and configure.
- README referred to a non-existent file So per a suggestion on IRC, I took the reference out. Patch by Jesse Weinstein.
- Win32: Update libxslt version, but it needs its own copy of libxml2.dll. Apparently the gnome-provided libxml2 has the DLL filename libxml2-2.dll, but the binary from xmlsoft.org still has the filename libxml2.dll.
- Win32: And one more dependency upgrade (causes missing libxml2.dll complaints otherwise)
- More win32 dependency version updates.
- Update libpng package dependency for win32 to 1.4.0
- Small spelling fixes in the comments
- Re-indentation of source code, next batch. This also strips trailing whitespaces from lines where they existed. This re-indentation was done using astyle-1.24 using the following options: astyle --indent=spaces=4 --brackets=break --pad-oper --pad-header Discussed at
- Update gnome package versions.
- GDate values weren't being properly fetched from objects to be saved in a database column if they were fetched as a gobject property.
- Clean up account column in the lot table to specify that the guid is an account reference. Simplifies the code a bit, and makes future use of foreign keys easier.
- If building for WIN32, use webkit_web_frame_print_full() so that a GtkPrintOperation object with the correct units can be used to prevent font size problems (see bug 591177). On other platforms, use webkit_web_frame_print() because some distros seem not to have webkit_web_frame_print_full() (and also don't have the font size problem so on those distros, we don't need to create our own GtkPrintOperation object).
- Cutecash:
- Some of the GnuCash developers have decided to rewrite the UI for the cross-platform Qt toolkit from TrollTech. The goal is a simpler UI which is more powerful and easier to develop. This project has gotten the name "Cutecash". It uses the same back-ends and engine as gnucash. Only the UI is different. The source for the Cutecash UI is in the same tree (and therefore, the tarballs) as GnuCash, but at this point, no MAC or Win32 builds are being produced.
- Cutecash Add Commodity wrapper. Use gnc-exp-parser for numbers. - Allow amounts to be edited. - Let the date column be handled by the QDate delegate with a QDateEdit widget
- Cutecash: Enable entering of more cells in register. Some code cleanup. Add class documentation.
- Enable editing of the "Description" column in the split list view - WITH UNDO! The Qt Undo framework is almost like magic. We just have to create a command object instead of directly manipulating the value, and suddenly the undo/redo just works. This is fun!
- Cutecash: Add QUndoStack to implement all editing through the Command pattern and make it undoable.
- Cutecash: Enable closing and re-opening the different tab views. Also, change many main window slots to make use of the auto-connection feature because it makes the slot intention much easier to read. Also, note how we store the Tab position, title, isEnabled state in dynamically allocated properties in the Tab widget itself - this is a rather cool feature of QObject here (see reallyRemoveTab() and viewOrHideTab()).
- Cutecash: Add Recent-File menu.
- Cutecash: Enable tab moving and other UI features of Qt.
- Cutecash: Add Timespec conversion to QDateTime. Add display of transaction date in register tabs.
- Cutecash: Display account balance in tree and split amount in account register.
- Cutecash: Add gnc::Numeric wrapper for gnc_numeric.
- Implement a table widget with the list of the splits of one account, and open this if an account in the tree is double-clicked. Date and values/amounts can follow next, once those types are suitably wrapped into C++ as well.
- Cutecash: Add progress bar during loading the file.
- Implement the account list data model as a specialization of the account tree model. This is helpful in order to understand Qt's Model/View structure, so both (list and tree) are still available.
- Cutecash: Fix guile version number query. Patch by Herbert Thoma.
- Cutecash: Add a tree view of the accounts.
- Cutecash: Fix CMakeLists for change in guile lookup, r18846
- Cutecash: Remove QSharedPointer because manual delete is sufficient. Also, the QSharedPointer cannot be used for bookkeeping of a C pointer to any gnucash object because it refuses to work if it doesn't know the actual struct definition, which in gnucash is always private. The boost::shared_ptr would work without (by the custom deleter argument in the constructor), but QSharedPointer doesn't (the custom deleter is accepted only in addition to the known storage size, not alternatively), so it is pointless here.
- Cutecash: Add version check for guile and define HAVE_GUILE18 if appropriate.
- Adapt cutecash to r18842.
- Cutecash: Fix extern "C" usage: Must not enclose system includes, supposedly.
- Cutecash: Allow older glib versions as well.
- Cutecash: Add business-core including business-core/xml into the executable.
- Add copyright notices in cutecash source code files.
- Cutecash: Copy some more icons into the program. Add a clickable hyperlink.
- More C++/Qt4 frontend work.
- Add example main window in C++ and Qt that links against gnucash-engine. The example was based on Qt4's "application" example, but the main window layout is done through the .ui file already.
- Finish cmake build system for the C++ experiment. To build this: mkdir build-cpp cd build-cpp cmake .. make ./src/gnc/cutecash
- C++ experiment: Extend the AccountModel into a table with name and description. Use QString everywhere as well.
- C++ experiment: Add first simple model/view widget for the loaded account list.
- Some more C++ work. Opening an existing file works, even though nothing is visible so far. The implementation of a scoped_ptr wrapper around a C object uses the boost library, though, because writing our own implementation of a scoped_ptr with custom deletion function is too non-trivial and I rather re-use the boost::shared_ptr here instead of making our own mistakes.
New in version 2.3.5 (August 31st, 2009)
- Partly revert r18246: disable writing of "hidden" and "placeholder" so that XML files written by 2.3.5 can be read by 2.2.9
- Avoid CRIT messages when loading root account which has NULL commodity
- Fix compilation problem - add GPOINTER_TO_UINT() cast
- Fix bug 592357: Cannot specify port for database connection. You can now add a port number using ":" (e.g. ":100") to the end of the host specification in the Open and Save As dialog for databases.
- Fix bug 592021: Budget Report: Options to show actual, budgeted and diff don't work
- Fix minor i18n issues. 1) Don't translate gtk stock button labels. 2) Don't split sentences when translating. 3) Exclude formatting from translatable messages when possible
- Updated German translation
- Fix bug 592719 - postgres backend aborts with date problems
- Merge latest pot tempate into all .po translation files
- Add win32 version of gmtime_r
- Fix bug 575778: QIF import: fix crash when a security list omits the "T" (type) line
New in version 2.3.1 (June 8th, 2009)
- Major changes in the 2.3.x.
- Changes between 2.3.0 and 2.3.1 include:
- Bug #582976 – install.sh - webkit-1.1.5-win32.zip is not available
- Bug #583535 - Problem with mysql database
- Bug #583883 – Customer report produces error
- Bug #584564: Patch by Chris Dennis to allow a report to be either a string or html-doc
- Fix all business exports to force file type QSF
- Fix SQL statement which calculates account balances
- Fix port number, especially for postgresql
- Clean up include files and code related to goffice.
- Add qsf:// as a valid URI type
- Fix handling of GObjects when deleting a report
- Update aqbanking version to 3.8.3, which means one patch isn't needed
- Fix WEBKIT path so that correct DLLs will be copied to output directory
- Register: Add some header comments for a confusing function.
- Create and upload the WIN32 daily builds
- If postgres database does not exist, create it.
- Update German translation.
- Minor i18n string improvements
- Remove obsolete glade file.
- Modify packing on URI type combo box to fix its size
- Patch by Mike Alexander to speed up price db loading in sql backend.
- Add Lithuanian translation by Tadas Masiulionis
New in version 2.3.0 (May 20th, 2009)
- Major changes in this.
-.
New in version 2.2.9 (February 24th, 2009)
- Fixed Bugs:
- #339027: Reconcile window should display the date
- #435642: Crash editing results of a find
- #438132: Warning about commodity being NULL for root account on save
- #462148: Report output is vertically inverted and bottom up printed (mirror, reverse, &c.)
- #514455: Dutch (Netherlands) translation of account templates
- #526775: Win32: Crashes when importing brokerage account data
- #542382: Assign GnuCash to file name extension .gnucash
- #564209: Improved debuggability for module loading
- #564450: HUF currency handling incorrect as 1HUF divided into 100FILLERs
- #564928: Segfault when closing a invoice tab
- #565421: gnc-date-edit.c did not compile with Gtk < 2.10
- #565721: Multicolumn report options: Report names are not translated
- #566198: Slovakia joined the Euro
- #566352: Crash during OFX import under Win 2000 / SP4
- #566567: Scheme modifications are not built on windows
- #567174: Files with NIS stocks fail to open
- #568327: Using most "budget" reports, without a budget defined crashes gnucash
- #568653: Add SKR49 template
- #568945: The gnc_pricedb_convert_balance_... methods should look for the reciprocal of the exchange rate
- #569734: Give the template root account a name
- #570166: Weird text entry box when typing on Account Tree page
- #570894: Use of symbol t, which is not defined in all guile versions
- #571220: Program won't start if SCHEME_LIBRARY_PATH is set
- Other Changes:
- Added German account template for a Wohnungswirtschaft business
- Fixed french business account templates
- Updated translations: Catalan, Chinese, German, Italian
New in version 2.2.8 (December 14th, 2008)
- Fixed Bugs:
- #115066: "Search For" dialog shows all when criteria is left as default
- #128774: "Edit exchange rate" context menu item disfunctional often
- #137017: date of transaction change with time zone change
- #339433: TiaaCref price quote dates off by one day
- #340041: 0 as an amount should be allowed in Exchange Editor
- #345980: changing Stylesheet doesn't commit
- #347274: to track the difference between budgeted and actual amounts in the budget report
- #348860: Error with saved multicolumn reports
- #405472: Unable to save changes on files opened over FUSE and sshfs
- #432457: Security/stock import should follow tutorial regarding Account Name
- #435427: "Generic import transaction matcher" dialog does not sort by date
- #436342: Currency exchange druid does not show on changed
- #436920: crash on loading OFX data for a commodity that exists without cusip field
- #492417: currency mapping of New Israeli Shekel
- #529494: Wrong fractional precision in register with multi-currency transactions
- #532889: Monthly scheduled payments preview shows wrong dates
- #536299: Fix two underlinking issues
- #539947: OpenSolaris:__FUNCTION__ not defined in sun cc
- #543332: Severe performance regression in Average Balance report
- #548218: OpenSolaris: $(expression) cause configure error on solaris
- #554042: OpenSolaris: configure fail on checking 'unsigned long is at least as big as guint32'
- #557604: date-utilities.scm typos
- #557374: MT940 import does not work
- #563160: Multicolumn report: Confusing order of "Column span" and "Row span"
- #563273: crash in GnuCash Finance Management: Starting GnuCash
- #564033: aqbanking plugin: g_module_open failed: WEXITSTATUS undefined
- Other Changes:
- Fix account defaulting for posting vendor bill
- Fix tax-related inconsistency in UI
- Fix the average cost price source computation for a certain case
- Add account templates: Dutch, Finnish
- Update account templates: Italian, Slovak
- Update translations: Finnish, German, Hebrew, Italian, Japanese, Russian, Slovak, Simplified Chinese | http://linux.softpedia.com/progChangelog/GnuCash-Changelog-3824.html | CC-MAIN-2015-40 | refinedweb | 9,652 | 55.84 |
Tutorial: Using BizTalk Service Bridges to Send and Receive Messages from Service Bus Relay Service
Updated: November 27, 2015
This tutorial provides instructions on how to send XML messages with different schemas to a single bridge endpoint deployed using Microsoft Azure BizTalk Services. The bridge processes the message and routes them to more than one relay services based on the business logic defined as part of the solution. Using this scenario, the tutorial also showcases other capabilities of BizTalk Services such as:
Route Filters: The bridge enables you to route messages to the intended recipient based on filters. The filters are set on certain values that are passed as part of the message. For example, if the value in the element <Recipient> in the XML message is set to Finance, send the message to Service A. Otherwise, send the message to Service B. For more information, see The Routing Condition.
Route Action: Route actions help in bridging protocol mismatch. For example, consider two applications, App A and App B. App A sends messages by using the REST protocol while App B receives only SOAP messages. If App A sends the message to the bridge instead, the bridge includes SOAP headers on the message as part of Route Action. The bridge then sends the message over to App B. For more information, see The Routing Action.
Reply Action: Reply Action provides the same capability while sending a response back to the client, that Route action provides while sending a message to the receiver. So, if App B sends a response to App A, bridges use the Reply Action capabilities to stamp the response with headers that the client requires. For more information, see the Reply Action.
This tutorial demonstrates these capabilities of the bridge, in addition to other, using a business scenario.
Northwind Traders is an automobile insurance company. Northwind Traders receive request for new policy quotes in an XML format compliant with the standard ACORD schema, an industry standard for insurance messages. The incoming messages can be in any ACORD-compliant format. So, Northwind Traders must configure a solution that can process XML messages that conform to more than one XML schema. After Northwind Traders receive the message, it is validated against the provided ACORD message schemas and transformed into a schema internal to Northwind. Northwind then sends the message to a backend service that processes the message further. However, there are certain routing conditions before the message is sent to the service.
If the quote amount in the message is less than $10000, it must be sent to a relay service, say RelayReceiverServiceA. Before sending the message to the relay service, a SOAP header called QuoteType must be added to the message header. The value of this header must be set to SmallAmounts.
If the quote amount in the message is greater than $10000, it is treated as a high-risk claim and is sent to another relay service, say RelayReceiverServiceB. Before sending the message to the service, a SOAP header called QuoteType must be added to the message header. The value of the header must be set to LargeAmounts.
After receiving the message the services generate a response, add headers, and send a response back to the bridge. The services add the following headers:
The response from the service is in the same format as the Northwind’s internal request format. After the bridge receives the response, it transforms it to the response message schema compliant with ACORD standards. The bridge also extracts the value from the MsgStatus header and assigns it to an element in the response schema. Finally, before sending the message back to the client, the bridge adds another header called ProcessingStatus and sets its value to Complete. The following illustration represents this scenario.
Northwind Traders use BizTalk Services to set up this scenario. Here’s what Northwind Traders do at their end for this scenario to work end-to-end:
Northwind creates two relay services, RelayReceiverServiceA and RelayReceiverServiceB. RelayReceiverServiceA receives messages with quote amount less than $10000. RelayServiceB receives messages with quote amount greater than $10000. After receiving the message, both the services generate a response message and stamp it with the headers, as described in the business scenario.
Northwind creates a BizTalk Service project and adds a XML Request-Reply Bridge to process the incoming XML messages and send a response. Northwind also adds two-way relay service components, one each for RelayReceiverServiceA and RelayReceiverServiceB.
Northwind adds all the required artifacts (schemas and transforms) to the BizTalk Service project.
Northwind configures the request path of the XML Request-Reply Bridge to do the following:
Configures the Validate stage to validate the XML messages against the ACORD schemas.
Configures the Enrich stage to promote properties based on which the messages are routed to the backend services.
Configures The Transform stage to transform messages from the ACORD schema to Northwind’s internal schema.
Northwind configures the response path of the XML Request-Reply Bridge to do the following:
Configures the Enrich stage to extract the MsgStatus header that the relay services added to the response message.
Configures the Transform stage to transform the response from the relay services into a message schema compliant with ACORD standards. In this stage, the bridge also assigns the value from the MsgStatus header into an element in the response schema.
Configures the Reply Action to include the ProcessingStatus header in the response message that is sent to the client.
Northwind adds two external relay endpoints to the BizTalk Service project representing the two relay services and connects them to the XML Request-Reply Bridge bridge. As part of these routing connectors, Northwind does the following:
Connects all the components on the Bridge Configuration design surface and sets the filter conditions based on the quote amount.
Stamps the QuoteType header on the message and sets its value to either SmallAmounts or LargeAmounts depending on which service the message is being routed to.
Finally, Northwind deploys the two relay service on Service Bus and the BizTalk Service project to BizTalk Services and sends a message to the bridge endpoint.
This tutorial is written around a sample, Bridges_RelayServices.zip, which is available as part of the download from the MSDN Code Gallery. You could use the sample and go through this tutorial to understand how the sample was built. Or, you could use this tutorial to create your own application. This tutorial is targeted towards the second approach so that you understand how this application was built. Also, as much as possible, the tutorial is consistent with the sample and uses the same names for artifacts (for example, schemas, transforms) as used in the sample.
Even though Microsoft recommends that you follow the tutorial to understand the concepts and procedures, do the following if you wish to use the sample:
Download the Bridges_RelayServices sample and make relevant changes like providing your Service Bus namespace, issuer name, issuer key. After making the required changes, build and deploy the application.
Build and host the two relay services to accept request messages received via the bridge.
Use the MessageSender tool provided with the package to send request messages to the bridge. Look at the command prompts for the services as well as the MessageSender tool to see if the messages were processed successfully. If the messages are successfully processed, the request and response schemas are saved under the project’s \bin\Debug folder. The location and name of the message files are also displayed on the respective command prompts.
From the BizTalk Services download location (), download and install the BizTalk Services SDK. For instructions, see Install Azure BizTalk Services SDK. Installing the SDK installs the BizTalk Service project template in Visual Studio. This project template is used to create bridges that validate, Transform, and route messages to different endpoints as described in the business scenario. | https://msdn.microsoft.com/nl-nl/library/jj158971.aspx | CC-MAIN-2016-07 | refinedweb | 1,310 | 61.67 |
i need to create a program which is taking information from printer , so that i cannot use os namespace , so there is any way without using the os namespace
You may use a way as follows.
An example is as follows.
Python 2.7.5 (default, Nov 6 2016, 00:28:07)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> file = open("/tmp/file.jar", "rb")
>>> file.seek(0, 2) # 2 is os.SEEK_END
>>> filesize = file.tell()
>>> print filesize
3364
Here, the value of os.SEEK_END (2) is used directly. This piece of code is not 100% portable. But as you have no access to the os module, this may be a way to work around of that.
os.SEEK_END
os | https://www.systutorials.com/qa/2376/how-to-get-the-size-python-file-without-using-the-os-namespace?show=2377 | CC-MAIN-2017-34 | refinedweb | 135 | 86.91 |
RIF example UC8: Vocabulary Mapping for Data Integration
Contents
Summary
This use case is about rules which handle RDF data.
To write any such rules in the XML syntax of RIF Core WD1 we have to make some assumptions about the mapping from RDF to RIF. It is easy to invent such mappings but there are several alternatives.
Once we have the mapping then to express the rules in a concrete XML syntax as opposed to the abstract syntax we have to fill in the blanks on the tedious details like namespace handling and datatypes.
We would also like to be able to annotate the rules and rulesets in various ways. This example does so using RDF.
It was fairly easy to guess what the intended XML syntax was like from the current write up by my first guesses had mistakes. This may just be my fault but I think it suggests the need for a rather clearer specification of the syntax.
Background
Use case Vocabulary Mapping for Data Integration is about integrating data from multiple sources. The sources are provided as RDF conforming to RDFS/OWL vocabularies. Rules are used to translate the individual source representations to a common vocabulary.
The use case is loosely based on several existing applications of Jena and JenaRules, at least one of which is shipping commercially.
Source rules
These are artificial rules loosely based on the existing applications. They have been chosen to illustrate the typical range of features used in this class of applications.
@prefix it: <>. @prefix fn: <>. @prefix bp: <>. @prefix t: <>. # Simple data mapping # - a ComputeNode with a network interface card is mapped to a # Server with an IP address (no explicit NIC) [r1-computeNodeToServer: (?x rdf:type it:ComputeNode) (?x it:hasNIC ?i) (?i it:hasIP ?p) -> (?x rdf:type t:Server) (?x t:address ?p)] # Simple join # - find the cage housing the rack housing the compute node # and find the maintanance control for that cage [r2-joinBasedOnLocation: (?x rdf:type it:ComputeNode) (?x it:rack ?r) (?r it:cage ?c) (?mc fn:maintenaceContractForCage ?c) -> (?x rdf:type t:Server) (?x t:maintenanceContract ?mc)] # Object introduction # - the application data doesn't have an explicit representation # of the database hosting server so we invent one [r3-applicationHost: (?a rdf:type bp:Application) (?a bp:discoveredAtIP ?p) makeTemp(?n) -> (?n rdf:type t:Server) (?n t:address ?p) (?n t:hosts ?a)] # Datatypes and builtins # - assume that bulk maintenance contracts will get 25% discount [r4-discount: (?mc fn:baseCost ?c) (?mc fn:category fn:Bulk) product(?c, 0.75, ?cd) -> (?mc t:assumedCost ?cd)] # Vocabulary access and predicate variables # - there are several relationships between an application # and its subcomponents but any of them should induce a # dependency [r5-dependency: (?a rdf:type bp:Application) (?a ?P ?subApp) (?P rdfs:subPropertyOf bp:comprises) (?n t:hosts ?subApp) -> (?a t:dependsOn ?n)]
Analysis and issues
Core is horn
The simple rules fall within RIF core in that the rules have bodies which are conjunctions of triple patterns and variables are universally quantified across each rule. There is no negation.
The syntax:
[rulename: B1 .. Bn -> H1 .. Hm]
is simply syntactic sugar for a set of Horn rules:
B1 .. Bn -> H1 ... B1 .. Bn -> Hm
RDF triple mapping
To map the sample rules to RIF we have to decide how to map RDF triple patterns to RIF Core Expressions (Uniterms). There are (at least) three reasonable options:
- Use an "rdf" ternary relation.
Map all RDF (s P o) triples to binary relations P(s,o)
Map all RDF type triples (s rdf:type T) to unary relations T(s) and map all other triples to binary relations P(s,o)
The first is the simplest and supports quantification over RDF predicates without requiring quantification over RIF relations. The second is in some ways the most "natural" since we would normally regard an RDF triple as representing an instance of a binary relation.
For this exercise we chose the second option.
RDF Resource mapping
Next we have to decide how the map all the URIs like it:ComputeNode into Const(ant)s.
They could be simply strings, they could be instances of some URI sort or they could be called out as special cases in the abstract syntax.
Strings is the easiest but for the concrete syntax we would prefer some sort of qname/curie syntax. At the abstract syntax level this is irrelvant and boring. At the concrete syntax level handling namespaces in XML is one tedious headache. To simplify this we extend the syntax to use attributes for (c)URI(es).
So for example the first triple pattern in the first rule would look like:
<Uniterm> <Const rif: <Var>x</Var> <Const rif: </Uniterm>
or in the bipartioned graph proposal this would be:
<Uniterm> <Const rif: <Var>x</Var> <Const rif: </Uniterm>
This assumes some RIF-mandated rule about expansion of curies. This may not be acceptable W3C practice in which case wherever you see "pre:foo" imagine you actually see "⪯foo" where pre is an XML Entity.
Quantification over predicates
Having chosen the "natural" mapping that RDF predicates map to binary RIF relations (Consts) we have a problem with rule r5 which quantifies over such predicates.
To cope with this we extended the synatax in an "obvious" way so the second triple pattern in r5 would look like:
<Uniterm> <Const><Var>P</Var></Const> <Var>a</Var> <Var>subApp</Var> </Uniterm>
However, from discussion with Harold it seems that Const is intended to be a leaf node not a role specifier and there is a role specifier <op> that can be used in this situation so that the recommended syntax is:
<Uniterm> <op><Var>P</Var></op> <Var>a</Var> <Var>subApp</Var> </Uniterm>
Datatypes
Rule r4 has a numeric constant (the rule syntax 0.75 will translate into the RDF literal "0.75"^^xsd:double). RIF has no agreed concrete syntax for such constants so we adopt an obvious one using an attribute to give the datatype, assume all reasonable XSD atomic datatypes are supported and that curie/qname syntax is supported.
So we assume the constant will look like:
<Const rif:0.75</Const>
in the bipartitioned proposal this would become:
<Data rif:0.75</Data>
Builtins
Rule r4 also refers to a builtin function ("product"). We haven't yet discussed specific sets of builtins for RIF. Since we are using XSD for atomic types it might be logical to use XQuery functions and operators but that doesn't supply URIs to identify the operators like "*". Similarly we could use MathML but that only gives us QNames and not URIs. So we'll just pretend RIF has defined a set of builtins.
So the third pattern in rule r4 becomes:
<Equal> <Var>cd</Var> <Uniterm> <Const rif: <Var>c</Var> <Const rif:0.75</Const> </Uniterm> </Equal>
bNodes
This class of JenaRule application goes outside Horn in that the rules can manufacture new bNodes to represent objects we know to be present but are not assigning a URI. This is treating bNodes simply as Skolem constants. We've represented this as the makeTemp builtin in rule r3. To translate this rule we assume some equivalent genSym function than can manufacture a skolem constant.
Rule naming
A boring but sometimes useful feature of the source rules is the syntactic rule label. We'd like be able to attach arbitrary descriptive metadata to rules such as names, descriptions, authors etc
For the sake of this example we are going to use the sugestion in
We could have a single Literal for the entire rule and follow the B.1 rule syntax for that literal. However, then for the rules with repeated bodies (lots in this example) we end up with a lot of duplication. To make the translation marginally less unreadable we've chosen to go with a head/body/vars split to enable us to have multiple heads as a purely syntactic convenience and just use the A.1 syntax for those components.
[Note that rif:vars as used here implicitly implies universal quantification, if we were to adopt something like it then the quantification should be explicit.]
This not a fundamental issue and switching to a single rif:ruleSrc property which points to a B.1 literal with all rules expanded in full would be perfectly acceptable.
Rule and Ruleset labelling
It would be convenient to be able to label these rules as being indended for processing RDF data so a translator knows to expect only binary predicates.
It would also be convenient to be able to label them as intended for model transformation rather than deductive closure. In the original application the rules are actually preduction rules with implicit "asserts" for each triple in the conclusion. The desired output of the rule processor is just the set of newly asserted conclusions not the full deductive closure. This procedural usage is presumably outside RIF core but we can at least annotate the ruleset to indicate this was the original intended usage.
For both of these we've invented RDFS/OWL classes and used them as annotations on the base Ruleset. One can argue if they should be Rule rather than Ruleset classifications.
RIF Translation
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE rdf:RDF [ <!ENTITY rdf ''> <!ENTITY rdfs ''> <!ENTITY xsd ''> <!ENTITY owl "" > <!ENTITY rif "" > <!ENTITY jena "" > <!ENTITY dc "" > <!ENTITY it "" > <!ENTITY fn "" > <!ENTITY bp "" > <!ENTITY t "" > ]> <rdf:RDF xmlns: <rif:Ruleset rdf: <!-- label outer ruleset as only expecting RDF compatible rules --> <rdf:type rdf: <!-- label outer ruleset with a jena-specific concept of transformation rules, can be ignored by other processors --> <rdf:type rdf: <!-- The first rule --> <rif:rule><rif:Implies rdf: <!-- Descriptive metadata --> <rdfs:label>r1-computeNodeToServer</rdfs:label> <rdfs:comment>Simple data mapping</rdfs:comment> <dc:creator>Dave Reynolds</dc:creator> <!-- Rule variables, universally quantified --> <rif:vars rdf: <Var>x</Var> <Var>i</Var> <Var>p<:hasNIC" /> <Var>x</Var> <Var>i</Var> </Uniterm> <Uniterm> <Const rif: <Var>i</Var> <Var> <!-- multiple heads, syntactic sugar for repeated rules with same body --> <rif:then rdf: <Uniterm> <Const rif: <Var>x</Var> <Var>p</Var> </Uniterm> </rif:then> </rif:Implies></rif:rule> <rif:rule><rif:Implies rdf: <rdfs:label>r2-joinBasedOnLocation</rdfs:label> <rdfs:comment>Simple join</rdfs:comment> <dc:creator>Dave Reynolds</dc:creator> <!-- Rule variables, universally quantified --> <rif:vars rdf: <Var>x</Var> <Var>r</Var> <Var>c</Var> <Var>mc<:rack" /> <Var>x</Var> <Var>r</Var> </Uniterm> <Uniterm> <Const rif: <Var>r</Var> <Var>c</Var> </Uniterm> <Uniterm> <Const rif: <Var>mc</Var> <Var> <rif:then rdf: <Uniterm> <Const rif: <Var>x</Var> <Var>mc</Var> </Uniterm> </rif:then> </rif:Implies></rif:rule> <rif:rule><rif:Implies rdf: <rdfs:label>r3-applicationHost</rdfs:label> <rdfs:comment>Object introduction</rdfs:comment> <dc:creator>Dave Reynolds</dc:creator> <!-- Rule variables, universally quantified --> <rif:vars rdf: <Var>a</Var> <Var>p</Var> <Var>n</Var> </rif:vars> <!-- rule body --> <rif:if rdf: <And> <Uniterm> <Const rif: <Var>a</Var> <Const rif: </Uniterm> <Uniterm> <Const rif: <Var>a</Var> <Var>p</Var> </Uniterm> <!-- genSym built in assumed to take n-1 bound variables and constants as keys and bind the final variable to an Ind keyed from them --> <Uniterm> <Const rif: <Var>a</Var> <Var>p</Var> <Const>r3</Const> <Var>n</Var> </Uniterm> </And> </rif:if> <!-- rule head --> <rif:then rdf: <Uniterm> <Const rif: <Var>n</Var> <Const rif: </Uniterm> </rif:then> <rif:then rdf: <Uniterm> <Const rif: <Var>n</Var> <Var>p</Var> </Uniterm> </rif:then> <rif:then rdf: <Uniterm> <Const rif: <Var>n</Var> <Var>a</Var> </Uniterm> </rif:then> </rif:Implies></rif:rule> <rif:rule><rif:Implies rdf: <!-- Descriptive metadata --> <rdfs:label>r4-discount</rdfs:label> <rdfs:comment>Datatypes and builtins</rdfs:comment> <dc:creator>Dave Reynolds</dc:creator> <!-- Rule variables, universally quantified --> <rif:vars rdf: <Var>mc</Var> <Var>cd</Var> <Var>c</Var> </rif:vars> <!-- rule body --> <rif:if rdf: <And> <Uniterm> <Const rif: <Var>mc</Var> <Const rif: </Uniterm> <!-- not sure if this should be a builtin relation or use equality --> <Equal> <Var>cd</Var> <Uniterm> <!-- assuming builtin multiply function --> <Const rif: <Var>c</Var> <Const rif:0.75</Const> </Uniterm> </Equal> </And> </rif:if> <!-- rule head --> <rif:then rdf: <Uniterm> <Const rif: <Var>mc</Var> <Var>cd</Var> </Uniterm> </rif:then> </rif:Implies></rif:rule> <rif:rule><rif:Implies rdf: <!-- Descriptive metadata --> <rdfs:label>r5-dependency</rdfs:label> <rdfs:comment>Vocabulary access and predicate variables</rdfs:comment> <dc:creator>Dave Reynolds</dc:creator> <!-- Rule variables, universally quantified --> <rif:vars rdf: <Var>a</Var> <Var>P</Var> <Var>n</Var> <Var>subApp</Var> </rif:vars> <!-- rule body --> <rif:if rdf: <And> <Uniterm> <Const rif: <Var>a</Var> <Const rif: </Uniterm> <!-- Variable in relation position --> <Uniterm> <op><Var>P</Var></op> <Var>a</Var> <Var>subApp</Var> </Uniterm> <Uniterm> <Const rif: <Var>P</Var> <Const rif: </Uniterm> <Uniterm> <Const rif: <Var>n</Var> <Var>subApp</Var> </Uniterm> </And> </rif:if> <!-- rule head --> <rif:then rdf: <Uniterm> <Const rif: <Var>a</Var> <Var>n</Var> </Uniterm> </rif:then> </rif:Implies></rif:rule> </rif:Ruleset> </rdf:RDF>
Changes
30/10/06 Fixed the syntax slightly after suggestions from Harold to stick closer to the core syntax (dropped use of separate Ind, fixed up use of <Rel>).
31/10/06 Changed nesting of <Equal> in response to change/clarification of A.1 BNF.
31/10/06 Switched to Harold's proposal of <op><Var> to designate variables in the Relation position.
- 31/10/06 Added comments on use of vars/head/body versus ruleSrc.
21/05/07 Updated Dave's use case towards the XML syntax of RIF Core WD1. | http://www.w3.org/2005/rules/wg/wiki/UC8_Worked_Example.html | CC-MAIN-2014-15 | refinedweb | 2,280 | 53.1 |
User talk:Marth23
From Uncyclopedia, the content-free encyclopedia
edit Welcome!
Hello, Marth23,.) 01:55, August 18, 2007
edit Game Online
Make sure when you're making new pages for the game, that they stay withing the Game:Game Online namespace (for example, you made a page "Stay in here", whereas it should have been made at Game:Game Online/Multi Player/2/ZZZZZZ, and you can replace the Zs with whatever else you want. -- 02:35, 18 August 2007 (UTC)
edit Adoption
I saw you wanted adoption, Want me to:05, 18 August 2007 (UTC)
- I adopted you, and I'll play your game in a bit, if you have questions and concerns, message me. Welcome. -:25, 18 August 2007 (UTC) | http://uncyclopedia.wikia.com/wiki/User_talk:Marth23 | CC-MAIN-2015-40 | refinedweb | 122 | 60.48 |
C++ is a mid-level programming language—it easy to write and it runs very quickly. As a result, it is widely used to develop games, business apps, and software, such as Google Chrome and Microsoft Office Suite.[1] X Research source If you are a Windows user, you may also use C++ programs to execute batch files. These are script files that contain commands to be executed in sequence by a command line interpreter.
Steps
Method 1 of 4:
Getting Started with C++
Method 1 of 4:
- 1Introduce yourself to C++ language. C++ is related to C programming language. Unlike its predecessor, C++ is an object-oriented programming language. The object is the primary unit of this language—every object has specific properties, functions, and methods.[2] X Research source
- 2Download and install a compiler. In order to create viable programs with C++, you will need to download and install a compiler. Compilers transform your code into operational programs. There are free compilers available for Windows, Mac, and Linux users.
- Windows: Code::Blocks
- Mac: Xcode
- Linux: g++.
- 3Find useful introductory resources and tutorials. Learning C++ is equivalent to learning a foreign language. Books, courses, and tutorials will help you establish a foundational understanding of this programming language. You will find a variety of free and purchasable resources online.
Advertisement
- Consult a comprehensive list of books and guides.[3] X Research source
- Enroll in a C++ programming course. You may find courses at your local college, library, adult education center, and/or online. You could even join a MOOC (Massive Open Online Course).
- Complete a step-by-step tutorial. You can work your way through free tutorials or subscribe to a tutorial service, like Khan Academy or Lynda.[4] X Research source
Method 2 of 4:
Creating a Basic C++ Program
Method 2 of 4:
- 1Launch your compiler and create a new C++ project.
- 2Select ’’main.cpp.’’
- 3Write a “Hello World” program. Traditionally, the first program people create simply reads “Hello World!”. When you create a new C++ project, the “Hello World!” program will automatically appear in the file. Erase the existing code and rewrite it for yourself:
#include <iostream> using namespace std; //main () is where program execution begins. int main () { cout <<”Hello World”; //prints Hello World return 0; }
- 4
- 5
- 6Understand comments. Programmers use comments to annotate their code so that they (or anyone else reading the code) can understand more about what a particular section of code is meant to do. Comments appear in the code text but do not affect the program. In the "Hello world" program, "//main () is where program execution begins" is an example of a single line comment.
- Single line comments always begin with "//" and stop when the line ends.
- 7Understand the program’s function. In C++, functions execute individual tasks. In the “Hello World” program, int main() is the main function. Program execution begins at this line of code. The statements inside the brackets describe the actual function.Advertisement
Method 3 of 4:
Exploring Batch Files
Method 3 of 4:
- 1Understand batch files. Batch files are exclusive to Windows—the Mac counterpart is a bash file. Batch files contain a one or more commands that are executed in sequence by a command line interpreter. These files are used to simplify basic and/or repetitive jobs such as opening multiple programs, deleting files, and backing up files.[8] X Research source You may incorporate batch files into your C++ programs.[9] X Research source
- 2
- 3
- 4
- 5Understand “@echo.” In batch, commands are echoed, or displayed, on the output screen by default. When a program runs, you will see the command and its output. Preceding this command with an "@" turns off echoing for a specific line. When the program runs, you will only see "Hello world."[13] X Research source
- You can turn of all echoing with the command “@echo OFF.” If you use this command, you can rewrite the program as:
@echo Off echo Hello world. pause
- 6
- 7Run your batch file. The fastest way to run your batch file is to simply double-click on the file. When you double-click on the file, the batch file is sent to the DOS command line processor. A new window will open and your batch file will close. Once the user presses a key to continue, the program will end and the window will close.[15] X Research sourceAdvertisement
Method 4 of 4:
Applying Your New Knowledge
Method 4 of 4:
- 1Incorporate functions into your code. A function is a group of statements, or instructions, that perform a specific task. Each function is assigned a type, a name, parameter(s), and statements. You will use the C++ function “system” to run a batch file. To explore functions, try coding this program:
// function example #include <iostream> Using namespace std; int addition (int a, int b) { int r; r=a+b return r; } int main ( ) { int z; z = addition (5,3); cout << “The result is “ << z; }
- This program contains two functions: ‘’addition’’ and ‘’main’’. The compiler will always call ‘’’main’’ first—in this program it will call the variable “z” of type “int’’. The call will pass along two values, 5 and 3, to the “‘addition”’ function. These values correspond to the parameters declared by the “addition” function—“int a, int b”.
- Inside the “addition” function, there is a third variable: “(int r)”, that is directly related to the expression r=a+b. The two values from the “main” function, 5 and 3, will be added together to equal “r.” In this instance, r equals 8.
- The final statement, “return r;” ends the “addition” function and returns control to the “main” function. Since “return” has a variable, “r,” the call to return to “main” is evaluated as a specific value and sends this variable to the “main” function.
- The “main” function resumes where it left off when it was called to “addition”: “cout << “The result is “ << z;.” This line of code prints “The result is 8” on the screen.[16] X Research source
- 2Experiment with flow control statements. Statements are individual instructions that are always executed in sequential order. C++ programs, however, are not limited to linear sequences. You may incorporate flow control statements to alter the path of your program. The “while loop” statement is a common flow control statement—it tells the program to execute a statement a specific number of times or while the condition is fulfilled.
// custom countdown using while #include <iostream> using namespace std; int main () { int n = 10; while (n>0) { cout << n << ", "; --n; } cout << "liftoff!\n"; }
- “int n= 10”: This line of code sets the variable “n” to 10. 10 is the first number in the countdown.
- “while (n>0)”: The loop will continue as long as the value of “n” is greater than 0.
- If the condition is true, the program executes the the following code: “cout << n << ", "; --n;”. The number “10” will appear on the screen. Each time the loop is executed, the number “n minus 1” will appear on the screen.
- “cout << "liftoff!\n";”: When the statement is no longer true—when “n” equals “0”—the phrase “liftoff!” will appear on the screen.[17] X Research source
- 3Run a batch file with C++. When you run a batch file with your C++ program, you will use the “system ( )” function. The “system” function tells the command line processor to execute a command. Enter the batch file’s name within the parentheses of the “system ( )” function.[18] X Research source
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About This Article
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- Contents
- JNA Development First Steps
- A Proxy for the DLL
- Linkage: What's in a Name?
- Parameter and Return Types
- C structs in Java
- < li>Pointers and Strings
- Converting from JNI to JNA
- Detecting a Struct Memory Alignment Problem
- Reproducing the Struct Alignment Error
- Preven ting Struct Alignment Errors
- Running the Sample Code
- Resources
This article describes the Java Native Access (JNA) approach to integrating native libraries with Java programs. It shows how JNA enables Java code to call native functions without requiring glue code in another language. The examples illustrate usage patterns, common pitfalls, and troubleshooting techniques. The article also enables a comparison of JNA and JNI (Java Native Interface) by describing the conversion of sample JNI code from an earlier java.net article to JNA.
It is useful to know JNA because the Java APIs, with their architecture-neutral emphasis, will never support platform-specific functionality. So, for example, if that killer app you've just invented needs to play the Windows "Critical Stop" sound you'll be stuck as the Windows MessageBeep()function can't be called via the standard APIs.
Though Java itself is architecture-neutral, the example code used in this article is, perforce, platform-specific. The code has been developed and tested on a Laptop PC running 32-bit Microsoft Windows XP and Sun JRE 1.6.0 update 16. However, the code is quite generic and should run on a range of Windows and JVM versions. Features new in Java 1.6, Windows 2008, and Windows Vista have not been used.
JNA Development First Steps
Here are a few things you have to take care of when starting a JNA project:
Download jna.jar from the JNA project site and add it to your project's build path. This file is the only JNA resource you need. Remember that jna.jar must also be included in the run-time classpath.
Find the names of the DLLs that your Java code will access. The DLL names are required to initialize JNA's linkagemechanisms.
Create Java interfaces to represent the DLLs your application will access. The sample code accompanying this article contains example interfaces for three DLLs: kernel32.dll,user32.dll, and Twain_32.dll.
Test linkage of your Java code to the native functions. The first example below, "Linkage: What's in a Name?", describes the exceptions to expect when JNA can't find a DLL or a function in a DLL.
If your project is large or complex, it may be a good idea to complete these steps in an early phase. If a proof of concept (POC) is required, consider including a significant portion of JNA interface code in the POC. This helps to validate assumptions about JNA's suitability for the job, and reduces overall project risk.
A Proxy for the DLL
JNA uses the proxy patternto hide the complexity of native code integration. It provides a factory method that Java programs use to obtain a proxy object for a DLL. The programs can then invoke the DLL's functions by calling corresponding methods of the proxy object. The sequence diagram in Figure 1 below depicts the creation and use of a proxy object.
Figure 1. Creation of a Java proxy object for a DLL
JNA takes care of all run-time aspects, but it requires your help to create the proxy's Java class. So the first piece of code you need to create is a Java interface with method definitions that match the DLL's C functions. To play with JNA's run-time correctly, the interface must extend
com.sun.jna.Library. The code below shows an abbreviated view of a proxy interface for the Windows user32 DLL. Note that there should be one such Java interface for each DLL.
package libs; import com.sun.jna.win32.Library; public interface User32 extends Library { ... (lines deleted for clarity) ... boolean LockWorkStation(); boolean MessageBeep(int uType); ... (lines deleted for clarity) ... }
Many DLLs, such as those in the Windows API, host a large number of functions. But the proxy interface need only contain declarations for the methods your application actually uses.
Linkage: What's in a Name?
Our first example (LockWorkStation.java) is extremely simple, and locks the workstation when it is run (same effect as pressing the Windows logo + Lkeys together). It uses the
User32 interface shown above to create a proxy for the Windows user32 DLL. It then calls the proxy's
LockWorkStation() method -- which in turn invokes the DLL's
LockWorkStation()function. The run-time mapping of the proxy method to the DLL function is handled transparently by JNA -- the user just has to ensure that the method name matches the function name exactly.
import com.sun.jna.Native; // JNA infrastructure import libs.User32; // Proxy interface for user32.dll public class LockWorkStation { public static void main(String[] args) { // Create a proxy for user32.dll ... User32 user32 = (User32) Native.loadLibrary("user32", User32.class); // Invoke "LockWorkStation()" via the proxy ... user32.LockWorkStation(); } }
To compile and run this program follow the instructions at "Running the Sample Code" below.
The absence of parameters and a return value in the
LockWorkStation() call eliminates the possibility of any programming errors. But there are still two things that can go wrong with code as simple as this:
loadLibrary()throws a
java.lang.UnsatisfiedLinkErrorwith the message "Unable to load library ... The specified module could not be found." If this error occurs check the spelling of the DLL name, and verify that the DLL is in one of the searched directories (check JNA documentation).
A proxy method (such as
LockWorkStation()) throws a
java.lang.UnsatisfiedLinkErrorwith the message "Error looking up function ... The specified procedure could not be found." If this error occurs check the spelling of the function name, and verify that the "function" is not actually amacro. The Windows API DLLs contain quite a few such macros (e.g. GetMessage(), defined in Winuser.h), so read the DLL's documentation (and the associated header files) carefully. Macro names must be translated manually.
You shouldn't get either of these exceptions when runningLockWorkStation.java. But you can simulate these errors just by changing the name of a DLL or a function and recompiling the code. JNA does, in fact, have mechanisms to allow you to use a method name (in the proxy interface) that is different from the function name (in the DLL). More information on this feature can be found in the JNA documentation.
Parameter and Return Types
Our next example, BeepMorse.java shown below, uses the Windows Beep()function to literally beep "Hello world" in Morse code.
import com.sun.jna.Native; // JNA infrastructure import libs.Kernel32; // Proxy interface for kernel32.dll public class BeepMorse { private static Kernel32 kernel32 = (Kernel32) Native.loadLibrary("kernel32", Kernel32.class); private static void toMorseCode(String letter) throws Exception { for (byte b : letter.getBytes()) { kernel32.Beep(1200, ((b == '.') ? 50 : 150)); Thread.sleep(50); } } public static void main(String[] args) throws Exception { String helloWorld[][] = { {"....", ".", ".-..", ".-..", "---"}, // HELLO {".--", "---", ".-.", ".-..", "-.."} // WORLD }; for (String word[] : helloWorld) { for (String letter : word) { toMorseCode(letter); Thread.sleep(150); } Thread.sleep(350); } } }
Beep() takes two arguments, frequency and duration, both of type
DWORD which is definedas
unsigned long. Since an
unsigned longoccupies 32 bits in all current flavors of Windows, we use a Java
int for both arguments in the proxy interface definition shown below:
package libs; import com.sun.jna.Library; public interface Kernel32 extends Library { // ... (lines deleted for clarity) ... boolean Beep(int frequency, int duration); int GetLogicalDrives(); // ... (lines deleted for clarity) ... }
It is important to deduce the argument types correctly as you can verify by changing the type of
Beep()'s arguments. Changing the definition to
Beep(long, long) or
Beep(float, float) does not cause any run-time error, but you will hear no sound at all. The JNA web-site has some information on translating Windows types to Java types. More details can be found at wikibooks' Windows Programming/Handles and Data Types page and Microsoft's Windows Data Types page.
To compile and run this program follow the instructions at "Running the Sample Code" below, but remember to turn the volume down first!
Beep() returns a boolean value, although it is ignored in this example. But if the value returned by a function has to be used, the return type must be mapped to a suitable Java type using the same guidelines as for parameter types. The code below (GetLogicalDrives.java) illustrates the use of the
int value returned by
GetLogicalDrives()in the kernel32 DLL.
import com.sun.jna.Native; import libs.Kernel32; public class GetLogicalDrives { public static void main(String[] args) { Kernel32 kernel32 = (Kernel32) Native.loadLibrary("kernel32", Kernel32.class); int drives = kernel32.GetLogicalDrives(); for (int i = 0; i < 32; ++i) { int bit = (1 << i); if ((drives & bit) == 0) continue; System.out.printf("%c:\\%n", (char) ((int) 'A' + i)); } } }
Note, however, that in practice a Java program should never have to call
GetLogicalDrives() using JNA as
java.io.File.listRoots() provides the same information.
To compile and run this program follow the instructions at "Running the Sample Code" below.
The article's introduction mentioned the use of Windows standard sounds for indicating specific events. These sounds can be produced by calling the
MessageBeep(int type) function. Example code showing the use of
MessageBeep() can be found in the fileMessageBeep.java.
C structs in Java
C Functions often use
structs as arguments. But since Java does not have structs, JNA uses classes instead. Classes are closely related to structs, so the associated Java code looks intuitive, and works well. The following code extracted fromKernel32.java, the proxy interface for kernel32.dll, illustrates the conversion of
struct SYSTEMTIME into a Java class to support the
GetSystemTime()function.
import com.sun.jna.Library; import com.sun.jna.Structure; public interface Kernel32 extends Library { // ... (other members deleted) ... public static class SYSTEMTIME extends Structure { public short wYear; public short wMonth; public short wDayOfWeek; public short wDay; public short wHour; public short wMinute; public short wSecond; public short wMilliseconds; } void GetSystemTime(SYSTEMTIME st); // ... (other members deleted) ... }
Note that Java classes that substitute C structs must extend JNA's
com.sun.jna.Structure base class. Embedding these classes inside the proxy interface helps to keep everything neatly organized in a single file. This is particularly effective when the struct is only used by functions in the same proxy interface. These classes can, however, also be defined as standalone public classes (outside the proxy interface) if that is required or preferred. The JNA web site has more information on these aspects.
The code shown below, GetSystemTime.java in the sample code, illustrates the use of structs. In this example the called function uses the struct to pass information "out", but structs can be used to pass information "in" (as in the Windows
SetSystemTime()function) or "in and out" as well.
import libs.Kernel32; import libs.Kernel32.SYSTEMTIME; import com.sun.jna.Native; public class GetSystemTime { public static void main(String[] args) { Kernel32 kernel32 = (Kernel32) Native.loadLibrary("kernel32", Kernel32.class); SYSTEMTIME st = new SYSTEMTIME(); kernel32.GetSystemTime(st); System.out.printf("Year: %d%n", st.wYear); System.out.printf("Month: %d%n", st.wMonth); System.out.printf("Day: %d%n", st.wDay); System.out.printf("Hour: %d%n", st.wHour); System.out.printf("Minute: %d%n", st.wMinute); System.out.printf("Second: %d%n", st.wSecond); } }
To compile and run this program follow the instructions at "Running the Sample Code" below.
It is important to deduce the type of each member of a converted struct correctly. Erring here usually has catastrophic consequences that you can sample by changing the types in
SYSTEMTIME. There are other JNA tweaks that can be applied to specify whether a struct should be passed by reference (the default) or by value, and also how a struct embedded within another should be stored. The JNA web-site has much guidance on these aspects. The section titled "Converting from JNI to JNA" below has several examples of the conversion of C structs to Java classes.
No discussion of struct portability across languages is complete without also considering memory alignment requirements. Since this part of the article is dedicated to JNA basics we defer discussion of alignment requirements to a later section "Converting from JNI to JNA".
Pointers and Strings
Using pointers is a perfectly natural thing to do in C, C++, and certain other languages. But the use of pointers also proliferated certain errors and programming malpractices that Java's inventors wanted to prevent. So, although Java programs have an uncanny resemblance to C++ code, Java has no pointers. But pointers of one kind or another are commonly used as parameters in native functions, so JNA programs must be creative in working around this limitation.
The following example (GetVolumeInformation.java) exploits a language feature from Java's C heritage: an array reference is a pointer to the array's first element.
import libs.Kernel32; import com.sun.jna.Native; public class GetVolumeInformation { private static String b2s(byte b[]) { // Converts C string to Java String int len = 0; while (b[len] != 0) ++len; return new String(b, 0, len); } public static void main(String[] args) { Kernel32 kernel32 = (Kernel32) Native.loadLibrary( "kernel32", Kernel32.class); int drives = kernel32.GetLogicalDrives(); for (int i = 0; i < 32; ++i) { if ((drives & (1 << i)) == 0) continue; String path = String.format("%c:\\", (char) ((int) 'A' + i)); byte volName[] = new byte[256], fsName[] = new byte[256]; int volSerNbr[] = new int[1], maxCompLen[] = new int[1], fileSysFlags[] = new int[1]; boolean ok = kernel32.GetVolumeInformationA(path, volName, 256, volSerNbr, maxCompLen, fileSysFlags, fsName, 256); if (ok) System.out.printf("%s %08X '%s' %s %08X%n", path, volSerNbr[0], b2s(volName), b2s(fsName), fileSysFlags[0]); else System.out.printf("%s (Offline)%n", path); } } }
GetVolumeInformation()'s specificationstates that its 4th thru 6th arguments (highlighted above) are of type
LPDWORD which translates to "pointer to int". We circumvent Java's lack of pointers by using
int arrays for these arguments instead. So in the proxy's method declaration these arguments are defined to be of type
int[], and at run-time (see code above) we pass
int arrays of one element. The values returned by
GetVolumeInformation() are left in the single
int that populates each array.
The output from this program is shown below. On my computerD: is a CD-ROM drive that was not loaded at the time this output was captured. The device at G: was a USB flash drive.
C:\ 609260D7 'My-C-Drive' NTFS 000700FF D:\ (Offline) E:\ C8BCF084 'My-E-Drive' NTFS 000700FF G:\ 634BE81B 'SDG-4GB-DRV' FAT32 00000006
To compile and run this program follow the instructions at "Running the Sample Code" below.
Another thing to notice in the above code is the way strings are passed to and from native code. Java
Strings can be passed "in" to the native code without special effort (check variable
path in code above). But null-terminated strings passed "out" to Java require careful handling. Check the use of the variables
volName and
fsName, and the method
b2s(byte b[]) in the code above. Finally, note that
GetVolumeInformation()is a macro whose "real" name is
GetVolumeInformationA(). Read the function's specification for all the details.
Another approach to pointers in Java is based on the classes in the package
com.sun.jna.ptr and the class
com.sun.jna.Pointer. Examples of the use of these classes can be found in the code discussed under "Converting from JNI to JNA" below.
Converting from JNI to JNA
Having covered the basics, it's now time to pit your wits against something more substantial. The rest of this article describes issues faced in converting an existing application (based on JNI) to JNA, Reviewing the converted code (included with the sample code) should provide greater insight into how JNA can be used to handle the complexities of a "real" application. The JNI code used comes from the article "Java Tech: Acquire Images with TWAIN and SANE, Part 1", which describes how the TWAIN library is used to obtain images from scanners webcams, and other imaging devices.
To run the TWAIN code you should ideally have a TWAIN device (scanner, webcam, etc.) connected to your computer. But if your computer does not have a TWAIN device, you should download and install the TWAIN Developer Toolkit which contains a program that simulates an image source. To understand the code you should also have the TWAIN header fileavailable.
To run the TWAIN demo program execute JTwainDemo.bat as described at "Running the Sample Code" below. To understand the overall flow of the program, follow the instructions starting at Let There Be TWAIN in the original JNI article.
Figure 2 below depicts the changes that have been made to the sample code from the JNI article.
Figure 2. Changes to "code.zip" from the JNI article
jtwain.cpp and twain.h have been deleted as they contained only JNI-specific code. Philos.java has been deleted as it was unrelated to TWAIN or JNI. JTwain.java has been modified to contain a JNA implementation of the TWAIN functionality instead of the original JNA code. The package
libs is new. Its three files (Kernel32.java,User32.java, and Win32Twain.java) are the proxy interfaces discussed in this article. The remaining 3 files stay unchanged. Observe that the package
democode, containing the simple example programs described above, is not shown in Figure 2.
Converting the TWAIN code to JNA provides the usual learning experiences of any non-trivial project. But it also throws up a rare and elusive type of bug -- struct memory alignment error -- that is unique to Java projects using native-code. Since memory alignment errors are difficult to detect, and they may also be new to many Java users, the following sections provide a detailed guide to handling these errors.
Detecting a Struct Memory Alignment Problem
The devil is in the details here, so there can no simple, non-intrusive, way of concluding that a particular bug is caused by a memory alignment mismatch. But the following, necessarily tedious, discussion describes one approach. The affected code (shown below) is in JTwain.java, and can be located by searching for "Memory Alignment Problem Demo". The code creates an instance of
TW_IDENTITY (a Java substitute for a struct), and passes it to the TWAIN run-time. TWAIN then interacts with the user to select a source device. The
TW_IDENTITY instance is uninitialized when passed from Java to TWAIN, but is returned populated with information about the selected device. The
printf()s, and the
dump() at the end of the code display parts of the struct to help in detecting the problem.
// BEGIN: Memory Alignment Problem Demo TW_IDENTITY srcID = new TW_IDENTITY(Structure.ALIGN_DEFAULT); stat = SelectSource(g_AppID, srcID); if (stat != TWRC_SUCCESS) { //... (lines deleted for clarity) ... } System.out.printf("ProtocolMajor: %02x%n", srcID.ProtocolMajor); System.out.printf("ProtocolMinor: %02x%n", srcID.ProtocolMinor); System.out.printf("SupportedGroups: %04x%n", srcID.SupportedGroups); System.out.printf("Manufacturer: %s%n", new String(srcID.Manufacturer, 0, 34)); dump(srcID); // END: Memory Alignment Problem Demo
The output from the
printf() statements shown below give a strong hint that a memory alignment problem exists:
ProtocolMajor: 01 ProtocolMinor: 09 SupportedGroups: 694d0000 Manufacturer: crosoft Tw
The first two values,
ProtocolMajor and
ProtocolMinor, are correct but the next two are certainly corrupted. In a previous TWAIN call, the Java code negotiated the value 0x0003 for
SupportedGroups, so that same value should have been returned. Also the value of
Manufacturer certainly looks like "Microsoft" with the first two characters lopped off.
Now let's look at the output from
dump() shown below. The "dump" displays the contents of the struct as received from the native code, before separation by JNA into individual member values.
000: 11 04 00 00 01 00 00 00 0d 00 01 00 32 36 20 4a 000: . . . . . . . . . . . . 2 6 J 016: 75 6e 65 20 32 30 30 30 00 00 00 00 00 00 00 00 016: u n e 2 0 0 0 . . . . . . . . 032: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 032: . . . . . . . . . . . . . . . . 048: 09 00 03 00 00 00 4d 69 63 72 6f 73 6f 66 74 00 048: . . . . . . M i c r o s o f t . 064: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 064: . . . . . . . . . . . . . . . . 080: 00 00 00 00 00 00 00 00 54 77 61 69 6e 20 44 61 080: . . . . . . . . T w a i n D a ... (other lines deleted for clarity) ...
Each line of the dump displays the values of 16 bytes of "raw" memory. The number at the beginning of each line (before the colon) is the line's offset from the start of the struct. Each set of 16 bytes is printed twice -- first as hexadecimal integers, and then as ASCII characters. The colors (assigned manually) serve to delimit adjacent members of the struct, and the underlined part is the
struct TW_VERSION embedded within
struct TW_IDENTITY (see Win32Twain.java). The location and extent of each member in the struct's memory space is determined from the declaration order and size of each member.
Looking at the dump above, it is obvious that the information returned by the native code is correct (remember that the PC's Intel processor is little endian). Specifically, the values of
SupportedGroups and
Manufacturer are also correct in the dump:
ProtocolMajor(the 2 magenta bytes at offset 46) = 0x01
ProtocolMinor(the 2 cyan bytes at offset 48) = 0x09
SupportedGroups(the 4 magenta bytes at offset 50) = 0x0003
Manufacturer(the 34 cyan bytes at offset 54) = "Microsoft" (padded out to 34 bytes with 0-valued bytes)
Comparison of the values from the
printf()statements and those in the dump shows that JNA's sense of struct-member location has, mysteriously, slipped by 2 bytes starting at
SupportedGroups. This is the classic symptom of a memory alignment issue.
The alignment error occurs because the native code strings together the values of the struct's members without any intervening gaps, whereas the JNA code expects to find them at memory offsets that are multiples of the member's length. Thus, the native code places
SupportedGroups at offset 50, but JNA looks for it at offset 52 (a multiple of 4, the size of
SupportedGroups). The struct members following
SupportedGroups also get pushed back by 2 bytes, leading to the corruption of
Manufacturer's value shown above. You should now also be able to explain how the "Tw" creeps in at the end of
Manufacturer's value.
Finally, a short digression on another aspect of pointers: the code of
dump() shows how
Structure.getPointer() can be used to get a pointer to the beginning of a struct. The
com.sun.jna.Pointerobject returned by
getPointer() can be used to access the struct as an array of bytes (a C programmer's
void*).
Reproducing the Struct Alignment Error
The file JTwain.java actually contains the code with the memory alignment error so that readers may explore this further if they wish. But the TWAIN demo program still works correctly as it does not use the values in the struct.
To reproduce the memory alignment error compile the program as described at "Running the Sample Code" below, then executeJTwainDemo.bat. You should see the window titled "JTwain Demo" in Figure 3 below. At the menu bar select "File" -> "Select Source..." as shown in the figure. The window titled "Select Source" will pop up with a list of the installed TWAIN devices. Choose any TWAIN device, and click the button labelled "Select". This executes the code with the alignment error, and displays the contents of the
struct TW_VERSION in the command window.
Figure 3. Running JTwainDemo
Note that the
struct TW_VERSION contents you see will likely differ from the example values shown above (unless you have the same TWAIN device installed). But you should be able to see the same kind of evidence of a memory alignment problem.
If the pop-up window titled "Select Source" displays no TWAIN devices, you should download and install the TWAIN developer toolkit. The toolkit simulates an image source (the first entry in the "Select Source" window in Figure 3 above) that returns an image of the TWAIN logo.
Preventing Struct Alignment Errors
Native libraries come in various memory alignment flavors (because of differences between compilers and compiler options). So, since JNA is typically used in situations where re-compiling the native code is not an option, it has facilities for setting the alignment strategy used.
The alignment strategy for members of a Java class that extend
Structure can be set by invoking
Structure.setAlignType(int alignType) method. There are four options for alignment type as described in the table below.
The output from
dump() shown above makes it clear that the TWAIN native code uses no particular alignment strategy (
ALIGN_NONE in the table above). But since this is not also JNA's default setting, all of the Java classes that substitute C structs have a default constructor that sets alignment type to
ALIGN_NONE (see Win32Twain.java). The following code is an abbreviated view of the Java class for
struct TW_IDENTITY with the default constructor.
public class TW_IDENTITY extends Structure { public TW_IDENTITY() { setAlignType(Structure.ALIGN_NONE); } public int Id; public TW_VERSION Version = new TW_VERSION(); public short ProtocolMajor; public short ProtocolMinor; . . . }
In general, there is no way of knowing the alignment strategy used by any particular native library. So, if a DLL's documentation does not specify this information some experimentation will be required to determine the correct alignment setting to use.
Running the Sample Code
To run the sample code described in this article proceed as follows:
- Download the zip containing the sample code, and extract it into a directory (say, samples)
- Open a command window, and use the "CD" command to navigate to the samples\code directory.
- Execute the batch file build.bat. This compiles all of the code (and is required to be run just once). The class files are located in a directory called samples\bin.
- To run a program execute the batch file with the same name (e.g. LockWorkStation.bat, BeepMorse.bat,GetLogicalDrives.bat, GetSystemTime.bat,GetVolumeInformation.bat, or JTwainDemo.bat)
The samples zip containsjna.jar, so you don't have to download anything else. The batch files listed above also have the classpath specified, so you don't have to change anything to compile and run the sample code.
Resources
- Sample code for this article
- JNA project site
- Windows API Reference
- Windows Data Types
- No More Pointers
- Wikipedia Pointers Page
- Wikipedia "Windows Programming/Handles and Data Types"
- C Strings
- Java Tech: Acquire Images with TWAIN and SANE, Part 1
- TWAIN Developer's Toolkit
- TWAIN Header File | https://community.oracle.com/docs/DOC-982919 | CC-MAIN-2016-30 | refinedweb | 4,458 | 56.76 |
Function
Creates a new empty image Field.
Syntax
#include <dx/dx.h>
Field DXMakeImage(int width, int height)
Functional Details
Simplifies creating a Field that represents an image of the specified width and height.
An image Field is a regular 2-dimensional grid of "positions" and "connections," with a "colors" component that is floating-point, 3-vector. The sign of the deltas of the "positions" component determines the orientation of the image. This routine creates each of these components, adds them to a Field, and returns the Field.
The Field created can be deleted with DXDelete. See 4.2 , "Memory Management".
Return Value
Returns the image or returns NULL and sets an error code.
See Also
DXGetImageSize, DXGetImageBounds, DXGetPixels
16.9 , "Image Fields".
[Data Explorer Home Page | Contact Data Explorer | Same document on Data Explorer Home Page ] | http://www.cc.gatech.edu/scivis/dx/pages/progu234.htm#HDRDXMI | crawl-003 | refinedweb | 137 | 52.05 |
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Attribute condition for field to limit possible values?
Is there some good simple way to limit what values can be entered in specific field?
For example I want that in my field you could only enter positive values. I could do that by overriding that models create and write methods and checking if that specific field value is positive. If not I would throw exception. But maybe there is some simpler better way like it is with required attribute or similar?
For exmaple is there some similar way like:
'my_field': fieds.integer('My field' limit=[('val', '>=', 0)])
P.S. How can I change my text format look like code format in this new odoo forum?..
Two ways I can think of:
- 1. Use custom constraints:
def _check_my_field(self, cr, uid, ids, context=None):
for obj in self.browse(cr, uid, ids, context=context):
if obj.my_field < 0:
return False;
return True;
_constraints = [
(_check_my_field, 'ErrorMessage', ['my_field'])
]
- 2. Use on_change method:
def onchange_my_field(self, cr, uid, ids, field_value):
result = {};
if field_value < 0:
result = {'value': {'my_field': 0}}
return result;
<field name="my_field" on_change="onchange_my_field(my_field)"/>
Best regards.
About This Community
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Access to our E-learning platform and experience all Odoo Apps through learning videos, exercises and Quizz.Test it now | https://www.odoo.com/forum/help-1/question/attribute-condition-for-field-to-limit-possible-values-53683 | CC-MAIN-2017-13 | refinedweb | 239 | 59.09 |
May 13, 2014 02:50 PM|tyler_at_work|LINK
Hi gang,
I'm trying to upgrade from SignalR 2.0.2 to 2.0.3 to take advantage of the "death spiral" fix. With 2.0.3, I'm hitting a change in behavior w.r.t. HubCallerContext.User.
Some background:
We've created a custom authorize attribute based on IAuthorizeHubConnection and IAuthorizeHubMethodInvocation.. here it is below:
[AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)] public class OurCustomAuthorizeAttribute : Attribute, IAuthorizeHubConnection, IAuthorizeHubMethodInvocation { public bool RequireSsl { get; set; } public bool AuthorizeHubMethodInvocation(IHubIncomingInvokerContext hubIncomingInvokerContext, bool appliesToMethod) { return true; } public bool AuthorizeHubConnection(HubDescriptor hubDescriptor, IRequest request) { bool result; try { var context = request.GetHttpContext(); using (context.NewScope()) // Extension method that sets up a DB access context so we can access the user repository { result = context.Authenticate(); // Extension method that (if successful) creates a custom principal and assigns it to context.User } } catch { result = false; } return result; } }
In 2.0.2, when my hub methods are called, the HubCallerContext.User property is the custom principal that was initialized and assigned within the AuthorizeHubConnection(..) method invocation.
In 2.0.3, when the hub method is called, HubCallerContext.User has reverted to the generic principal (i.e. not the one set up within AuthorizeHubConnection).
Is this a bug introduced in 2.0.3? If it's actually a "feature", then what is the "right" way to initialize a custom principal once for the connection, then have it available on client hub method invocations?
Thanks for your help,
Tyler
principal bug context 2.0.3
Member
190 Points
Microsoft
May 13, 2014 05:27 PM|DamianEdwards|LINK
That could be a bug. We fixed an issue regarding Context.User in 2.0.3 but it's possible you may have uncovered a regression.
Would you mind creating an issue at please and provide a simple repro app we can use to see the problem?
principal bug context 2.0.3
May 13, 2014 09:40 PM|tyler_at_work|LINK
Hi Damian,
I've worked out a braindead simple repro and raised a bug over on github ().
Thanks for the quick response! Let me know if I'm doing something strange, or if there's anything else I can do to help. In the meantime, I'm noodling on a workaround for the short-term.
Tyler
principal bug context signalr 2.0.3
May 20, 2014 03:00 PM|tyler_at_work|LINK
Hi Damian,
Just a quick check-in to see if you were able to reproduce the bug using the sample code I'd included in the bug report I raised over here:
Did I raise the bug in the right spot? anything else you need?
Also, I've tried a workaround that boils down to:
This has been sort of working, but it looks like there are edge cases where the hub method for a given client is not always receiving my custom userIdContext variable? I'm still digging, but wanted to run that by you to see if there are red flags?
Thanks,
Tyler
principal bug context 2.0.3
3 replies
Last post May 20, 2014 03:00 PM by tyler_at_work | https://forums.asp.net/t/1986897.aspx?SignalR+2+0+3+vs+2+0+2+Context+User+is+no+longer+taking+on+value+applied+to+HttpContextBase+User+during+AuthorizeHubConnection | CC-MAIN-2018-47 | refinedweb | 521 | 58.58 |
I am a beginner so please excuse my ignorance. I am posting one component from a larger app that I am building. This component has a handleClick function that changes the state when an image is clicked. When the image is clicked, a new component is rendered. Currently, the same 'new component' is rendered no matter which image is clicked. I'd like the component to be based on which image was clicked.
var AllocationDiv = React.createClass({
getInitialState: function(){
return {clicked: false};
},
handleClick: function() {
this.setState (
{clicked: true}
);
},
render: function () {
var handleFunc = this.handleClick; //because it wasn't brining this.handleClick into the render function
var chartMap = pieCharts.map(function(prop){
return <img onClick={handleFunc} id={prop} src={prop} />;
});
return (
<div id='bottomSection'>
<h2>Select Desired Asset Allocation</h2>
<div id='pieCharts'>
<table>
<tr>{pieHeadMap}</tr>
</table>
<div>
{chartMap}
<div id='test'>
{this.state.clicked ? <TestComponent /> : null}
</div>
</div>
</div>
</div>
);
}
});
So, here is what I would do for this. Instead of having a boolean value for your clicked state, you should have a string. The string should be the name of the image being clicked. (you need to assign names or ID's or anything to differentiate them)
so.. initial state is:
getInitialState: function(){ return {clicked:''}; },
next your handleClick would have to change and you'd need to pass the image name/Id in to it.
handleClick: function(image) { this.setState ({ clicked: image }); },
then, inside your render..
(make sure to
.bind(this) in your map so you can use the component scope if you want to call your methods.
var self = this; type workarounds show a misunderstanding of scope)
render: function () { var chartMap = pieCharts.map(function(prop){ // pass in your image name to your callback using bind, null value here skips over the scope portion and is what you need return <img onClick={this.handleClick.bind(null, prop)} id={prop} src={prop} />; }.bind(this)); // get the component you want for each specific image and save to a variable for display var imgVar = null; switch (this.state.image) { case 'image1': imgVar = <NewComponent />; break; case 'image2': imgVar = <DifferentComponent />; break; } return ( <div id='bottomSection'> <h2>Select Desired Asset Allocation</h2> <div id='pieCharts'> <table> <tr>{pieHeadMap}</tr> </table> <div> {chartMap} <div id='test'> {imgVar} </div> </div> </div> </div> ); } | https://codedump.io/share/NEe8F18XS7HN/1/how-to-get-my-handleclick-to-render-different-components | CC-MAIN-2017-34 | refinedweb | 376 | 58.58 |
std::ranges::pop_heap
From cppreference.com
Swaps the value in the position
first and the value in the position
last-1 and makes the subrange
[first, last-1) into a max heap. This has the effect of removing the first element from the heap defined by the range
[first, last).
1) Elements are compared using the given binary comparison function
compand projection object
proj.
2) Same as (1), but uses
ras the equal to
[edit] Complexity
Given N = ranges::distance(first, last), at most 2log(N) comparisons and 4log(N) projections.
[edit] Notes
The max heap is a range of elements
[f, l), arranged with respect to comparator
comp and projection
proj, that has the following properties:
- With N == l - f, for all
0 < i < N, p == f[(i - 1) / 2], and q == f[i], the expression std::invoke(comp, std::invoke(proj, p), std::invoke(proj, q)) evaluates to false.
- a new element can be added using ranges::push_heap(), in 𝓞(log N) time.
- the first element can be removed using ranges::pop_heap(), in 𝓞(log N) time.
[edit] Example
Run this code
#include <algorithm> #include <array> #include <iostream> #include <iterator> #include <string_view> template <class I = int*> void print(std::string_view rem, I first = {}, I last = {}, std::string_view term = "\n") { for (std::cout << rem; first != last; ++first) { std::cout << *first << ' '; } std::cout << term; } int main() { std::array v { 3, 1, 4, 1, 5, 9, 2, 6, 5, 3 }; print("initially, v: ", v.cbegin(), v.cend()); std::ranges::make_heap(v); print("make_heap, v: ", v.cbegin(), v.cend()); print("convert heap into sorted array:"); for (auto n {std::ssize(v)}; n >= 0; --n) { std::ranges::pop_heap(v.begin(), v.begin() + n); print("[ ", v.cbegin(), v.cbegin() + n, "] "); print("[ ", v.cbegin() + n, v.cend(), "]\n"); } }
Output:
initially, v: 3 1 4 1 5 9 2 6 5 3 make_heap, v: 9 6 4 5 5 3 2 1 1 3 convert heap into sorted array: [ 6 5 4 3 5 3 2 1 1 9 ] [ ] [ 5 5 4 3 1 3 2 1 6 ] [ 9 ] [ 5 3 4 1 1 3 2 5 ] [ 6 9 ] [ 4 3 3 1 1 2 5 ] [ 5 6 9 ] [ 3 2 3 1 1 4 ] [ 5 5 6 9 ] [ 3 2 1 1 3 ] [ 4 5 5 6 9 ] [ 2 1 1 3 ] [ 3 4 5 5 6 9 ] [ 1 1 2 ] [ 3 3 4 5 5 6 9 ] [ 1 1 ] [ 2 3 3 4 5 5 6 9 ] [ 1 ] [ 1 2 3 3 4 5 5 6 9 ] [ ] [ 1 1 2 3 3 4 5 5 6 9 ] | https://en.cppreference.com/w/cpp/algorithm/ranges/pop_heap | CC-MAIN-2021-43 | refinedweb | 433 | 72.5 |
Eclipse Community Forums - RDF feed Eclipse Community Forums Display not updating while application menu is open <![CDATA[I'm running an application that uses a timer execution to update the display, creating a new composite and hiding the old one once the specified time has expired. In most cases this works fine, but if the application menu is open when the timer event fires then the new composite is not displayed. It appears that this is due to layout being called on the new composite with a flag of SWT.DEFER, meaning the layout will be deferred until display.readAndDispatch() is called. It appears that this call is not made while the menu is open. This leads me to two questions: 1.) Is it expected that display.readAndDispatch() will not be called while the application menu is open? 2.) Is there a way to programatically dismiss the open menu? I've found a couple very hacky ways to dismiss it, but don't really like them. Here is a quick snippet that demonstrates the update behavior while the menu is open. There's a composite with a label added about every second. When the menu is not open, you'll see the labels added (up to 30). Once the menu is open, the application does not display the new labels until the menu is dismissed and then all labels added while the menu was open will be visible. If you uncomment the display.readAndDispatch() line, then the newly added labels will be visible in the display while the menu is open. import org.eclipse.swt.SWT; import org.eclipse.swt.layout.FillLayout; import org.eclipse.swt.layout.GridLayout; import org.eclipse.swt.widgets.Composite; import org.eclipse.swt.widgets.Control; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Label; import org.eclipse.swt.widgets.Menu; import org.eclipse.swt.widgets.MenuItem; import org.eclipse.swt.widgets.Shell; public class MenuTestApp { private static int RUN_COUNT = 0; /** * @param args */ public static void main(String[] args) { final Display display = new Display(); final Shell shell = new Shell(display, SWT.DIALOG_TRIM); GridLayout gridLayout = new GridLayout(10, true); gridLayout.marginTop = 20; shell.setLayout(gridLayout); shell.setSize(800, 200); final Menu menu = new Menu(shell, SWT.BAR); final MenuItem menuItem = new MenuItem(menu, SWT.CASCADE); menuItem.setText("Open Menu"); final Menu menu2 = new Menu(menuItem); menuItem.setMenu(menu2); final MenuItem menuItem2 = new MenuItem(menu2, SWT.CASCADE); menuItem2.setText("Display stops updating"); shell.setMenuBar(menu); final Runnable timer = new Runnable() { @Override public void run() { ++RUN_COUNT; final Composite composite = new Composite(shell, SWT.NONE); composite.setLayout(new FillLayout()); final Label label = new Label(composite, SWT.NONE); label.setText("Updated " + RUN_COUNT); final Control[] controls = { label }; composite.layout(controls, SWT.DEFER); shell.layout(true, true); shell.update(); if (RUN_COUNT < 30) { display.timerExec(1000, this); } // Uncomment this line and the display will update correctly // display.readAndDispatch(); } }; display.timerExec(500, timer); shell.open(); while (!shell.isDisposed()) { if (!display.readAndDispatch()) { display.sleep(); } } display.dispose(); } }]]> Sarah Missing name 2011-10-25T13:41:33-00:00 Re: Display not updating while application menu is open <![CDATA[Are you talking about the OS X application menu?]]> Thomas Singer 2011-10-25T15:22:34-00:00 Re: Display not updating while application menu is open <![CDATA[I can see the problem both in the OS X application menu as well as with the Windows application menu.]]> Sarah Missing name 2011-10-25T17:07:54-00:00 | http://www.eclipse.org/forums/feed.php?mode=m&th=257907&basic=1 | CC-MAIN-2016-30 | refinedweb | 571 | 53.17 |
Member since 06-06-2016
38
14
Kudos Received
2
Solutions
06-02-2017 03:50 PM
06-02-2017 03:50 PM
If I set up authentication with Kerberos I can use principal.to.local.class=kafka.security.auth.KerberosPrincipalToLocal to map the principal name to local names. If I understand correctly it will change something like kafka/_HOST@REALM and allow me to write User:kafka in the ACLs. How do I do this if I authenticate with 2-way ssl (i.e. I as the client present my certificate as authentication rather than a kerberos principle)? ... View more
Labels:
Hey @Joshua Adeleke, I haven't experienced this directly but looks like it could be a bug or rendering issue. Is it possible to check with another browser? ... View more
05-24-2017 07:56 PM
05-24-2017 07:56 PM
05-24-2017 01:56 PM
05-24-2017 01:56 PM
I want to set up Kafka like so: SASL_SSL://locahost:9092,SSL://localhost,9093 Where the keystore's and truststore's are different for each endpoint. Is this possible at the moment? ... View more
Labels:
05-15-2017 03:07 PM
05-15-2017 03:07 PM
I'm not moving all directories to new places, but consolidating 8 locations to 3 - I wasn't sure how all the metadata and splits would copy over given some of the filenames are the same in each directory ... View more
05-15-2017 09:15 AM
05-15-2017 09:15 AM What version are you using? ... View more
05-12-2017 01:21 PM
05-12-2017 01:21 PM
Thanks! Will try. Its still in the early stages so load is not a huge concern right now ... View more
I'm decommissioning some storage heavy nodes that are taking a really long time (days) to move all the blocks over. There doesn't seem to be much out there showing how to increase the speed () but there must be something. At this rate it will take a weeks to decommission the required nodes ... View more
Labels:
05-11-2017 11:05 AM
05-11-2017 11:05 ... View more
05-11-2017 09:44 AM
05-11-2017 09:44 AM
If? ... View more
Labels:
04-26-2017 03:45 PM
04-26-2017 03:45 PM
The automated SSL setup (either with Ambari or the tls-toolkit) is awesome, however I can only get it to work with self-signed certs. Is there anyway to get it to work with a company (or external) CA? ... View more
04-12-2017 12:07 PM
04-12-2017 12:07 PM
Looking at suggests that HiveMetastore might not be running, but it is and we haven't received alerts to suggest it wasn't. We connect (Hive Metastore) to an external Oracle database though, wondering if network latency with this database could cause this error? ERROR [HiveServer2-Background-Pool: Thread-102344]: metastore.RetryingHMSHandler (RetryingHMSHandler.java:invoke(159)) - AlreadyExistsException(message:Database clickstream already exists) at org.apache.hadoop.hive.metastore.HiveMetaStore$HMSHandler.create_database(HiveMetaStore.java:901) at sun.reflect.GeneratedMethodAccessor142.invoke(Unknown Source) ... To clarify, this is happening only intermittently when run though a NiFI processor. Typcially early in the morning ... View more
Labels:
04-03-2017 12:18 PM. ... View more
04-02-2017 05:21 PM
04-02-2017 05:21 PM
Legend! This is perfect. Even gone the extra step of submitting the improvement ticket! Can't upvote this enough ... View more
03-31-2017 11:38 AM
03-31-2017 11:38 AM
: Have transformXML take a list of xslt's? Use a list file on the xslt dir and then somehow generate Z copies of the xml with a different version of the XSLT. (I know this isn't really how NiFi is designed to work) Execute script is the best I could come up with but thought there might be a native way Thanks, Seb ... View more
# * Search for existing rule to import * Change port number and associated label 2. Must now change the port in two different places if it were to change I would look like: ## ExecuteScript Processor This again allows me to keep all the configuration in one place and makes it much easier to make changes. I created a processor that stores the mappings in a hash and adds the correct attribute appropriately. It looks like so:. ... View more
- Find more articles tagged with:
- Data Ingestion & Streaming
- How-ToTutorial
- NiFi
- Script
01-23-2017 03:09 PM
01-23-2017 03:09 PM
Hey @Rohit Ravishankar, thanks for moving this to a comment! Short answer: Not Really Longer answer: It's not really what NiFi does It still sounds like you want NiFi to process a batch. Something like users put files into a directory and then after some external trigger start the job and report any failures. Is there a reason why NiFi cannot just continually listen for input? Does it have to sync up with other 'jobs' further up or down stream? If so, a better use would be to have the scheduler (e.g. control m) 'trigger' NiFi just by moving the files into the pickup directory for example. Apologies, I can't be more specific without more details on your use case ... View more
Hey @Rohit Ravishankar, could you move this into a comment on my answer? Otherwise it will be difficult to follow that it is a reply to what I posted above ... View more
Hi @Rohit Ravishankar, Could you elaborate more on what you are trying to achieve with NiFi? NiFi doesn't really have a concept of a 'job' or a 'batch' which you would trigger. The usual workflow with NiFi is for it to wait for data to appear and then process that data. Waiting for data could be listening for syslog messages, or waiting for files to appear in a directory or many other options. Processing data is done using a flow where each processor performs a different step. Each processor has a concept of input and outputs (usually success and failure but not necessarily - it depends on the processor). Even if files are routed to a 'failure' relationship it doesn't necessarily mean the job has failed. For example, lets presume there is a file of JSON records I want to convert to AVRO records; if only one record fails conversion just that record will be routed to failure. This could then be routed to another converter with a different (maybe more general schema). Does this helps! ... View more
01-18-2017 03:57 PM
01-18-2017 03:57 PM
Hi @Andy Liang, In addition to @Pierre Villard's answer. There are three aspects of data processing joined up here: Streaming - Simple Event Processing This is what NiFi is very good at. All the information needed to do the processing is contained in the event. For example: Log processing: If the log contains an error then separate from the flow and send an email alert Transformation: Our legacy system uses XML but we want to use AVRO. Convert each XML event to AVRO Streaming - Complex Event Processing This is what Storm is good at covered by Pierre. Batch This is where MR/Hive/Spark (not spark streaming) come in. Land on HDFS and then the data can be processed and/or explored. ... View more
01-17-2017 04:40 PM
01-17-2017 04:40 PM
Thanks @Matt, thats a big help! It aligns with my understanding although I didn't know about the attributes. I currently have: 3.91GB of heap space allocated with 97% usage 6k/170MB flow files in just two queues No files seem to have large attributes (not checked all - just sample) 0 active threads? ... View more
My ... View more
01-12-2017 12:35 AM
01-12-2017 12:35 AM
I have a custom NiFi processor that worked great up until me trying use a distributedMapCache. I tried to include it like: import org.apache.nifi.distributed.cache.client.DistributedMapCacheClient; ... public class ListBox extends AbstractListProcessor { ... public static final PropertyDescriptor DISTRIBUTED_CACHE_SERVICE = new PropertyDescriptor.Builder() .name("Distributed Cache Service") .description("Specifies the Controller Service that should be used to maintain state about what has been pulled from HDFS so that if a new node " + "begins pulling data, it won't duplicate all of the work that has been done.") .required(false) .identifiesControllerService(DistributedMapCacheClient.class) .build(); But then when I mvn clean install and copy the nar over I get the following error: java.util.ServiceConfigurationError: org.apache.nifi.processor.Processor: Provider org.hortonworks.processors.boxconnector.ListBox could not be instantiated at java.util.ServiceLoader.fail(ServiceLoader.java:232) ~[na:1.8.0_91] at java.util.ServiceLoader.access$100(ServiceLoader.java:185) ~[na:1.8.0_91] at java.util.ServiceLoader$LazyIterator.nextService(ServiceLoader.java:384) ~[na:1.8.0_91] at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:404) ~[na:1.8.0_91] at java.util.ServiceLoader$1.next(ServiceLoader.java:480) ~[na:1.8.0_91] at org.apache.nifi.nar.ExtensionManager.loadExtensions(ExtensionManager.java:116) ~[nifi-nar-utils-1.1.0.jar:1.1.0] at org.apache.nifi.nar.ExtensionManager.discoverExtensions(ExtensionManager.java:97) ~[nifi-nar-utils-1.1.0.jar:1.1.0] at org.apache.nifi.NiFi.<init>(NiFi.java:139) ~[nifi-runtime-1.1.0.jar:1.1.0] at org.apache.nifi.NiFi.main(NiFi.java:262) ~[nifi-runtime-1.1.0.jar:1.1.0] Caused by: java.lang.NoClassDefFoundError: org/apache/nifi/distributed/cache/client/DistributedMapCacheClient I also have the dependancy configured in my pom.xml file: <dependency> <groupId>org.apache.nifi</groupId> <artifactId>nifi-distributed-cache-client-service-api</artifactId> </dependency> If I copy over the distributed map cache nar before bundling it works fine. Is there somewhere else I have to list the dependancy to get it bundled into the nar? ... View more
01-03-2017 12:37 PM
01-03-2017 12:37 PM
01-03-2017 11:30 AM
01-03-2017 11:30 AM
Trying to work out the message consumption rate per time slice is fairly difficult with the current format where the stats are presented in a sliding 5 min window but updated every minute. Is it possible to get stats on a per minute or per second basis? ... View more
Hi @Mehdi El Hajami, A NiFi web would probably be a good solution for this problem. You could have NiFi installed on all the hubs, reading the sensor data and sending to a central NiFi instance which then stores the data for future processing. If the hubs can't read the sensor data directly you could have the web extend out one more layer to send from sensor -> hub -> central A good use for minifi would be if the 'hubs' or 'sensors' are too resource constrained to run full NiFi. Thats a fairly general reply but the solution depends mainly on what you mean by 'hubs' and 'sensors'. Could you clarify? Hope that helps! Seb ... View more
11-22-2016 12:13 PM
11-22-2016 12:13 PM
I have ConsumeJMS reading form a Tibco Queue at NiFi version 0.6.1. NIFI-1628 only refers to the SSL integration. However use the latest version if that is possible as there are improvements that are worth having. ... View more
Hi @m mary, Looks like you're out of disk space. Can you check your disks have space? Regards, Seb ... View more
10-31-2016 09:20 AM
10-31-2016 09:20 AM
I am fairly certain this was caused by the disks being remounted in different positions on restart. ... View more
It's my understanding that HDF2 can be managed with Ambari but it must be a different Ambari to the one that manages the main cluster. Is there a way to have the client files (e.g. *-site.xml) from the main cluster automatically pushed to the HDF cluster to support some HDP specific processors such as PutHiveStreaming? Without HDF Ambari I could just install the HDP clients on the NiFi nodes, but this appears to not work as the HDF ambari-agent's would need to point to both Ambari instances for this to work. ... View more | https://community.cloudera.com/t5/user/viewprofilepage/user-id/51020 | CC-MAIN-2021-17 | refinedweb | 2,055 | 64.41 |
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CLINTON TOWNSHIP.
Governor Jewett 173 j Tod 9A i
U. Geverooe--MerehaH 171, Stanton 97.'.
a.. lnrf..Hmllh 17I SoMt 97.:.: . :
Treesnrer of Sta,Holmee 17i Doreey 97.
Secretary of Btett Armstrong 175j lowen
r iaaold 171 1 Rile? 93
Boirdoi Fubllo Werke ftwh I73j Torreoce
Common Pleee Judge-Hedges 174 Btee
98. . . i : ,nr2-;-
Senetor-Perrill 173 Warden SC. ,
RepreteouiiiTei Conferee 187J Dreeel 73;
Rekin84j Potter 96 . i
SoetinVHuffmen l74j Berber 96. ,.;,-;
Anlitor Murtln 169j E-tabrook 7S , ,
Treasurer Tbompson 181; Babo 90. ... ,i c;
Reooider-Coleltil FT 91. i
Commlaiioner 81 jb. 176j Hendereoa 93. ,
Coronoi Safer 176j Siepbene 9. , ,
Inflrniarj Directs Heee 183 hb Slt
MIFFLIN TOWNSHIP.
-
GeTwnf Mwrehill 164; B lea
ton 100. ' - " - : ' ' ' " ' "
Sapreme Jadgt Smith 164; Seolt 100. 13
Treasurer ot State Holmee 163) Dereey 101.
Secretary of State Armstrong 164f Cowen
inn .i... -4 1- J - .'kij. C'. Jt
HnmntMllMi GfiaoId 162: Riler 103.
Board or Poblio Work Fitoh 163; .Torreaca
101., . ' 'u " I h J " ' ' '' '
Common Pleas Jodge-r-Hedgee 164; Bates
100.. .. - :., - - . r i.. -uj- a.-
R.ntnf Prill 163: Warden 101. : -' --i
Repreeeoutieee ConTerse 164; Dreeel 165;
Rankin u; rottee 3 r i -",!:-,.
Sheriff Huffman 163; Barber 95.. , t i
Auditor Martin 163; Eatabrook 104., v u:
Treasurer Tbwnoaon 163; Bobo 9S.r..vt
Recorder-Cole 173; Fay 9Q.. . ... .j :
CommiaMoeer Slrh 164; Hendereoa 92.
CoroaerGarer 165; Stephens 'J8- .u ' .
Infirmary Director Hees 163; Ktumm 99. ,.
PERRY TOWNSHIP.
Goremor-Tod 126- Jewett 112.
Lt. Governor Stinton 126; Marshall 112.
Sapreme Jodge-Scott 127; Smith '
Treasurer of .State Dotsey 126; Holmes 112.
Secretary of State Cowen 127; Armstrong
111.
Comr.trollnr RtleT 127: Grlswoid 111.'
Board of Public Worka Torrence 127; Fitch
Common Pleas Xa'dge Bites 127; Hedges
111.' -
Smatoi Warden 127 Pmitt 111.'
Repreieuuiivei Rankin 127; Potter 127;
Converse 111; Drepellll.' " ,
Sheriff-Birber 127; Huffman 111. " 1 '
Anditar Eubrook 127; Martin 111. -Treaorer
Bubo 126; Thompson 112 ,'-
Recorder Fay 115; Cole 113.-""
Commiaeioner Henderson 121; Slyblll.
Coroner Stephens 127;.Gaver 111. 't f.
lofirmarj Oireotoc Kmaua 124; Heu 113.
WASHINGTON TOWNSHIP.
Goverubr Jewett 157,- Tod 108. ' ' : f"Z
Lleeienant Governor Marshall 158; Stanton
m . . - . -
Sapreme Jadge Smith 158; Seott 10T. ," :
Treasurer of State Holmes 158; Dorsey 107.
Recretar? of State Armstrong 158; Cowen
107. .
Comptrollsr Griswold 158; Riley 107.' -Baard
of Poblio Works Fitch 158; Torrence
108.
Common Pleas Jadge Hedgee 156; - Bates
Senator-PerriH 158; Warden 101.' s '
Repreecntatives Converse 160; Dresel 158;
Rankin 1U2; Potter 106. . i,i
Shoriff-Huffman 159; Barber 106.
Auditor Martin 158; E-tabro&k 106. i
Treaanrtr Thompson 165; Bobo 105.
Recorder Cole 158; Fay 105. , -,,
Commiaaioner Slyhl57; Henderson 107.
Coroner Gaver 165; Stephens 107. - -InQrmary
Director Hess 156; Krnmm 104.
PRAIRIE TOWNSHIP.
Governor Jeeett
Lt. Governor MarehaU 169; Stanton 83,
Suoreme Judge Smith 169; Scott 83.
Treasurer of St tie Holmee l6!f; Dorsey 83.
Secretary of State Armstrong Ib'J; Cowen
f!3. - ...... i ... ii t .... .;. v.
Comptroller Grlewold 169; Riley 83. r!.,.'
Board of Public Works-Fitcb 169; Terrene
3. , . ; .... .; ... .....,.- -i
Common riess Jadge Hedges 169; Bates
va. : . .' :
Senator Ferrill 171; Warden 71. '
Repreaeotativee Convent 195; Dreeel 185;
Rankin 83; Potter 99. -Sberiff-Huffmaa
193; Barber 58. ... , :
A iditor Martin 169; Eitabrook 61. i: .
Treasurer Thompson 191; Bobo 61.' '
Recorder Cole 189; Fay 63. . V '
Comuleeioow 8lyh 170; Henderson 82. .
Coroner Gaver 173; Stephens 80.-
Iofirmary Director Hess 179; Krtmm 80. v
JACKSON TOWNSHIP.
Governor Jewett's majority 205; and the
Ibalanca of tbe Bute ticket about ibe same. , ,
Tbe ssaioritiea on tbe Legislative and Coon
ty Demnoratio ticket, reported as ranging from
PLAIN TOWNSHIP.
Gtavernor Jewett I84t Tod 125.
Lteuunant Governor Marshall J 85; Stan-
Ion 125. . " - . - .
Supreme Judgt Smith 185; Scott 124.
Treasurer M State Holmes ,186; , Dorsey
324. .. :i. " j '..W' I '.ii. a fe fi: -,.;,.,
' Secretary of State Armstrong 185; Coweo
jgj mi. i-. '. .-'"- , - . -. ,.
ComplroIIer (Jytsweld 185; fedey
Boud o,r Publia Wetka-Fitek 185, Torrence
J24. - '
Common Pleas Judge Hedges 183p Bates
128 a T MV 11 ' - ' t .-- -
oenaior rcrrtii itoi nt"ii u
Repreaeotulvea Coeveraa 188; Dresel 188;
tfaukio U9; TeHef ra: - .p .
Sheriff-Huffman ll I Barber 118"." iw
Auditei Mtn 187; Gceabrook 123.'4 Mi
TraerarTbinttwa 189; KW IVU X.
Recordei Cole 189; F.t 121. , f . r . ,
Commiaeioe Slh 187, HencerMrl 123
Coroner Qver Ib&l Stepbeoa 121."-J
Directoi Uesa 187, Krumm 123
BLENDON TOWNSHIP.
Governor Jewett 90; Tod 244. tr . i ru
Lieatenant Geterpot MarebaU 93; jStanlon
843. ... . -r - -V
Suprenr JufJeSmith 94; 8tt 841. ,j
Treasurer ol State Holmee 73; Doreey ill
8aiy,,"Ma4aJ"aakisyBWrtffO j ?
JlK ju -c r.Hiu , t .- n r. ti
Comptroller Qrf.wold 92? RUt2. J'--
Board of rublic Works Fitch J5; Ton woe
111;
i CoaiBionPlM Jnflet Kedsee94 Bti?41.
: fi.n., '!: Wudin 240.- "V
Representatives Converee 104; Dreeel 91;
Kankln 220; Volter 240. ' ,
bbenii tiuamaa iui, uiiner jko --v -
AnrtiUir Mnin 91i ElUbrOok 238. J
Treasnrer Thompeon 98j Bobo Vn.
Coumlelooer Slyh 93 Hendereoa 28S
Coroner Gaet 95; 8teBhene 934. 4 '
Direetot-Hese 93; Krtmm C37.
HAMILTON TOWNSHIP.
Goernr Jewetll21j Tod 169.
' LlenUnant Goyeroof-Maraball 120, Sientoa
Supreme Jndge-Smitt J "T'.0,
Treasurer ol . gtate-rHolmea. 121; Poreey
l62ecretaVy of 8U-Aiwlwng 12l', Cowen
iplroliert:Grfeld'ia6 '
li!..iir pnhiifl Wotki Fitok 121vTortnc
vwwii erw r-
169.
Common Pleas Judge Hedges .121;
Patee
.-.-d.mi lQa. nTudan 1C4. ; i
Represenutivee Converee: 121; Dresel l21;
Ruklnlbbi rotter ioo-. - ' a
Sheriff Huffman 141, Barber 149. n v M ,
Auditor-Martin 120; Eubrook 169.
Treasurer Thomoaon 138; Bobe 158 ,,
Recorder Col 125, Fay 165. ; - s
Commieeionej iljh 121 Hendereoa 6a, v
Coroner Gaver 131; Btephena 169. .. : - ;
Infirmary Dlrectot Hees 122; Krumm. 167,
HAMILTON TOWNSHIP. FRANKLIN TOWNSHIP.
r 003. Trvl 174.
' Tha kiUnea af tba State ticket doef not
vary from the abov la any ease more than two
or tbre veeee, ana tne majoruiea
iatlva and Countv DemoeraUe ticket are about
tha same. ' '. ;
MADISON TOWNSHIP.
nnnr.r Jtt 354: Tod S62.
The balance of the Bute ticket differs but two
r three votes bom tbe Governor; aaa tne ieg
ialatlve and County tickete are about tbe same.
MONTGOMERY TOWNSHIP.
(lMMnrawtaHtt 326: Tod 187.
The remainder of the Stat ticket about tbe
same. Too Legieiative ana vuoij
run about with the State ticket, varying but
very little. t . .,,
MONTGOMERY TOWNSHIP. The War and the Union Men of the
South.
Tbe people of th North are almost ananl
iods In demanding a vigorous prosecution of
tbe war. But to what eud7 , not for tne tup-
jugatloo of. tha South not to bring the Sooth-
era people under th absolute control of tbetr
Northern neighbors aot to make the Southern
States conquered provinces by a war of ezter
minatloe, to be afterward re-eolontaed and gov
erned as so many territories, aatil re-admitted
into the Union a so many new States. No
wise, human or patriotic man contemplates
socb a tragedy and snob a deneumtnt as tola.
ft Is said that the Sonbera people may, by
their obstinacy, union and perseverance to the
rebellion, bring thla result upon themselves.
Bat we at th North must eoneider that in car
rying on a war of subjugation and extermina
tion against th South, tbe end will be far off
la th dark , iuturo, and that we shall, though
possibly successful, most certainly bring ruin
upon ourselves and our Immediate posterity
.. i It it not possible, then, to avoid such a horri
ble alternative with honor to onrselve and
safety to the country! This is the momentous
question noi'.tj be Tigbtly put aside by . any
clamor of.lh fanatic or tbe mar politician.
W are all for a rigorous prosecution of the
war agslnet rebellion. But are the whole peo
ple of tbe Sonth or oi th acceded State to be
inoluded . (a. tha category of rebels? It would
teem so Irons tha eiproasion used by oertala
prominent men and leading Journals, that tpeak
of th war at war against lb Sotith, and sym
pathy for tbe South as a eyaspatby for traitors
aud rebels. i'lJ'-J "-" L
If this It to, a continued tud vigorous prose
cution of the war implies, in ease the South re
fute to return to its allegiance, a war of aubjo
gstion and termination. - Bat there are strong
reasons for (he belief that a large portion, prob
ably a majority of the Southern people are at
heart loyal to Um Union, although there are aot
wanting fanatics and demagogue among us,
who seek to fasten noon th Northern mind a
contrary impression.
How strong tbe real Union sentiment may
be la the Southern States, It ft ;lmpossttl to
form a correct estimate, tine tecessioa bat in
stltoted a "reign of terror" there. Yet it can
hardly be questioned that if all th legal voters
lii those State were at free aa were th voters
In Ohio at our State eleotioa jurt passed, to
esprees their honest convictions at th polls,
not only in the border States, but even In the
seceded one, a majority would be In favor of
the re establishment ef th old order of things
la the Union under tb Constitution and the
Federal lawt. ' ', ' '
Now, it it obviously on of th plainest dic
tates of eomntoa tenee, that while we vigorous
ly prosecute the war against the rebels In arms,
we should labor just a earnestly and just as
vigorously to conciliate and co-operate with
those in the South who are Unloa men at heart,
and as (very legitimate effort to indue them to
remain loyal, and increase their number. . If
tola were done, th rebel leader could ne longer
count upon a united South, and the days of their
usurpation would toon b numbered. ,
Bat how can w cherish, eastaia and increase
th Union sentiment la th South t Thi it a
difflcult problem to be spired, and it Is growing
more perplexing every hour. It It manifest
that unless something be speedily done, it eo
lation will become Impracticable. By our
arms, w may protect Southern Union men in
the assertion of their righla, wherever Federal
troops can be concentrated In tuffioient fore
But It If evidently Impracticable to garrison th
whol oountry. We must bar something that
shall operate quietly, yet actively and nulver
eally throughout th entire Sooth, invigorating
the feeling o( loyalty and producing a popular
reaction la favor ot th Union and tgtlnst tbt
Confederate leader. ...... - v .
On thing w eaa do. W eaa to aom cx
teat at least disabuse th Booth ern paopl of th
lmpreeslon, In which lies th great strength of
tha rebellion, that w NortMraere are deter
mined to auk thla a war of subjugation, or
for' assimilating tb social condition of the
Sooth to that of the North by means pf cenqueet
and extermination. We have it m our power,
if w will.bf tb pollc with blch w Carry
en (he war, wlthoui abating any of Its vigor; by
th ton of our. leading journals aud public
speakers both on the roetraat aad ia th pulpit;
by th voice of potmiar ateeibblies, and fa
weusand bthr wsyit, to "demonstrate that the
sectional hatred ,04 amitr which tb, rebel
leader and nettegegaet bavw beea la the habit
of impuflui w haV," ii regarde the grJ
body ot.oor ople, jio iexlatenae,vf in the
heated imagination f fanatic -or itt th malt
of those wbo would hesltat at aoatrodtf to
eomnase the destruction of the'UnionT10 ''
, Tbe Korthera people eaa maqiteet tola" ipj-1
I men in tb etmtn tbetr teal s&tiM&u a:
ward them and ,tbetr,arden,t desire Meastald,
protect arid 'fo bpertfe with them, through the
allot-box, and ibroujh beirjrepresentatlve In
tb legiUt'hiaHt',f) Miio'l a t'tr, ' V
- W eaa ye ear th Uhlan by lostering the
(pifft of loyalty tn'tfi SoMj without. thit, It
must 9 U destruction, of rtr'gitopw ittUta
don a td b hardly worth taring. '- '
it
1
the Ohio Statesman.]
A Save More Than Twenty
Thousand Dollars Annually to the
State.
ft tiu Ottnnr and General AHfmblf tf tit
.SIHtti 01
'" By tbe 15th section of th 4th article of the
CtoatiM.iloa,,lhe General. Assembly " may In
oreas ot diminish tba number of th Judge of
the Supreme Court, the. number of the districts
of the Court of Common Pleas, th number of
Judeet in any district, change tb dlatrict,' or
the subdivisions thereof, or establish other
Courts, whenever two thirds of tbe members
elected to each Houae shall concur therein i but
no inch change, addition, or diminution, thai!
vacate the office of any Jadge."
lt la eroDosed that the General Assembly x
ralaa this newer durinc tbe month ot January
next, by diminishing tbe number of tha Judge
ol the Court of Common Pleat. These Judges
are now forty two in number twenty-eeven of
them die, offiolally, in rebrnary next. Tbeir
nlacea will tbea be eupplled by twenty.tevea
ptrtoat to be elected next Tuesday." Thee are
tne twenty seven vommon neea juugce pro
vided for by tbe Constitution, and their term
expire every five jeara. i , ; f ,,, , ,:
The other fifteen have been oreated by law
sine tbe adoption of tba Constitution, and their
terms expire at different periods It it essnmed
that over thoss fifteen tbe next General Assem
bly poaaeas no power, .Thia assumption may
be erroneous, but tbe error is unimportant. It
is better, in (educing tbe judicial lore, to abol
bh office sot now niiad, thaa oast Jadgee
whose term it now running. The object ot tbit
present appeal to the Executive aad Legislative
power ot tb Stat i to reduce the number ol
the Common Pleas Judges now to bo elected,
That reduction may extend to fifteen, or a leee
number, . Whether it be fifteen or one, the
Judge now in commission, and whose terms
will not expire, any or teem, aniu me tapee ui
more thaa a year from tuls time, may, by law,
be directed to take the place of those whose
offices will be abolished by tb proposed reduc
tion. . .. , : ... .- - ,
' The concurrence of the Governor ia thla ab
it essential lo its success., Indeed, without hie
tetrlotlo aid, tbe plan cannot even be considered
by tb Legislature, . It will be observed that
tbe last clause of the section of tbe Constitution
auoted above provides that n ehanee aball va
cate lb cms oi any juage. . i pe perron wno
mar be elected Judge next Tuesday have
oo duties to perform until tbe trcond Monday
of February, 1863.. , , . , ....... .
Their commissions need not issue until a
short timt before thai date. Until that day the
Commissions can do tbe publio no good and
can do them no good. But many may be ol tbe
ooinion t ialon receipt of tne commission and
tbe oatb taken and Indorsed the person is invested
with the office of Judge, aod beyond legislative
control. - ret nape this opinion ia right, tbougb
it seems toicetblog like sticking ia the bark.
What, then, ie the duty of tbe Governor 7 By
followiuc tbe law literally, he may deprive the
Legislature of tbe power to do a great good,
aad make a considerable earing ia our annual
expenditures. He should obviously decline ta
ttling tbe commitsiont until tbe Legislature
meets in January. It tbey promptly, by a two
thirds vote, make tuoh changes ia one or more
of the district as may dispense wi Ji one or
more of the Judges, he may issue tbe commit
siont in conformity with the new law. If the
Legislator do not thus act, be may issue to ail
tbe Judgee elected, aod "nobody ie hurt." But
the Governor may be compelled by mandamus
to Issue the committlontl .So be may, if the
Judges have no mora eense than the objector.
A writ of mandamus doet not lie to compel an
act to be dona to-day which may at well be
done to-morrow Suppose aa alternative writ
to issue, aod tb Governor retarnt upoa it that
he contemplates recommending to the Legisla
ture to vacate tome of these effioee, and with
holds the commission un'll they meet and take
tbe matter Into consideration. , Do you doubt
that tha Court would postpone their decision
until after the meeting of tb General Assem
bly t . ...... , ,... T : ! -
1 bit communication it prepared for to two
leading daily paper ia Columbua before tbe
election, though not designed to be made public
ontil tbe election U passed. : ' .-
There are matter of detail to b considered,
obvious diffioultlet to b met and answered, for
which there ie ample time. ,
Th present object of th writer It to call
publio attention to the subject, and to induce
tbe Governor to withhold the oommiseiont until
tha Legislature meets.
A MEMBER OF THE BAR.
ZANESVILLE, Oct. 5, 1861.
Visit of Jeff. Davis to the Rebel Army
Visit of Jeff. Davis to the Rebel Army of the Potomac.
' Tb Richmond Ditpatck of Thursday, Oct. 4,
bad tb following dispetoa from rairux C. H
dated Wednesday! , nf !?.: :..
The President arrived night befor last.
Yesterday, teoorted by tb Adam Troop, of
JUiesistippt, a mad a personal reoonnoteoance
ia tha vicinity and toward tbe outpost. : At
Beauregard' headquarter tb rain to day era
vented a general review of tha troope by tht
President. . He was rreeted, however, br the
soldiers wherever ha appeared, with enthuei-
asm. . : ! ', j i - i
Tha Federals advance cautlouslv and hold
Falls Church, and press our line near A nan
dale. -i r.ii--v . '.
Tb Richmond xsrier aayar . ; .-A
The people of Richmond were again intense
ly agitated yesterday in inoculations on the
general tnbject of affaire on the' Potomac. Ra
mon of various credibility wer circulated. It
wat said that President Davie, in hie address to
the soldiers at tb railroad etatlon, had told
them -it Out ktndied their wnukttt weU. 6 neat
Saturday night ley vtald 6 ia Baltimore."
Other evidences equally emphatie of au ap
preaching actioa were told and circulated
through the city. , The well authenticated facta
ia relation to tbe movement on tha Potomac
art vary few. There Is no doubt bnt that on
last week orders were issued to the Confeder
ate force at Fairfax Court Hobs to hold
themselves in readiness, with three daye ra
tions, to move forward. Thia order was a gen
eral one to the wbol army. .Tha occasion of
it it aoderetoed to hav been tbe advaoee of
several thousand of tb enemy in the direction
of Lewlnsville, from which, however, they bad
at last aoeennta retired. : 1 -
Visit of Jeff. Davis to the Rebel Army of the Potomac. Secession no Longer Orthodox in the
South.
an experiment worthy being
tried, If there wer non to b compromised by
bat tb seceded State, t eee bow long they
would bold together with tb outtid preeear,
ecasionad by tbe war, removed. ' Tbs South
Carolina would indulg la new fanteetlea aad a
aew secession ia leee thaa two months who eaa
doabt? and that the turbulence end arrogance
eeeeeateated la euch men as Mason aad Wis,
af Virginia, would revolutionise matter egaia,
just as oertala. - 8 far it haa taken almost
tbe entire fore of tba Southwest le make any
Impreasiea apon I we at tha States which) they i
elalm ae In affinity with then? Confederacy we
mean Missouri and Kentucky and wer they
special alliance with thee, w bo dee not know
that secession, s a doctrine, would never be
thought of ae permissible tor a tingle Instant.
Indeed, what Could tha recent actioa of Ken
tucky mean, through her ontitnted aataorl
ties, but a aeeretie rem 1 ffeaiAera Cnfed.
tract, which baa sought to impress it to itt pur
poses, aad th same ef .Missouri and Maryland!
Thai actioa may be termed aeoeeeioa s a
at; but tbeir people are answered that their
territory" ie essential te th needs of this new
power, aod therefore they eannot be permitted
to withdraw from the company of those so mneh
attached to faejavt 7 . ; !u m . r i
' But look aew at the eroea folly and inoon
fittency of this thing Thee mska law fuada
mental jonditiott,r priaeiple, that a State It
sovereign, and may choose its own statu. .. Up-1
eo this rock bs eeoession eoaghtt build aa
impreirnabl fortress; npoa this it ha inatita-
ted a war; open 4btn It claim -th wight to ha
recognitea oy tn ctiuuea world, .a p .m
;A4 , now lei it neat Its csvetoor xiaoc
ripest th f territory W aiaur State, let the
tatter claim be right of detsminlog irs htb
aoailioa. and ao arm j ia tra gbttae put ia mo
tion to compel it e accept a dtloy la th bigb
"Le'Sat0 tti&Z
had in tb teat joioed th Cunfederaey 1 form i
ally, wit as much ad or ebow of iaw aa tbey1
manifatudia tt eat of Georgia or Louiriao..,,
Aad luppoee by thia Um that, eickftf tbe-Bare-
nenh'?, they propoeed to reUrc rTh ewtd
weuU at oc be met by tbee tupriBoiplod me
rauden by tb WotrbM of a "military aecet-
'
,
-
I
slty,"eod fir and. slaughter would be brou .bt
into requisition, as cow, to compel tbe continu
ation oi' a ruinous and b itcful alliance. -
Tb fact la that it it the behest ninn-v ti th
States In revolt to rescue them from tut anar
chical dominion of each other. Unabl to guide
themselves aright, their-euocee Ittfa worst
disaster that oould befall them, and they must
be made to feel, la the preeenoaof a ooatroll,
Ing power, thai, their- revolutionary madness
cannot be further Indulged. Haitimn Advtr
Kentucky and the West.
In th midst of this grand atraggl. every
eye Ie now directed to Kentucky, at tba, point
at which the great conflict la to take ple,ad
everywhere the eye of the people are turned to
our Stat at th sbect-sncbor ot th Union, u li
Kentucky ie subjugated, . the , Union falls to
piece Ilka a bonis of udv jLA-uji
i It i proclaimed by aeoeeslonltti on tha atreeta
mat evsBtyavs thousand men will be thrown
into our State In aids of month. They hav
bragged aad blustered ee atronf and loudly that
w caa expect nothing else but boasting. The
wis man, hwvr, take th eounoil of bis on-
emiee. and acta as though it waa ail true.
i Kentucky aaa now 11,000 man In th field tor
tn union, beside "Xoung'e Uavalry," and
ether hermaphrodite regiments, eompoeed part
ly of Keatacklan and partly of other; bnt still
thia Stat hat not fulfilled th grand destiny
belonging to her beyond all ethers. These men
should be ordered borne. ' It Vr not .only th
National bonor but tb Stat honor which I
Insulted. We, of all othwn, ought to spring to
trms, and w know from th spirit already ex.
hibited that there will b 40,00J Kentucklana in
th field by December. In the meanwhile, w
hav the beet right to eall apon th northwest
tor aid. i na scat neutrality baa in a manner
disarmed us. . General Baokncr beeoarruDted
many of our young men, bnt atill w kaow that
in tn mat uaard there le a majority wno only
want auoh leadera a Crittenden end Anderson
to eome Into tb field- ,
But lath aat doing its doty? , Ha New
England, who, after South Carolina, did meat
to provokt thee dilllcul tire, toted np to lte duty 1
Tne Boston P it of tbs 3d, Bays: "And do our
Countrymen, generally, appreciate tbe magni
tude and the eUemnity of this awful hour t W
fee thai th aoawer muet be in the negative;
and especially in th Interior district through-
out tne country... it it true met in disparage
ment of th power of tbe rebellion, and tbe
eoofldenoe felt in our undisciplined army, at
ine null Knn battle, may, in. a good measure,
have paased away, aod that thsra baa beea a
vinlble and moat Braiifylog deoline of parly
spirit; yet a work baa cot to b don, especially
in tbe rural distriots, not only In this state, but
throughout New England, to bring publio opin
ion up to tbe pitch that i needed, mat indeed
is absolutely necessary, in order to sars in
oountry." -
Tbit war nta been lougbt by tn west, and
a repeat again, notwithstanding the outcry
sgainat the But, that Kentucky has more mea
in tha field than Maine and New .Hampshire
combined, end more, we believe, than any New
Epgland State, except !'J,lttl Kbody" and
Massachusetts. ? , . , ,
Kentucky opposed this war, and 111 inaugu
ration. These New England Stite favored
it. w ' T .? li f ..'a
Th Atlantic Statet ought to fight tbe battle
in front of Washington, ani'leat th West to
take care of itself. If tbey will do ao, or if
they will tend West the Indiana and Illinois
troops, they, with Kentuoky, will "bold, occupy
poeeeee" all th points an tha Mississippi
before tbe winter closes Zwitvw IXmtent.
What Ohio Has Done for the War.
Tb following particulars ara taken; from
report made by Adjutut-General Bvcxiroham,
of Ohio, to U. 8. Adjatant-Generai Taotiaa:
Th whol number of thro month' men fur
nished by Ohio we 21,498. - Tb whol num.
bee of men enlieted ia Ohio for tb war, under
tb auspice of th State authorities, np to Oo
tober 4ih. was 61.000. - Or- thi Bomber. 29.904
are infantry soldiers, over 692 artillery and 462
cavalry, are in active aervioe, distributed as fol
low: .:(f3 j. -'1 m, ... . r..;s3
In Watt Tlrgioia. ' 81 rtrlmsnts. ; 'f- ' 3 '
IaKntnekT - - V :
In ltistoari..... ............ I A
i .A 'V. i t.U
'jiZL . rejlwtstt tt J04 arn.
aamuar. .,,.rj
IaWsatTirglnU,
la Ktatoeky....!
asanenes,
, fvi t -,-ij'l - t
la van on i
. ... 4,
I
,., . - ..tbatleries i
Oil
1 CiViLaV.
IoWetVirjlDti. ....... t sempaalei. ' '
IsKenU.ekyfl....M.,....., 1, i4'i r: 'VI !
IaMiuonil .. '
- leoaipanle tSSmea
Whole eoatar Ohio loldtsrs In satire ser
vice 31.0S8 tasa.
td wnun raitnt ot turned two e(Dtaekj reg. .
IdmdM to call
........... j,WW
i ' Total..'... ..'...It,. ....... T. .'...'....,
, There r now in cam full, or nearly full
ana repiaiy snug, nueea regimeott or mian
try, one regiment of artillery, and flv regi
me numoer ot oiuir mat eaa be immedl
ately called from camp Into eervlcei mar be
siatea aa loiiowa . " '. -
A lnfeutTj....t..' .4,. .,, .9,99 a
Cavalry.....,..... M.c..K,...m... 3,73
AiUltery ..! 37 , i
, Total. ...... M897 '. .
Tb whole aumber of Infantrr now In' eamo.
however, ie 13,926, and tbe number of author
ised infantry regiment, October 5ih, waeaev-
enty seven
Between AprU 15th and October 1st, Ohio
issued 45,996 muskets and 7,641 Eufleld rifles
(purchssed out of Stat appropriation). -,i ia
tba aeme tlm eh issued 471,823 rations,
tnd expended $263 .303.35 for aabtletenc of
troops. . ' - ' . ?r .
Escape of Colonel De Villiers from
Richmond.
Much Joy waa expreeaed veeterdav at th tel-
rgrapbio account of the oop of Colonel D
Viilier from Richmond. Colonel D Villi ere.
it will be recollected, wat with Colon! Neff
aad woodruff at the time they fall Into aa am.
bnicade aod ware taken by Wiee'e army, ia tb
jvanawna oountry. tie waa ooaveyed to nUch
mond and oonfined, with th other prleonert, In
the old tsbtooo factory, but managed to break
out with eleven others, all of whom wer re
taken except him. v After cndarlng alavoat In
credible hardship, tb gallant Colon si mad
hit way to Fortress Monro, and from thence
to Washington. W ar only sorry that hie
eempaniona in captivity, Neff and Woodruff,
could not have been equally fortanet In mak
ing tbeir escape. Te prevent is tbe rebel Gov
ernment has sent them, with most of the other
officers, to . Castle Plnckney,- at Charleston,
South Carolina. Gin. Enq., 8f. , , , . .,
Death of Senator Bingham.
Tba Hon. Kingsly B. Biagbam, U. 8. Senator
from Michigan, died of apoplexy, at bt reel
deooe, at Or sen Oak, oa Saturday, Oct 5. He
wat bora In Camilla, Onondaga ooanty. New
York, December 16, 1808. He received a fair
aoademio education, and was early placed In
the offioe of a lawyer ae clerk, where be aerved
three yean. In 1833 he emigrated to Mlotalgea
aod eettled apon a farm.,- icted tn 1837 t
the Michigan Leglalatare, h rved fir yew
u a member of that body. Ha afterward
served three year as spsaker of tb earn body
Ha was a Representative in Congress frees
Miehigsa from 1849 to 1851, and eerred wur-
Sig that term on tb Commltt of Commerce
0 1854 h as elected Governor of tn Stata,
and held that poeitlon till 1859, when h waa
elected. to the United State Seaate, y , x t
si- 'wmwmwmremMBwmWameamwaMeimiMMaaB
HEADQUARTERS, OHIO MILITIA,
ADJUTANT OFFICE.
COLUMBUS, Oct. 8,
GENERAL ORDER NO. 56.
nT
dsairing appointment ere recommended te eead
tblr papere by mall, toi olily to com In per.
.v.,. .. ,x 2 ' i
Lieutenant will not be bereafter eppolottd
(xcept on rrqoeat of .the Military Committee
ofeountie. CMBtaadanteef reglmenUeboulJ,
la all esses, befor Jnaibg fefomm'endatlont,
know that thoeo tbey desire appointed art ap.
proved by tba Cannty CbmmiUctt. and Uif
mutt la aoeas xced ten for tbetr rV'clthetit.
ae'wmnra t K4, ,4Wimm4wi.vt hw Mmtm Pjim.
GENERAL ORDER NO. 56. C. P. BUCKINGHAM.
GENERAL ORDER NO. 56. C. P. BUCKINGHAM. Adj't Gen'l Ohio.
A Stampede of
Heroes.
The telegnph la t'reai ' me: 'one-' v s
frightful ta:npdo of taval fV 'ea tj 6(.
Charles, Mo., on Thuisd4y 4at. ; It appears
that Col. Mcuui'a 1st Kissouri regiment of
note wee on- tt way to Tchaarcr rreiuont, and
quartered for the night at St. Charles. About
10 o'olock the horse of papt) Charles Huntt
eomptny' Ibectme irlghtehad, tnd broke loo.
Tb Paulo waa shared bt the others, end soon
J fourteen bandred horse, maddened with fear.
went rushing ovee tbe encampment, treading
tsntat and men Into the ,artb, aod creating'
lofaa of unparalleled- r xeitementi Twelv
men 'are known to hav been frightfully Wan
gled, and probably fatally; hot (bo pnly menv
ierof th eompuilel compoaing the regiment,
Which were orgsnized, la Ohio, at all injured,
waa Capt. Henry Wilson, brother to Cept, Lewie
Wilson, U. 8. A. Hit skull wat fraotnred and
an arm and leg broken: ; W regret to learn
that little hope of bit recovery I entertained
Pin. Com. 81. ' - u " . V . - "I '
The Gen. Fremont.
Th Waahlneton feorrssnondent of th Tf
York 3Vt6aiae telegraph that paper that tb
Attorny.i?oerel ol the United etatee, who it
a Cabinet offloer, -k narctereeoT In his xpree
aioa of opinion eenoernlng General Fremont,
and does not hesitate to pronounce hi retention
t public crime." " i nc r. ic.i m,i
I Also, that "tba President ha decided that,
hereafter, all eontraota aad appolntmaatt for
lb Weetern Department shall, a mad in
Washington, In' th regular way and. through
th ordinary channels.' "Heretofore? General
Fremont mad th contracts and appointment
himself. Tbey are now taken out of hi beads,
Which ia saying that be baa net ataaaged ereU '
aw far. .ri'.tt mtii
I Also, that "Brlcadier-Geaeral W. JL Street
Will also b authorized t make an oh chansee
la Missouri, as Chief of th Staff, as ha thall
deem beet," which ie eimply taylng that warn
ot .venerai rremont appolntmeata era bie-
tiooable, and General Strong will dismia all
anehv. -. . u.. ,.i
Also, that a full consultation on th whole
tubject of General Fremont 'e conduct in Mia
aouri, would be held yesterday. Oct. a. In Cab!
not meeting. - ., .. . ,:,-,tM r:,,:
T7"TTi Hon. Eli ThaiM ki thtlA fnim
Seoretary Chase tb appointment of General
taperlntwdent of th agents of th National
Loan for New England. . Tba offloa it a tem
porary on, but of some importaooe. II bat
already oommenoed bit labor lu Connection t,. :
ADVERTISEMENTS
Sealed: Proposals:
1 1 . -.
ryit-i. be beccived at mEOr.
' IlOn ef ths Ooartsnaatter Osaeral, Ooiaake,
Ohio, eatll U If IATTJKDAY, ltth O0C0BU, fee ths
IblUwtog artloles army sletouf: : i-, .-,rr.-;, ? t .
.000 KSfalatloa forsre OspssadOevsn, Was Olotta.
e.000 :tr : ; LuMdBieasss. 1 v:.:.r: ; ;.i ,H to
1,500 : : do " ' Cavalry Jackets, iu-wealdarkbla
oor-;o Artillery to. 1 Keieejr. -
,000 do Troasirs.sU wool Sir bias Csrstr
3,000 de ' do '( Ke-snforcsd r- do. ! . i
18,000 amy ghlrts. Unloa Henael.' "?. ' ''-" x '' .; :
UO0 Pairs Drawers, do. ";- , ' -.
e.OOtratrstboes. rj.r:, . r ,
ma . ru, B..4. ' V'-i-f?
. MUV V.I.I, , 4WIWI
OfiO Pairs Woollsa teeks.
.K.
B.00O Iobntry Overcoats, all-Wool sky fclas Kersey.
1 000 Cavalry 4o . ", do do '.' de.
4,500 Pairs alsaksts, ah-wool, I ts 10 lbs. fas pair.
'All the rAoveerUsles ere required tekeef material
end style eorreipeadlng la every respect te tb TJ,
Amy BegalaUoa. '. e--. vSt-sx t -ri'.:;:.
i laaiple patten ef sachartlsle may atsssaat thssf
aoeef IbsQaartsmastarfisaeral, Oelambae. .n:.y
; lis meet as msee sepsratsly far sack ertleM, tad
state the assise et two ar meresarstlet. 'f-. i.
ler allMseptsd Has, the arUat will be rtqulrsd to
ties tends with sufficient ssearlty, rnr the faithful per
fsrswae ef (be eoalraeti end la cess ef tailors la the
tune ef delivery er la the eoalltj ef the ertlelee, tfas
Btats reserves the right toparehass theaa elsswheras
tha eznanaa af flia emrraetor.'
Fay saeat will be awae within sixty eayrfrea eomple-
tloa of eoatract. '-
Delivery ef Cavalry aad ArtUUry olsUUo't to be msds
at Oslaaba wltbU 90 day Tram dam at eentret,lB
qoal srovortloas aach waek. r;.,,,, , i;-. s -) nnn t
Dslrvsry ef Infaatrr elottttai and ef Cape aad Ken
ktts, tobs mads within forty-flve days, la seaal propap
ttons sack wtck. ; ; . ;,.;.". "jvi.
rrppeaalswlllbsaiiraiMd lo ,.,,...:i.
j ) "u ')' ' j - "' v. - :9t0. 9 WAIOaX, inn,,
n -.:' i - -it ii ' Aa'IQr.. at. ansrst,-y
oeta-td! :" ' ' ' " '- 'Oelambas.'-1
T Witt, DELITEU A Iff qcahti-at
ja.
Of im Bast or
J'
at fh
HOOKING
COAL
, v --..
I - t -"
fht vary lowest snrkel yriot..
Bav Banay If order'
Ins SOON
leave orders, wttk rath, at the store ef A
M-Danl,
a Oa., 3t H.
ai,k Stitet,
.oetv-ei
tr: a. ot:
'" STotloea
A IX PERSON ABB HEREBY Iff.
TirlBO Uut my wlfa, MAtT ANM, ea the Beth
ear or Bepteaner, a. o. icoi. Ian a to ea kaa
wlihoalJastaanMorprovooatlon.aadikarabrgive m
Uco thai t will aot be retpoosisle for any debts ea:
tmetad by bar.
eew-aw - - - JOHW WBAW.
I-TEW STOHR
HEA.DLEY & EBEHXY
TTATE KEMOTE D IO THEIR NE iT
Sot. 250 tad 252 goat High Street.
sod have saaoclattd with thenuslves WJC ilCHAlDi,
v w lira ai , .... . ,.,,,..
. : - w. 1. ''4ia.4,J V M4i.t'l,'
Heidlej, Eberlj & llithids,
rBralae eae of lbs lima Di Oaaaa Uhm, a, th
wawi.- ........ ,..;.., - - - .4 , J ;
This Botu la eoutaatl Mnlh Ih OaaJa
sachas r - ; " 7 r
NEW STYLES OF DRESS GOODS, , m.
IRISH BILK AND WOOtT POPLtNsf
PLAIN AND FIGURED REPP GOODS,
. PLAIN AND FANCY SILKS
Iks Kawest aad Vastest stylos sf
', ft -r.
Hamilton? Maichester, and Pacific
UIaiTif!t 1 1
iW
d-Zl
C-t
14 tbs Oity, caa bs foasd at
,-r.l-'.T '
HEADLEY, EBERLT 4. RICHARD3-
in treat variety, Jaat teetivad by mw ' wc,' ,..
HEADLEY. EBERLY A &1CHARD3 .
, . astv, . .wti-vr.
2EPHIR W0RiTED3r-ZT.
1 1 .EMBOipEMS4
A,AJU41S5;i,U Jil fiaOaaV,
Of Ois Vewest gtylos.loat toeetved, aad Was nmde to
-."vi vftaYeVi ltiM '( 11M
fiEADLEY, E'BERLY Hi RICCLASC3,
BAWI.,k,
tnuTtoir.
run)!.
TlIStBgT
H" Htt (k tltTtt YttTWOI,
?T i ""'VtriiTivna.' rr !
OttltlTl.'
JtBBBlMAO rBIHT, 'OOf IIIITI,'
jotros caAi asd cAint WAJitTjL,.v
this Una, bavtff adptsd lbs OsA eyetaai to fha par
ism and sale of faootl,, sra enabiad to l L on
mmn.i- ti.sa etbar boue ujjau oe;,,.
04
uli2,Souilv Ll!rh --?'w"-
"-t-
Clatw.aa Jhi,
er-V
W-
t
,
I-
c
"9(B'l'','lMMnHWi''
HE ADVERT!
-BUY-..- GOOIM
119
OTSSGWkff?E
OPEN AGAIN
) Ii sow rsestvlng large aad enlrabl sio.k cf
t.,tl-i:naJ tiT-JAjl ill
Fill aad i Winter totioods!
Which he sill tall at erkwrhU will u te-
tala the repatatloa ths (land already enjoys ef ealng It
I - l'v.V''f- ui'Jlii-l t ;lM,
CUioap Otoro .
, .,.., ,. ,,.,,, ,,Tt;rr iv
mi lbs Olgr. aeb W th gtoek was boegbt for Cask
fccfoie tka twta axlraorttaary sdvance, and all can b
itE's'tHAN CUkRENfklCEa.
i(Ml- tTIMV ;
U-HOOKIRTSI
? JBW Ua.iwie 'ihttd idtpiiseMW
ofttMViry Wakoaalltf and makev erliallf tavile
UneM iwaUMMr, tt lae aeatet aa everreety elaa, 'te
eaUsad sasmlae atr steaks feafete pejcbeauaf shewhtve.
,'J--v.,i
1 OnlOa'illiWlCJ&li V'h
eott-dtf
va'.yu:) o'.irH minnl I'rti ,, nl.l K"fc
a- .U9fl3 ta it iJ l'
i ;.,. ,i..
JShftniri Xa . i H4,-uo
T. W . 0rD4mi S: B rk -r 1 Ir-'.mb'! .-. ,-t
, va. V lfslawars Oommoa Flsas:
! J. O. Kaappdt C."3 :rj.O J',;" u..; ,t .
tit vturv r a xrntr or rut A
13 la tii abova eata. and alw two atber write, oa In
Tavor af John P: Buna vs. I. Q. Knapp tt Co., aad ea
la favoret Wllllaai O. tana Vs. 1. 0. Kaapa k Oo ,t
an OifOoiM rroa, the Oaanaf tman raws ar veiawar
mum OU. I will etrar tarsals at the store room Mo
M Xoat BrMa atMst. Buora Blok, la ttWfUy ot.OO'
wuuuay, hi nay in un At juowi
at o'clock: a. e..a toe eenrtajant ef 4nr Iroods aad
aeMoae, twe slaves, on step tedder, two sats ralrUnkw
ataias. eaa desk, one etaht Oav alookk aa..-caJ J
l Printer's toes !! Bt. v il-rt -
1 BrBe. D,vlt. Dapaty.
w. m, Bjwr, aaeaaator.- i .yi a ..y,..'M kuw
aspWdtd. .f ...iiLj,!v,,.!:,-Tl J.-IB .nT
... .- -.v--..t ' ,t. j .11 -0
.l"M i' I)
oueria s exue. -oi-k
r' .'ovoaS m4ni i'anu .Iflxil A. -S
Jtltai, WbaalockC.
siockOe. r.. v-k-; ,.;.,-.vi 4 . A
' ,. Order, f sjUs bv ttaoiunopt,
aappetOs. , ,V. .. ... - ....
3. a. Knapp
BT VIKTUE Oa? AM. OA0ER OF a ALE
to me dlraolad Croat tbe BeoorlavOowrt of rrank
lle eonntv, Ohio, la tbe hoove sua. and another cut.
waaMia Fise Jiattarnaia, aaugaaa ac irori Arm
otroof a Uo.. are paletlffs, vs- 9. Knapp A Co., Bra
eafantlants, I will agar lor sale ol the atoie-roam, an
after Iks exaeaUons ere aattiaad ae dssartbsd la tbs
above adverUsemenl, the remaloing' psrtlaa pf said
w aaia aomaianaint ea i ,, f u -r i
Friday, th 18th darot October,' i
itBe'elodt,'!. at. ' - J-;'
.a'i rv,- .ac it
ni J idvij
Printer sfcas, S SO.
vi n i wvi .wan) punui,
!- eetSdU.
ly Bs. DiTta, Sepaty, ,
3 ft Ltrt
HI
r.'EDIOAL COLLCIZ,
rtw
flf 1,
TntJ REGCLAU COTJBSE OF. LtCa
TURBS la this Initltntlon will eommsaca on
anuBBuai, too xttn or uuiyuxa, ana coqiinm nn
til tha Lt af Ihna. lHKi- '
T ' . . .... . ... , .L4. .-hTuU
. t-i ! UJ" - .' ""i.' 1"
3 -3
Ik
, U t-r-
S. U. SMITH. M. D
r Professor of Theory sad rrasties, aad Deaa,;
FEANCI3 CARTER, M. D
f rof. pf Ototstrks A Dlssastiof Woaea A Childrtn
j mt f rot. of Aastomy and Pbyatology a -r.
f "iUiIs
( Prof, at largery.1
-at! Arfr . i ' v ' ' ' ' T'
f a LOVING, M. D-,
Prof. Mat. Med., Tasfap. Med. Jarlrpradsnrs.
'tHEO.. 6.' WORMLEy, M.. j).,'
-. r ( J..),"iejt;'.t CbeaUtry.l. .....J..',,
. 1-n ru '
t DeBJoastrsto of
AnattBry." Ve'i
. 31" 'Hi-
turw ! iy,-w a
Tlekota foall ha lrelaian. . ..a ....... U ... , BCO eo
BUtiioalaUan ticket (only paid oooa).....W,;.. - 00
OradaaUoa taa--...4.M...,,., Ou
DaaMoatratloa Borrloos....... t 00
awaraing f x to mt per wotB, mciaaiug ttxbl and lask
i tbe Oltnloal aad Boapltal advaaaaias eeaelet ia the
larga aad dtvenlded eollago Ollalo and the Hospital ef
na sraaaun voaair innraary. ' naolde UMte, lbm
aiuiary u am pa la we aeigiiaoriwa will ke aaosaUM,
KmIImJ BteanU.
i All toilers of inqalry w!U be prtsstlr aarwtred, IT
a air- ( J l' T.' - - r.ln .
. -m I. M. IMITB,.Dea
The Gen. Fremont. NOTICE.
Baiaeeatnas O. Marru um T. Mitrrie,) 1
fteaaTwaiuaioa-Oatiaajt's Otnoa.V ''
. Golaatma, Oct. t, J861. . )
FBOM Alt 0 AFT EH THIt DATE, MO
1AMII wlU In sm by tbs BtaW ,ef Ohle to eel-
dUr eaBrioBgb, tope tefaadader kept eat of Ibetr
psy. , '
AnfBear trmupfiattm wUl bsreaftw be mtUtd
ah paid by tbe Amlatsat Qaartsroiaster. TJ. 8. A., at
Mo. M, Rtata Aeuat, Colnakus, Ohio. .. , j ii I
'
estttf
, 1 u t i terisbuit O,oartennaitr antral.
special noTicEs::
MANHOOD...
E0?r lost, bow, xurosio..
Jest FuklJjaed la a aealed Invslops; Price ets.'l
A 110TUBB OV THB HATTJBB, TRIATMBBT AND
KADIOAI, CUkJ Of CPIKklAIOEtitiJIA Or ealaai
WoakMss, lnvalnnavra Asriaataoe, Banal DeMltt, aad
bapodlmeBts to taantago faaarallly, Narvtmanaaa, Coo
aaaiptlsm. IrIIcm, aaa gila. Utalal aad PbTtiaal la.
eapaotty.raaalUagfraa, Balf-aboao, o. By koiMit-J.
OalveraeU, at. P., aataer ef the Arena Book, fee. .-, .,
A Bm t Thwasaaae mi vtaffordra
teat aoder eaat, la a plain envelope, to any address,
BON paid, an reeetpt ef twe stamps, by Dr. CUA8,
). O- KUHB, 187 Bowery, Now Xork, Poet Offloa Box
"a !S. , ;., .- apT Jmda '
T
rarawae tall kablte. Whs art subject to
Obsttveasss, Emeaoba, fiktdiaasa, Drewslaess and tlar
logia tbe sera, arista from toe peat a lew ef bleed to
the heed, abeald never ke without Brand reth'i flUt, aa
away highly daagereus tymptoas wul he romeVad by
alt anmtdkls am. ' ' ... e..aiaiawi
tbe Sea. . Baat.ef .Wartckertel ' 6suatr:r!'3L:
ttveatr Ave rears of age, km atat BraadraiVs t lUa tor
tweaty Bve reart as his sole tseetetot. When kt fetll
lo'Jtpessd, bs It from Cold, Jtkeuiia'UmLAtUuiia. Bad
aes,BUIoas Affsetlena, CotttTsaeat er trrltattea ef tbe
kldDsys er bladder, he doss aofnlut bnt takf a rdoft
l . m vm w . Wi.
Sit ataal tntaod.lt io taks tlx pills, and teas ma
see sack wight, rin. Is every attack of tic near
for twenty -4 s year, Oil, Mapls method has never failed
to aastere hUa te btalib,- aad few an are to lte foand to
omrre ana tsortv as l.., ,..iol ..i:-.i
laid ty Job B. Coca, pTinrtat, Oolnabwa, an by
"7."
lO a.U40U4t)-.1'
.i:ii 4
aa1tLilW' '" '-loi '
a: v'4 . Hi
ac,4 .im tjiH.
I J " '
i. Im
kite written by Iil4v. J- B. UvXmt, pastor at tbe
rierreeetot rnwt t - U f ir- Btulya,at. T.,to
tbtsararU aU Uawiiri" t .iumtt, eat sy isk
votaase la feror af that wet ii-tvaowaiit mialntoi, Kas,
WaaaeW'S ?-wrff :a l OOTaaua tmaTi ...
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Macfarlane463 Points
Stuck after first line. I have def add_list(a,b,c): as my first line of code but I'm unsure what to do after that.
Hey I've looked at this for a while now so any help would be greatly appreciated. I know the syntax I need to use to start the function I just don't know how to plug in numbers for the variables I created and I have no Idea why I would need a for loop for this exercise.
# add_list([1, 2, 3]) should return 6 # summarize([1, 2, 3]) should return "The sum of [1, 2, 3] is 6." # Note: both functions will only take *one* argument each. def add_list(a,b,c): summarize = a+b+c
2 Answers
Logan R22,989 Points
Your problem is that you assumed they would enter in the list manually but really they are passing in a list, so instead you should change your arguments to take in a list.
def add_list(list): summarize = 0 # A for loop that loops through all of the items in the list and adds each one to summarize return summarize
Hopes this helps you out!
Tristan Gaebler6,204 Points
Here is what I did. Tell me if It works
'' def add_list(arg): return sum(arg) | https://teamtreehouse.com/community/stuck-after-first-line-i-have-def-addlistabc-as-my-first-line-of-code-but-im-unsure-what-to-do-after-that | CC-MAIN-2022-27 | refinedweb | 216 | 76.76 |
Pythonista 300015 [BUGS]
import rauthdoes not work in beta 300015. I believe it worked in the previous build, although I'm not sure. It definitely does work in Pythonista 2.
ImportError: No module named 'rauth'
Are you sure you didn't install the module yourself? Under Pythonista 2
import rauthdoesn't work for me. If this is a Python 2 module that you want to use in Python 2 under Pythonista 3, you need to install it into the new
site-packages-2folder - previously Pythonista 3's Python 2 would get user-installed modules from the Pythonista 2
site-packagesfolder. If the module works on Python 2 and 3, you should install it into the
site-packagesfolder without a number, then the same module can be imported by Python 2 and 3.
Oops. You're completely correct. I forgot I had installed that separately, using StaSh, pip install rauth.
Sorry. | https://forum.omz-software.com/topic/3168/pythonista-300015-bugs/1 | CC-MAIN-2019-35 | refinedweb | 150 | 64.1 |
How to make <restrict> work without an action?Bob Thule Apr 3, 2009 8:22 PM
The restrict element in pages.xml is not causing a security exception when users navigate to a page (ie: clicks a link to). The exception is only being thrown when a user calls an action. To work around the problem, I added a default no-opp page action. This works, but it doesn't seem like it should be necessary.
Is this expected behavior, or does Seam have a bug, or is there some setting that I have wrong?
My work-around code is below. I don't think I should have to have the action element in the pages.xml.
pages.xml
<page view- <restrict>#{s:hasRole('Admin')}</restrict> <action execute="#{app.noOp}" on- </page>
App.java
Name("app") public class App{ public void noOp() { } }
1. Re: How to make <restrict> work without an action?Arbi Sookazian Apr 4, 2009 1:00 AM (in response to Bob Thule)
I am using the following successfully in my app:
<page view- <restrict>#{s:hasRole('manager') || s:hasRole('admin')}</restrict> </page>
So that means you don't need to specify an action for Seam to execute...
Have you tried this? Page-level security in Seam using s:hasRole was one of the easier and nicer things I liked about this fwk when I started using Seam 1.2.x...
You need to make sure that the Seam identity instance is populated with the current session's user's role(s) during authentication/authorization process...
ex:
if (theUser.isMemberOf(sid)) { log.debug("(TokenGroup) Found match for: " + secRole.getSecurityRoleName()); identity.addRole(secRole.getSecurityRoleName()); continue; }
2. Re: How to make <restrict> work without an action?Bob Thule Apr 8, 2009 10:53 PM (in response to Bob Thule)Hi Arbi,
If you login to you app with a user who does not have a 'manager' or 'admin' role and then try to go directly to, do you get a security exception?
In my app, if I were to do the same thing, it would render the page just fine! The only time it fails is if I try to call an action from that page. For example, if I click a button with an action "#{whateverAction.doThis}". Stranger yet, when it fails, it still doesn't cause an exception-- it simply does not run the action before re-rendering the page. If I login with a user who passes the restriction, it renders the page (as expected) and the action runs and the page re-renders when the button is clicked (as expected). So the settings in the restrict element are being used, just not fully correctly.
If I add in the no-op page action, the exception occurs as expected-- but I don't think I am supposed to have to add that no-op page action, so I am wondering what is going on!
I am using Seam 2.1.1.GA with Facelets 1.1.15.B1 and JSF 1.2_12. Maybe it has something to do with the newer Facelets or JSF. I can't remember why our team had to move to these newer libs, but it was because of some issues we were having.
3. Re: How to make <restrict> work without an action?Arbi Sookazian Apr 9, 2009 5:41 AM (in response to Bob Thule)
We are using NTLM (silent) authentication with IE browser via JCIFS library in our Authenticator component.
So basically anybody already logged into our network will be authenticated for any of our Seam apps.
Then the authorization routine will not add any roles for that user to the Seam identity instance if they are not a member of any security groups in Active Directory (although the roles/groups can be stored in a DB with Seam 2.1 Identity Management API, specifically JpaIdentityStore).
So the answer to your question (without trying this myself :), is that the user will be forwarded to the error.xhtml with verbage like
you do not have permission to view this page. You need to add something like the following to your pages.xml:
<exception class="org.jboss.seam.security.AuthorizationException"> <redirect view- <message>You don't have permission to do this</message> </redirect> </exception>
4. Re: How to make <restrict> work without an action?Bob Thule Apr 14, 2009 9:21 PM (in response to Bob Thule)
Thanks Arbi, it's fixed based on your exception section. I knew I could add that section, but I never bothered because I wasn't seeing any exceptions in the log and I wasn't being directed to debug page.
But, apparently Seam must be swallowing the AuthorizationExceptions if pages.xml is not setup to catch and redirect on them specifically. | https://developer.jboss.org/thread/187135 | CC-MAIN-2018-17 | refinedweb | 796 | 65.12 |
Applied Linear Algebra¶
Prerequisites
Outcomes
Refresh some important linear algebra concepts
Apply concepts to understanding unemployment and pricing portfolios
Use
numpyto do linear algebra operations
# Uncomment following line to install on colab #! pip install
# import numpy to prepare for code below import numpy as np import matplotlib.pyplot as plt %matplotlib inline
Vectors and Matrices¶
Vectors¶
A (N-element) vector is \(N\) numbers stored together.
We typically write a vector as \(x = \begin{bmatrix} x_1 \\ x_2 \\ \dots \\ x_N \end{bmatrix}\).
In numpy terms, a vector is a 1-dimensional array.
We often think of 2-element vectors as directional lines in the XY axes.
This image, from the QuantEcon Python lecture
is an example of what this might look like for the vectors
(-4, 3.5),
(-3, 3), and
(2, 4).
In a previous lecture, we saw some types of operations that can be done on vectors, such as
x = np.array([1, 2, 3]) y = np.array([4, 5, 6])
Element-wise operations: Let \(z = x ? y\) for some operation \(?\), one of the standard binary operations (\(+, -, \times, \div\)). Then we can write \(z = \begin{bmatrix} x_1 ? y_1 & x_2 ? y_2 \end{bmatrix}\). Element-wise operations require that \(x\) and \(y\) have the same size.
print("Element-wise Addition", x + y) print("Element-wise Subtraction", x - y) print("Element-wise Multiplication", x * y) print("Element-wise Division", x / y)
Element-wise Addition [5 7 9] Element-wise Subtraction [-3 -3 -3] Element-wise Multiplication [ 4 10 18] Element-wise Division [0.25 0.4 0.5 ]
Scalar operations: Let \(w = a ? x\) for some operation \(?\), one of the standard binary operations (\(+, -, \times, \div\)). Then we can write \(w = \begin{bmatrix} a ? x_1 & a ? x_2 \end{bmatrix}\).
print("Scalar Addition", 3 + x) print("Scalar Subtraction", 3 - x) print("Scalar Multiplication", 3 * x) print("Scalar Division", 3 / x)
Scalar Addition [4 5 6] Scalar Subtraction [2 1 0] Scalar Multiplication [3 6 9] Scalar Division [3. 1.5 1. ]
Another operation very frequently used in data science is the dot product.
The dot between \(x\) and \(y\) is written \(x \cdot y\) and is equal to \(\sum_{i=1}^N x_i y_i\).
print("Dot product", np.dot(x, y))
Dot product 32
We can also use
@ to denote dot products (and matrix multiplication which we’ll see soon!).
print("Dot product with @", x @ y)
Dot product with @ 32
Exercise
See exercise 1 in the exercise list.
nA = 100 nB = 50 nassets = np.array([nA, nB]) i = 0.05 durationA = 6 durationB = 4 # Do your computations here # Compute price # uncomment below to see a message! # if condition: # print("Alice can retire") # else: # print("Alice cannot retire yet")
Matrices¶
An \(N \times M\) matrix can be thought of as a collection of M N-element vectors stacked side-by-side as columns.
We write a matrix as
In numpy terms, a matrix is a 2-dimensional array.
We can create a matrix by passing a list of lists to the
np.array function.
x = np.array([[1, 2, 3], [4, 5, 6]]) y = np.ones((2, 3)) z = np.array([[1, 2], [3, 4], [5, 6]])
We can perform element-wise and scalar operations as we did with vectors. In fact, we can do these two operations on arrays of any dimension.
print("Element-wise Addition\n", x + y) print("Element-wise Subtraction\n", x - y) print("Element-wise Multiplication\n", x * y) print("Element-wise Division\n", x / y) print("Scalar Addition\n", 3 + x) print("Scalar Subtraction\n", 3 - x) print("Scalar Multiplication\n", 3 * x) print("Scalar Division\n", 3 / x)
Element-wise Addition [[2. 3. 4.] [5. 6. 7.]] Element-wise Subtraction [[0. 1. 2.] [3. 4. 5.]] Element-wise Multiplication [[1. 2. 3.] [4. 5. 6.]] Element-wise Division [[1. 2. 3.] [4. 5. 6.]] Scalar Addition [[4 5 6] [7 8 9]] Scalar Subtraction [[ 2 1 0] [-1 -2 -3]] Scalar Multiplication [[ 3 6 9] [12 15 18]] Scalar Division [[3. 1.5 1. ] [0.75 0.6 0.5 ]]
Similar to how we combine vectors with a dot product, matrices can do what we’ll call matrix multiplication.
Matrix multiplication is effectively a generalization of dot products.
Matrix multiplication: Let \(v = x \cdot y\) then we can write \(v_{ij} = \sum_{k=1}^N x_{ik} y_{kj}\) where \(x_{ij}\) is notation that denotes the element found in the ith row and jth column of the matrix \(x\).
The image below from Wikipedia, by Bilou, shows how matrix multiplication simplifies to a series of dot products:
After looking at the math and image above, you might have realized that matrix multiplication requires very specific matrix shapes!
For two matrices \(x, y\) to be multiplied, \(x\) must have the same number of columns as \(y\) has rows.
Formally, we require that for some integer numbers, \(M, N,\) and \(K\) that if \(x\) is \(N \times M\) then \(y\) must be \(M \times K\).
If we think of a vector as a \(1 \times M\) or \(M \times 1\) matrix, we can even do matrix multiplication between a matrix and a vector!
Let’s see some examples of this.
x1 = np.reshape(np.arange(6), (3, 2)) x2 = np.array([[1, 2], [3, 4], [5, 6], [7, 8]]) x3 = np.array([[2, 5, 2], [1, 2, 1]]) x4 = np.ones((2, 3)) y1 = np.array([1, 2, 3]) y2 = np.array([0.5, 0.5])
Numpy allows us to do matrix multiplication in three ways.
print("Using the matmul function for two matrices") print(np.matmul(x1, x4)) print("Using the dot function for two matrices") print(np.dot(x1, x4)) print("Using @ for two matrices") print(x1 @ x4)
Using the matmul function for two matrices [[1. 1. 1.] [5. 5. 5.] [9. 9. 9.]] Using the dot function for two matrices [[1. 1. 1.] [5. 5. 5.] [9. 9. 9.]] Using @ for two matrices [[1. 1. 1.] [5. 5. 5.] [9. 9. 9.]]
print("Using the matmul function for vec and mat") print(np.matmul(y1, x1)) print("Using the dot function for vec and mat") print(np.dot(y1, x1)) print("Using @ for vec and mat") print(y1 @ x1)
Using the matmul function for vec and mat [16 22] Using the dot function for vec and mat [16 22] Using @ for vec and mat [16 22]
Despite our options, we stick to using
@ because
it is simplest to read and write.
Exercise
See exercise 2 in the exercise list.
Other Linear Algebra Concepts¶
Transpose¶
A matrix transpose is an operation that flips all elements of a matrix along the diagonal.
More formally, the \((i, j)\) element of \(x\) becomes the \((j, i)\) element of \(x^T\).
In particular, let \(x\) be given by
then \(x\) transpose, written as \(x'\), is given by
In Python, we do this by
x = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) print("x transpose is") print(x.transpose())
x transpose is [[1 4 7] [2 5 8] [3 6 9]]
Identity Matrix¶
In linear algebra, one particular matrix acts very similarly to how 1 behaves for scalar numbers.
This matrix is known as the identity matrix and is given by
As seen above, it has 1s on the diagonal and 0s everywhere else.
When we multiply any matrix or vector by the identity matrix, we get the original matrix or vector back!
Let’s see some examples.
I = np.eye(3) x = np.reshape(np.arange(9), (3, 3)) y = np.array([1, 2, 3]) print("I @ x", "\n", I @ x) print("x @ I", "\n", x @ I) print("I @ y", "\n", I @ y) print("y @ I", "\n", y @ I)
I @ x [[0. 1. 2.] [3. 4. 5.] [6. 7. 8.]] x @ I [[0. 1. 2.] [3. 4. 5.] [6. 7. 8.]] I @ y [1. 2. 3.] y @ I [1. 2. 3.]
Inverse¶
If you recall, you learned in your primary education about solving equations for certain variables.
For example, you might have been given the equation
and then asked to solve for \(x\).
You probably did this by subtracting 7 and then dividing by 3.
Now let’s write an equation that contains matrices and vectors.
How would we solve for \(x = \begin{bmatrix} x_1 \\ x_2 \end{bmatrix}\)?
Unfortunately, there is no “matrix divide” operation that does the opposite of matrix multiplication.
Instead, we first have to do what’s known as finding the inverse. We must multiply both sides by this inverse to solve.
Consider some matrix \(A\).
The inverse of \(A\), given by \(A^{-1}\), is a matrix such that \(A A^{-1} = I\) where \(I\) is our identity matrix.
Notice in our equation above, if we can find the inverse of \(\begin{bmatrix} 1 & 2 \\ 3 & 1 \end{bmatrix}\) then we can multiply both sides by the inverse to get
Computing the inverse requires that a matrix be square and satisfy some other conditions (non-singularity) that are beyond the scope of this lecture.
We also skip the exact details of how this inverse is computed, but, if you are interested, you can visit the QuantEcon Linear Algebra lecture for more details.
We demonstrate how to compute the inverse with numpy below.
# This is a square (N x N) non-singular matrix A = np.array([[1, 2, 0], [3, 1, 0], [0, 1, 2]]) print("This is A inverse") print(np.linalg.inv(A)) print("Check that A @ A inverse is I") print(np.linalg.inv(A) @ A)
This is A inverse [[-0.2 0.4 0. ] [ 0.6 -0.2 0. ] [-0.3 0.1 0.5]] Check that A @ A inverse is I [[ 1.00000000e+00 0.00000000e+00 0.00000000e+00] [ 2.77555756e-17 1.00000000e+00 0.00000000e+00] [-1.38777878e-17 0.00000000e+00 1.00000000e+00]]
Portfolios¶
In control flow, we learned to value a stream of payoffs from a single asset.
In this section, we generalize this to value a portfolio of multiple assets, or an asset that has easily separable components.
Vectors and inner products give us a convenient way to organize and calculate these payoffs.
Static Payoffs¶
As an example, consider a portfolio with 4 units of asset A, 2.5 units of asset B, and 8 units of asset C.
At a particular point in time, the assets pay \(3\)/unit of asset A, \(5\)/unit of B, and \(1.10\)/unit of C.
First, calculate the value of this portfolio directly with a sum.
4.0 * 3.0 + 2.5 * 5.0 + 8 * 1.1
33.3
We can make this more convenient and general by using arrays for accounting, and then sum then in a loop.
import numpy as np x = np.array([4.0, 2.5, 8.0]) # portfolio units y = np.array([3.0, 5.0, 1.1]) # payoffs n = len(x) p = 0.0 for i in range(n): # i.e. 0, 1, 2 p = p + x[i] * y[i] p
33.3
The above would have worked with
x and
y as
list rather than
np.array.
Note that the general pattern above is the sum.
This is an inner product as implemented by the
np.dot function
np.dot(x, y)
33.3
This approach allows us to simultaneously price different portfolios by stacking them in a matrix and using the dot product.
y = np.array([3.0, 5.0, 1.1]) # payoffs x1 = np.array([4.0, 2.5, 8.0]) # portfolio 1 x2 = np.array([2.0, 1.5, 0.0]) # portfolio 2 X = np.array((x1, x2)) # calculate with inner products p1 = np.dot(X[0,:], y) p2 = np.dot(X[1,:], y) print("Calculating separately") print([p1, p2]) # or with a matrix multiplication print("Calculating with matrices") P = X @ y print(P)
Calculating separately [33.3, 13.5] Calculating with matrices [33.3 13.5]
NPV of a Portfolio¶
If a set of assets has payoffs over time, we can calculate the NPV of that portfolio in a similar way to the calculation in npv.
First, consider an example with an asset with claims to multiple streams of payoffs which are easily separated.
You are considering purchasing an oilfield with 2 oil wells, named
A and
B where
Both oilfields have a finite lifetime of 20 years.
In oilfield
A, you can extract 5 units in the first year, and production in each subsequent year decreases by \(20\%\) of the previous year so that \(x^A_0 = 5, x^A_1 = 0.8 \times 5, x^A_2 = 0.8^2 \times 5, \ldots\)
In oilfield
B, you can extract 2 units in the first year, but production only drops by \(10\%\) each year (i.e. \(x^B_0 = 2, x^B_1 = 0.9 \times 2, x^B_2 = 0.9^2 \times 2, \ldots\)
Future cash flows are discounted at a rate of \(r = 0.05\) each year.
The price for oil in both wells are normalized as \(p_A = p_B = 1\).
These traits can be separated so that the price you would be willing to pay is the sum of the two, where we define \(\gamma_A = 0.8, \gamma_B = 0.9\).
Let’s compute the value of each of these assets using the dot product.
The first question to ask yourself is: “For which two vectors should I compute the dot product?”
It turns out that this depends on which two vectors you’d like to create.
One reasonable choice is presented in the code below.
# Depreciation of production rates gamma_A = 0.80 gamma_B = 0.90 # Interest rate discounting r = 0.05 discount = np.array([(1 / (1+r))**t for t in range(20)]) # Let's first create arrays that have the production of each oilfield oil_A = 5 * np.array([gamma_A**t for t in range(20)]) oil_B = 2 * np.array([gamma_B**t for t in range(20)]) oilfields = np.array([oil_A, oil_B]) # Use matrix multiplication to get discounted sum of oilfield values and then sum # the two values Vs = oilfields @ discount print(f"The npv of oilfields is {Vs.sum()}")
The npv of oilfields is 34.267256487477496
Now consider the approximation where instead of the oilfields having a finite lifetime of 20 years, we let them produce forever, i.e. \(T = \infty\).
With a little algebra,
And, using the infinite sum formula from Control Flow (i.e. \(\sum_{t=0}^{\infty}\beta^t = (1 - \beta)^{-1}\))
The \(V_B\) is defined symmetrically.
How different is this infinite horizon approximation from the \(T = 20\) version, and why?
Now, let’s compute the \(T = \infty\) version of the net present value and make a graph to help us see how many periods are needed to approach the infinite horizon value.
# Depreciation of production rates gamma_A = 0.80 gamma_B = 0.90 # Interest rate discounting r = 0.05 def infhor_NPV_oilfield(starting_output, gamma, r): beta = gamma / (1 + r) return starting_output / (1 - beta) def compute_NPV_oilfield(starting_output, gamma, r, T): outputs = starting_output * np.array([gamma**t for t in range(T)]) discount = np.array([(1 / (1+r))**t for t in range(T)]) npv = np.dot(outputs, discount) return npv Ts = np.arange(2, 75) NPVs_A = np.array([compute_NPV_oilfield(5, gamma_A, r, t) for t in Ts]) NPVs_B = np.array([compute_NPV_oilfield(2, gamma_B, r, t) for t in Ts]) NPVs_T = NPVs_A + NPVs_B NPV_oo = infhor_NPV_oilfield(5, gamma_A, r) + infhor_NPV_oilfield(2, gamma_B, r) fig, ax = plt.subplots() ax.set_title("NPV with Varying T") ax.set_ylabel("NPV") ax.plot(Ts, NPVs_A + NPVs_B) ax.hlines(NPV_oo, Ts[0], Ts[-1], color="k", linestyle="--") # Plot infinite horizon value ax.spines["right"].set_visible(False) ax.spines["top"].set_visible(False)
It is also worth noting that the computation of the infinite horizon net present value can be simplified even further by using matrix multiplication. That is, the formula given above is equivalent to
and where \(x_0 = \begin{bmatrix} x_{A0} \\ x_{B0} \end{bmatrix}\).
We recognize that this equation is of the form
Without proof, and given important assumptions on \(\frac{1}{1 + r}\) and \(A\), this equation reduces to
Using the matrix inverse, where
I is the identity matrix.
p_A = 1.0 p_B = 1.0 G = np.array([p_A, p_B]) r = 0.05 beta = 1 / (1 + r) gamma_A = 0.80 gamma_B = 0.90 A = np.array([[gamma_A, 0], [0, gamma_B]]) x_0 = np.array([5, 2]) # Compute with matrix formula NPV_mf = G @ np.linalg.inv(np.eye(2) - beta*A) @ x_0 print(NPV_mf)
34.99999999999999
Note: While our matrix above was very simple, this approach works for much more
complicated
A matrices as long as we can write \(x_t\) using \(A\) and \(x_0\) as
\(x_t = A^t x_0\) (For an advanced description of this topic, adding randomness, read about
linear state-space models with Python).
Unemployment Dynamics¶
Consider an economy where in any given year, \(\alpha = 5\%\) of workers lose their jobs and \(\phi = 10\%\) of unemployed workers find jobs.
Define the vector \(x_0 = \begin{bmatrix} 900,000 & 100,000 \end{bmatrix}\) as the number of employed and unemployed workers (respectively) at time \(0\) in the economy.
Our goal is to determine the dynamics of unemployment in this economy.
First, let’s define the matrix.
Note that with this definition, we can describe the evolution of employment and unemployment from \(x_0\) to \(x_1\) using linear algebra.
However, since the transitions do not change over time, we can use this to describe the evolution from any arbitrary time \(t\), so that
Let’s code up a python function that will let us track the evolution of unemployment over time.
phi = 0.1 alpha = 0.05 x0 = np.array([900_000, 100_000]) A = np.array([[1-alpha, alpha], [phi, 1-phi]]) def simulate(x0, A, T=10): """ Simulate the dynamics of unemployment for T periods starting from x0 and using values of A for probabilities of moving between employment and unemployment """ nX = x0.shape[0] out = np.zeros((T, nX)) out[0, :] = x0 for t in range(1, T): out[t, :] = A.T @ out[t-1, :] return out
Let’s use this function to plot unemployment and employment levels for 10 periods.
def plot_simulation(x0, A, T=100): X = simulate(x0, A, T) fig, ax = plt.subplots() ax.plot(X[:, 0]) ax.plot(X[:, 1]) ax.set_xlabel("t") ax.legend(["Employed", "Unemployed"]) return ax plot_simulation(x0, A, 50)
<AxesSubplot:
Notice that the levels of unemployed an employed workers seem to be heading to constant numbers.
We refer to this phenomenon as convergence because the values appear to converge to a constant number.
Let’s check that the values are permanently converging.
plot_simulation(x0, A, 5000)
<AxesSubplot:
The convergence of this system is a property determined by the matrix \(A\).
The long-run distribution of employed and unemployed workers is equal to the left-eigenvector of \(A'\), corresponding to the eigenvalue equal to 1.
Let’s have numpy compute the eigenvalues and eigenvectors and compare the results to our simulated results above:
eigvals, eigvecs = np.linalg.eig(A.T) for i in range(len(eigvals)): if eigvals[i] == 1: which_eig = i break print(f"We are looking for eigenvalue {which_eig}")
We are looking for eigenvalue 0
Now let’s look at the corresponding eigenvector:
dist = eigvecs[:, which_eig] # need to divide by sum so it adds to 1 dist /= dist.sum() print(f"The distribution of workers is given by {dist}")
The distribution of workers is given by [0.66666667 0.33333333]
Exercise
See exercise 3 in the exercise list.
Exercises¶
Exercise 1¶
Alice is a stock broker who owns two types of assets: A and B. She owns 100 units of asset A and 50 units of asset B. The current interest rate is 5%. Each of the A assets have a remaining duration of 6 years and pay $1500 each year, while each of the B assets have a remaining duration of 4 years and pay $500 each year. Alice would like to retire if she can sell her assets for more than $500,000. Use vector addition, scalar multiplication, and dot products to determine whether she can retire.
Exercise 2¶
Which of the following operations will work and which will create errors because of size issues?
Test out your intuitions in the code cell below
x1 @ x2 x2 @ x1 x2 @ x3 x3 @ x2 x1 @ x3 x4 @ y1 x4 @ y2 y1 @ x4 y2 @ x4
# testing area
Exercise 3¶
Compare the distribution above to the final values of a long simulation.
If you multiply the distribution by 1,000,000 (the number of workers), do you get (roughly) the same number as the simulation?
# your code here | https://datascience.quantecon.org/scientific/applied_linalg.html | CC-MAIN-2022-40 | refinedweb | 3,421 | 65.93 |
HI,
I have followed the article:
This is working with no issue.
However I am struggling to make the results clickable. When the row is clicked I want to linked to the relevant product page.
I have searched but cannot find a solution.
I have added an on row select handler. here is my code. What am I missing?
import wixData from "wix-data"; import wixLocation from 'wix-location'; $w.onReady(function () { $w("#resultsTable").columns = [{ "id": "col1", "dataPath": "mainMedia", "label": "Image", "visible": true, "type": "image", }, { "id": "col2", "dataPath": "name", "label": "Product", "type": "string", }, { "id": "col3", "dataPath": "formattedPrice", "label": "Price", "type": "string", }]; }); export function searchButton_click(event) { // Runs a query on all products wixData.query('Stores/Products') .contains("name", $w("#searchBox").value) .find() // Run the query .then(res => { $w("#resultsTable").rows = res.items; $w("#resultsTable").expand(); }); } export function resultsTable_rowSelect(event) { let product let rowData = event.rowData; let rowIndex = event.rowIndex; const myRow = event.target.rows[rowIndex]; wixLocation.to("product.productPageUrl") }
Thanks in advance.
I have also tried:
this can't find product but does link to product page
I have got a little further, now a product page opens but returns "product not found".
Please can someone just resolve the last hurdle for me:)
Thanks
SOLVED | https://www.wix.com/corvid/forum/community-discussion/link-search-results-in-table-to-product-page-based-on-row-solved | CC-MAIN-2020-05 | refinedweb | 204 | 60.41 |
for connected embedded systems
setstate()
Reset the state of a pseudo-random number generator
Synopsis:
#include <stdlib.h> char *setstate( const char *state );
Arguments:
- state
- A pointer to the state array that you want to use.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
Once the state of the pseudo-random number generator has been initialized, setstate() allows switching between state arrays. The array defined by the state argument is used for further random-number generation until initstate() is called or setstate() is called again. The setstate() function returns a pointer to the previous state array.
This function is used in conjunction with the following:
- initstate()
- Initialize the state of the pseudo-random number generator.
- random()
- Generate a pseudo-random number using a default state.
- srandom()
- Set the seed used by the pseudo-random number generator.
After initialization, you can restart a state array at a different point in one of two ways:
- Call initstate() with the desired seed, state array, and size of the array.
- Call setstate() with the desired state, then call srandom() with the desired seed. The advantage of using both of these functions is that the size of the state array doesn't have to be saved once it's initialized.
Returns:
A pointer to the previous state array, or NULL if an error occurred.
Examples:
See initstate().
Classification:
See also:
drand48(), initstate(), rand(), random(), srand(), srandom() | http://www.qnx.com/developers/docs/6.4.0/neutrino/lib_ref/s/setstate.html | crawl-003 | refinedweb | 244 | 56.55 |
Details
- Type:
Bug
- Status: Closed
- Priority:
Minor
- Resolution: Fixed
- Affects Version/s: 2.0.0-beta2
- Fix Version/s: 2.0.0-beta3
- Component/s: None
- Labels:None
- Environment:Mac OS X, OpenJPA 2.0.0-beta2, Spring 3.0
Description.
Activity
- All
- Work Log
- History
- Activity
- Transitions
Basic unit test showing the failure. Note that there is a parallel email thread in which Fay Wang could not reproduce the issue. <>
Which Spec level did you specify in your persistence.xml and what properties did you set?
A JPA 1.0 level persistence.xml will automatically use compatibility settings to behave like OpenJPA 1.x -
Add post 2.0.0-beta2, the fix for
OPENJPA-1097 has been integrated, which fixes a bug where EM.clear() was not removing some $proxy class wrappers from the entities....
Donald: interesting suggestions. My persistence.xml file is pulling in the 2.0 namespace and specifies version 2.0. I am now running against the OpenJPA-2.0.0.SNAPSHOT.jar and the behavior is unchanged.
Donald: I think you are on the right track. At DEBUG level, I see 'PersistenceVersion=1.0' during OpenJPA initialization. Now to figure out why.
Spring 3.0 is reporting the wrong version (1.0) for the PersistenceVersion. <>
Considerable progress. Now only one of the twenty tests fails.
TestEntity refreshRemoved = new TestEntity("refresh removed");
em.persist(refreshRemoved);
em.flush();
em.remove(refreshRemoved);
em.flush();
em.refresh(refreshRemoved);
This should throw an IllegalArgumentException, but does not.
I have reproduced this latest problem with remove/refresh and am looking into it.
Revised the bug description to reflect the narrowed scope and changed the state to minor as there are clear workarounds.
Attached patch for this problem.
Thanks for the patch Dianne, but I have a couple of questions.
1. The javadoc for lock() and refresh() is very similar regarding detached entities :
For lock() :
@throws IllegalArgumentException if the instance is not an
entity or is a detached entity
For refresh() :
@throws IllegalArgumentException if the instance is not
an entity or the entity is not managed
Seems like we'd want to the same thing for refresh and lock (basically the if check for REFRESH can be removed).
2. This is more of a general question - your patch didn't introduce it but the assertValidAttchedEntity() method is very similar to contains(). There is a subtle difference in that contains checks whether the type is managed by this persistence context, and assertValidAttachedEntity checks whether the StateManager is persistent. There's also a slight difference in the exceptions thrown. Still it seems like we'd want to reuse the logic, and rather than duplicating the code.
Thanks for reviewing this patch Mike.
For question #1:
When I first made the change and ran all of the tests, one set of lock tests failed because of remove followed by lock.
So, I searched through the spec related to this. Section 3.2.5 says, for a refresh operation, "If X is a new, detched, or removed entity, the IllegalArgumentException is thrown." In other parts of the spec (including the javadoc that you quoted), it says an IllegalArgumentException is thrown for a Lock request on a "detached" entity. But, I couldn't find any such statement fot a "removed" entity.
For question #2
At this point, I don't have an answer. I'll do a little digging.
Hi Dianne, you're right per the spec a managed entity is one that has a persistent identity and is associated with the persistence context. A removed entity fits that description.
I still think we can be a bit smarted about code reuse, but that's secondary to this issue - consider both my questions answered
Committed patch.txt dated 2010-03-15 04:44 PM for Dianne under revision 923849.
The patch works for me. I tested with beta3 build from the staging area.
Closing on Jerry's behalf.
Here are the test cases and their output. | https://issues.apache.org/jira/browse/OPENJPA-1562 | CC-MAIN-2015-22 | refinedweb | 659 | 60.01 |
This is a quickie. I have some other blog posts about interesting material on the horizon, but I'm always wary of posting information without knowing whether I'm going to violate NDA by writing about it. There should be a real flurry of activity when we finally get the Whidbey Beta 1 out our doors, but I don't expect that to happen for months, yet. We're in “heads-down“ mode in the FE team, hard at work delivering features that we think will excite and engage our users.
About aggregate initialization. How do you do it with managed arrays? I held the suspicion that you couldn't do it, that we didn't provide a way to do it in the new syntax. Stan showed me how:
using namespace System;
using namespace stdcli::language;
int main(){
array<int>^ numbers = gcnew array<int>{4, 6, 8, 10};
for ( int i=0; i<numbers->Length; i++ )
Console::WriteLine( numbers[i] );
}
That's it. Pretty straightforward, pretty simple. | https://blogs.msdn.microsoft.com/arich/2004/03/17/status-aggregate-initialization-of-cli-arrays/ | CC-MAIN-2020-16 | refinedweb | 168 | 62.88 |
Looking at the JavaScript API in Hybrid MobileFirst Apps
This post is more than 2 years old.
I've been blogging lately about hybrid apps and MobileFirst, and today I thought I'd start investigating the JavaScript client-side API portion of the product. These are API methods you have available to you in your hybrid application. For today, I'm going to focus on the WL.App namespace.
Here are the (non-deprecated) methods of WL.App, along with some thoughts and suggestions on how you could possibly use them in your application.
getDeviceLanguage/getDeviceLocale
The first returns the language code, not the name, so for me it would be
en, not English. Locale will also be the code, so
en_US for example. So how does this compare to the Globalization API? The biggest difference is that these are synchronous, which to me seems to make a bit more sense.
getServerUrl/setServerUrl
These get and set the MobileFirst server url. I don't imagine there are often times when you would want to set the URL, but perhaps for testing purposes you may want to switch the URL being used on the fly. I could see the getter then being used to provide feedback about which server is currently being used. Make note that the API here uses
Url in the method names. Later on you will see a method using
URL.
hideSplashscreen/showSplashscreen
I've already talked a bit about this in regards to bootstrapping an Ionic application under MobileFirst.
overrideBackButton/resetBackButtonOnly applicable to Android and Windows Phone 8, this lets you change the behavior of the device back button. Having a reset there is handy to quickly go back to the system default.
openURL
So yes - this is
URL not
Url! This opens up a new browser to a particular URL. There's options you can pass in (see full docs here) but they don't apply to Android and iOS. Note that this does not work like the InAppBrowser. This opens the system browser as a new activity. On Android you can hit Back to return to the app, but on iOS you would need to return to the app using the double click/select behavior. (That I don't think many users really know about.) I think in most cases you will probably want InAppBrowser instead, but this is another option.
BackgroundHandler.setOnAppEnteringBackground / BackgroundHandler.setOnAppEnteringForeground
Note that these methods are on the BackgroundHandler object (so the full API is
WL.App.BackgroundHandler.etc). These two methods are iOS only but are really freaking neat. When an app is put in the background, iOS takes a snapshot of the current view. This could be a security issue since sensitive information may be on the screen. By using these events, you can hide/show sensitive information so it doesn't show up when the user is viewing running apps in the background. You can either specify a custom function (to hide specific items) or tell the handler to just blank it out.
Here is a screenshot. Note that the scratch app is blanked out.
addActionReceiver/removeActionReceiver/sendActionToNative
Now - this is cool one. Typically when you want to use native code, you have to build a plugin. Plugins are necessarily difficult to write, but you may not necessarily want to go that far for everything you do. MobileFirst's client-side API provides a simpler solution. You can use
sendActionToNative to send a message to your native code. Your native code can then do... whatever. There's a reverse to this as well. You can tell your hybrid app to listen in for actions sent from the native side and react appropriately. As an example, imagine this within your JavaScript:
var data = {someproperty:1234}; WL.App.sendActionToNative("doSomething", data);
Then on the native side - you can listen for it and do something:
-(void) onActionReceived:(NSString *)action withData:(NSDictionary *) data { NSLog(@"The action receiver"); if ([action isEqualToString:@"doSomething"]){ NSLog(@"Yes, doing it"); UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Wait" message:@"Are you sure you want to delete this. This action cannot be undone" delegate:self cancelButtonTitle:@"Delete" otherButtonTitles:@"Cancel", nil]; [alert show]; } }
As you can see, you can listen for the action string and do something with it. You could also handle the args sent to it. In my example I just open an alert (which, to be clear, you do not need to do this way, just use the Dialogs plugin) but I could do pretty much anything here. And again - I could broadcast back to the JavaScript code as well. For times when you don't want a full plugin and just need to quickly talk to the native side, this is a pretty cool option.
Archived Comments
Nice writeup. As always, I look forward to more on this topic.
On the setServerUrl(), this is often used when a single app is white labeled for use by multiple companies. We do this in our IBM Maximo Anywhere product. One app, used by many different companies, which they obviously want hosted on different specific URLs (er Urls!). As part of install/setup, user would enter a specific company code on a generic view, then a call is made to a common server to get company details (logos, Url, themes, auth server, etc), then the target MFP Server url is set and we now have a custom App specifically for that user. Works quite well.
Cool - thanks for sharing that! Yeah, I hope to get more posts on this topic once I get done with some travel. | https://www.raymondcamden.com/2015/04/28/looking-at-the-javascript-api-in-hybrid-mobilefirst-apps | CC-MAIN-2021-39 | refinedweb | 927 | 64.51 |
So, my assignment is to write a program that puts a password input from the user through various tests and output its level of security. I've not had much training in this as my teacher doesn't really help much, and I'm supposed to do this over spring break.
#include <iostream> #include <string> bool is_even(string); //prototype using namespace std; int main() { string password, verbose; int sec1, sec2; cout << "Passowrd Strength Checker!"<<endl; cout << endl; cout << "Enter the password to check: "; cin >>password; cout << "Enter the two security codes: "; cin >>sec1>>sec2; cout << "Verbose? (y/n) "; cin >>verbose; cout << "--------------------------------------"<<endl; return 0; } bool is_even(string password) { if((password.size() >=8) && (password.size()<=14)) return true; else return false; }
I'm using XCode on my Mac, and when I try to compile this it says that string wasn't declare in the scope and that bool is_even(string password) was redeclared as a different kind of symbol. I can't find an example of doing what exactly what I want to do. Basically, this part of the code needs to take the password from the user, and see that it's between 8 and 14 characters, and also even. Any help is very appreciated. | https://www.daniweb.com/programming/software-development/threads/267172/password-security-test-program | CC-MAIN-2017-39 | refinedweb | 205 | 69.31 |
Hey guys. This is my first Time in these forums. i just started learning java on my own. i just started learning the basics and now all of a sudden this advance programming came in front of me. what i really wanted to do is to convert a character into hammingcode. i am not using any java compiler. i am using secure SSh client to compile java codes with no dialogbox to be displayed. if i enter A it should convert into binary which is 1000010 and then convert it into hammingcode by using paritybits. any help would be really appreciated.
Thanks
This is the following code i am using it will convert an Ascii char to binary but now i am stuck how to convert that binary number into hammingcode.
public class printBits2{
public static void main( String args[] ){
printBits2 pb = new printBits2( args[ 0 ] );
}
public printBits2( String message ){
System.out.print( message + "\n\n" );
char chA[] = new char[ message.length() ];
chA = message.toCharArray();
char displayMask = 1 << 9 ;
for( int i = 0; i < message.length(); i++ ){
System.out.print( chA[ i ] );
// printCharBits( chA[ i ] );
System.out.print( "\n" );
}
}
// private void printCharBits( char c ) int displayMask = 1 << 9;
for ( int bit = 1; bit < ; bit++ ){
if( ( c & displayMask ) == 0 ){
System.out.print( "0" );
if( bit % 7 == 0 ){ System.out.print( " " ); }
}
/* else{
System.out.print( "1" );
if( bit % 7 == 0 ){ System.out.print( " " ); }
}
c <<= 1;
} */ System.out.print( "\n" );
}
}
~
Forum Rules | http://forums.devx.com/showthread.php?148961-Page-Loading-Java-Applet&goto=nextnewest | CC-MAIN-2013-20 | refinedweb | 239 | 69.38 |
I spent my last hour on learning JS Array Functions. Here What I have learned!
I can hardly remember popular Javascript built-in functions especially array functions. So, I spent my last hour reading the “Javascript Arrays” chapter of “Javascript Cookbook” book. I am sharing my learning here.
** indexOf
Purpose: Searching item in an array
Return: index of the searched item
var animals = ['dog', 'cat', 'seal']
console.log(animals.indexOf('dog')) // Prints 0
** findIndex
Purpose: Searching item in an array based on a test function
Return: index of the searched item
var allNums = [2, 4, 9, 6, 7, 1, 1]
var over = allNums.findIndex(function (element){
return (element>=6) // Returns 2
})
console.log(allNums[over]) // Prints 9
** Combination Concat() and Apply()
You can flatten a 2d Array by using both of these functions
var fruitArray = []
fruitArray[0] = ['strawberry', 'orange']
fruitArray[1] = ['lime', 'peach']
fruitArray[2] = ['banana', 'kiwi']
var newFruitArray = fruitArray.concat.apply([],fruitArray)
console.log(newFruitArray)
// Prints [ 'strawberry', 'orange', 'lime', 'peach', 'banana', 'kiwi' ]
** splice
Purpose: Removing/Replacing/Adding Array Elements
To replace the first item with new items,
var animals = ['dog', 'cat', 'seal', 'lion', 'tiger']
animals.splice(0, 1, "zeba", "elephent")
console.log(animals) // Prints [ 'zeba', 'elephent', 'cat', 'seal', 'lion', 'tiger' ]
It can take multiple arguments. The first one is mandatory. It represents the index where the splicing would take place. The second one is optional. It is the number of elements you want to remove. The rest of the parameters is going to be placed in between the block of array made from the first two arguments.
If you just pass the first arguments, all elements from this in the array will have vanished. For the above animals array,
var animals = ['dog', 'cat', 'seal', 'lion', 'tiger']
animals.splice(2)
console.log(animals) // Prints [ 'dog', 'cat' ]
** slice
Unlike Splice, it will not affect the main array. Slice will create a new array from the existing array like below,
var animals = ['dog', 'cat', 'seal', 'lion', 'tiger']
console.log(animals.slice(0,2)) // Prints [ 'dog', 'cat' ]
The first argument represents where to start. And the second one represents till which index (exclusive) you want to slice the array.
** map
Suppose you want to make an array a1 based on another array b1. a1 will contain the remainder (for ex. mod by 2) of the b1 array. You may think then what is the difference between map and forEach. Actually, they both iterate the whole array. But map must have return statement whereas forEach not necessarily have return statement.
var b1 = [2, 4, 9, 6, 7, 1, 1]
var a1 = b1.map(function (element){
return element%2
})
console.log(a1) // Prints [ 0, 0, 1, 0, 1, 1, 1 ]
** filter
You can filter in an array by this function. For example, you like to have only the numbers whose remainders are 0.
var b1 = [2, 4, 9, 6, 7, 1, 1]
var a1 = b1.filter(function (element){
return element%2==0
})
console.log(a1) // Prints [ 2, 4, 6 ]
** reduce
You can use that function to sum up all elements of an array. Here, reduce takes two arguments. First n1 is the sum of the previous, and n2 is the new element of the array.
var b1 = [2, 4, 9, 6, 7, 1, 1]
var sum = b1.reduce(function (n1, n2){
return n1+n2
})
console.log(sum) // Prints 30
Here, I have showed some of the commonly used Javascript Array functions. Don’t forget to claps!!!!
If you like this article, make sure to follow my Medium profile and check out some other articles of mine! | https://arifulislam-ron.medium.com/i-can-hardly-remember-popular-javascript-built-in-functions-especially-array-functions-357dd82e2305 | CC-MAIN-2021-25 | refinedweb | 591 | 67.15 |
During the 2018 Microsoft Hack Week, members of the Mono team explored the idea of replacing the Mono’s code generation engine written in C with a code generation engine written in C#.
In this blog post we describe our motivation, the interface between the native Mono runtime and the managed compiler and how we implemented the new managed compiler in C#.
Motivation.
This idea has been explored by research projects like the JikesRVM, Maxime and Graal for Java. In the .NET world, the Unity team wrote an IL compiler to C++ compiler called il2cpp. They also experimented with a managed JIT recently.
In this blog post, we discuss the prototype that we built. The code mentioned in this blog post can be found here:
Interfacing with the Mono Runtime
The Mono runtime provides various services, just-in-time compilation, assembly
The code generation engine in Mono is called
mini and is used both for static
compilation and just-in-time compilation.
Mono’s code generation has a number of dimensions:
- Code can be either interpreted, or compiled to native code
- When compiling to native code, this can be done just-in-time, or it can be batch compiled, also known as ahead-of-time compilation.
- Mono today has two code generators, the light and fast
miniJIT engine, and the heavy duty engine based on the LLVM optimizing compiler. These two are not really completely unaware of the other, Mono’s LLVM support reuses many parts of the
miniengine..
To move the JIT to the managed world, we introduced the
ICompiler interface
which must be implemented by your compilation engine, and it is invoked on
demand when a specific method needs to be compiled.
This is the interface that you must implement:
interface ICompiler { CompilationResult CompileMethod (IRuntimeInformation runtimeInfo, MethodInfo methodInfo, CompilationFlags flags, out NativeCodeHandle nativeCode); string Name { get; } }
The
CompileMethod () receives a
IRuntimeInformation reference, which
provides services for the compiler as well as a
MethodInfo that represents
the method to be compiled and it is expected to set the
nativeCode parameter
to the generated code information.
The
NativeCodeHandle merely represents the generated code address and its length.
This is the
IRuntimeInformation definition, which shows the methods available
to the
CompileMethod to perform its work:); }
We currently have one implementation of
ICompiler, we call it the the “
BigStep” compiler.
When wired up, this is what the process looks like when we compile a method with it:
The
mini runtime can call into managed code via
CompileMethod upon a
compilation request.
For the code generator to do its work, it needs to obtain some information
about the current environment.
This information is surfaced by the
IRuntimeInformation interface.
Once the compilation is done, it will return a blob of native instructions to
the runtime.
The returned code is then “installed” in your application.
Now there is a trick question: Who is going to compile the compiler?
The compiler written in C# is initially executed with one of the built-in engines (either the interpreter, or the JIT engine).
The BigStep Compiler
Our first
ICompiler implementation is called the
BigStep
compiler..
The BigStep compiler implements an IL to LLVM compiler. This was convenient to build the proof of concept and ensure that the design was sound, while delegating all the hard compilation work to the LLVM compiler engine.
A lot can be said when it comes to the design and architecture of a compiler, but our main point here is to emphasize how easy it can be, with what we have just introduced to Mono runtime, to bridge IL code with a customized backend.
The IL code is streamed into to the compiler interface through an iterator, with information such as op-code, index and parameters immediately available to the user. See below for more details about the prototype.
Hosted Compiler
Another beauty of moving parts of the runtime to the managed side is that we can test the JIT compiler without recompiling the native runtime, so essentially developing a normal C# application.
The
InstallCompilationResult () can be used to register compiled method with
the runtime and the
ExecuteInstalledMethod () are can be used to invoke a
method with the provided arguments.
Here is an example how this is used code:); }
We can ask the host VM for the actual result, assuming it’s our gold standard:
int mjitResult = (int) runtimeInfo.ExecuteInstalledMethod (irc, 666, 1337); int hostedResult = AddMethod (666, 1337); Assert.AreEqual (mjitResult, hostedResult);
This eases development of a compiler tremendously.
We don’t need to eat our own dog food during debugging, but when we feel ready
we can flip a switch and use the compiler as our system compiler.
This is actually what happens if you run
make -C mcs/class/Mono.Compiler run-test
in the mjit branch: We use this
API to test the managed compiler while running on the regular Mini JIT.
Native to Managed to Native: Wrapping Mini JIT into
ICompiler
As part of this effort, we also wrapped Mono’s JIT in the
ICompiler interface.
MiniCompiler calls back into native code and invokes the regular Mini JIT.
It works surprisingly well, however there is a caveat: Once back in the native
world, the Mini JIT doesn’t need to go through
IRuntimeInformation and just
uses its old ways to retrieve runtime details.
Though, we can turn this into an incremental process now: We can identify those
parts, add them to
IRuntimeInformation and change Mini JIT so that it uses
the new API.
Conclusion
We should also note that
IRuntimeInformation can be implemented by any other
.NET VM: Hello
CoreCLR folks 👋
If you are curious about this project, ping us on our Gitter channel.
Appendix: Converting Stack-Based OpCodes into Register Operations
Since the target language was LLVM IR, we had to build a translator that converted the stack-based operations from IL into the register-based operations of LLVM.
Since many potential target are register based, we decided to design a framework to make it reusable of the part where we interpret the IL logic. To this goal, we implemented an engine to turn the stack-based operations into the register operations.
Consider the
ADD operation in IL.
This operation pops two operands from the stack, performing addition and pushing back the result to the stack. This is documented in ECMA 335 as follows:
Stack Transition: ..., value1, value2 -> ..., result
The actual kind of addition that is performed depends on the types of the values in the stack. If the values are integers, the addition is an integer addition. If the values are floating point values, then the operation is a floating point addition..
Each temporary value is assigned a unique name.
Then an IL instruction can be unambiguously presented in a form using temporary names instead of stack changes.
For example, the
ADD operation becomes
Temp3 := ADD Temp1 Temp2.
As we mentioned earlier, the execution engine is a common layer that merely
translates the instruction to a more generic form.
It then sends out each instruction to
IOperationProcessor, an interface that
performs actual translation.
Comparing to the instruction received from
ICompiler, the presentation here,
OperationInfo, is much more consumable:
In addition to the op codes, it has an array of the input operands, and a result operand:
public class OperationInfo { ... ... internal IOperand[] Operands { get; set; } internal TempOperand Result { get; set; } ... ... }
There are several types of the operands:
ArgumentOperand,
LocalOperand,
ConstOperand,
TempOperand,
BranchTargetOperand, etc.
Note that the result, if it exists, is always a
TempOperand.
The most important property on
IOperand is its
Name,:
LocalOperand: fetch the value from pre-allocated address
ConstOperand: use the const value carried by the operand
BranchTargetOperand: use the index carried by the oper.
We use LLVMSharp binding to communicate with LLVM. | https://www.mono-project.com/news/2018/09/11/csharp-jit/ | CC-MAIN-2020-50 | refinedweb | 1,287 | 50.57 |
On Tue, May 28, 2002 at 10:16:49AM -0700, H. Peter Anvin wrote: > Hi, > > Transmeta Crusoe CPUs support the instructions that gcc considers > definitial of a "i686"; mainly CMOV. Howver, due to "compatibility > issues with certain non-Linux operating systems" it reports as family=5 > and thus RPM considers it to be incompatible with things like the i686 > glibc. > > Unfortunately, Crusoe will not run a Pentium Pro kernel, solely because > of the following code in include/asm-i386/pgtable.h: > > /* > * Do not check the PGE bit unnecesserily if this is a PPro+ kernel. > */ > #ifdef CONFIG_X86_PGE > # define __flush_tlb_all() __flush_tlb_global() > #else > # define __flush_tlb_all() \ > do { \ > if (cpu_has_pge) \ > __flush_tlb_global(); \ > else \ > __flush_tlb(); \ > } while (0) > #endif I can add Yet More Mysterious Inline ASM VooDOO (the current paradigm) ... > > > What would be the best way to deal with this? ... but the right thing to do is to roll an explicitly dynamic probe dependency and get rpm out of this arch madness entirely. By that I mean, that any package that contains an executable that uses CMOV can/will pick up a probe dependency like (exact syntax yet to be decided) Requires: cpu(HAVE_CMOV) and then export the cpu(foo) probe mechanism on a per-platform basis with either static or dynamic resolutionh of the dependency. Me and rpm don't need no steenkin' CMOV :-) 73 de Jeff -- Jeff Johnson ARS N3NPQ jbj@redhat.com (jbj@jbj.org) Chapel Hill, NC | http://www.redhat.com/archives/rpm-list/2002-May/msg00257.html | CC-MAIN-2013-48 | refinedweb | 234 | 59.94 |
Implementing a Trie in C#
Download Trie.zip Trie is a tree like data structure that can be used for fast text search. While there are a lot of examples on the internet, very few if any are written in C#. In this post, I would like to show a complete implementation in C#. In my implementation, the Trie nodes are represented by an array of pointers. While it is not the most efficient way to do, it nevertheless gets the point through. An alternative and more efficient way to do would utilize a linked list in place of the array of pointers. The following figure illustrates how I implement the Trie structure.
Here is the code for the TrieNode class.
class TrieNode {
public TrieNode[] nodes;
public bool isEnd = false;
public const int ASCIIA = 97;
public TrieNode() {
nodes = new TrieNode[26];
}
public bool Contains(char c) {
int n = Convert.ToByte(c) - ASCIIA;
if (n < 26)
return (nodes[n] != null);
else
return false;
}
public TrieNode GetChild(char c) {
int n = Convert.ToByte(c) - ASCIIA;
return nodes[n];
}
}
Whenever the TrieNode gets initialized, an array (representing 26 letters) of pointers is created. And Contains() method returns true if the corresponding node contains a reference (think of pointers) to a child. And finally, GetChild() function returns a child tree that is rooted at the character passed in. Note that the GetChild function only works level by level, e.g. for word “boot”, you will need to pass in the whole word and then scanning from left to right, and at each letter, you would call GetChild to get a tree that representing the current tree from that letter on. This makes intuitive sense, because if you do not call this function sequentially, how would you tell which “o” you are referring to? Take a look at the Tries class, and this concept should become clearer.
class Tries {
private TrieNode root = new TrieNode();
public TrieNode Insert(string s) {
char[] charArray = s.ToLower().ToCharArray();
TrieNode node = root;
foreach (char c in charArray) {
node = Insert(c, node);
}
node.isEnd = true;
return root;
}
private TrieNode Insert(char c, TrieNode node) {
if (node.Contains(c)) return node.GetChild(c);
else {
int n = Convert.ToByte(c) - TrieNode.ASCIIA;
TrieNode t = new TrieNode();
node.nodes[n] = t;
return t;
}
}
public bool Contains(string s) {
char[] charArray = s.ToLower().ToCharArray();
TrieNode node = root;
bool contains = true;
foreach (char c in charArray) {
node = Contains(c, node);
if (node == null) {
contains = false;
break;
}
}
if ((node == null) || (!node.isEnd))
contains = false;
return contains;
}
private TrieNode Contains(char c, TrieNode node) {
if (node.Contains(c)) {
return node.GetChild(c);
} else {
return null;
}
}
}
Now let’s see how we would use our Trie class to check whether a given string is present from an input string.
class Program {
static void
Tries tries = new Tries();
TrieNode n;
string s = @"
In computer science, a trie, or prefix tree,
is an ordered tree data structure that is used to
store an associative array where the keys are strings.
Unlike a binary search tree, no node in the tree
stores the key associated with that node;
instead, its position in the tree shows what key
it is associated with. All the descendants
of any one node have a common prefix of the string
associated with that node, and the root is associated
with the empty string. Values are normally not associated
with every node, only with leaves and some inner nodes
that happen to correspond to keys of interest.
";
s = s.Replace("\r\n", "");
string[] ay = s.Split(‘ ‘, ‘,’, ‘;’, ‘.’);
foreach (string str in ay) {
if (str != "")
n = tries.Insert(str);
}
Console.WriteLine(tries.Contains("prefix"));
Console.WriteLine(tries.Contains("come"));
Console.ReadKey();
}
}
Is there any way to look for more than one word, with common letters in the same node position? For example, if the user gives “tr**”, it will return “trie” and “tree”.
If I were to store both “Read” and “Reader” then how will the tree look like.
Root->R->E->A->D(IsEnd = True)
Root->R->A->D->E->R(IsEnd = true)
Is this not duplication ? Also as we have only 26 nodes under each node, there is no scope for duplication also and we cannot have the below scenario:
Root->R->E->A->D(isEnd = True)->E->R(IsEnd = True)
Then how will the 2 words “Read” and “Reader” will ge stored in the tree ?
Kris,
I ran across this looking for ways to build the Trie. I suspect in the past couple of years the answer as come, but I figured I would post and answer if anyone else comes across the same thing.
The use of the bool value “IsEnd” is unfortunate as it would lead to a misconception. It would be better to use “IsWord”, or “EndsWord”. The value is there to indicate the transversed keys constitute a word, NOT the end of the nodes in the trie. In your example the keys might look more like this.
Think words (Read, Reader, Reading);
Root->R->E->A->D(EndsWord = True)->E->R(EndsWord = true)->S(EndsWord=true)
->I->N->G(EndsWord=true) | http://www.kerrywong.com/2006/04/01/implementing-a-trie-in-c/ | CC-MAIN-2015-11 | refinedweb | 848 | 72.26 |
CodePlexProject Hosting for Open Source Software
I need to redirect a certain, very complex class of URL's to a different website altogether. To take one example, if the URL comes in and would normally trigger a 404 error, I'd like to check an account database to see if the parameter
"ken" matches an existing user, and then redirect that request to. If the URL "ken" doesn't match an existing user, I need to display a normal 404 page.
I've had luck in the past with overriding some of Orchard's built-in controllers, so I thought that something like this (in my business-specific custom module) would work for me:
[Themed]
[OrchardSuppressDependency("Orchard.Core.Common.Controllers.ErrorController")]
public class ErrorController : Controller
{
public ActionResult NotFound(string url)
{
// If this is a valid room URL, redirect to app.alanta.com.
if (RepositoryHelper.IsRoomUrl(null, url))
{
return Redirect("" + url);
}
return HttpNotFound();
}
}
Unfortunately, when I do that, that code never gets hit, and I just get a standard IIS 404 page (as opposed to the custom Orchard 404 page).
David Hayden describes a couple different ways to do this (e.g.,), but with the custom logic I need, it doesn't seem like placing an
extra NotFound.cshtml view in my theme is the right approach.
Any other thoughts about the best way to do this?
You can clone the ErrorController and give the route that triggers it a higher priority.
That's precisely what I was trying to do. I've cloned the ErrorController, I've created a route pointing to it (with a priority of int.MaxValue), I've suppressed the original controller (and also tried not suppressing it) . . . not sure what else to try.
Are you sure you want to delete this post? You will not be able to recover it later.
Are you sure you want to delete this thread? You will not be able to recover it later. | http://orchard.codeplex.com/discussions/354169 | CC-MAIN-2017-43 | refinedweb | 323 | 64 |
Well, this is my first time get here.
I'm trying to figure out the correct way to replace number into letter. In this case, I need two steps.
First, convert letter to number. Second, restore number to word.
Words list: a = 1, b = 2, f = 6 and k = 11.
I have word: "baafk"
So, for first step, it must be: "211611"
Number "211611" must be converted to "baafk".
But, I failed at second step.
Code I've tried:
Result for converting to number: baafk = 211611Result for converting to number: baafk = 211611public class str_number { public static void main(String[] args){ String word = "baafk"; String number = word.replace("a", "1").replace("b","2").replace("f","6").replace("k","11"); System.out.println(word); System.out.println(number); System.out.println(); String text = number.replace("11", "k").replace("6","f").replace("2","b").replace("1","a"); System.out.println(number); System.out.println(text); } }
But, result for converting above number to letter: 211611 = bkfk
What do I miss here?
How to distinguish if 11 is for "aa" and for "k"? Do you have any solutions or other ways for this case?
Thank you. | http://www.javaprogrammingforums.com/whats-wrong-my-code/36246-java-replace-correct-number-into-letter.html | CC-MAIN-2014-42 | refinedweb | 191 | 68.06 |
KDEUI
#include <kmultitabbar.h>
Detailed Description
A Widget for horizontal and vertical tabs.
(Note that in Qt4, QTabBar can be vertical as well)
It is possible to add normal buttons to the top/left The handling if only one tab at a time or multiple tabs should be raisable is left to the "user".
Definition at line 57 of file kmultitabbar.h.
Member Enumeration Documentation
Definition at line 64 of file kmultitabbar.h.
The list of available styles for KMultiTabBar.
- VSNET - Visual Studio .Net like, always shows icon, only show the text of active tabs
- KDEV3ICON - Kdevelop 3 like, always shows the text and icons
Definition at line 71 of file kmultitabbar.h.
Constructor & Destructor Documentation
Definition at line 464 of file kmultitabbar.cpp.
Definition at line 494 of file kmultitabbar.cpp.
Member Function Documentation
append a new button to the button area.
The button can later on be accessed with button(ID) eg for connecting signals to it
- Parameters
-
Definition at line 501 of file kmultitabbar.cpp.
append a new tab to the tab area.
It can be accessed lateron with tabb(id);
- Parameters
-
Definition at line 529 of file kmultitabbar.cpp.
get a pointer to a button within the button area identified by its ID
Definition at line 535 of file kmultitabbar.cpp.
Definition at line 609 of file kmultitabbar.cpp.
return the state of a tab, identified by its ID
Definition at line 579 of file kmultitabbar.cpp.
get the tabbar position.
- Returns
- position
remove a button with the given ID
Definition at line 552 of file kmultitabbar.cpp.
remove a tab with a given ID
Definition at line 567 of file kmultitabbar.cpp.
set the real position of the widget.
- Parameters
-
Definition at line 598 of file kmultitabbar.cpp.
set the display style of the tabs
Definition at line 588 of file kmultitabbar.cpp.
set a tab to "raised"
- Parameters
-
Definition at line 572 of file kmultitabbar.cpp.
get a pointer to a tab within the tab area, identiifed by its ID
Definition at line 547 of file kmultitabbar.cpp.
get the display style of the tabs
- Returns
- display style
Definition at line 514 of file kmultitabbar.cpp.
Property Documentation
Definition at line 61 of file kmultitabbar.h.
Definition at line 62 of file kmultitabbar. | https://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMultiTabBar.html | CC-MAIN-2019-30 | refinedweb | 379 | 50.02 |
In this article, we will learn about the solution and approach to solve the given problem statement.
Given a positive integer N as input . We need to compute the value of 12 + 22 + 32 + ….. + N2.
Problem statement:This can be solved by two methods
Here we run a loop from 1 to n and for each i, 1 <= i <= n, find i2 and add to sm.
def sqsum(n) : sm = 0 for i in range(1, n+1) : sm = sm + pow(i,2) return sm # main n = 5 print(sqsum(n))
55
As we all know that the sum of squares of natural numbers is given by the formula −
(n * (n + 1) * (2 * n + 1)) // 6n * (n + 1) * (2 * n + 1)) // 6 (n * (n + 1) * (2 * n + 1)) // 6(n * (n + 1) * (2 * n + 1)) // 6
def squaresum(n) : return (n * (n + 1) * (2 * n + 1)) // 6 # Driven Program n = 10 print(squaresum(n))
385
In this article, we learned about the approach to find the Sum of squares of first n natural numbers. | https://www.tutorialspoint.com/python-program-for-sum-of-squares-of-first-n-natural-numbers | CC-MAIN-2021-25 | refinedweb | 174 | 63.97 |
#include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h>
s = socket(AF_INET, SOCK_STREAM, 0);
#include <paths.h> #include <fcntl.h> #include <netinet/ip_var.h>
#include <netinet/tcp.h> #include <netinet/in_pcb.h> #include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
fd = open(_PATH_TCP, flags);
Sockets using the TCP protocol are either ``active'' or ``passive''. Active sockets initiate connections to passive sockets. By default TCP sockets are created active; to create a passive socket the listen(SSC) system call must be used after binding the socket with the bind(SSC) system call. Only passive sockets may use the accept(SSC) call to accept incoming connections. Only active sockets may use the connect(SSC) call to initiate connections.
Passive sockets may ``underspecify'' their location to match incoming connection requests from multiple networks. This technique, called ``wildcard addressing'', allows a single server to provide service to clients on multiple networks. To create a socket that several socket options which are set with setsockopt and tested with getsockopt (see getsockopt(SSC)).
Under most circumstances, TCP sends data when it is presented; when outstanding data has not yet been acknowledged, it gathers small amounts of output to be sent in a single packet once an acknowledgment is received. For a small number of clients, such as window systems that send a stream of mouse events which receive no replies, this packetization may cause significant delays. Therefore, TCP provides a boolean option, TCP_NODELAY (from <netinet/tcp.h>, to defeat this algorithm. The option level for the setsockopt call is the protocol number for TCP, available from getprotobyname (see getprotoent(SLIB)).
It is possible to retrieve or change the value being used for the maximum segment size of an active connection with the TCP_MAXSEG option. TCP_MAXSEG cannot be set to a value larger than TCP has already determined; it can only be made smaller.
The TCP_KEEPIDLE option can be used to control the start interval for TCP keep-alive messages. Normally, when enabled via SO_KEEPALIVE, keep-alives do not start until the connection has been idle for 2 hours. This option can be used to alter this interval. The option value should be specified in seconds. The minimum is restricted to 10 seconds. Setting TCP_KEEPIDLE to 0 restores the keep-alive start interval to the default value.
Normally TCP will send a keep-alive every 75 seconds once the connection has been idle for the KEEPIDLE period. Keep-alives may be sent more frequently by using the TCP_KEEPINTVL option to specify the interval in seconds. The minimum is restricted to 1 second. Setting TCP_KEEPINTVL to 0 restores the keep-alive interval to the default value.
Normally TCP will send 8 keep-alives prior to giving up. This number may be altered by using the TCP_NKEEP option to specify the desired number of keep-alives. The minimum value is constrained to be 1. Setting TCP_NKEEP to 0 restores the keep-alive interval to the default value.
Normally TCP will try to retransmit for 511 seconds before dropping a connection. This value can be changed using the TCP_MAXRXT option. Setting TCP_MAXRXT to a value between 180 and 2^32-2 causes TCP to wait that number of seconds before giving up. Setting TCP_MAXRXT to 0 restores the retransmission interval to the default value. Setting the retransmission interval to 2^32-1 (0xffffffff) causes TCP to retransmit forever. The retransmission period cannot be set to less than three minutes (180 seconds).
Note that many of the default values may be changed by the system administrator using inconfig(ADMN). getsockopt(SSC) or t_optmgmt(NET) may be used to determine the current system default values.
Options at the IP network level may be used with TCP; see ip(ADMP). Incoming connection requests that are source-routed are noted, and the reverse source route is used in responding.
TCP is also available as a TLI connection-oriented protocol via the special file /dev/inet/tcp. Interpreted TCP options are supported via the TLI options mechanism (see t_optmgmt(NET)).
TCP provides a facility, one-packet mode, that attempts to improve performance over Ethernet interfaces that cannot handle back-to-back packets. One-packet mode may be set by ifconfig(ADMN) for such an interface. On a connection that uses an interface for which one-packet mode has been set, TCP attempts to prevent the remote machine from sending back-to-back packets by setting the window size for the connection to the maximum segment size for the interface.
Certain TCP implementations have an internal limit on packet size that is less than or equal to half the advertised maximum segment size. When connected to such a machine, setting the window size to the maximum segment size would still allow the sender to send two packets at a time. To prevent this, a ``small packet size'' and a ``small packet threshold'' may be specified when setting one-packet mode. If, on a connection over an interface with one-packet mode enabled, TCP receives a number of consecutive packets of the small packet size equal to the small packet threshold, the window size is set to the small packet size.
A TCP endpoint can also be obtained by opening the TCP driver directly. Networking statistics can be gathered by issuing ioctl directives to the driver. The following ioctl commands, defined in <netinet/ip_var.h> and <netinet/tcp_var.h>, are supported by the TCP driver:
struct tcp_stuff { struct tcpstat tcp_stat; int tcp_rto_algorithm; int tcp_max_rto; int tcp_min_rto; int tcp_max_conn; int tcp_urgbehavior; };Note that the member
int tcp_urgbehavioris not used.
gi_sizeset to 0. This returns the size of the table. Second, allocate sufficient memory (found in step 1) and issue the ioctl again with
gi_sizeset to the value returned in the step above (or any value greater than 0). The TCP driver will copy the TCP connection table to the user allocated area. tcb_entry is the format of the entries extracted by the ioctl. Structures gi_arg and tcb_entry are as defined below:
struct gi_arg { caddr_t gi_where; /* user addr. */ unsigned gi_size; /* table size */ };
struct tcb_entry { struct inpcb in_pcb; struct tcpcb tcp_pcb; };
typedef struct _tcpconn { struct in_addr local_ip_addr; u_short local_port; struct in_addr rmt_ip_addr; u_short rmt_port; } TcpConn_t;The local and remote addresses and ports serve to uniquely identify an active TCP connection. Only root may use this ioctl.
struct tcp_dbg_hdr { caddr_t tcp_where; /* where to copy-out result */ u_int tcp_size; /* size of buffer */ u_int tcp_debx; /* current slot in debug ring */ u_int tcp_ndebug; /* number of debug records */ };First issue the ioctl with
tcp_wherepointing to the address of the structure and
tcp_sizeset to the size of the structure. TCP will fill in the number of debugging entries in the
tcp_ndebugfield. This information can be used to allocate a buffer large enough to hold the debugging information. The buffer size is calculated as:
sizeof(struct tcp_dbg_hdr) + sizeof(struct tcp_debug) * tcp_ndebugIssuing the ioctl again with
tcp_whereset to the start of the buffer and
tcp_sizeset to the size as computed above will return a buffer consisting of the tcp_dbg_hdr structure followed by tcp_ndebug tcp_debug structures. The
tcp_debxfield will be set to the current offset into the buffer.
ioc_countis not TRANSPARENT for a transparent ioctl
RFC 1337
RFC 793 (STD 7), RFC 1122 (STD 5) | http://osr507doc.xinuos.com/en/man/html.ADMP/tcp.ADMP.html | CC-MAIN-2019-30 | refinedweb | 1,199 | 56.35 |
FlyteConsole¶
FlyteConsole is the web UI for the Flyte platform. Here’s a video that dives into the graph UX:
Running FlyteConsole¶
Install Dependencies¶
Running FlyteConsole locally requires NodeJS and
yarn. Once these are installed, all of the dependencies
can be installed by running
yarn in the project directory.
Environment Variables¶
Before we can run the server, we need to set up an environment variable or two.
ADMIN_API_URL (default: window.location.origin)
FlyteConsole displays information fetched from the FlyteAdmin API. This environment variable specifies the host prefix used in constructing API requests.
Note
This is only the host portion of the API endpoint, consisting of the protocol, domain, and port (if not using the standard 80/443).
This value will be combined with a suffix (such as
/api/v1) to construct the
final URL used in an API request.
Default Behavior
In most cases,
FlyteConsole is hosted in the same cluster as the Admin
API, meaning that the domain used to access the console is the same as that used to
access the API. For this reason, if no value is set for
ADMIN_API_URL, the
default behavior is to use the value of window.location.origin.
``BASE_URL`` (default: ``undefined``)
This allows running the console at a prefix on the target host. This is
necessary when hosting the API and console on the same domain (with prefixes of
/api/v1 and
/console for example). For local development, this is
usually not needed, so the default behavior is to run without a prefix.
``CORS_PROXY_PREFIX`` (default: ``/cors_proxy``)
Sets the local endpoint for CORS request proxying.
Run the Server¶
To start the local development server, run
yarn start. This will spin up a
Webpack development server, compile all of the code into bundles, and start the
NodeJS server on the default port (3000). All requests to the NodeJS server will
be stalled until the bundles have finished. The application will be accessible
at (if using the default port).
Development¶
Storybook¶
FlyteConsole uses Storybook.
Component stories live next to the components they test in the
__stories__
directory with the filename pattern
{Component}.stories.tsx.
You can run storybook with
npm run storybook, and view the stories at
Protobuf and the Network tab¶
Communication with the FlyteAdmin API is done using Protobuf as the request/response format. Protobuf is a binary format, which means looking at responses in the Network tab won’t be helpful. To make debugging easier, each network request is logged to the console with its URL, followed by the decoded Protobuf payload. You must have debug output enabled (on by default in development) to see these messages.
Debug Output¶
This application makes use of the debug
libary to provide namespaced debug output in the browser console. In
development, all debug output is enabled. For other environments, the debug
output must be enabled manually. You can do this by setting a flag in
localStorage using the console:
localStorage.debug = 'flyte:*'. Each module in
the application sets its own namespace. So if you’d like to only view output for
a single module, you can specify that one specifically
(ex.
localStorage.debug = 'flyte:adminEntity' to only see decoded Flyte
Admin API requests).
CORS Proxying¶
In the common hosting arrangement, all API requests are made to the same origin
serving the client application, making CORS unnecessary. For any requests which
do not share the same
origin value, the client application will route
requests through a special endpoint on the NodeJS server. One example would be
hosting the Admin API on a different domain than the console. Another example is fetching execution data from external storage such as S3. This is done to
minimize the extra configuration required for ingress to the Admin API
and data storage, as well as to simplify local development of the console without
the need to grant CORS access to
localhost.
The requests and responses are piped through the NodeJS server with minimal overhead. However, it is still recommended to host the Admin API and console on the same domain to prevent unnecessary load on the NodeJS server and extra latency on API requests due to the additional hop. | https://docs.flyte.org/en/latest/concepts/console.html | CC-MAIN-2022-21 | refinedweb | 688 | 54.02 |
Add Column to pandas DataFrame in Python (2 Examples)
In this tutorial, I’ll show how to append a new column to a pandas DataFrame in the Python programming language.
The tutorial consists of two examples for the addition of a new column to a pandas DataFrame. To be more precise, the tutorial will contain these contents:
Let’s start right away!
Example Data & Add-On Libraries
We first need to load the pandas library to Python, to be able to use the functions that are contained in the library.
import pandas as pd # Load pandas
The following pandas DataFrame is used as basement for this Python tutorial:
data = pd.DataFrame({"x1":range(15, 20), # Create pandas DataFrame "x2":["a", "b", "c", "d", "e"], "x3":range(5, 0, - 1)}) print(data) # Print pandas DataFrame
Have a look at the table that got returned after running the previous syntax. It shows that our example data has five rows and three columns called “x1”, “x2”, and “x3”.
Next, we have to create a list on Python that we can add as new column to our DataFrame:
new_col = ["new", "so_new", "very_new", "the_newest", "neeeew"] # Create list print(new_col) # Print list # ['new', 'so_new', 'very_new', 'the_newest', 'neeeew']
Our example list contains several different character strings. Note that the length of this list is equal to the number of rows of our DataFrame.
Example 1: Append New Variable to pandas DataFrame Using assign() Function
Example 1 illustrates how to join a new column to a pandas DataFrame using the assign function in Python.
Have a look at the Python syntax below:
data_new1 = data.assign(new_col = new_col) # Add new column print(data_new1) # Print new DataFrame
After running the previous Python code, the pandas DataFrame with one additional variable shown in Table 2 has been constructed.
Example 2: Append New Variable to pandas DataFrame Using Square Brackets
The following Python programming syntax demonstrates how to use square brackets to concatenate a new variable to a pandas DataFrame:
data_new2 = data.copy() # Create copy of original DataFrame data_new2["new_col"] = new_col # Add new column print(data_new2) # Print new DataFrame
After running the previous syntax, exactly the same DataFrame as in Example 1 has been created. However, this time we have used square brackets instead of the assign function.
Video, Further Resources & Summary
Do you want to learn more about the addition of new columns to a pandas DataFrame? Then I recommend having a look at the following video on Corey Schafer’s YouTube channel.
In the video, he illustrates how to add and remove rows and columns to a pandas DataFrame in a live session: posts on my website.
- Insert Column at Specific Position of pandas DataFrame in Python
- Add Row to pandas DataFrame in Python
- Check if Column Exists in pandas DataFrame in Python
- All Python Programming Examples
Summary: This post has illustrated how to merge a new variable to a pandas DataFrame in the Python programming language. If you have additional questions, tell me about it in the comments section. | https://statisticsglobe.com/add-column-to-pandas-dataframe-in-python | CC-MAIN-2021-31 | refinedweb | 500 | 63.93 |
Related
Question
How to automate deployments on DOKS with ArgoCD?
How To Setup Automated Deployments using ArgoCD on DigitalOcean Kubernetes
Introduction
Developing applications on Kubernetes has taken off over the last few years. Kubernetes has helped developers realize the potential of containerized application deployment paradigms. Though containerized development has changed the tools and ways people deploy applications, it has not replaced the need for streamlined integration and deployment. Having a proper deployment pipeline can be the difference between releasing that killer feature today and 4 weeks from now.
In this tutorial, we are going to set up a simple continuous deployment pipeline on DigitalOcean Kubernetes to enable automated deployments for your project..
- Github account
- Helm chart
Step 1 — Installing the argocd CLI
ArgoCD provides us with a UI but I find it much simpler and more convenient when writing code to make use of its command line interface (CLI). The instructions for installing it are simple and can be found here
For Linux you can perform the following in a bash shell:
This command will query the argo repository for the latest release version and set a local variable equal to that version number.
- VERSION=$(curl --silent "" | grep '"tag_name"' | sed -E 's/.*"([^"]+)".*/\1/')
This command will then download the version of the
argocd binary that we retrieved from the previous command and and save the binary as
/usr/local/bin/argocd.
- curl -sSL -o /usr/local/bin/argocd
Finally we need to ensure that we give execute permissions to the newly downloaded binary:
- chmod +x /usr/local/bin/argocd
We now can run argocd commands however we need to configure our client binary to talk to our ArgoCD service. We will configure that in the next step.
Step 2 — Installing ArgoCD in your Kubernetes Cluster
We will be using ArgoDC as our CICD tool. Luckily for us ArgoCD is very simple to install! You can see the official instructions here. But for simplicity I will provide them below:
Lets create the namespace for ArgoCD to live in:
- kubectl create namespace argocd
Then we can create all of the ArgoCD manifests in our namespace using the command:
- kubectl apply -n argocd -f
For simplicity I am going to expose this argo service locally in a separate terminal using the following command:
- kubectl -n argocd port-forward svc/argocd-server -n argocd 8080:443
This command takes the argoCD service port and proxies it to my local machine on port 8080. I can now access the service by simply querying.
Now we are going to authenticate our argocd commandline interface we installed earlier.
We can get the default password for the argocd server using the command here:
- kubectl get pods -n argocd -l app.kubernetes.io/name=argocd-server -o name | cut -d'/' -f 2
This should output what looks like the name of a pod and thats because it is. It will double as the initial password to authenticate as the
admin user. We now can authenticate using this command:
- argocd login localhost:8080 --insecure --username admin
You should see output similar to the following:
Output'admin' logged in successfully Context 'localhost:8080' updated
The
--insecure flag is used here because our service is not setup with SSL certificates to authenticate the server. This is outside the scope of this tutorial but is recommended for production installs.
You can get instructions on configuring ArgoCD with TLS in their documentation.
We now should have the basics of argoCD installed in our cluster and the service exposed at
localhost:8080. Though there’s not much we can really do with it yet until we have a application to deploy with it. In the next steps we are going to tell argocd about our application so that it can configure our deployments.
Step 3 — Creating the Application
ArgoCD can help us deploy our applications in a repeatable way. This can make for an automated and rather seamless deployment pipeline. ArgoCD is capable of working with both plain git repos as well as helm charts. In this tutorial we will be deploying a helm chart.
If you do not have a helm chart in a repository you can perform the following:
- Download an NGINX helm chart.
- Extract the files from the tar of your choice version of NGINX.
- Push all the files up to a git based repo so that your repository looks like the below structure:
Output> tree . ├── Chart.yaml ├── ci │ ├── daemonset-customconfig-values.yaml ... │ └── deployment-webhook-values.yaml ├── OWNERS ├── README.md ├── templates │ ├── admission-webhooks │ │ ├── job-patch │ │ │ ├── clusterrolebinding.yaml │ │ │ ... │ │ │ └── serviceaccount.yaml │ │ └── validating-webhook.yaml │ ├── clusterrolebinding.yaml │ ├── clusterrole.yaml ... │ ├── _helpers.tpl │ └── NOTES.txt └── values.yaml
Once you have that in your repository using
git push you will be ready to continue!
The first thing we need to do is tell ArgoCD about our application so it knows where the helm chart lives. We can accomplish this using the
argocd app create command like so:
** Note: ** Your
--repo value will be different.
- argocd app create helm-nginx --repo --path . --dest-namespace default --dest-server --helm-set-string 'app=helm-nginx' --self-heal --sync-policy auto
Lets break down what this is doing.
argocd app create Is telling the argo server that we would like to create and app for the ArgoCD server to track and manage.
helm-nginx is the arbitrary name I decided on for my application. This value could be any meaningful description you choose.
--repo is the git repository that my helm chart can be found in. If we want ArgoCD to be deploying our helm chart we have to tell ArgoCD where the chart can be found!
--path is the path within the repository where the helm chart lives. My helm chart is not nested in a directory but exists at the root of the repository so here I just provide the path as
..
--dest-namespace default is the Kubernetes namespace that I would like the application to be deployed into.
--dest-server is the url to the kuberentes cluster we are using. If you have deployed the ArgoCD server within a Kubernetes cluster you can simply use to specify the cluster ArgoCD is deployed into.
--helm-set-string is setting helm values on the Commandline if needed
--self-heal is allowing argocd to self heal or auto deploy itself if it is found to be out of sync.
--sync-policy setting this to auto will allow augocd to automatically sync the changes to the application.
After this command completes you should see output similar to the following:
Outputapplication 'helm-nginx' created
We now have our app successfully created within ArgoCD! Once ArgoCD knows about your application, it can then start to do some more advanced tasks with it. In the next step we are going to be syncing the application that will deploy our chart into our Kubernetes cluster.
Step 4 — Syncing the application
Next we need to sync the application in ArgoCD. When we sync the application, ArgoCD is going to be comparing the git repository values and object definitions to what is currently deployed in the cluster. If it finds a difference between the definitions in the repository and the currently deployed objects, it will modify the objects in the cluster to reflect the configuration of the repository. Because we have only added the application to ArgoCD, you will see that the application is not yet Sync’d or deployed. We simply told ArgoCD about the application but we havent told ArgoCD to do anything with it yet. This is where sync comes in.
We currently have none of our helm chart deployed after completing step 1. To initiate a sync we can perform the following
argocd command. This can take a few minutes to complete:
- argocd app sync helm-nginx
Alternatively, you could also achieve this using the ArgoCD web console. To do this simply you can expose the service locally. Using kubectl port-forward can be helpful for quickly exposing services via ports on your local machine:
- kubectl port-forward svc/argocd-server -n argocd 8080:443
Then you can access and login to your argoCD server by opening your browser and navigating to. This will be an insecure connection as we have not set up any certificates for the server. Any browser warning when accessing our server should be safe to ignore.
This should now bring your repository’s defined chart into your Kubernetes cluster. Though this is a very basic example this actually can be quite powerful for managing deployed applications and updating them. This methodology encourages the repository to be the source of truth and allows you to control and simplify your deployments by delegating that control to ArgoCD. However, it can be annoying to have to manually trigger deployments each time we make a change. In the next step we are going to configure a webhook to automatically tell Argo to about repository changes when we push code to the repository.
Step 5 – Configuring Git Webhooks
Too many developers are still using manual and troublesome deployment methods. There are so many variables that can affect deployment that it is no wonder some of the most dynamic and innovative companies have moved to some form of continuous deployment. Automating the deployment of your application can greatly increase the velocity in which you develop your application. Having a smooth and automated pipeline is crucial to timely and less error prone deployments. One way to implement a continuous deployment model is to automate deployments to trigger on a specific action. A good example action to trigger a deployment on would be a push to a git repository. This specifically would be helpful for a quickly developing git branch that will allow for quick test and QA feedback loops for developers. In this step we are going to configure automatic deployments by triggering ArgoCD’s Sync operation with git webhooks.
First navigate to you git provider. Under your repository’s settings page you should be able to find a section to configure webhooks for your repository. For your Payload URL specify where your ArgoCD server is accessible by your git provider.This URL could be or an IP such as.
To expose your service via a LB you can use:
- kubectl -n argocd patch svc argocd-server -p '{ "spec": { "type" : "LoadBalancer" }}'
The
Content-type should be set to
application/json.
You also have the options to configure SSL validation (or to disable it) for your ArgoCD instance if you specify
https:// in your URL.
Lastly you may want to use a shared secret to further secure your server. Setting a secret on a git webhook can help prevent against DDoS attacks if your Argo server is publicly avialable. To configure a webhooks secret enter an arbitrary secret value in your webhooks git provider. You then need to edit your Argo servers secret to let your server know what the value of the secret is. You can perform that using the steps outlined here.
Now that your webhooks is configured lets make a change and look into how this works!
Next we are going to trigger an automatic sync in ArgoCD by pushing a change to our repository. With the configured webhook our repository should notify ArgoCD that a change has occurred. We next need to enable automatic syncing to fully automate this process and allow argo to automatically rollout our changes.
Now that the sync policy is set we should be able to push a change. For example I am going to be changing my
values.yml file to modify my image’s tag from
latest to
1.16.
Now as long as a difference is detected by ArgoCD the sync process will occur. Go ahead and push a change to your helm chart and watch the automated magic!
Conclusion
In this article you created a helm chart that will automatically deploy your latest code changes automatically. You added webhooks to your git provider to tell ArgoCD about code changes, configured your app to an automated sync policy, and pushed a change to your repository to trigger a deployment.
This was a demonstration of the power of CICD and the time and reliability benefits of automating common deployment workflows. Now you can further tweak the configuration to fit your particular use cases. Be sure to poke around the ArgoCD Project docs for help and info on configuration options and other functionality. Also, check out the ArgoCD User Guide see all the great capabilities of ArgoCD!.
If you would like to do more with Kubernetes, head over to our Kubernetes Community page or explore our Managed Kubernetes service.
These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.× | https://www.digitalocean.com/community/questions/how-to-automate-deployments-on-doks-with-argocd | CC-MAIN-2020-40 | refinedweb | 2,135 | 53 |
Input, Selectables, Navigation, and Transitions
A free video tutorial from 3D BUZZ Programming and Digital Art training
4.2 instructor rating • 17 courses • 110,842 students
Lecture description.
Learn more from the full courseModern UI Development in Unity 4.6/5.0
This series goes over the core concepts of Unity's UI system and also shows the creation of an entire game using the UI.
13:30:32 of on-demand video • Updated May 2015
- Become familiar with Unity's UI system
- Create an entire game using the UI for all of its visual aspects.
- Apply all of what is learned in a real world scenario.
- Learn to think like a UI developer.
English [Auto] This video we're going to talk about user input. So in the last video we showed how we can pretty much make anything look like what we want it to look like at least we we talked about the base objects that we would manipulate in order to achieve a desired visual look. However we haven't yet talked about how we can accept input from the user. Now we're not going to get all crazy and put together a custom control or something like that but I do want to go over the built in controls there similarities and how to handle their events. So all of this is actually going to be pretty straightforward because all of the things that accept input all share the same base class called selectable. And if you know how to use one you're probably good on using the rest of them. So the way I'm going to organize this this video is I'm going to go over each one of the items each one of the input items first and then I'm going to talk about their shared attributes and how we can hook up to events. So let's just look at each one of the built in types know that the system is very extensive. Like previously I said that you could pretty much construct your own input types as well if you wanted to. That's a little bit beyond the scope of this video series however. But you guys should be able to see though how you can take these UI elements and actually combine them into more complex things like if you make a tab for example you could kapos that as a combination of toggle buttons and panels for example. But again I just want to show you guys just the basic stuff that the folks over at Unity decided to throw into the engine by default. So let's go and get that started. The first thing I'm going to do is go to my higher key and create a canvas and just like before I'm going to leave this in screen space overlay inside of my canvas which is huge. As always I'm going to create a panel. I am just going to make this look a little bit nicer by centering. I'm not going to. I don't care about the anchors at this point. OK. So I want to go ahead and instantiate each one of the controls going to be talking about today go over each one of their unique features and then go over what they share in common. So inside this panel I'm going to go to UI and I'm going to first create a button that I'm going to go into UI and I'm going to create a slider rather than going to go on panel. I'm going to create a I'm not going to create a scroll bar scroll bar is an interactive UI element that we're going to talk about that in a later video. I mean a creative toggle. However I'm also going to create two more toggles. And the reason why we'll be a parent later. And then in the panel I'm also going to create a input field so if I go ahead and hit play all of these things will behave the way that we expect them to. We can click on our buttons we can slider sliders we can toggle our toggles and we can input in our input so let's go ahead and talk about each one of these individually. First off the button now the button is composed of a transform because it's underneath the canvas canvas render because it's the visual element in the image. I wonder where we saw that before. And then a button. Now interestingly this button is actually largely by not specific to buttons. In fact intractable transition all of these colors color multiplier fédération and navigation all come from the base type selectable. Now a selectable is basically a component that can retrieve receive user input. So all of what we're looking at are selectable. So the brain itself isn't really that interesting because ultimately it's the simplest form of input control. And largely it its behavior comes from the selectable base class which all of these components share. So I'm not going to talk about it too much but I do want to point out again it is composed of an image that's important and a text so you'll notice that the image is going to be the same size as the transform in its entirety. The text is going to be set by default to fill and stretch this or this. But it's important to realize though that the text itself is really irrelevant. I could delete the text and now the button doesn't have text I can hit play and I can click on the button all I want it'll fire off its events. It'll function just as it should. So it's important to understand that that text is really just text that happens to come along for the ride. And it is there for decoration purposes only. So to read the text I can right click the button go down to you I select text. Now you'll notice it doesn't look quite right and that's because the default text isn't going to automatically go into stretch mode with the anchors but we can fix that really easily by going into the transform holding down alt and shift and clicking on the uniform stretch. Now you notice that the text isn't aligned the way we might want it to be. So that means we just go into the text component that we talked about in the last video and select center. And we've now deleted and replaced the text that was in the button. So remember just like what I said the last video everything is composed of images and text. And of course we can go ahead and change the text inside of it. Say this is a button. Again if I hit play the button will behave just as it did before OK. One other interesting thing you'll notice about Button is that we have this on click list but we're going to talk about that when we talk about events. Next let's move onto the slider. Very simple control. If I hit play we can slide it forwards and backwards. So what exactly is going on here. Well we can see that the slider is made up of the fill area to fill the slide area and the handle. So the fill area and the fill determine how much of that is filled. So for example go ahead and well I'm going to drag the game window off screen and I'm going to play around with that so you can see that what's going on here is that the fill area is actually getting smaller and smaller the fill itself is getting smaller. As you can see right there. Unfortunately I'm not getting any feedback right here. On the transform of the fill one we can see it's quite obviously moving and that's most likely due to a small bug in the way that the system is built. But as you see it will be getting bigger and smaller depending on how much we filled it. So then we have the handle slide area and the handle. So it's pretty straightforward stuff. These are just made up of images. Getting back to the slider itself really all the slider needs is a image first of all for the background that's just there for decoration purposes. Then you'll notice these are the same things that were in a button because all of these components are all these attributes were inherited from the selectable based type. Then you'll notice we give it a fill rect and a handle rect. So the fill recked is the fill in the handle rectors the handle. So that's how it knows which game object to increase the size of as we move it up and down. So you can really construct a slider by yourself if you really wanted to you could create a slider out of anything. And what's cool about Sliders is that you could do things like take this handle for instance just disable it. And now we have a helper. So it's really cool how we can kind of dissect these these intractable elements and make them behave in the way that we want anyway. So again just to repeat the slider component simply needs a reference to the Philbert Act and the handle recked and that's it. You can really think about these controls as just prefabs that are preconfigured for us. Next up we have our direction. We can go left to right right to left bottom to top and top to bottom. Now you'll notice that when I do a bottom to top and top to bottom it looks kind of messed up and that's because I don't have any height. But if I add height to it you'll notice the bottom to top and top to bottom. Now look like they should. Next up you'll notice the men valued max value is pretty straight forward. A slider allows you to select a value between them in value on a max value. So for example if we wanted to select between a hundred and a thousand. Notice that visually the slider didn't change at all. But if we look at this value right here it did so in reality the minimax value aren't going to change how the slider behaves or how it looks. But they will change what value it dumps out. Next up we have whole numbers pretty self-explanatory whole numbers just make it so we can't have fractional units. So for example if we had a value of five and a max value 15 you'll notice that the only acceptable values are whole numbers between 5 and 15. And you kind of see it snapping a little bit then finally we have a value which values the current well value of the slider and that's really the slider those. That's what makes us lighter. All that makes the sliders as a filler act and handler act and a couple of constraints on its value and that's it. Next up we have the event on you changed which allows us to have some code happen when the value of the slider changes. We'll look at that here shortly when we talk about events OK toggle buttons. I'm going to look at the first one in isolation and then the second two I'm going to put into a group now toggle button as you can see has the selectable as interactive transition has all of our stuff has our navigation that it has the toggle specific things. For example is on which is toggled by clicking then Tuggle transitions none are Faid which just makes it so the toggle checkbox inside of it. This guy right here this checkmark whether or not he slowly transitions or not that checkmark is determined by this graphic right here. So really all the toggle is is it's a control that when you click on it it'll toggle whether or not a graphic is being shown and that's it. So I don't even need this background or this checkmark or the background or this label at all if I didn't want it. I mean again there's nothing special about this particular hierarchy of objects. Again all this control is as it happens to be a particular hierarchy of objects that was created for us that we can modify in any way that we want. Which is really cool. So again we have our checkmark which is an image and we have a label which is a text. And of course we can change this to whatever you want if we do that we also should make sure that we have our size big enough to contain it. And of course we could even go ahead and if we really wanted to we could throw a. And this applies to every single control we can throw a canvas render and an image directly on the control as well if we want to set up a source image of like. I think background looks kind of nice. So again we can configure. Once we understand how recked transforms images and text work we can make these look however we want. So the only thing that makes a toggle a toggle is the fact it has a graphic somewhere in its hierarchy. OK. Moving on the toggles we now have groups so you might be familiar if you're familiar with working with goolies. Like maybe for example TNL or Windows Forms or XML you might be familiar with the differentiation between a checkbox and a radio. But if you're not a checkbox is like what we see here with our toggles. We can just toggle them on and off as much as we want but a radio button however always exists in a group where only one item can be selected at a time. We can accomplish the same thing by adding a toggle group component to any game object we want and then adding our toggle. There are individual toggle items to that toggle group so let's go ahead and take a look at doing that. I'm going to go ahead and exit play mode and then so that we can modify the scene without it without the changes being lost. And then actually going to go ahead and create a panel. So I'm going to reichlich this panel go to you I know I'm going to create another panel. And this panel I'm going to do the same thing I'm going go ahead and set it to center and then I'm going to resize it a little bit. And the reason I'm doing this is just to give you guys some visual distinction for toggles that I'm going to take these two toggles right here and I'm going to Child them to panel. So now we have a nice little panel that we can put together a toggle group and so zooming in here. Like I said the way that we make turn these checkboxes into radio buttons is really just a matter of creating a toggle group component summer and matching it to these tutorials. Now what I want to really stress the fact that the toggle group does not need to be in the canvas it doesn't need to be anywhere in particular it just needs to exist. However I highly recommend when creating radio buttons by using toggles that you add the toggle group component to a parent of the toggles that you want to group that could be an empty game object if you want. Or it could be a panel or whatever you want. So I want to come up here to a panel and I'm going to add a component and I'm going to say toggle group. Now you noticed that Tuggle group does not have any public properties on it. So there's nothing that we can play around with in the group itself. And in fact it doesn't really do anything until we plug in some toggles into it. So let's go ahead and do that. I'm going to click on the toggle scroll down find its group parameter click and drag panel on to that then I'm going to do the same thing with the other toggle. I'm going to click on the other toggle click and drag panel onto the group. Now both of these toggles are associated with the toggle group component on its parent panel. So to see the behavior of that let's go ahead and hit play and right off the bat we notice that the toggle group parent or the toggle group decided first of all that only one toggle can be selected that time anyway and it de-selected the second one. Now we see that as we click on the other toggle only one is selected at that time this toggles uneffected. So let's say we wanted to add another toggle to this group. Well I can go ahead and move this and put down a little bit. Increase the size of the parent panel maybe move these guys up a little bit. I'm simply going to duplicate the Stargell now by duplicating the toggle. It's now still reference this group because I duplicated the game object it's going to contain the same parameters because it contains the same parameters. It's now tied to that same group. Meaning if I come back here and hit play you'll notice that that toggle now appears in the group. Now I want to stress this one more time. The actual higher key of these objects are relevant meaning I can take this toggle and move it outside of the panel and move it all the way over here into the canvas and hit play as long as that toggle still references the same toggle group. Notice how it still behaves as a radio button instead of a checkbox. Now when doing stuff like this you may want to actually follow the typical design paradigms and instead of using a checkbox use a radio button instead. Now doing that would be very trivial because we would simply select the checkmark and change its source image. In this case I'm going to change the source image to gooey sprite then I'm going to do the same on the other toggles as well but open up the other toggle click on each checkmark. Now you notice that the check mark is currently invisible. And that again is due to the toggle group turning off this checkbox because it turned off the checkbox the alpha of the checkmark was set to none so let's go ahead and change this to a gooey sprite. Now let's do this on the last toggle. I'm going to go check mark change this to. Now when I hit play it looks a little bit more like radio buttons. I mean not great but obviously you guys can see that if you went in and wrote your put together your own sprites you can make it look however you want. And again I'm just I really really really want to stress that these these components these game objects these these input elements are really just combinations of the primitive things that we have been learning about throughout this entire series. They're just really transforms in images and text. I mean I can come up here as long as this toggle still has this checkmark game object. I can do whatever I want to it. I can do this checkmark game object above here I can delete the background and the label if I wanted to and then I can hit play and notice how it still works. I could even take the check mark and I can move it not even be a parent in the system at all. I don't think this will work as I think it will have some issues recasting which we do. So what I can do with this toggle is I can simply throw in an image to a and then hit play. So see this checkmark checkmark flew all the way over here but it still works. And again understanding how these elements are created is incredibly important because once you understand that you can create very very complex you wiser self. OK so that's about toggle buttons for now. We'll be coming back to them shortly. Let's talk about input fields input fields. Very straightforward. We have a starting value so I can say test and we see it starts with test. So super exciting. That's good work. That so that's a starting value. We have an input type we have auto correct and password password will do exactly what you expect it'll just be password. Now it seems to be a bug where after we click off the panel or the password it shows the password I don't think that's exactly what it is that it should be doing. But it's bad after all. Oh yeah. Character limit. Pretty straightforward. We can restrict how many characters they can have. We have active text colors selection text color just gives us the different colors for text that we've typed in or the selection that we've had. We have multi line which we can enable or disable and that's actually it. As far as that input field everything else is inherited from selectable intractable transition and navigation all come from the selectable base type. So again the only thing that makes a text component a text component or an input field component is that we have the text component the starting value the input type the character limit text color and multiline. Now the text component inside of the edit field is going to just be what the what the label is like. For example we could say user name for this duplicate this to create another one click in here and change it to password. Now you'll notice that these input fields have these text components and what they're going to do is when we hit play you'll notice that those those labels change. Then finally you'll notice that we're not going to have any events with our text fields. OK so those are going to be our major interactive components and they really will work for a variety of scenarios both in interaction and non interaction because you can certainly tell a slider for example to not accept input and then simply use the slider as a health bar. Like I had mentioned earlier so I talk to a whole lot about the individual properties of these different techs these different controls but in reality they're much more similar than you might expect because remember that base class that's selectable base class. Let's start off with a button. And the reason I want to start off the button is the button literally has nothing else interesting about it except for it's on click handler. And what it inherited from selectable and once you understand how to work with collectibles it'll just be the same on every single one of them. Now the first thing you'll notice about collectibles is they had this inner actable checkbox the entire simple checkbox determines if that button is or if this selectable is enabled or not. Remember this is also controlled by canvass groups. Meaning if I were to come up here to my panel here add component and type in canvass group I can uncheck intractable and will override it for every one of my controls so we have intractable again turning intractable off. If I hit play I can no longer press the button. Now that's really important for things for for while guiding people through user interfaces but it's also really important like Ed mentioned earlier for controls that are not meant to be interacted with maybe controls that you're just using the behavior of a control for display purposes but not necessarily expecting the user to actually interact with it. Next up we have our transition now a transition is a big one. Basically the transition allows us to respond to events transitions replace the old Goose-Skin on hover and on active and all that stuff. Now it's all replaced by transition. Transition is going to first of all have a transition type. The simplest of a transition type is none. So when I hit none notice that all of those items disappear and I can no longer modify the tent color. Now when I hit play. Notice how the button doesn't respond to my input. At least it doesn't appear to. Now of course if we bound to the on click event handler we would know the button was receiving that event but we don't get any visual indication if the mouse is hovering it or not. So none that's going to be the simplest transition. Then we have color tint now color tent is going to require a target graphic. In this case the target graphic is the image component that is on the button object itself. Note while I turn on and off that image component look what happens to the button. So that image actually comes from the button object itself. And in this case a simple gooey Sprite I could change it to a background or an input field background or a pop up highlight or whatever I want. Or a custom button as well. And it'll change appropriately. It's important to understand though as we're going to see shortly that the target graphic on your transition does not need to be on the same game object as the button or as the selectable component itself. OK so the color tint effectively just tends to color have a particular image when we something happens and we just see that by going to move my game view up the side again and I'm going to have my button and we're going to notice that unfortunately it's not going to show up in the editor lots to about what we should have seen however is the tent of this image changing as I hovered over the button and clicked it. And it's going to change according to these values. So for example I can set the normal color the highlight color to blue. This can be a really ugly button. Press color to retina melting purple and let's throw in some green for disabled. Now let's play and notice how the color tint changes you can even set all the values for example if in the normal color we want it to be not very very transparent. We can do that and notice how it gets less transparent as we transition to the other colors. Then we have color multiplier color multiplier effects. The strength of how these colors affect the button see this. Yeah this is melting my retina right now but if we tone it down a little bit you'll notice it's much much more muted. Then we have the fédération fédération should be pretty straightforward. It's a five. It's going to take five seconds to fade into a particular color. If we select the Federation 2.5 it's going to take half a second to fade into a particular color. If we set to its default of point one you'll notice it's very instant. So that's our Cullerton transition. Next up we have our sprite swap sprite swap transition now or siteswap transition is exactly what it sounds like. It's basically going to change the Spryte of an image when something happens again it operates under a target graphic. And again that target graphic is the image component that's underneath this but what we can come in here and we can just change what sprites appear when certain things happen. So in this case I just looked at a bunch of random built sprites. Now when I hit play. Notice how those sprites change hurt so that's all you know well and good. Honestly at this point you're mostly going to be working with non color tends I find Spryte swap to be a little jarring for some user interfaces. It might be appropriate but it's kind of old school their transition you should really spend some time getting acquainted with however is the most powerful one and the most powerful one is the animation. The animation transition you'll notice does nothing by default as you see. So you might assume that it's broken but in actual fact what it's doing is it's attaching to an animation controller. And sending triggers into it. When something changes so let's go ahead and put this together. I'm not going to hit auto generate animation. The reason I'm not going to do that is because I want to show you guys how that process is handled manually. Because it's really important to understand the animation transition so that we can make the most use of it. So what I'm going to do is in my project window I'm just like create and I'm going to create an animation controller and I'm going to call this button animation. This is then I'm going to click on my button. I'm going to say add component and I'm going to add an animation and animator's sorry. And then I'm going to click and drag button animations on the controller. Notice how the second we added the button animation controller to our animator component that button disappeared to automatically generator animation controller. And that's because the all the generate all the animation control does is does what we just did plus it sets up some triggers in our controller for us. So basically what's going to happen is the normal trigger will be fired when a normal thing happens to highlight a trigger will happen will highlighted thing happens. Pressed pressed and disabled disabled and all those triggers will allow me to go in to the animation and play around with the visual aspect of anything to do with the button. Like I mean anything I can change the color I can change the scale I could bring in an element I can do fading. I can do anything. So let's take a look at all that flexibility that we got. The first thing I want to do is notice that my animator. There's really nothing going on here. Well the first thing I do is I'm going to create a clip on my button for a normal state. So I'm going to create great clip create new clip. I want to call this button normal the normal state is going to be empty. It's not going to have anything in it because I want the normal state to look like exactly what we see in the inspector. Next up I'm going to create our are highlighted pressed and disabled States. I'm not going to fill them in with any animation yet. We'll do that in a momentarily. So next up I'm going to say button highlighted which is going to be empty then I'm going to say button disabled which is going to be empty. The last can be pressed OK. So that's all well and good. If we go ahead and fire up the game and move over to our animator we notice that button normally is sitting there and playing and so that's well plain because it's their default state. So how do we perform the actual state transition. Well basically all we need to do is we need to create triggers for all four of these bits. So going to create new parameter I'm going to create a new trigger and I'm going to say normal then I'm going to create a new trigger and I'm going to say highlight it that I'm going create a new trigger and say preste then I get a brand new trigger and say disabled. So now we have all four of our triggers added in as parameters for animation controller which we can change. For example I could say the normal trip triggers one to three but of course if I did that I would have to make sure I updated the parameter inside of our animator controller but we have we have the parameters now but we don't have any transitions. Meaning how do we go from one state to another. Well it's actually pretty straightforward to do we simply right click any state say make transition click on the state we want to go to click on the transition and select a trigger. In this case I'm going to select the normal trigger. Now I'm going to do the same thing for highlight it make transition highlight it make transition disabled make transition. So now if I'm going to move my game view off to the side here and I'm going to keep my animator open and I want you to see what happens as I interact with this button when I hover over it. Notice how we're in the highlighted state. When I click we're in the press state when I unclick we're in the highlighted state and when I mouseover we're now in the normal state of course this isn't going to actually do anything yet because our clips are actually empty. So let's go ahead and see what we can do about that. I want to jump into the scene view. I'm going to make sure my button is selected. I'm going to open up my highlighted. I'm going to click on the first key frame and make sure record mode is open and I'm going to set my scale to one point one point five in the x axis. Now when I hit play there was the button gets bigger ok for the pressed. I want to do something interesting when we press the button. I want it to first of all I want to start it off in the highlighted states so I'm going to copy or actually I'm just going to go into the press state and make sure that the X is 1.5. So we had a smooth transition from the highlighted to pressed and then I'm going to I don't know. Rotate it a little bit and then I don't know wiggle it. Why not. Make this a little bit faster. And then at the end of this we could have the capacity of the button going down to claw and making it read OK. So that's what we want to have happen when we pressed. I'm not a designer I'm not an animator. I know that looks ugly but it's the process that counts. So now we hit play and highlight Eric hover it expanse which is good but if we click you'll notice it's going to sit here and just wiggle constantly. I don't want it to constantly wiggle. I want it to just do that. Play that clip once doing that's actually very straightforward. I simply click on the button pressed clip in my project view and I just say loop times now when I hit play and I hover I still get that really nice expand effect. But when I click it only does that once. OK. So that's really all there is with the animation so you can animate anything anything that's a child a button you can go ahead and animate you can animate the text you could add an element you can remove elements change the opacity make it fly around the screen whatever it is that you want. You can do with the animation transition and that's what makes the animation transition so powerful. Now remember there is a very easy way to automatically create a animation transition that can go ahead and show you guys how to do that now. Using the slider as an example because you'll notice the slider also has all of these values that we saw before from the button including ball and transition. But an important distinction is if we click on the target graphic of our slider we'll notice that the target graphic is actually a child component not the component itself. So with the button the target graphic would be the button image itself with a slider the target graphic is the handle anyway. A really easy way to set up an animation controller is simply to set the transition to animation and then say auto generate animation and then I can call this slider animation. Now if we click on the slider we see it already created all of these for us. Now one interesting thing about the slider though is it's you're not going to see all those individual clips. The way that the auto generate slider animation works is it uses some sort of assett API that makes it so the individual clips won't be visible. If I'm not mistaken they're supposed to expand here. You're supposed to be able to expand slider animations and see the individual clips. But again it might have to do with a bug here. But the point is is that all the clips get created just like what we did manually moments ago. But hopefully the experience of seeing it done manually makes more sense why it's set up in this way. Anyway so now that we have it set to an animation transition we can come in here we can say highlighted go into record mode. Let's set the handle to read hit play now when we're highlighted Of course when we press it switches it reverts back. So for example we can have it be highlighted and read it with a little bit faint color and then we can go to preste and make it red as well but a little bit more opaque. And now we have a nice little red transition of course that's not the only thing we can modify with the animation. We can also come in here and say when we have when we hover over it we want the background to turn this ugly teal ish kind color. Whoops I meant to do that as a right to do that as a highlighted or we could really annoy people and make it legal whatever it is that we want to do we can do it with the animation. I just really want to drive that point home. So that's really about it as far as transitions go. There's nothing stopping you from doing your own transitions. Maybe you want to hook into the invent system and send off your own sugars into the animation controller. You're certainly welcome to do that as well. Maybe give you some more flexibility on things. But that's that's all there is really to say about transitions. Next up we have navigation so navigation and Mark has been a whole lot of time talking about it. Basically it boils down to how do we navigate from one UI element to another. I can show you an example of that by hitting play. Notice how. Right now I'm moving my Or I'm hitting the up and down arrows on my keyboard keyboard and left and right and I'm hitting space or inner or whatever and I'm able to select different controls. Well the order in which the elements appear in the navigation list is controlled by the navigation right here so we can visualize that by hitting the visualized button and seeing that when we hit up and down we get up to the different controls. But things can get a little trickier than that because I can move this panel over here come back here and now I'm visualizing the navigation and things got a little bit more complicated. But the automatic lay out the engine determined it for me which is really nice of it. Basically the way to read this diagram is we can see that when we're on the button and we sit down we go to this control when we're on this control and we get up we get this control. When we hit right we can get this control and mega-hit left at that control and so on and so on. There's a couple other ways we can do navigation. We can do it horizontally. We can do it vertically we can do it automatically and we can do it explicitly and explicitly will require that I fill in each one of these four items with another selectable player. There's not a whole lot to say about navigation. The automatic system will work 99 percent of the time I'm sure. If it doesn't you can override it using explicit navigation. And the good news is you only have to overwrite it for things that you know need to be overridden. You can use automatic navigation for most everything and then use explicit navigation for one or two controls that you want to modify the behavior of and at the end of the day you can always just visualize and make sure you've got it right before having to come in and play around with it and the game itself. All right. So the last thing I wanted to talk about are events and we already talked about them to an extent. It doesn't I don't really need to go into too much more detail on them. I just wanted to point out a couple other important things. Just to recap what we talked about before. Events such as the On Click for a button or the value changed for a toggle or the on value changed for a slider what they allow us to do is they allow us to register a function on a particular component that's on a particular object to be invoked with the particular parameter when that event is fired. That's really it. So we can create events out of any component that has a method on it that follows a particular criteria. For example it needs to be public. It needs to return void and it cannot zero its one parameters the only parameters you can specify are primitive types and game objects are and objects. So again we saw that in the first video there's not a whole lot more to it. The only thing I really want to add on to a discussion about events right now is the fact that we can actually do a couple interesting things. For example if I wanted to let's go ahead and create a critic C-Sharp script and I'm going to name this on mouse over. Handler because I want to show you guys how you can actually handle an event through code or just code without having to mess around with the inspector. I find this to be an appropriate way to handle certain events especially events that are in kind of an integrated pre-fab that you might create for a custom control. It's really sort of like it's really straightforward. I'm just showing a guy is really simply how we can really quickly just get this going. So let's say you wanted to create a mano behavior and let's say I wanted this behavior to be attached to a button and let's say I want it to print out to the console every time someone hovered over the button. Well I can just inherit or implement a particular interface. The interface is going to be unity engine Daut UI and Bersani events event system when you have tools automatically tell you which namespace certain classes are and you totally forget that name spaces they're in. But the reason I want to bring up the namespace though is because we could implement any one of these events and we'll be notified of that event so we can implement. I begin drag Hendler I cancel ID select I drag I drop I move I POINAR click like for example if we wanted to do I plane turn into a handler we would implement this interface which would require that we implement the on point or interim method right there. And of course that method is going to need to receive a pointer or Event Data parameter. Now I can simply say debug don't log you are over me. And that's it. So just by implementing this interface and implementing this method I can now attach this component to a button and this behavior will happen. Now I can show you guys an example of that by coming into unity selecting the button going down to add component and typing in on mouse over Hendler hitting enter. Now when I hit play you'll see that when the mouse cursor enters the button we get that debug message there's one more way to handle events like these because you see there's that you'd think OK there's a big limitation right here I can only add handlers to on click and if I want to handle mouse movement for example I need to go and create them a behavior not actually true. There is an additional component you can attach to also collectibles that allow you to handle more events than just the ones they decide to expose. So what I can do is I can come up here to add component and I can type an event trigger the event trigger component allows me to arbitrarily add more event handlers for any of the defaults supported events in a selectable. So I can simply hit add new and I can say let's do let's do I don't know pointier exit and then I can add and I don't know it doesn't it really doesn't matter what I'm doing here. I can add again. Actually let me go ahead make this example little bit more better. I mean not another method public avoid print something to my on mouseover handler that just logs out some parameter. This way you can actually show you guys me tying up into an actual event. So now on this event trigger I can select the component I want which is the on mouseover handler and then I can select print something and I can pass in a parameter on mouse over. I can add a new trigger for how about a pointer or click and then say point or click and then I could add a new one like pointer down and say pointer down for example so I can get as many of these event triggers as I want from within the inspector and I can target any method that can be targeted through an event in the entire scene. If I wanted to and then pass in those parameters. So now I can hit play and you'll notice that when I get over it says POINAR down in POINAR click and it says on mouseover. So you see these events are indeed getting fired in the way that they should be. All righty. Well I think that just about wraps up the concept of selectable is again selectable is just the base type that gives us a variety of function bits of functionality and unity was so kind to have provided a handful of selectable components out of the box such as buttons and sliders and toggles and fields. So I hope that you guys enjoyed learning about these. Again we have buttons sliders toggles toggle groups and fields. I think that just about wraps up this video and we'll see you guys in the next one. | https://www.udemy.com/tutorial/modern-ui-development-in-unity-46-or-50/input-selectables-navigation-and-transitions/ | CC-MAIN-2020-24 | refinedweb | 8,279 | 68.1 |
Eclipse Debugging. This article describes how to debug a Java application in Eclipse. This article is based on Eclipse 4.6 (Eclipse Neon).
1. Overview
1.1. What is debugging?
Debugging allows you to run a program interactively while watching the source code and the variables during the execution.
A breakpoint in the source code specifies where the execution of the program should stop during debugging. Once the program is stopped you can investigate variables, change their content, etc.
To stop the execution, if a field is read or modified, you can specify watchpoints.
1.2. Debugging support in Eclipse
Eclipse allows you to start a Java program in Debug mode.
Eclipse provides a Debug perspective which gives you a pre-configured set of views. Eclipse allows you to control the execution flow via debug commands.
1.3. Setting Breakpoints
To define a breakpoint in your source code, right-click in the left margin in the Java editor and select Toggle Breakpoint. Alternatively you can double-click on this position.
For example in the following screenshot we set a breakpoint on
the
line
Counter counter = new Counter();.
1.4. Starting the Debugger
To debug your application, select a Java file with a main method. Right-click on it and select.
If you have not defined any breakpoints, program as normally. To debug the program you need to define breakpoints. Eclipse asks you if you want to switch to the Debug perspective once a stop point is reached. Answer Yes in the corresponding dialog. Afterwards Eclipse opens this perspective.
1.5. Controlling the program execution
Eclipse provides buttons in the toolbar for controlling the execution of the program you are debugging. Typically, it is easier to use the corresponding keys to control this execution.
You can use allow use shortcut key to step through your coding. The meaning of these keys is explained in the following table.
The following picture displays the buttons and their related keyboard shortcuts.
The call stack shows the parts of the program which are currently executed and how they relate to each other. The current stack is displayed in the Debug view.
1.6. Breakpoints view and deactivating breakpoints
The Breakpoints view allows you to delete and deactivate breakpoints and watchpoints. You can also modify their properties.
To deactivate a breakpoint, remove the corresponding checkbox in the Breakpoints view. To delete it you can use the corresponding buttons in the view toolbar. These options are depicted in the following screenshot.
If you want to disable all breakpoints at the same time, you can press the Skip all breakpoints button. If you press it again, your breakpoints are reactivated. This button is highlighted in the following screenshot.
1.7. Evaluating variables in the debugger
The Variables view displays fields and local variables from the current executing stack. Please note you need to run the debugger to see the variables in this view.
Use the drop-down menu to display static variables.
Via the drop-down menu of the Variables view you can customize the displayed columns.
For example, you can show the actual type of each variable declaration. For this select.
1.8. Changing variable assignments in the debugger
The Variables view allows you to change the values assigned to your variable at runtime. This is depicted in the following screenshot.
1.9. Controlling the display of the variables with Detail Formatter
By default the Variables view uses the
toString() method to determine how to display the variable.
You can define a Detail Formatter in which you can use Java code to define how a variable is displayed.
For example, the
toString() method in the
Counter class may show meaningless information, e.g.
com.vogella.combug.first.Counter@587c94.
To make this output more readable you can right-click on the corresponding variable and select the New Detail Formater… entry from the context menu.
Afterwards you can use a method of this class to determine the output.
In this example the
getResult() method of this class is used.
This setup is depicted in the following screenshot.
2. Advanced Debugging
The following section shows more options you have for debugging.
2.1. Breakpoint properties
After setting a breakpoint you can select the properties of the breakpoint, via. Via the breakpoint properties you can define a condition that restricts the activation of this breakpoint.
You can for example specify that a breakpoint should only become active after it has reached 12 or more times via the Hit Count property.
You can also create a conditional expression. The execution of the program only stops at the breakpoint, if the condition evaluates to true. This mechanism can also be used for additional logging, as the code that specifies the condition is executed every time the program execution reaches that point.
The following screenshot depicts this setting.
2.2. Watchpoint
A watchpoint is a breakpoint set on a field. The debugger will stop whenever that field is read or changed.
You can set a watchpoint by double-clicking on the left margin, next to the field declaration. In the properties of a watchpoint you can configure if the execution should stop during read access (Field Access) or during write access (Field Modification) or both.
2.3. Exception breakpoints
You can set breakpoints for thrown exceptions. To define an exception breakpoint click on the Add Java Exception Breakpoint button icon in the Breakpoints view toolbar.
You can configure, if the debugger should stop at caught or uncaught exceptions.
2.4. Method breakpoint
A method breakpoint is defined by double-clicking in the left margin of the editor next to the method header.
You can configure if you want to stop the program before entering or after leaving the method.
2.5. Breakpoints for loading classes
A class load breakpoint stops when the class is loaded.
To set a class load breakpoint, right-click on a class in the Outline view and choose the Toggle Class Load Breakpoint option.
Alternative you can double-click in the left border of the Java editor beside the class definition.
2.6. Step Filter
You can define that certain packages should be skipped in debugging. This is for example useful if you use a framework for testing but don’t want to step into the test framework classes. These packages can be configured via themenu path.
2.7. Hit Count
For every breakpoint you can specify a hit count in its properties. The application is stopped once the breakpoint has been reached the number of times defined in the hit count.
2.8. Remote debugging
Eclipse allows you to debug applications which runs on another Java virtual machine or even on another machine.
To enable remote debugging you need to start your Java application with certain flags, as demonstrated in the following code example.
java -Xdebug -Xnoagent \ -Djava.compiler=NONE \ -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5005
In you Eclipse IDE you can enter the hostname and port to connect for debugging via themenu.
Here you can create a new debug configuration of the Remote Java Application type. This configuration allows you to enter the hostname and port for the connection as depicted in the following screenshot.
NOTE:Remote debugging requires that you have the source code of the application which is debugged available in your Eclipse IDE.
2.9. Drop to frame
Eclipse allows you to select any level (frame) in the call stack during debugging and set the JVM to restart from that point.
This allows you to rerun a part of your program. Be aware that variables which have been modified by code that already run will remain modified.
To use this feature, select a level in your stack and press the Drop to Frame button in the toolbar of the Debug view.
The following screenshot depicts such a reset. If you restart your
for
loop, the field
result
is not set to its initial value and therefore the loop is not
executed as without resetting the execution to a previous point.
3. Exercise: Create Project for debugging
3.1. Create Project
To practice debugging create a new Java project called
de.vogella.combug.first. Also create
the package
de.vogella.combug.first
and create
the following classes.
package de.vogella.combug.first; public class Counter { private int result = 0; public int getResult() { return result; } public void count() { for (int i = 0; i < 100; i++) { result += i + 1; } } }
package de.vogella.combug.first; public class Main { /** * @param args */ public static void main(String[] args) { Counter counter = new Counter(); counter.count(); System.out.println("We have counted " + counter.getResult()); } }
3.2. Debugging
Set a breakpoint in the
Counter
class. Debug your program and follow the execution of the
count
method.
Define a
Detailed Formatter
for your
Counter
which uses the
getResult
method. Debug your program again and verify that your new formatter
is used.
Delete your breakpoint and add a breakpoint for class loading. Debug your program again and verify that the debugger stops when your class is loaded.
4. Links and Literature | https://www.vogella.com/tutorials/EclipseDebugging/article.html | CC-MAIN-2021-21 | refinedweb | 1,509 | 57.27 |
The format of the configuration file resembles the traditional INI file format with sections and options but with a few additional extensions.
Both forward slashes and backslashes are supported. Backslashes are unconditionally copied, as they do not escape characters.
The configuration file can contain comment lines. Comment lines
start with a hash (
#) or semicolon
(
;) and continue to the end of the line.
Trailing comments are not supported.
Each configuration file consists of a list of configuration sections where each section contains a sequence of configuration options. Each configuration option has a name and a value. For example:
[section name] option = value option = value option = value [section name:optional section key] option = value option = value option = value
A configuration file section header starts with an opening
bracket (
[) and ends with a closing bracket
(
]). There can be leading and trailing space
characters on the line, which are ignored, but no space inside
the section brackets.
The section header inside the brackets consists of a
section name and an optional
section key that is separated from the
section header with a colon (
:). The
combination of section name and section key is unique for a
configuration.
The section names and section keys consist of a sequence of one
or more letters, digits, or underscores (
_).
No other characters are allowed in the section name or section
key.
A section is similar to a namespace. For example, the
user option's meaning depends on its
associated section. A user in the
[DEFAULT] section refers to the system user
that MySQL Router is run as, which is also controlled by the
--user
command line option. Unrelated to that is defining
user in the
[metadata_cache] section, which refers to
the MySQL user that accesses a MySQL server's metadata.
The special section name
DEFAULT (any case)
is used for default values for options. Options not found in a
section are looked up in the default section. The default
section does not accept a section key.
After a section's start header, there can be a sequence of zero or more option lines where each option line is of the form:
name = value
Any leading or trailing blank characters on the option name or
option value are removed before being handled. Option names are
case-insensitive. Trailing comments are not supported, so in
this example the option
mode is given the
value "read-only # Read only mode" and will therefore generate
an error when starting the router.
[routing:round-robin] # Trailing comments are not supported so the following is incorrect mode = read-only # Read only mode
Option values support (variable
interpolation) using an option name given within
braces
{ and
}.
Interpolation is done on retrieval of the option value and not
when it is read from the configuration file. If a variable is
not defined then no substitutions are done and the option value
is read literally.
Consider this sample configuration file:
[DEFAULT] prefix = /usr/ [sample] bin = {prefix}bin/{name} lib = {prefix}lib/{name} name = magic directory = C:\foo\bar\{3a339172-6898-11e6-8540-9f7b235afb23}
Here the value of
bin is "/usr/bin/magic",
the value of
lib is "/usr/lib/magic", and the
value of
directory is
"C:\foo\bar\{3a339172-6898-11e6-8540-9f7b235afb23}" because a
variable named "{3a339172-6898-11e6-8540-9f7b235afb23}" is not
defined. | https://dev.mysql.com/doc/mysql-router/2.1/en/mysql-router-configuration-file-syntax.html | CC-MAIN-2017-51 | refinedweb | 549 | 52.8 |
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
#include "llvm/CodeGen/RegisterBankInfo.h"
#include <cassert>
#include <cstdint>
#include <memory>
Go to the source code of this file.
This file describes the interface of the MachineFunctionPass responsible for assigning the generic virtual registers to register bank.
By default, the reg bank selector relies on local decisions to assign the register bank. In other words, it looks at one instruction at a time to decide where the operand of that instruction should live.
At higher optimization level, we could imagine that the reg bank selector would use more global analysis and do crazier thing like duplicating instructions and so on. This is future work.
For now, the pass uses a greedy algorithm to decide where the operand of an instruction should live. It asks the target which banks may be used for each operand of the instruction and what is the cost. Then, it chooses the solution which minimize the cost of the instruction plus the cost of any move that may be needed to the values into the right register bank. In other words, the cost for an instruction on a register bank RegBank is: Cost of I on RegBank plus the sum of the cost for bringing the input operands from their current register bank to RegBank. Thus, the following formula: cost(I, RegBank) = cost(I.Opcode, RegBank) + sum(for each arg in I.arguments: costCrossCopy(arg.RegBank, RegBank))
E.g., Let say we are assigning the register bank for the instruction defining v2. v0(A_REGBANK) = ... v1(A_REGBANK) = ... v2 = G_ADD i32 v0, v1 <– MI
The target may say it can generate G_ADD i32 on register bank A and B with a cost of respectively 5 and 1. Then, let say the cost of a cross register bank copies from A to B is 1. The reg bank selector would compare the following two costs: cost(MI, A_REGBANK) = cost(G_ADD, A_REGBANK) + cost(v0.RegBank, A_REGBANK) + cost(v1.RegBank, A_REGBANK) = 5 + cost(A_REGBANK, A_REGBANK) + cost(A_REGBANK, A_REGBANK) = 5 + 0 + 0 = 5 cost(MI, B_REGBANK) = cost(G_ADD, B_REGBANK) + cost(v0.RegBank, B_REGBANK) + cost(v1.RegBank, B_REGBANK) = 1 + cost(A_REGBANK, B_REGBANK) + cost(A_REGBANK, B_REGBANK) = 1 + 1 + 1 = 3 Therefore, in this specific example, the reg bank selector would choose bank B for MI. v0(A_REGBANK) = ... v1(A_REGBANK) = ... tmp0(B_REGBANK) = COPY v0 tmp1(B_REGBANK) = COPY v1 v2(B_REGBANK) = G_ADD i32 tmp0, tmp1
Definition in file RegBankSelect.h. | https://www.llvm.org/doxygen/RegBankSelect_8h.html | CC-MAIN-2022-27 | refinedweb | 420 | 57.57 |
I recently added two more nodes to the cluster and getting following warning in logs
source node bb987ea7a0a0142 not found in migration rx state
following is config
# This stanza must come first. service { user root group root paxos-single-replica-limit 1 # Number of nodes where the replica count is automatically reduced to 1. pidfile /var/run/aerospike/asd.pid service-threads 16 transaction-queues 16 transaction-threads-per-queue 8 transaction-max-ms 10000 transaction-pending-limit 500 address 10.147.223.143 # IP of the NIC on which this node is listening port 3002 # IP address for seed node in the cluster mesh-seed-address-port 10.59.30.16 3002 mesh-seed-address-port 10.81.51.139 3002 mesh-seed-address-port 10.122.234.135 3002 mesh-seed-address-port 10.103.249.246 3002 mesh-seed-address-port 10.147.223.143 3002 interval 150 timeout 10 } fabric { port 3001 } info { port 3003 } } namespace bidder { replication-factor 2 memory-size 13G default-ttl 90D # use 0 to never expire/evict. ldt-enabled true storage-engine device { device /dev/disk/by-id/google-local-ssd-0 # raw device. Maximum size is 2 TiB scheduler-mode noop write-block-size 1M # adjust block size to make it efficient for SSDs. # See disable-odirect true } } | https://discuss.aerospike.com/t/source-node-bb987ea7a0a0142-not-found-in-migration-rx-state/1512 | CC-MAIN-2018-30 | refinedweb | 218 | 50.12 |
from IPython.display import display, HTML import spot from spot.jupyter import display_inline # display multiple arguments side-by-side import buddy spot.setup(show_default='.tvb')
a1 = spot.translate('FGa & GFb') a2 = spot.translate('G(Fc U b)') prod = spot.product(a1, a2) display_inline(a1, a2, prod)
The builtin
spot.product() function produces an automaton whose language is the intersection of the two input languages. It does so by building an automaton that keeps track of the runs in the two input automata. The states are labeled by pairs of input states so that we can more easily follow what is going on, but those labels are purely cosmetic. The acceptance condition is the conjunction of the two acceptance condition, but the acceptance sets of one input automaton have been shifted to not conflict with the other automaton.
In fact, that automaton printer has an option to shift those sets in its output, and this is perfect for illustrating products. For instance
a.show('+3') will display
a1 with all its acceptance sets shifted by 3.
Let's define a function for displaying the three automata involved in a product, using this shift option so we can follow what is going on with the acceptance sets.
def show_prod(a1, a2, res): s1 = a1.num_sets() display_inline(a1, a2.show('.tvb+{}'.format(s1)), res) show_prod(a1, a2, prod)
Let's now rewrite
product() in Python. We will do that in three steps.
First, we build a product without taking care of the acceptance sets. We just want to get the general shape of the algorithm.
We will build an automaton of type
twa_graph, i.e., an automaton represented explicitely using a graph. In those automata, states are numbered by integers, starting from
0. (Those states can also be given a different name, which is why the the
product() shows us something that appears to be labeled by pairs, but the real identifier of each state is an integer.)
We will use a dictionary to keep track of the association between a pair
(ls,rs) of input states, and its number in the output.
def product1(left, right): # A bdd_dict object associates BDD variables (that are # used in BDDs labeleing the edges) to atomic propositions. bdict = left.get_dict() # If the two automata do not have the same BDD dict, then # we cannot easily detect compatible transitions. if right.get_dict() != bdict: raise RuntimeError("automata should share their dictionary") result = spot.make_twa_graph(bdict) # This will be our state dictionary sdict = {} # The list of output states for which we have not yet # computed the successors. Items on this list are triplets # of the form (ls, rs, p) where ls,rs are the state number in # the left and right automata, and p is the state number if # the output automaton. todo = [] # Transform a pair of state number (ls, rs) into a state number in # the output automaton, creating a new state if needed. Whenever # a new state is created, we can add it to todo. def dst(ls, rs): pair = (ls, rs) p = sdict.get(pair) if p is None: p = result.new_state() sdict[pair] = p todo.append((ls, rs, p)) return p # Setup the initial state. It always exists. result.set_init_state(dst(left.get_init_state_number(), right.get_init_state_number())) # Build all states and edges in the product while todo: lsrc, rsrc, osrc = todo.pop() for lt in left.out(lsrc): for rt in right.out(rsrc): cond = lt.cond & rt.cond if cond != buddy.bddfalse: result.new_edge(osrc, dst(lt.dst, rt.dst), cond) return result p1 = product1(a1, a2) show_prod(a1, a2, p1)
Besides the obvious lack of acceptance condition (which defaults to
t) and acceptance sets, there is a less obvious problem: we never declared the set of atomic propositions used by the result automaton. This as two consequences:
p1.ap()will return an empty set of atomic propositions
print(a1.ap()) print(a2.ap()) print(p1.ap())
(spot.formula("a"), spot.formula("b")) (spot.formula("c"), spot.formula("b")) ()
bdd_dictinstance that is shared by the three automata knows that the atomic propositions
aand
bare used by automata
a1and that
band
care used by
a2. But it is unaware of
p1. That means that if we delete automata
a1and
a2, then the
bdd_dictwill release the associated BDD variables, and attempting to print automaton
p1will either crash (because it uses bdd variables that are not associated to any atomic proposition) or display different atomic propositions (in case the BDD variables have been associated to different propositions in the meantime).
These two issues are fixed by either calling
p1.register_ap(...) for each atomic proposition, or in our case
p1.copy_ap_of(...) to copy the atomic propositions of each input automaton.
This fixes the list of atomtic propositions, as discussed above, and also sets the correct acceptance condition.
The
set_acceptance method takes two arguments: a number of sets, and an acceptance function. In our case, both of these arguments are readily computed from the number of states and acceptance functions of the input automata.
def product2(left, right): bdict = left.get_dict() if right.get_dict() != bdict: raise RuntimeError("automata should share their dictionary") result = spot.make_twa_graph(bdict) # Copy the atomic propositions of the two input automata result.copy_ap_of(left) result.copy_ap_of(right) sdict = {} todo = [] def dst(ls, rs): pair = (ls, rs) p = sdict.get(pair) if p is None: p = result.new_state() sdict[pair] = p todo.append((ls, rs, p)) return p result.set_init_state(dst(left.get_init_state_number(), right.get_init_state_number())) # The acceptance sets of the right automaton will be shifted by this amount: # membership of this transitions to the new acceptance sets acc = lt.acc | (rt.acc << shift) result.new_edge(osrc, dst(lt.dst, rt.dst), cond, acc) return result p2 = product2(a1, a2) show_prod(a1, a2, p2) print(p2.ap())
(spot.formula("a"), spot.formula("b"), spot.formula("c"))
We could stop with the previous function: the result is a correct product from a theoretical point of view. However our function is still inferior to
spot.product() in a couple of points:
The former point could be addressed by calling
set_state_names() and passing an array of strings: if a state number is smaller than the size of that array, then the string at that position will be displayed instead of the state number in the dot output. However we can do even better by using
set_product_states() and passing an array of pairs of states. Besides the output routines, some algorithms actually retrieve this vector of pair of states to work on the product.
Regarding the latter point, consider for instance the deterministic nature of these automata. In Spot an automaton is deterministic if it is both existential (no universal branching) and universal (no non-deterministic branching). In our case we will restrict the algorithm to existantial input (by asserting
is_existential() on both operands), so we can consider that the
prop_universal() property is an indication of determinism:
print(a1.prop_universal()) print(a2.prop_universal()) print(prod.prop_universal()) print(p1.prop_universal())
maybe yes maybe maybe
Because
a1 and
a2 are deterministic, their product is necessarily deterministic. This is a property that the
spot.product() algorithm will preserve, but that our version does not yet preserve. We can fix that by adding
if left.prop_universal() and right.prop_universal(): result.prop_universal(True)
at the end of our function. Note that this is not the same as
result.prop_universal(left.prop_universal() and right.prop_universal())
because the results the
prop_*() family of functions take and return instances of
spot.trival values. These
spot.trival, can, as their name implies, take one amongst three values representing
yes,
no, and
maybe.
yes and
no should be used when we actually know that the automaton is deterministic or not (not deterministic meaning that there actually exists some non determinitic state in the automaton), and
maybe when we do not know.
The one-liner above is wrong for two reasons:
if
left and
right are non-deterministic, their product could be deterministic, so calling prop_universal(False) would be wrong.
the use of the
and operator on
trival is misleading in non-Boolean context. The
& operator would be the correct operator to use if you want to work in threed-valued logic. Compare:
yes = spot.trival(True) no = spot.trival(False) maybe = spot.trival_maybe() for u in (no, maybe, yes): for v in (no, maybe, yes): print("{u!s:>5} & {v!s:<5} = {r1!s:<5} {u!s:>5} and {v!s:<5} = {r2!s:<5}" .format(u=u, v=v, r1=(u&v), r2=(u and v)))
no & no = no no and no = no no & maybe = no no and maybe = no no & yes = no no and yes = no maybe & no = no maybe and no = maybe maybe & maybe = maybe maybe and maybe = maybe maybe & yes = maybe maybe and yes = maybe yes & no = no yes and no = no yes & maybe = maybe yes and maybe = maybe yes & yes = yes yes and yes = yes
The reason
maybe and no is equal to
maybe is that Python evaluate it like
no if maybe else maybe, but when a trival is evaluated in a Boolean context (as in
if maybe) the result is True only if the trival is equal to yes.
So our
if left.prop_universal() and right.prop_universal(): result.prop_universal(True)
is OK because the
if body will only be entered of both input automata are known to be deterministic.
However the question is in fact more general than just determinism: the product of two weak automata is weak, the product of two stutter-invariant automata is stutter-invariant, etc. So when writing an algorithm one should consider which of the property bits are naturally preserved by the algorithm, and set the relevant bits: this can save time later if the resulting automaton is used as input for another algorithm.
def product3(left, right): # the twa_graph.is_existential() method returns a Boolean, not a spot.trival if not (left.is_existential() and right.is_existential()): raise RuntimeError("alternating automata are not supported") bdict = left.get_dict() if right.get_dict() != bdict: raise RuntimeError("automata should share their dictionary") result = spot.make_twa_graph(bdict) result.copy_ap_of(left) result.copy_ap_of(right) pairs = [] # our array of state pairs sdict = {} todo = [] def dst(ls, rs): pair = (ls, rs) p = sdict.get(pair) if p is None: p = result.new_state() sdict[pair] = p todo.append((ls, rs, p)) pairs.append((ls, rs)) # name each state return p result.set_init_state(dst(left.get_init_state_number(), right.get_init_state_number())): acc = lt.acc | (rt.acc << shift) result.new_edge(osrc, dst(lt.dst, rt.dst), cond, acc) # Remember the origin of our states result.set_product_states(pairs) # Loop over all the properties we want to preserve if they hold in both automata for p in ('prop_universal', 'prop_complete', 'prop_weak', 'prop_inherently_weak', 'prop_terminal', 'prop_stutter_invariant', 'prop_state_acc'): if getattr(left, p)() and getattr(right, p)(): getattr(result, p)(True) return result p3 = product3(a1, a2) show_prod(a1, a2, p3) print(p3.prop_universal())
maybe
For development, it is useful to know that we can force the automaton printer to show the real state numbers (not the pairs) by passing option
1, and that we can retrieve the associated pairs ourselves. Note that the pairs also appear as tooltips when we mouse over the states.
display(p3.show('.1')) pairs = p3.get_product_states() for s in range(p3.num_states()): print("{}: {}".format(s, pairs[s]))
0: (0, 0) 1: (0, 1) 2: (1, 0) 3: (1, 1)
%timeit product3(a1, a2)
%timeit spot.product(a1, a2)
Depending on the machine where this notebook has been run, using the C++ version of the product can be 1 to 2 orders of magnitude faster. This is due to all the type conversions (converting Python types to C++ types) that occurs everytime a function/method of Spot is called from Python. When calling high-level C++ functions (such as
spot.product()) from Python, the overhead is negligible because most of the time is spent on the C++ side, actually executing the function. However when calling low-level functions (such as
new_edge(),
new_state(),
out()) most of the time is spent converting the arguments from Python to C++ and the results from C++ to Python.
Despite that speed difference, Python can be useful to prototype an algorithm before implementing it in C++. | https://spot.lrde.epita.fr/ipynb/product.html | CC-MAIN-2020-24 | refinedweb | 2,022 | 56.96 |
Struts 2 Login Application
Struts 2 Login Application
Developing Struts 2 Login Application
In this section we are going to develop login application based on Struts 2
Framework. Our current login application
struts- login problem - Struts
struts- login problem Hi all, I am a java developer, I am facing problems with the login application. The application's login page contains fields like username, password and a login button. With this functionality only
Struts 2.1.8 Login Form
application in Struts 2.8.1. In the next session we will also learn how...;
<title>Struts 2 Login Application!</title>
<link href="<.../showLogin.action in the browser.
Your web page should look like this:
Enter Login Name
Login Application
Login Application
This tutorial provides some simple steps for creating a website login
application that can be used later in any big Struts Hibernate and Spring based
How to code in struts for 3 Failed Login attempts - Struts
How to code in struts for 3 Failed Login attempts Hi,
I require help.
I am doing one application in struts where i have to incorporate.../struts-login-form.shtml
Thanks
Developing Simple Struts Tiles Application
will show you how to develop simple Struts Tiles
Application. You will learn how to setup the Struts Tiles and create example
page with it.
What is Struts...
Developing Simple Struts Tiles Application
Login or Cancel Application Using Ajax
implementation of login application with features like submit and cancel buttons
using... with
features like submit and cancel buttons. This login application first...Login or Cancel Application Using Ajax
JSF Simple Login Application
:view>
<html>
<head><title>JSF Simple Login Example<...
<%@ page contentType="text/html"%>
<%@ taglib</td>
<
How To Develop Login Form In Struts
How To Develop Login Form In Struts
....
This
article will explain how to develop login form in struts. Struts adopts... click here!
In this tutorial you have learned how to develop simple login
Struts 2 Application
Struts 2 Application
Developing user registration application based on
Struts 2 Framework
This Struts 2 Application is a simple user registration
application that will help you to learn how to develop real world applications using
Struts
Running and Testing Struts 2 Login application
Running and Testing Struts 2 Login application
Running Struts 2 Login Example
In this section we will run... developed and
tested your Struts 2 Login application. In the next section we
Simple Calculator Application In Java Script
Simple Calculator Application In Java
Script
... Calculator
The objective of this project is learn how to write a simple....
that is extremely simple JavaScript calculator, the HTML below shows you how
login application - Struts
application using struts and database? Hello,
Here is good example of Login and User Registration Application using Struts Hibernate and Spring.
In this tutorial you will learn
1. Develop application using Struts
2. Write
login page error
login page error How to configure in to config.xml .iam takin to one login form in that form action="/login" .when iam deployee the project... this request."
please suggest me.
if your login page is prepared
Struts
Struts Am newly developed struts applipcation,I want to know how to logout the page using the strus
Please visit the following link:
Struts Login Logout Application
About Struts 2.2.1 Login application
/ browser.
To create an login application At first create a login page in JSP...
.style1 {
margin-left: 80px;
}
About Struts2.2.1 login application
In the most common login application there is login form which is takes
struts application - Struts
struts login application form code Hi, As i'm new to struts can anyone send me the coding for developing a login form application which involves a database search like checking user name in database
Login page
Login page how to create Login page in java
JSF Validation In Login Application
:view>
<html>
<head><title>JSF Simple Login Example<...
<%@ page contentType="text/html"%>
<%@ taglib uri="......://
Developing Struts Hibernate and Spring Based Login/Registration Application
Application
This tutorial provides some simple steps for creating a website login...
Login and User Registration Application
In this tutorial we will learn how to develop login
Struts Tutorials - Jakarta Struts Tutorial
Login From In Struts
This simple struts application show you how... how to develop Struts applications using ant and deploy on the JBoss Application Server. Ant script is provided with the example code. Many advance topics like
Struts 2 Login Form Example
Struts 2 Login Form Example tutorial - Learn how to develop Login form in Struts 2 though this video tutorial
In this video tutorial I will explain you how...;title>Struts 2 Login Application!</title><link href="<s:url value
login page
login page How to login as different user in php
Struts Tutorials
. how to build a simple Struts HTML page using taglibs
6. how to code... how to start and stop Tomcat, install Struts, and deploy a Struts application... Struts application, specifically how you test the Action class.
The Action class
Using JMeter for a Simple Test
Using JMeter for a Simple Test
Lets see how to run JMeter now. We will conduct a
simple test to set up a test plan and stress test a Web application. Before
proceeding how to login admin and user with the same fields(name & password) in single login page while the table for admin and user is seprate in database(mysql)
please provide me solution
Simple Ajax Example, Developing Simple Ajax application
application that sends the user name on the server without refreshing the page... page.
This application is using the XMLHttpRequest object for making a call...Simple Ajax Example
Simple
login page
login page pls say how to create a login page in jsp and mysql using netbaens
Hi Friend,
Please visit the following links:
login how to create login page in jsp
Here is a jsp code that creates the login page and check whether the user is valid or not.
1...;tr><td></td><td><input type="submit" value="Login">
how to perform a validation for the field
how to perform a validation for the field hi,
function checkForm() {
var getBank=document.form.bname.value;
var alphaExp... in the jsp page,
onKeyPress="return isNumberKey(event)
<html>
User Login and Registration application
User Login and Registration application
... login page. The
authenticated user set the user name and password.... In the user login
page, there is a link named "New User" for the new user:-
<
Struts 2 Tutorial
.
Struts 2 Login Application
Developing Login Application in Struts 2
In this section we are going to develop login
application based on Struts 2 Framework. Our current login application does
Spring MVC Login Example
;
Now we will run this login application and see the out put like:
Now click on this hyperlink the application display user login form like:
Now input... MVC User Login Example
This section explains you how you can make Login example
Building a Simple EJB Application Tutorial
Building a Simple EJB Application - A Tutorial
... in
and
XDoclet.
This application, while
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program code for login page in struts by using eclipse
program code for login page in struts by using eclipse I want program code for login page in struts by using eclipse
Login Form
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Login form in struts: Whenever you goes to access data from... of this. In
this section of struts tutorial we will explain how to do coding for a
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login page in php
login page in php How to create a login page in php
Struts Projects
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and User Registration Application Using Struts... provides some simple steps for creating a website login
application... learning easy
Using Spring framework in your application
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Simple JSF Hello Application
like how to use JSF tags in JSP pages, how to configure the
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Simple Bank Application in JSP
Simple Bank Application in JSP
...: Create a Home Page ("index.jsp") to Login and New User Registration... a web page ("login.jsp") to login the user.
Login and User Registration Application
Creating Midlet Application For Login in J2ME
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Click on 'Launch' Button then the login page display like below...() function which
show the error page like figure below and it return on login page...
Creating MIDlet Application For Login in J2ME
how to perform a equqlity triangle in java
how to perform a equqlity triangle in java below the output
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JSF Simple Login Application - Java Server Faces Questions
JSF Simple Login Application Hi there, I have implemented all the things which you mentioned in " JSF Simple Login Application " . but as i insert USER_ID and PASSWORD then it is showing an exception which
How to perform search using AJAX?
How to perform search using AJAX? Hi,
I have following HTML code... and hit button, there is a Ajax call to retrieve search results from a simple txt file kept on my local. Please guide how do I achieve this? I have written loadDOC
Redirect to same jsp page on successful login
Redirect to same jsp page on successful login Hi,
I have an application where on successful login, the redirect should happen to same page... from the database. I am unable to create the session for the same login page
RichFaces: Login & Registration Application:
the responsiveness of the application.
In this application, Login page appears first...
RichFaces: Login & Registration Application
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module of any project. This tutorial explains how to implement login and
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what is struts flow of 1.2 version struts?
i have struts applicatin then from jsp page how struts application flows
Thanks
Kalins Naik
Please visit the following link:
Struts Tutorial
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I have to make a web application in which i have to give... then automatically it should
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Struts with Servlet Jsp - Development process
steps for developing simple web application with struts, Servlets, Jsp , javabeans and oracle. Like 1)First create jsp page with username and password... and validate method. 4)create action class to perform business logic 5)Finally how
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technologies like servlets, jsp,and struts.
i am doing one struts application where i...struts hi
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How to use filter to redirect to login page after session timeout
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Ask Questions?
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | http://www.roseindia.net/tutorialhelp/comment/14523 | CC-MAIN-2013-20 | refinedweb | 2,831 | 54.32 |
The sourcecode of the most important methods.
Created Nov 11, 2011
As always I won't discuss every single line of code in detail, but I'll talk about the most important methods and classes. These are the class LevelReader and its method readLevels() and the class Level itself. The classes Main, Stone and C_LevelEditor are pretty simple and you should be able to understand them by yourself.
LevelReader
First of all we have to read all defined levels into the applet. This happens in the class LevelReader using the method readLevels(). The method is pretty simple and self explanatory, the only special thing is, that we have to set a reference to the applet class in the class LevelReader. This reference to the Component = Applet is needed to use the getParameter() - method. Well, here comes the code:
import java.util.*; import java.applet.*; import java.awt.*; public class LevelReader { // Variables private int levels_in_total; // Array, stores all generated instances of the class Level private Level [] level_array; // Appletrefference private Component parent; public LevelReader (Component parent) { // Initialize appletrefference this.parent = parent; // Get number of levels in total
levels_in_total = Integer.parseInt (((Applet)parent).getParameter(C_LevelEditor.total_levels));// Initialize level_array level_array = new Level [levels_in_total]; } /* This method reads every level in the HTML - Page, generates a instance of the class Level (for every level) and stores it in the level_array*/ public Level [] readLevels () { for (int i = 1; i <= levels_in_total; i++) { // generate new level Level level = new Level (); // get and set information parameters
level.setAuthor (((Applet)parent).getParameter ( "Level" + i + "_" + C_LevelEditor.author));
level.setName (((Applet)parent).getParameter ("Level" + i + "_" + C_LevelEditor.name));
level.setComment (((Applet)parent).getParameter ("Level" + i + "_" + C_LevelEditor.comment));// read in all the lines and store them in the level for (int j = 0; j < C_LevelEditor.number_of_lines; j++) { level.setLine (((Applet)parent).getParameter ("Level" + i + "_Line" + j), j); } // store level level_array [i-1] = level; } return level_array; } }
The class Level
Now we are able to read in the levels and to store them in Level instances but we still don't know anything about the Level class in detail. Now we have to generate a real level, mainly the stone_map which holds the different level elements, out of the string information we get out of the level definition in the HTML - page. The stone_map 2D array stores the level elements at the same position where they appear in the level definition (for example a "r" occurs at line 3 as the third character of the string, then a red stone object is generated in the array in row 3 and column 3). First of all this class has some set and get methods to get and set the values of the level information parameters. Much more interesting is the method setLine. This method gets one line of the level definition (a string) and translates this string to stone objects and stores these stone instances in the stone_map. Last but not least the class has its own paint method.
import java.util.*; import java.awt.*; public class Level { // Variables private String author; private String name; private String comment; // Levelmatrix, stores the stone objects private Stone [] [] stone_map; public Level () { // Initialize the stone_map, all fields // are initialized with null stone_map = new Stone [C_LevelEditor.number_of_lines] [C_LevelEditor.number_of_cols]; } // Method translates information of one line of //the level definition to stone objects public void setLine (String line, int line_index) { char [] entrys = line.toCharArray(); // go through all chars and translate them // to stone objects for (int i = 0; i < C_LevelEditor.number_of_cols; i++) { Stone stone = null; // generate red stone if char equals "r" if (entrys[i] == 'r') { stone = new Stone (line_index, i,Color.red); } // generate different coloured // stones the same way ... // If char is unknown, generate no stone, // which means that this array field stays null else { // do nothing
} // store stone in array if it is not null if (stone == null) { // do nothing } else { stone_map [line_index] [i] = stone; } } } // set and get methods for the information strings ... // Method paints level public void paintLevel (Graphics g) { // go through the whole stone map and paint stones for (int i = 0; i < stone_map.length; i++) { for (int j = 0; j < stone_map[i].length; j++) { Stone stone = stone_map [i][j]; // paint stone or do nothing if stone is null if (stone == null) { // draw nothing } else { stone.drawStone(g); } } } // paint level information g.setColor (Color.yellow); g.drawString (comment, 50, 250); g.drawString (name, 50, 270); g.drawString (author, 50, 290); } }
Conclusion
In this chapter I showed you one way to define a level in a HTML - page, to read in this level using a LevelReader and one method to represent this level in our applet (2D array). As always there are many ways to do this maybe much better ones than mine, and even though we might have helped you, because you can use the methods to read in and store the level in the applet in almost every arraybased game the much harder work is still in front of you. You have to make your game work with every level someone defined (which is really hard) and of course you have to generate your own level elements, change the number of level lines... . Ok, I hope I could help you a little bit, if you wrote a game using this editor, I would be glad if you would send it to me. Well, we are finished, here comes the link to download the sourcecode and the link to the working level editor applet (take a look a the sourcecode of the HTML - page to see what the levels look like).
SourceCode download
Take a look at the applet | https://www.jguru.com/article/client-side/the-sourcecode-of-the-most-important-methods.html | CC-MAIN-2021-17 | refinedweb | 932 | 58.62 |
The
Hundred-
Page
Machine
Learning
Book
Andriy Burkov
“All models are wrong, but some are useful.”
— George Box
The book is distributed on the “read first, buy later” principle.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft
Preface
Let’s start by telling the truth: machines don’t learn. What a typical “learning machine”
does, is finding a mathematical formula, which, when applied to a collection of inputs (called
“training data”), produces the desired outputs. This mathematical formula also generates the
correct outputs for most other inputs (distinct from the training data) on the condition that
those inputs come from the same or a similar statistical distribution as the one the training
data was drawn from.
Why isn’t that learning? Because if you slightly distort the inputs, the output is very likely
to become completely wrong. It’s not how learning in animals works. If you learned to play
a video game by looking straight at the screen, you would still be a good player if someone
rotates the screen slightly. A machine learning algorithm, if it was trained by “looking”
straight at the screen, unless it was also trained to recognize rotation, will fail to play the
game on a rotated screen.
So why the name “machine learning” then? The reason, as is often the case, is marketing:
Arthur Samuel, an American pioneer in the field of computer gaming and artificial intelligence,
coined the term in 1959 while at IBM. Similarly to how in the 2010s IBM tried to market
the term “cognitive computing” to stand out from competition, in the 1960s, IBM used the
new cool term “machine learning” to attract both clients and talented employees.
As you can see, just like artificial intelligence is not intelligence, machine learning is not
learning. However, machine learning is a universally recognized term that usually refers
to the science and engineering of building machines capable of doing various useful things
without being explicitly programmed to do so. So, the word “learning” in the term is used
by analogy with the learning in animals rather than literally.
Who This Book is For
This book contains only those parts of the vast body of material on machine learning developed
since the 1960s that have proven to have a significant practical value. A beginner in machine
learning will find in this book just enough details to get a comfortable level of understanding
of the field and start asking the right questions.
Practitioners with experience can use this book as a collection of directions for further
self-improvement. The book also comes in handy when brainstorming at the beginning of a
project, when you try to answer the question whether a given technical or business problem
is “machine-learnable” and, if yes, which techniques you should try to solve it.
How to Use This Book
If you are about to start learning machine learning, you should read this book from the
beginning to the end. (It’s just a hundred pages, not a big deal.) If you are interested
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 3
in a specific topic covered in the book and want to know more, most sections have a QR
code. By scanning one of those QR codes with your phone, you will get a link to a page on
the book’s companion wiki theMLbook.com with additional materials: recommended reads,
videos, Q&As, code snippets, tutorials, and other bonuses.
The book’s wiki is continuously updated with contributions from the book’s author himself
as well as volunteers from all over the world. So this book, like a good wine, keeps getting
better after you buy it.
Scan the QR code below with your phone to get to the book’s wiki:
Some sections don’t have a QR code, but they still most likely have a wiki page. You can
find it by submitting the section’s title to the wiki’s search engine.
Should You Buy This Book?
This book is distributed on the “read first, buy later” principle. I firmly believe that paying
for the content before consuming it is buying a pig in a poke. You can see and try a car in a
dealership before you buy it. You can try on a shirt or a dress in a department store. You
have to be able to read a book before paying for it.
The read first, buy later principle implies that you can freely download the book, read it and
share it with your friends and colleagues. If you liked the book, only then you have to buy it.
Now you are all set. Enjoy your reading!
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 4
The
Hundred-
Page
Machine
Learning
Book
Andriy Burkov
“All models are wrong, but some are useful.”
— George Box
The book is distributed on the “read first, buy later” principle.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft
1 Introduction
1.1 What is Machine Learning
Machine learning is a subfield of computer science that is concerned with building algorithms
which, to be useful, rely on a collection of examples of some phenomenon. These examples
can come from nature, be handcrafted by humans or generated by another algorithm.
Machine learning can also be defined as the process of solving a practical problem by 1)
gathering a dataset, and 2) algorithmically building a statistical model based on that dataset.
That statistical model is assumed to be used somehow to solve the practical problem.
To save keystrokes, I use the terms “learning” and “machine learning” interchangeably.
1.2 Types of Learning
Learning can be supervised, semi-supervised, unsupervised and reinforcement.
1.2.1 Supervised Learning
In supervised learning1,). For instance, if each example x in our
collection represents a person, then the first feature, x(1), could contain height in cm, the
second feature, x(2), could contain weight in kg, x(3) could contain gender, and so on. For all
examples in the dataset, the feature at position j in the feature vector always contains the
same kind of information. It means that if x(2)i contains weight in kg in some example xi,
then x(2)k will also contain weight in kg in every example xk, k = 1, . . . , N . The label yi can
be either an element belonging to a finite set of classes {1, 2, . . . , C}, or a real number, or a
more complex structure, like a vector, a matrix, a tree, or a graph. Unless otherwise stated,
in this book yi is either one of a finite set of classes or a real number. You can see a class as
a category to which an example belongs. For instance, if your examples are email messages
and your problem is spam detection, then you have two classes {spam, not_spam}.
The goal of a supervised learning algorithm is to use the dataset to produce a model
that takes a feature vector x as input and outputs information that allows deducing the label
for this feature vector. For instance, the model created using the dataset of people could
take as input a feature vector describing a person and output a probability that the person
has cancer.
1
In this book, if a term is in bold, that means that this term can be found in the index at the end of the
book.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 3
1.2.2 Unsupervised Learning
In unsupervised learning, the dataset is a collection of unlabeled examples {xi}Ni=1.
Again, x is a feature vector, and the goal of an unsupervised learning algorithm is
to create a model that takes a feature vector x as input and either transforms it into
another vector or into a value that can be used to solve a practical problem. For example,
in clustering, the model returns the id of the cluster for each feature vector in the dataset.
In dimensionality reduction, the output of the model is a feature vector that has fewer
features than the input x; in outlier detection, the output is a real number that indicates
how x is di�erent from a “typical” example in the dataset.
1.2.3 Semi-Supervised Learning2.
1.2.4 Reinforcement Learning
Reinforcement learning is a subfield of machine learning where the machine “lives” in an
environment and is capable of perceiving the state of that environment as a vector of
features. The machine can execute actions in every state. Di�erent actions bring di�erent
rewards and could also move the machine to another state of the environment. The goal
of a reinforcement learning algorithm is to learn a policy. A policy is a function f (similar
to the model in supervised learning) that takes the feature vector of a state as input and
outputs an optimal action to execute in that state. The action is optimal if it maximizes the
expected average reward.
Reinforcement learning solves a particular kind of problems where
decision making is sequential, and the goal is long-term, such as game
playing, robotics, resource management, or logistics. In this book, I
put emphasis on one-shot decision making where input examples are
independent of one another and the predictions made in the past. I
leave reinforcement learning out of the scope of this book.
2.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 4
1.3 How Supervised Learning Works
In this section, I briefly explain how supervised learning works so that you have the picture
of the whole process before we go into detail. I decided to use supervised learning as an
example because it’s the type of machine learning most frequently used in practice.
The supervised learning process starts with gathering the data. The data for supervised
learning is a collection of pairs (input, output). Input could be anything, for example, email
messages, pictures, or sensor measurements. Outputs are usually real numbers, or labels (e.g.
“spam”, “not_spam”, “cat”, “dog”, “mouse”, etc). In some cases, outputs are vectors (e.g.,
four coordinates of the rectangle around a person on the picture), sequences (e.g. [“adjective”,
“adjective”, “noun”] for the input “big beautiful car”), or have some other structure.
Let’s say the problem that you want to solve using supervised learning is spam detection.
You gather the data, for example, 10,000 email messages, each with a label either “spam” or
“not_spam” (you could add those labels manually or pay someone to do that for us). Now,
you have to convert each email message into a feature vector.
The data analyst decides, based on their experience, how to convert a real-world entity, such
as an email message, into a feature vector. One common way to convert a text into a feature
vector, called bag of words, is to take a dictionary of English words (let’s say it contains
20,000 alphabetically sorted words) and stipulate that in our feature vector:
• the first feature is equal to 1 if the email message contains the word “a”; otherwise,
this feature is 0;
• the second feature is equal to 1 if the email message contains the word “aaron”; otherwise,
this feature equals 0;
• . . .
• the feature at position 20,000 is equal to 1 if the email message contains the word
“zulu”; otherwise, this feature is equal to 0.
You repeat the above procedure for every email message in our collection, which gives
us 10,000 feature vectors (each vector having the dimensionality of 20,000) and a label
(“spam”/“not_spam”).
Now you have a machine-readable input data, but the output labels are still in the form of
human-readable text. Some learning algorithms require transforming labels into numbers.
For example, some algorithms require numbers like 0 (to represent the label “not_spam”)
and 1 (to represent the label “spam”). The algorithm I use to illustrate supervised learning is
called Support Vector Machine (SVM). This algorithm requires that the positive label (in
our case it’s “spam”) has the numeric value of +1 (one), and the negative label (“not_spam”)
has the value of ≠1 (minus one).
At this point, you have a dataset and a learning algorithm, so you are ready to apply
the learning algorithm to the dataset to get the model.
SVM sees every feature vector as a point in a high-dimensional space (in our case, space
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 5
is 20,000-dimensional). The algorithm puts all feature vectors on an imaginary 20,000-
dimensional plot and draws an imaginary 20,000-dimensional line (a hyperplane) that separates
examples with positive labels from examples with negative labels. In machine learning, the
boundary separating the examples of di�erent classes is called the decision boundary.
The equation of the hyperplane is given by two parameters, a real-valued vector w of the
same dimensionality as our input feature vector x, and a real number b like this:
wx ≠ b = 0,
where the expression wx means w(1)x(1) + w(2)x(2) + . . . + w(D)x(D), and D is the number
of dimensions of the feature vector x.
(If some equations aren’t clear to you right now, in Chapter 2 we revisit the math and
statistical concepts necessary to understand them. For the moment, try to get an intuition of
what’s happening here. It all becomes more clear after you read the next chapter.)
Now, the predicted label for some input feature vector x is given like this:
y = sign(wx ≠ b),
where sign is a mathematical operator that takes any value as input and returns +1 if the
input is a positive number or ≠1 if the input is a negative number.
The goal of the learning algorithm — SVM in this case — is to leverage the dataset and find
the optimal values wú and bú for parameters w and b. Once the learning algorithm identifies
these optimal values, the model f(x) is then defined as:
f(x) = sign(wúx ≠ bú)
Therefore, to predict whether an email message is spam or not spam using an SVM model,
you have to take a text of the message, convert it into a feature vector, then multiply this
vector by wú, subtract bú and take the sign of the result. This will give us the prediction (+1
means “spam”, ≠1 means “not_spam”).
Now, how does the machine find wú and bú? It solves an optimization problem. Machines
are good at optimizing functions under constraints.
So what are the constraints we want to satisfy here? First of all, we want the model to predict
the labels of our 10,000 examples correctly. Remember that each example i = 1, . . . , 10000 is
given by a pair (xi, yi), where xi is the feature vector of example i and yi is its label that
takes values either ≠1 or +1. So the constraints are naturally:
• wxi ≠ b Ø 1 if yi = +1, and
• wxi ≠ b Æ ≠1 if yi = ≠1
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 6
x(2)
x(1)
wx
—
b
= 0
wx
—
b
= 1
wx
—
b
= —
1
b ||w||
2 ||w||
Figure 1: An example of an SVM model for two-dimensional feature vectors.
We would also prefer that the hyperplane separates positive examples from negative ones with
the largest margin. The margin is the distance between the closest examples of two classes,
as defined by the decision boundary. A large margin contributes to a better generalization,
that is how well the model will classify new examples in the future. To achieve that, we need
to minimize the Euclidean norm of w denoted by ÎwÎ and given by
ÒqD
j=1(w(j))2.
So, the optimization problem that we want the machine to solve looks like this:
Minimize ÎwÎ subject to yi(wxi ≠ b) Ø 1 for i = 1, . . . , N . The expression yi(wxi ≠ b) Ø 1
is just a compact way to write the above two constraints.
The solution of this optimization problem, given by wú and bú, is called the statistical
model, or, simply, the model. The process of building the model is called training.
For two-dimensional feature vectors, the problem and the solution can be visualized as shown
in fig. 1. The blue and orange circles represent, respectively, positive and negative examples,
and the line given by wx ≠ b = 0 is the decision boundary.
Why, by minimizing the norm of w, do we find the highest margin between the two classes?
Geometrically, the equations wx ≠ b = 1 and wx ≠ b = ≠1 define two parallel hyperplanes,
as you see in fig. 1. The distance between these hyperplanes is given by 2ÎwÎ , so the smaller
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 7
the norm ÎwÎ, the larger the distance between these two hyperplanes.
That’s how Support Vector Machines work. This particular version of the algorithm builds
the so-called linear model. It’s called linear because the decision boundary is a straight line
(or a plane, or a hyperplane). SVM can also incorporate kernels that can make the decision
boundary arbitrarily non-linear. In some cases, it could be impossible to perfectly separate
the two groups of points because of noise in the data, errors of labeling, or outliers (examples
very di�erent from a “typical” example in the dataset). Another version of SVM can also
incorporate a penalty hyperparameter for misclassification of training examples of specific
classes. We study the SVM algorithm in more detail in Chapter 3.
At this point, you should retain the following: any classification learning algorithm that
builds a model implicitly or explicitly creates a decision boundary. The decision boundary
can be straight, or curved, or it can have a complex form, or it can be a superposition of
some geometrical figures. The form of the decision boundary determines the accuracy of
the model (that is the ratio of examples whose labels are predicted correctly). The form of
the decision boundary, the way it is algorithmically or mathematically computed based on
the training data, di�erentiates one learning algorithm from another.
In practice, there are two other essential di�erentiators of learning algorithms to consider:
speed of model building and prediction processing time. In many practical cases, you would
prefer a learning algorithm that builds a less accurate model fast. Additionally, you might
prefer a less accurate model that is much quicker at making predictions.
1.4 Why the Model Works on New Data
Why is a machine-learned model capable of predicting correctly the labels of new, previously
unseen examples? To understand that, look at the plot in fig. 1. If two classes are separable
from one another by a decision boundary, then, obviously, examples that belong to each class
are located in two di�erent. To minimize
the probability of making errors on new examples, the SVM algorithm, by looking for the
largest margin, explicitly tries to draw the decision boundary in such a way that it lies as far
as possible from examples of both classes.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 8
The reader interested in knowing more about the learnability and un-
derstanding the close relationship between the model error, the size of
the training set, the form of the mathematical equation that defines
the model, and the time it takes to build the model is encouraged to
read about the PAC learning. The PAC (for “probably approximately
correct”) learning theory helps to analyze whether and under what
conditions a learning algorithm will probably output an approximately
correct classifier.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 9
The
Hundred-
Page
Machine
Learning
Book
Andriy Burkov
“All models are wrong, but some are useful.”
— George Box
The book is distributed on the “read first, buy later” principle.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft
2 Notation and Definitions
2.1 Notation
Let’s start by revisiting the mathematical notation we all learned at school, but some likely
forgot right after the prom.
2.1.1 Scalars, Vectors, and Sets
A scalar is a simple numerical value, like 15 or ≠3.25. Variables or constants that take scalar
values are denoted by an italic letter, like x or a.
Figure 1: Three vectors visualized as directions and as points.
A vector is an ordered list of scalar values, called attributes. We denote a vector as a bold
character, for example, x or w. Vectors can be visualized as arrows that point to some
directions as well as points in a multi-dimensional space. Illustrations of three two-dimensional
vectors, a = [2, 3], b = [≠2, 5], and c = [1, 0] is given in fig. 1. We denote an attribute of a
vector as an italic value with an index, like this: w(j) or x(j). The index j denotes a specific
dimension of the vector, the position of an attribute in the list. For instance, in the vector a
shown in red in fig. 1, a(1) = 2 and a(2) = 3.
The notation x(j) should not be confused with the power operator, like this x2 (squared) or
x3 (cubed). If we want to apply a power operator, say square, to an indexed attribute of a
vector, we write like this: (x(j))2.
A variable can have two or more indices, like this: x(j)i or like this x
(k)
i,j . For example, in
neural networks, we denote as x(j)l,u the input feature j of unit u in layer l.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 3
A set is an unordered collection of unique elements. We denote a set as a calligraphic
capital character, for example, S. A set of numbers can be finite (include a fixed amount
of values). In this case, it is denoted using accolades, for example, {1, 3, 18, 23, 235} or
{x1, x2, x3, x4, . . . , xn}. A set can be infinite and include all values in some interval. If a set
includes all values between a and b, including a and b, it is denoted using brackets as [a, b].
If the set doesn’t include the values a and b, such a set is denoted using parentheses like this:
(a, b). For example, the set [0, 1] includes such values as 0, 0.0001, 0.25, 0.784, 0.9995, and
1.0. A special set denoted R includes all numbers from minus infinity to plus infinity.
When an element x belongs to a set S, we write x œ S. We can obtain a new set S3 as
an intersection of two sets S1 and S2. In this case, we write S3 Ω S1 fl S2. For example
{1, 3, 5, 8} fl {1, 8, 4} gives the new set {1, 8}.
We can obtain a new set S3 as a union of two sets S1 and S2. In this case, we write
S3 Ω S1 fi S2. For example {1, 3, 5, 8} fi {1, 8, 4} gives the new set {1, 3, 4, 5, 8}.
2.1.2 Capital Sigma Notation
The summation over a collection X = {x1, x2, . . . , xn≠1, xn} or over the attributes of a vector
x = [x(1), x(2), . . . , x(m≠1), x(m)] is denoted like this:
nÿ
i=1
xi
def= x1 + x2 + . . . + xn≠1 + xn, or else:
mÿ
j=1
x(j)
def= x(1) + x(2) + . . . + x(m≠1) + x(m).
The notation def= means “is defined as”.
2.1.3 Capital Pi Notation
A notation analogous to capital sigma is the capital pi notation. It denotes a product of
elements in a collection or attributes of a vector:
nŸ
i=1
xi
def= x1 · x2 · . . . · xn≠1 · xn,
where a · b means a multiplied by b. Where possible, we omit · to simplify the notation, so ab
also means a multiplied by b.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 4
2.1.4 Operations on Sets
A derived set creation operator looks like this: S Õ Ω {x2 | x œ S, x > 3}. This notation means
that we create a new set S Õ by putting into it x squared such that that x is in S, and x is
greater than 3.
The cardinality operator |S| returns the number of elements in set S.
2.1.5 Operations on Vectors
The sum of two vectors x + z is defined as the vector [x(1) + z(1), x(2) + z(2), . . . , x(m) + z(m)].
The di�erence of two vectors x ≠ z is defined as the vector [x(1) ≠ z(1), x(2) ≠ z(2), . . . , x(m) ≠
z(m)].
A vector multiplied by a scalar is a vector. For example xc def= [cx(1), cx(2), . . . , cx(m)].
A dot-product of two vectors is a scalar. For example, wx def=
qm
i=1 w
(i)x(i). In some books,
the dot-product is denoted as w · x. The two vectors must be of the same dimensionality.
Otherwise, the dot-product is undefined.
The multiplication of a matrix W by a vector x gives another vector as a result. Let our
matrix be,
W =
5
w(1,1) w(1,2) w(1,3)
w(2,1) w(2,2) w(2,3)
6
.
When vectors participate in operations on matrices, a vector is by default represented as a
matrix with one column. When the vector is on the right of the matrix, it remains a column
vector. We can only multiply a matrix by vector if the vector has the same number of rows
as the number of columns in the matrix. Let our vector be x def= [x(1), x(2), x(3)]. Then Wx
is a two-dimensional vector defined as,
Wx =
5
w(1,1) w(1,2) w(1,3)
w(2,1) w(2,2) w(2,3)
6 S
U
x(1)
x(2)
x(3)
T
V
def=
5
w(1,1)x(1) + w(1,2)x(2) + w(1,3)x(3)
w(2,1)x(1) + w(2,2)x(2) + w(2,3)x(3)
6
=
5
w
(1)
x
w
(2)
x
6
If our matrix had, say, five rows, the result of the above product would be a five-dimensional
vector.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 5
When the vector is on the left side of the matrix in the multiplication, then it has to be
transposed before we multiply it by the matrix. The transpose of the vector x denoted as x€
makes a row vector out of a column vector. Let’s say,
x =
5
x(1)
x(2)
6
,
then,
x
€ def=
Ë
x(1), x(2)
È
.
The multiplication of the vector x by the matrix W is given by x€W,
x
€
W =
Ë
x(1), x(2)
È 5w(1,1) w(1,2) w(1,3)
w(2,1) w(2,2) w(2,3)
6
def=
#
w(1,1)x(1) + w(2,1)x(2), w(1,2)x(1) + w(2,2)x(2), w(1,3)x(1) + w(2,3)x(2)
$
As you can see, we can only multiply a vector by a matrix if the vector has the same number
of dimensions as the number of rows in the matrix.
2.1.6 Functions
A function is a relation that associates each element x of a set X , the domain of the function,
to a single element y of another set Y , the codomain of the function. A function usually has a
name. If the function is called f , this relation is denoted y = f(x) (read f of x), the element
x is the argument or input of the function, and y is the value of the function or the output.
The symbol that is used for representing the input is the variable of the function (we often
say that f is a function of the variable x).
We say that f(x) has a local minimum at x = c if f(x) Ø f(c) for every x in some open
interval around x = c. An interval is a set of real numbers with the property that any number
that lies between two numbers in the set is also included in the set. An open interval does
not include its endpoints and is denoted using parentheses. For example, (0, 1) means greater
than 0 and less than 1. The minimal value among all the local minima is called the global
minimum. See illustration in fig. 2.
A vector function, denoted as y = f(x) is a function that returns a vector y. It can have a
vector or a scalar argument.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 6
global minimum
local minimum
6
4
2
0
–2
–4
–6
f(x)
Figure 2: A local and a global minima of a function.
2.1.7 Max and Arg Max
Given a set of values A = {a1, a2, . . . , an}, the operator,
max
aœA
f(a)
returns the highest value f(a) for all elements in the set A. On the other hand, the operator,
arg max
aœA
f(a)
returns the element of the set A that maximizes f(a).
Sometimes, when the set is implicit or infinite, we can write maxa f(a) or arg max
a
f(a).
Operators min and arg min operate in a similar manner.
2.1.8 Assignment Operator
The expression a Ω f(x) means that the variable a gets the new value: the result of f(x).
We say that the variable a gets assigned a new value. Similarly, a Ω [a1, a2] means that the
two-dimensional vector a gets the value [a1, a2].
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 7
2.1.9 Derivative and Gradient
A derivative f Õ of a function f is a function or a value that describes how fast f grows (or
decreases). If the derivative is a constant value, like 5 or ≠3, then the function grows (or
decreases) constantly at any point x of its domain. If the derivative f Õ is a function, then the
function f can grow at a di�erent pace in di�erent regions of its domain. If the derivative f Õ
is positive at some point x, then the function f grows at this point. If the derivative of f is
negative at some x, then the function decreases at this point. The derivative of zero at x
means that the function’s slope at x is horizontal.
The process of finding a derivative is called di�erentiation.
Derivatives for basic functions are known. For example if f(x) = x2, then f Õ(x) = 2x; if
f(x) = 2x then f Õ(x) = 2; if f(x) = 2 then f Õ(x) = 0 (the derivative of any function f(x) = c,
where c is a constant value, is zero).
If the function we want to di�erentiate is not basic, we can find its derivative using the
chain rule. For example if F (x) = f(g(x)), where f and g are some functions, then F Õ(x) =
f Õ(g(x))gÕ(x). For example if F (x) = (5x + 1)2 then g(x) = 5x + 1 and f(g(x)) = (g(x))2.
By applying the chain rule, we find F Õ(x) = 2(5x + 1)gÕ(x) = 2(5x + 1)5 = 50x + 10.
Gradient is the generalization of derivative for functions that take several inputs (or one
input in the form of a vector or some other complex structure). A gradient of a function
is a vector of partial derivatives. You can look at finding a partial derivative of a function
as the process of finding the derivative by focusing on one of the function’s inputs and by
considering all other inputs as constant values.
For example, if our function is defined as f([x(1), x(2)]) = ax(1) + bx(2) + c, then the partial
derivative of function f with respect to x(1), denoted as ˆf
ˆx(1)
, is given by,
ˆf
ˆx(1)
= a + 0 + 0 = a,
where a is the derivative of the function ax(1); the two zeroes are respectively derivatives of
bx(2) and c, because x(2) is considered constant when we compute the derivative with respect
to x(1), and the derivative of any constant is zero.
Similarly, the partial derivative of function f with respect to x(2), ˆf
ˆx(2)
, is given by,
ˆf
ˆx(2)
= 0 + b + 0 = b.
The gradient of function f , denoted as Òf is given by the vector [ ˆf
ˆx(1)
, ˆf
ˆx(2)
].
The chain rule works with partial derivatives too, as I illustrate in Chapter 4.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 8
(a) (b)
Figure 3: A probability mass function and a probability density function.
2.2 Random Variable
A random variable, usually written as an italic capital letter, like X, is a variable whose
possible values are numerical outcomes of a random phenomenon. There are two types of
random variables: discrete and continuous.
A discrete random variable takes on only a countable number of distinct values such as red,
yellow, blue or 1, 2, 3, . . ..
The probability distribution of a discrete random variable is described by a list of probabilities
associated with each of its possible values. This list of probabilities is called probability mass
function (pmf). For example: Pr(X = red) = 0.3, Pr(X = yellow) = 0.45, Pr(X = blue) =
0.25. Each probability in a probability mass function is a value greater than or equal to 0.
The sum of probabilities equals 1 (fig. 3a).
A continuous random variable takes an infinite number of possible values in some interval.
Examples include height, weight, and time. Because the number of values of a continuous
random variable X is infinite, the probability Pr(X = c) for any c is 0. Therefore, instead
of the list of probabilities, the probability distribution of a continuous random variable (a
continuous probability distribution) is described by a probability density function (pdf). The
pdf is a function whose codomain is nonnegative and the area under the curve is equal to 1
(fig. 3b).
Let a discrete random variable X have k possible values {xi}ki=1. The expectation of X
denoted as E[X] is given by,
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 9
E[X] def=
kÿ
i=1
xi Pr(X = xi) = x1 Pr(X = x1) + x2 Pr(X = x2) + · · · + xk Pr(X = xk), (1)
where Pr(X = xi) is the probability that X has the value xi according to the pmf. The
expectation of a random variable is also called the mean, average or expected value and is
frequently denoted with the letter µ. The expectation is one of the most important statistics
of a random variable. Another important statistic is the standard deviation. For a discrete
random variable, the standard deviation usually denoted as ‡ is given by:
‡
def=
E[(X ≠ µ)2] =
Pr(X = x1)(x1 ≠ µ)2 + Pr(X = x2)(x2 ≠ µ)2 + · · · + Pr(X = xk)(xk ≠ µ)2,
where µ = E[X].
The expectation of a continuous random variable X is given by,
E[X] def=
⁄
R
xfX(x) dx, (2)
where fX is the pdf of the variable X and
s
R is the integral of function xfX .
Integral is an equivalent of the summation over all values of the function when the function
has a continuous domain. It equals the area under the curve of the function. The property of
the pdf that the area under its curve is 1 mathematically means that
s
R fX(x) dx = 1.
Most of the time we don’t know fX , but we can observe some values of X. In machine
learning, we call these values examples, and the collection of these examples is called a
sample or a dataset.
2.3 Unbiased Estimators
Because fX is usually unknown, but we have a sample SX = {xi}Ni=1, we often content
ourselves not with the true values of statistics of the probability distribution, such as
expectation, but with their unbiased estimators.
We say that ◊̂(SX) is an unbiased estimator of some statistic ◊ calculated using a sample SX
drawn from an unknown probability distribution if ◊̂(SX) has the following property:
E
Ë
◊̂(SX)
È
= ◊,
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 10
where ◊̂ is a sample statistic, obtained using a sample SX and not the real statistic ◊ that
can be obtained only knowing X; the expectation is taken over all possible samples drawn
from X. Intuitively, this means that if you can have an unlimited number of such samples
as SX , and you compute some unbiased estimator, such as µ̂, using each sample, then the
average of all these µ̂ equals the real statistic µ that you would get computed on X.
It can be shown that an unbiased estimator of an unknown E[X] (given by either eq. 1 or
eq. 2) is given by 1N
qN
i=1 xi (called in statistics the sample mean).
2.4 Bayes’ Rule
The conditional probability Pr(X = x|Y = y) is the probability of the random variable X to
have a specific value x given that another random variable Y has a specific value of y. The
Bayes’ Rule (also known as the Bayes’ Theorem) stipulates that:
Pr(X = x|Y = y) = Pr(Y = y|X = x) Pr(X = x)Pr(Y = y) .
2.5 Parameter Estimation
Bayes’ Rule comes in handy when we have a model of X’s distribution, and this model f◊ is a
function that has some parameters in the form of a vector ◊. An example of such a function
could be the Gaussian function that has two parameters, µ and ‡, and is defined as:
f◊(x) =
1Ô
2fi‡2
e≠
(x≠µ)2
2‡2 ,
where ◊ def= [µ, ‡].
This function has all the properties of a pdf. Therefore, we can use it as a model of an
unknown distribution of X. We can update the values of parameters in the vector ◊ from the
data using the Bayes’ Rule:
Pr(◊ = ◊̂|X = x) Ω Pr(X = x|◊ = ◊̂) Pr(◊ = ◊̂)Pr(X = x) =
Pr(X = x|◊ = ◊̂) Pr(◊ = ◊̂)
q
◊̃ Pr(X = x|◊ = ◊̃)
. (3)
where Pr(X = x|◊ = ◊̂) def= f◊̂.
If we have a sample S of X and the set of possible values for ◊ is finite, we can easily estimate
Pr(◊ = ◊̂) by applying Bayes’ Rule iteratively, one example x œ S at a time. The initial value
Pr(◊ = ◊̂) can be guessed such that
q
◊̂ Pr(◊ = ◊̂) = 1. This guess of the probabilities for
di�erent ◊̂ is called the prior.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 11
First, we compute Pr(◊ = ◊̂|X = x1) for all possible values ◊̂. Then, before updating
Pr(◊ = ◊̂|X = x) once again, this time for x = x2 œ S using eq. 3, we replace the prior
Pr(◊ = ◊̂) in eq. 3 by the new estimate Pr(◊ = ◊̂) Ω 1N
q
xœS Pr(◊ = ◊̂|X = x).
The best value of the parameters ◊ú given one example is obtained using the principle of
maximum-likelihood:
◊ú = arg max
◊
NŸ
i=1
Pr(◊ = ◊̂|X = xi). (4)
If the set of possible values for ◊ isn’t finite, then we need to optimize eq. 4 directly using a
numerical optimization routine, such as gradient descent, which we consider in Chapter 4.
Usually, we optimize the natural logarithm of the right-hand side expression in eq. 4 because
the logarithm of a product becomes the sum of logarithms and it’s easier for the machine to
work with the sum than with a product1.
2.6 Classification vs. Regression
Classification is a problem of automatically assigning a label to an unlabeled example.
Spam detection is a famous example of classification.
In machine learning, the classification problem is solved by a classification learning algorithm
that takes a collection of labeled examples as inputs and produces a model that can take
an unlabeled example as input and either directly output a label or output a number that
can be used by the data analyst to deduce the label easily. An example of such a number is
a probability.
In a classification problem, a label is a member of a finite set of classes. If the size of
the set of classes is two (“sick”/“healthy”, “spam”/“not_spam”), we talk about binary
classification (also called binomial in some books).
Multiclass classification (also called multinomial) is a classification problem with three
or more classes2.
While some learning algorithms naturally allow for more than two classes, others are by nature
binary classification algorithms. There are strategies allowing to turn a binary classification
learning algorithm into a multiclass one. I talk about one of them in Chapter 7.
Regression is a problem of predicting a real-valued label (often called a target) given an
unlabeled example. Estimating house price valuation based on house features, such as area,
the number of bedrooms, location and so on is a famous example of regression.
1Multiplication of many numbers can give either a very small result or a very large one. It often results in
the problem of numerical overflow when the machine cannot store such extreme numbers in memory.
2There’s still one label per example though.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 12
The regression problem is solved by a regression learning algorithm that takes a collection
of labeled examples as inputs and produces a model that can take an unlabeled example as
input and output a target.
2.7 Model-Based vs. Instance-Based Learning
Most supervised learning algorithms are model-based. We have already seen one such
algorithm: SVM. Model-based learning algorithms use the training data to create a model
that has parameters learned from the training data. In SVM, the two parameters we saw
were wú and bú. After the model was built, the training data can be discarded.
Instance-based learning algorithms use the whole dataset as the model. One instance-based
algorithm frequently used in practice is k-Nearest Neighbors (kNN). In classification, to
predict a label for an input example the kNN algorithm looks at the close neighborhood of
the input example in the space of feature vectors and outputs the label that it saw the most
often in this close neighborhood.
2.8 Shallow vs. Deep Learning
A shallow learning algorithm learns the parameters of the model directly from the features
of the training examples. Most supervised learning algorithms are shallow. The notorious
exceptions are neural network learning algorithms, specifically those that build neural
networks with more than one layer between input and output. Such neural networks are
called deep neural networks. In deep neural network learning (or, simply, deep learning),
contrary to shallow learning, most model parameters are learned not directly from the features
of the training examples, but from the outputs of the preceding layers.
Don’t worry if you don’t understand what that means right now. We look at neural networks
more closely in Chapter 6.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 13
The
Hundred-
Page
Machine
Learning
Book
Andriy Burkov
“All models are wrong, but some are useful.”
— George Box
The book is distributed on the “read first, buy later” principle.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft
3 Fundamental Algorithms
In this chapter, I describe five algorithms which are not just the most known but also either
very e�ective on their own or are used as building blocks for the most e�ective learning
algorithms out there.
3.1 Linear Regression
Linear regression is a popular regression learning algorithm that learns a model which is a
linear combination of features of the input example.
3.1.1 Problem Statement
We have a collection of labeled examples {(xi, yi)}Ni=1, where N is the size of the collection,
xi is the D-dimensional feature vector of example i = 1, . . . , N , yi is a real-valued1 target
and every feature x(j)i , j = 1, . . . , D, is also a real number.
We want to build a model fw,b(x) as a linear combination of features of example x:
fw,b(x) = wx + b, (1)
where w is a D-dimensional vector of parameters and b is a real number. The notation fw,b
means that the model f is parametrized by two values: w and b.
We will use the model to predict the unknown y for a given x like this: y Ω fw,b(x). Two
models parametrized by two di�erent pairs (w, b) will likely produce two di�erent predictions
when applied to the same example. We want to find the optimal values (wú, bú). Obviously,
the optimal values of parameters define the model that makes the most accurate predictions.
You could have noticed that the form of our linear model in eq. 1 is very similar to the form
of the SVM model. The only di�erence is the missing sign operator. The two models are
indeed similar. However, the hyperplane in the SVM plays the role of the decision boundary:
it’s used to separate two groups of examples from one another. As such, it has to be as far
from each group as possible.
On the other hand, the hyperplane in linear regression is chosen to be as close to all training
examples as possible.
You can see why this latter requirement is essential by looking at the illustration in fig. 1. It
displays the regression line (in light-blue) for one-dimensional examples (dark-blue dots). We
can use this line to predict the value of the target ynew for a new unlabeled input example
xnew. If our examples are D-dimensional feature vectors (for D > 1), the only di�erence
1To say that yi is real-valued, we write yi œ R, where R denotes the set of all real numbers, an infinite set
of numbers from minus infinity to plus infinity.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 3
Figure 1: Linear Regression for one-dimensional examples.
with the one-dimensional case is that the regression model is not a line but a plane (for two
dimensions) or a hyperplane (for D > 2).
Now you see why it’s essential to have the requirement that the regression hyperplane lies as
close to the training examples as possible: if the blue line in fig. 1 was far from the blue dots,
the prediction ynew would have fewer chances to be correct.
3.1.2 Solution
To get this latter requirement satisfied, the optimization procedure which we use to find the
optimal values for wú and bú tries to minimize the following expression:
1
N
ÿ
i=1...N
(fw,b(xi) ≠ yi)2. (2)
In mathematics, the expression we minimize or maximize is called an objective function, or,
simply, an objective. The expression (f(xi) ≠ yi)2 in the above objective is called the loss
function. It’s a measure of penalty for misclassification of example i. This particular choice
of the loss function is called squared error loss. All model-based learning algorithms have
a loss function and what we do to find the best model is we try to minimize the objective
known as the cost function. In linear regression, the cost function is given by the average
loss, also called the empirical risk. The average loss, or empirical risk, for a model, is the
average of all penalties obtained by applying the model to the training data.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 4
Why is the loss in linear regression a quadratic function? Why couldn’t we get the absolute
value of the di�erence between the true target yi and the predicted value f(xi) and use that
as a penalty? We could. Moreover, we also could use a cube instead of a square.
Now you probably start realizing how many seemingly arbitrary decisions are made when we
design a machine learning algorithm: we decided to use the linear combination of features to
predict the target. However, we could use a square or some other polynomial to combine the
values of features. We could also use some other loss function that makes sense: the absolute
di�erence between f(xi) and yi makes sense, the cube of the di�erence too; the binary loss
(1 when f(xi) and yi are di�erent and 0 when they are the same) also makes sense, right?
If we made di�erent decisions about the form of the model, the form of the loss function,
and about the choice of the algorithm that minimizes the average loss to find the best values
of parameters, we would end up inventing a di�erent machine learning algorithm. Sounds
easy, doesn’t it? However, do not rush to invent a new learning algorithm. The fact that it’s
di�erent doesn’t mean that it will work better in practice.
People invent new learning algorithms for one of the two main reasons:
1. The new algorithm solves a specific practical problem better than the existing algorithms.
2. The new algorithm has better theoretical guarantees on the quality of the model it
produces.
One practical justification of the choice of the linear form for the model is that it’s simple.
Why use a complex model when you can use a simple one? Another consideration is that
linear models rarely overfit. Overfitting is the property of a model such that the model
predicts very well labels of the examples used during training but frequently makes errors
when applied to examples that weren’t seen by the learning algorithm during training.
An example of overfitting in regression is shown in fig. 2. The data used to build the red
regression line is the same as in fig. 1. The di�erence is that this time, this is the polynomial
regression with a polynomial of degree 10. The regression line predicts almost perfectly the
targets almost all training examples, but will likely make significant errors on new data, as
you can see in fig. 1 for xnew. We talk more about overfitting and how to avoid it Chapter 5.
Now you know why linear regression can be useful: it doesn’t overfit much. But what
about the squared loss? Why did we decide that it should be squared? In 1705, the French
mathematician Adrien-Marie Legendre, who first published the sum of squares method for
gauging the quality of the model stated that squaring the error before summing is convenient.
Why did he say that? The absolute value is not convenient, because it doesn’t have a
continuous derivative, which makes the function not smooth. Functions that are not smooth
create unnecessary di�culties when employing linear algebra to find closed form solutions
to optimization problems. Closed form solutions to finding an optimum of a function are
simple algebraic expressions and are often preferable to using complex numerical optimization
methods, such as gradient descent (used, among others, to train neural networks).
Intuitively, squared penalties are also advantageous because they exaggerate the di�erence
between the true target and the predicted one according to the value of this di�erence. We
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 5
y
x
new
new
Figure 2: Overfitting.
might also use the powers 3 or 4, but their derivatives are more complicated to work with.
Finally, why do we care about the derivative of the average loss? Remember from algebra
that if we can calculate the gradient of the function in eq. 2, we can then set this gradient to
zero2 and find the solution to a system of equations that gives us the optimal values wú and
b
ú. You can spend several minutes and check it yourself.
3.2 Logistic Regression
The first thing to say is that logistic regression is not a regression, but a classification learning
algorithm. The name comes from statistics and is due to the fact that the mathematical
formulation of logistic regression is similar to that of linear regression.
I explain logistic regression on the case of binary classification. However, it can naturally be
extended to multiclass classification.
3.2.1 Problem Statement
In logistic regression, we still want to model yi as a linear function of xi, however, with a
binary yi this is not straightforward. The linear combination of features such as wxi + b is a
function that spans from minus infinity to plus infinity, while yi has only two possible values.
2To find the minimum or the maximum of a function, we set the gradient to zero because the value of the
gradient at extrema of a function is always zero. In 2D, the gradient at an extremum is a horizontal line.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 6
Figure 3: Standard logistic function.
At the time where the absence of computers required scientists to perform manual calculations,
they were eager to find a linear classification model. They figured out that if we define a
negative label as 0 and the positive label as 1, we would just need to find a simple continuous
function whose codomain is (0, 1). In such a case, if the value returned by the model for
input x is closer to 0, then we assign a negative label to x; otherwise, the example is labeled
as positive. One function that has such a property is the standard logistic function (also
known as the sigmoid function):
f(x) = 11 + e≠x ,
where e is the base of the natural logarithm (also called Euler’s number ; ex is also known as
the exp(x) function in Excel and many programming languages). Its graph is depicted in fig.
3.
By looking at the graph of the standard logistic function, we can see how well it fits our
classification purpose: if we optimize the values of x and b appropriately, we could interpret
the output of f(x) as the probability of yi being positive. For example, if it’s higher than or
equal to the threshold 0.5 we would say that the class of x is positive; otherwise, it’s negative.
In practice, the choice of the threshold could be di�erent depending on the problem. We
return to this discussion in Chapter 5 when we talk about model performance assessment.
So our logistic regression model looks like this:
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 7
fw,b(x)
def= 1
1 + e≠(wx+b)
. (3)
You can see the familiar term wx + b from linear regression. Now, how do we find the best
values wú and bú for our model? In linear regression, we minimized the empirical risk which
was defined as the average squared error loss, also known as the mean squared error or
MSE.
3.2.2 Solution
In logistic regression, instead of using a squared loss and trying to minimize the empirical
risk, we maximize the likelihood of our training set according to the model. In statistics, the
likelihood function defines how likely the observation (an example) is according to our model.
For instance, assume that we have a labeled example (xi, yi) in our training data. Assume
also that we have found (guessed) some specific values ŵ and b̂ of our parameters. If we now
apply our model fŵ,b̂ to xi using eq. 3 we will get some value 0 < p < 1 as output. If yi is
the positive class, the likelihood of yi being the positive class, according to our model, is
given by p. Similarly, if yi is the negative class, the likelihood of it being the negative class is
given by 1 ≠ p.
The optimization criterion in logistic regression is called maximum likelihood. Instead of
minimizing the average loss, like in linear regression, we now maximize the likelihood of the
training data according to our model:
Lw,b
def=
Ÿ
i=1...N
fw,b(xi)yi(1 ≠ fw,b(xi))(1≠yi). (4)
The expression fw,b(x)yi(1 ≠ fw,b(x))(1≠yi) may look scary but it’s just a fancy mathematical
way of saying: “fw,b(x) when yi = 1 and (1 ≠ fw,b(x)) otherwise”. Indeed, if yi = 1, then
(1 ≠ fw,b(x))(1≠yi) equals 1 because (1 ≠ yi) = 0 and we know that anything power 0 equals
1. On the other hand, if yi = 0, then fw,b(x)yi equals 1 for the same reason.
You may have noticed that we used the product operator
r
in the objective function instead
of the sum operator
q
which was used in linear regression. It’s because the likelihood of
observing N labels for N examples is the product of likelihoods of each observation (assuming
that all observations are independent of one another, which is the case). You can draw
a parallel with the multiplication of probabilities of outcomes in a series of independent
experiments in the probability theory.
Because of the exp function used in the model, in practice, it’s more convenient to maximize
the log-likelihood instead of likelihood. The log-likelihood is defined like follows:
LogLw,b
def= ln(L(w,b(x)) =
Nÿ
i=1
yi ln fw,b(x) + (1 ≠ yi) ln (1 ≠ fw,b(x)).
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 8
Because ln is a strictly increasing function, maximizing this function is the same as maximizing
its argument, and the solution to this new optimization problem is the same as the solution
to the original problem.
Contrary to linear regression, there’s no closed form solution to the above optimization
problem. A typical numerical optimization procedure used in such cases is gradient descent.
I talk about it in the next chapter.
3.3 Decision Tree Learning
A decision tree is an acyclic graph that can be used to make decisions. In each branching
node of the graph, a specific feature j of the feature vector is examined. If the value of the
feature is below a specific threshold, then the left branch is followed; otherwise, the right
branch is followed. As the leaf node is reached, the decision is made about the class to which
the example belongs.
As the title of the section suggests, a decision tree can be learned from data.
3.3.1 Problem Statement
Like previously, we have a collection of labeled examples; labels belong to the set {0, 1}. We
want to build a decision tree that would allow us to predict the class of an example given a
feature vector.
3.3.2 Solution
There are various formulations of the decision tree learning algorithm. In this book, we
consider just one, called ID3.
The optimization criterion, in this case, is the average log-likelihood:
1
N
Nÿ
i=1
yi ln fID3(xi) + (1 ≠ yi) ln (1 ≠ fID3(xi)), (5)
where fID3 is a decision tree.
By now, it looks very similar to logistic regression. However, contrary to the logistic regression
learning algorithm which builds a parametric model fwú,bú by finding an optimal solution
to the optimization criterion, the ID3 algorithm optimizes it approximately by constructing a
non-parametric model fID3(x)
def= Pr(y = 1|x).
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 9
S={(x1, y1), (x2, y2), (x3, y3),
(x4, y4), (x5, y5), (x6, y6),
(x7, y7), (x8, y8), (x9, y9),
(x10, y10), (x11, y11), (x12, y12)}
x
Pr(y = 1|x) = (y1+y2+y3+y4+y5
+y6+y7+y8+y9+y10+y11+y12)/12
Pr(y = 1|x)
(a)
x
Pr(y = 1|x) = (y1+y2+y4
+y6+y7+y8+y9)/7
Pr(y = 1|x)
x(3) < 18.3?
S = {(x1, y1), (x2, y2),
(x4, y4), (x6, y6), (x7, y7),
(x8, y8), (x9, y9)}
Pr(y = 1|x) =
(y3+y5+y10+y11+y12)/5
Pr(y = 1|x)
S+ = {(x3, y3), (x5, y5), (x10, y10),
(x11, y11), (x12, y12)}
Yes No
(b)
Figure 4: An illustration of a decision tree building algorithm. The set S contains 12 labeled
examples. (a) In the beginning, the decision tree only contains the start node; it makes the
same prediction for any input. (b) The decision tree after the first split; it tests whether
feature 3 is less than 18.3 and, depending on the result, the prediction is made in one of the
two leaf nodes.
The ID3 learning algorithm works as follows. Let S denote a set of labeled examples. In the
beginning, the decision tree only has a start node that contains all examples: S def= {(xi, yi)}Ni=1.
Start with a constant model fSID3:
f
S
ID3 =
1
|S|
ÿ
(x,y)œS
y. (6)
The prediction given by the above model, fSID3(x), would be the same for any input x. The
corresponding decision tree is shown in fig 4a.
Then we search through all features j = 1, . . . , D and all thresholds t, and split the set S
into two subsets: S≠
def= {(x, y) | (x, y) œ S, x(j) < t} and S+ = {(x, y) | (x, y) œ S , x(j) Ø t}.
The two new subsets would go to two new leaf nodes, and we evaluate, for all possible pairs
(j, t) how good the split with pieces S≠ and S+ is. Finally, we pick the best such values (j, t),
split S into S+ and S≠, form two new leaf nodes, and continue recursively on S+ and S≠ (or
quit if no split produces a model that’s su�ciently better than the current one). A decision
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 10
tree after one split is illustrated in fig 4b.
Now you should wonder what do the words “evaluate how good the split is” mean. In ID3, the
goodness of a split is estimated by using the criterion called entropy. Entropy is a measure of
uncertainty about a random variable. It reaches its maximum when all values of the random
variables are equiprobable. Entropy reaches its minimum when the random variable can have
only one value. The entropy of a set of examples S is given by:
H(S) = ≠fSID3 ln fSID3 ≠ (1 ≠ fSID3) ln(1 ≠ fSID3).
When we split a set of examples by a certain feature j and a threshold t, the entropy of a
split, H(S≠, S+), is simply a weighted sum of two entropies:
H(S≠, S+) =
|S≠|
|S| H(S≠) +
|S+|
|S| H(S+). (7)
So, in ID3, at each step, at each leaf node, we find a split that minimizes the entropy given
by eq. 7 or we stop at this leaf node.
The algorithm stops at a leaf node in any of the below situations:
• All examples in the leaf node are classified correctly by the one-piece model (eq. 6).
• We cannot find an attribute to split upon.
• The split reduces the entropy less than some ‘ (the value for which has to be found
experimentally3).
• The tree reaches some maximum depth d (also has to be found experimentally).
Because in ID3, the decision to split the dataset on each iteration is local (doesn’t depend
on future splits), the algorithm doesn’t guarantee an optimal solution. The model can be
improved by using techniques like backtracking during the search for the optimal decision
tree at the cost of possibly taking longer to build a model.
The entropy-based split criterion intuitively makes sense: entropy
reaches its minimum of 0 when all examples in S have the same label;
on the other hand, the entropy is at its maximum of 1 when exactly
one-half of examples in S is labeled with 1, making such a leaf useless
for classification. The only remaining question is how this algorithm
approximately maximizes the average log-likelihood criterion. I leave it
for further reading.
3In Chapter 5, we will see how to do that when we talk about hyperparameter tuning.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 11
3.4 Support Vector Machine
We already considered SVM in the introduction, so this section only fills a couple of blanks.
Two critical questions need to be answered:
1. What if there’s noise in the data and no hyperplane can perfectly separate positive
examples from negative ones?
2. What if the data cannot be separated using a plane, but could be separated by a
higher-order polynomial?
Figure 5: Linearly non-separable cases. Left: the presence of noise. Right: inherent
nonlinearity.
You can see both situations depicted in fig 5. In the left case, the data could be separated by
a straight line if not for the noise (outliers or examples with wrong labels). In the right case,
the decision boundary is a circle and not a straight line.
Remember that in SVM, we want to satisfy the following constraints:
a) wxi ≠ b Ø 1 if yi = +1, and
b) wxi ≠ b Æ ≠1 if yi = ≠1
We also want to minimize ÎwÎ so that the hyperplane was equally distant from the closest
examples of each class. Minimizing ÎwÎ is equivalent to minimizing 12 ||w||
2, and the use of
this term makes it possible to perform quadratic programming optimization later on. The
optimization problem for SVM, therefore, looks like this:
min 12 ||w||
2
, such that yi(xiw ≠ b) ≠ 1 Ø 0, i = 1, . . . , N. (8)
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 12
3.4.1 Dealing with Noise
To extend SVM to cases in which the data is not linearly separable, we introduce the hinge
loss function: max (0, 1 ≠ yi(wxi ≠ b)).
The hinge loss function is zero if the constraints a) and b) are satisfied, in other words, if wxi
lies on the correct side of the decision boundary. For data on the wrong side of the decision
boundary, the function’s value is proportional to the distance from the decision boundary.
We then wish to minimize the following cost function,
CÎwÎ2 + 1
N
Nÿ
i=1
max (0, 1 ≠ yi(wxi ≠ b)) ,
where the hyperparameter C determines the tradeo� between increasing the size of the
decision boundary and ensuring that each xi lies on the correct side of the decision boundary.
The value of C is usually chosen experimentally, just like ID3’s hyperparameters ‘ and d.
SVMs that optimize hinge loss are called soft-margin SVMs, while the original formulation is
referred to as a hard-margin SVM.
As you can see, for su�ciently high values of C, the second term in the cost function will
become negligible, so the SVM algorithm will try to find the highest margin by completely
ignoring misclassification. As we decrease the value of C, making classification errors is
becoming more costly, so the SVM algorithm will try to make fewer mistakes by sacrificing
the margin size. As we have already discussed, a larger margin is better for generalization.
Therefore, C regulates the tradeo� between classifying the training data well (minimizing
empirical risk) and classifying future examples well (generalization).
3.4.2 Dealing with Inherent Non-Linearity
SVM can be adapted to work with datasets that cannot be separated by a hyperplane in
its original space. However, if we manage to transform the original space into a space of
higher dimensionality, we could hope that the examples will become linearly separable in this
transformed space. In SVMs, using a function to implicitly transform the original space into
a higher dimensional space during the cost function optimization is called the kernel trick.
The e�ect of applying the kernel trick is illustrated in fig. 6. As you can see, it’s possible
to transform a two-dimensional non-linearly-separable data into a linearly-separable three-
dimensional data using a specific mapping „ : x ‘æ „(x), where „(x) is a vector of higher
dimensionality than x. For the example of 2D data in fig. 5 (right), the mapping „ for
example x = [q, p] that projects this example into a 3D space (fig. 6) would look like this
„([q, p]) def= (q2,
Ô
2qp, p2), where q2 means q squared. You see now that the data becomes
linearly separable in the transformed space.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 13
Figure 6: The data from fig. 5 (right) becomes linearly separable after a transformation into
a three-dimensional space.
However, we don’t know a priori which mapping „ would work for our data. If we first
transform all our input examples using some mapping into very high dimensional vectors and
then apply SVM to this data, and we try all possible mapping functions, the computation
could become very ine�cient, and we would never solve our classification problem.
Fortunately, scientists figured out how to use kernel functions (or, simply, kernels) to
e�ciently work in higher-dimensional spaces without doing this transformation explicitly. To
understand how kernels work, we have to see first how the optimization algorithm for SVM
finds the optimal values for w and b.
The method traditionally used to solve the optimization problem in eq. 8 is the method of
Lagrange multipliers. Instead of solving the original problem from eq. 8, it is convenient to
solve an equivalent problem formulated like this:
max
–1...–N
Nÿ
i=1
–i ≠
1
2
Nÿ
i=1
Nÿ
k=1
yi–i(xixk)yk–k subject to
Nÿ
i=1
–iyi = 0 and –i Ø 0, i = 1, . . . , N,
where –i are called Lagrange multipliers. When formulated like this, the optimization
problem becomes a convex quadratic optimization problem, e�ciently solvable by quadratic
programming algorithms.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 14
Now, you could have noticed that in the above formulation, there is a term xixk, and this is
the only place where the feature vectors are used. If we want to transform our vector space
into higher dimensional space, we need to transform xi into „(xi) and xj into „(xj) and
then multiply „(xi) and „(xj). It would be very costly to do so.
On the other hand, we are only interested in the result of the dot-product xixk, which, as
we know, is a real number. We don’t care how this number was obtained as long as it’s
correct. By using the kernel trick, we can get rid of a costly transformation of original
feature vectors into higher-dimensional vectors and avoid computing their dot-product. We
replace that by a simple operation on the original feature vectors that gives the same
result. For example, instead of transforming (q1, p1) into (q21 ,
Ô
2q1p1, p21) and (q2, p2) into
(q22 ,
Ô
2q2p2, p22) and then computing the dot-product of (q21 ,
Ô
2q1p1, p21) and (q22 ,
Ô
2q2p2, p22)
to obtain (q21q22 +2q1q2p1p2 +p21p22) we could find the dot-product between (q1, p1) and (q2, p2)
to get (q1q2 +p1p2) and then square it to get exactly the same result (q21q22 +2q1q2p1p2 +p21p22).
That was an example of the kernel trick, and we used the quadratic kernel k(xi, xk)
def= (xixk)2.
Multiple kernel functions exist, the most widely used of which is the RBF kernel:
k(x, xÕ) = exp
3
≠Îx ≠ x
ÕÎ2
2‡2
4
,
where Îx ≠ xÕÎ2 is the squared Euclidean distance between two feature vectors. The
Euclidean distance is given by the following equation:
d(xi, xk)
def=
Ú1
x
(1)
i ≠ x
(1)
k
22
+
1
x
(2)
i ≠ x
(2)
k
22
+ · · · +
1
x
(N)
i ≠ x
(N)
k
22
=
ı̂ıÙ
Dÿ
j=1
1
x
(j)
i ≠ x
(j)
k
22
.
It can be shown that the feature space of the RBF (for “radial basis function”) kernel has
an infinite number of dimensions. By varying the hyperparameter ‡, the data analyst can
choose between getting a smooth or curvy decision boundary in the original space.
3.5 k-Nearest Neighbors
k-Nearest Neighbors (kNN) is a non-parametric learning algorithm. Contrary to other
learning algorithms that allow discarding the training data after the model is built, kNN
keeps all training examples in memory. Once a new, previously unseen example x comes in,
the kNN algorithm finds k training examples closest to x and returns the majority label (in
case of classification) or the average label (in case of regression).
The closeness of two points is given by a distance function. For example, Euclidean distance
seen above is frequently used in practice. Another popular choice of the distance function is
the negative cosine similarity. Cosine similarity defined as,
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 15
s(xi, xk)
def= cos(\(xi, xk)) =
qD
j=1 x
(j)
i x
(j)
kÚ
qD
j=1
1
x
(j)
i
22ÚqD
j=1
1
x
(j)
k
22 ,
is a measure of similarity of the directions of two vectors. If the angle between two vectors
is 0 degrees, then two vectors point to the same direction, and cosine similarity is equal to
1. If the vectors are orthogonal, the cosine similarity is 0. For vectors pointing in opposite
directions, the cosine similarity is ≠1. If we want to use cosine similarity as a distance metric,
we need to multiply it by ≠1. Other popular distance metrics include Chebychev distance,
Mahalanobis distance, and Hamming distance. The choice of the distance metric, as well as
the value for k, are the choices the analyst makes before running the algorithm. So these
are hyperparameters. The distance metric could also be learned from data (as opposed to
guessing it). We talk about that in Chapter 10.
Now you know how the model building algorithm works and how the prediction is made. A
reasonable question is what is the cost function here? Surprisingly, this question has not
been well studied in the literature, despite the algorithm’s popularity since the earlier 1960s.
The only attempt to analyze the cost function of kNN I’m aware of was undertaken by Li
and Yang in 20034. Below, I outline their considerations.
For simplicity, let’s make our derivation under the assumptions of binary classification
(y œ {0, 1}) with cosine similarity and normalized feature vectors5. Under these assumptions,
kNN does a locally linear classification with the vector of coe�cients,
wx =
ÿ
(xÕ,yÕ)œRk(x)
y
Õ
x
Õ
, (9)
where Rk(x) is the set of k nearest neighbors to the input example x. The above equation
says that we take the sum of all nearest neighbor feature vectors to some input vector x
by ignoring those that have label 0. The classification decision is obtained by defining a
threshold on the dot-product wxx which, in the case of normalized feature vectors, is equal
to the cosine similarity between wx and x.
Now, defining the cost function like this:
L = ≠
ÿ
(xÕ,yÕ)œRk(x)
y
Õ
x
Õ
wx +
1
2 ||w||
2
and setting the first order derivative of the right-hand side to zero yields the formula for the
coe�cient vector in eq. 9.
4F. Li and Y. Yang, “A loss function analysis for classification methods in text categorization,” in ICML
2003, pp. 472–479, 2003.
5We discuss normalization later; for the moment assume that all features of feature vectors were squeezed
into the range [0, 1].
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 16
The
Hundred-
Page
Machine
Learning
Book
Andriy Burkov
“All models are wrong, but some are useful.”
— George Box
The book is distributed on the “read first, buy later” principle.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft
4 Anatomy of a Learning Algorithm
4.1 Building Blocks of a Learning Algorithm
You may have noticed by reading the previous chapter that each learning algorithm we saw
consisted of three parts:
1) a loss function;
2) an optimization criterion based on the loss function (a cost function, for example); and
3) an optimization routine that leverages training data to find a solution to the optimization
criterion.
These are the building blocks of any learning algorithm. You saw in the previous chapter
that some algorithms were designed to explicitly optimize a specific criterion (both linear and
logistic regressions, SVM). Some others, including decision tree learning and kNN, optimize
the criterion implicitly. Decision tree learning and kNN are among the oldest machine
learning algorithms and were invented experimentally based on intuition, without a specific
global optimization criterion in mind, and (like it often happens in scientific history) the
optimization criteria were developed later to explain why those algorithms work.
By reading modern literature on machine learning, you often encounter references to gradient
descent or stochastic gradient descent. These are two most frequently used optimization
algorithms used in cases where the optimization criterion is di�erentiable.
Gradient descent is an iterative optimization algorithm for finding the minimum of a function.
To find a local minimum of a function using gradient descent, one starts at some random
point and takes steps proportional to the negative of the gradient (or approximate gradient)
of the function at the current point.
Gradient descent can be used to find optimal parameters for linear and logistic regression,
SVM and also neural networks which we consider later. For many models, such as logistic
regression or SVM, the optimization criterion is convex. Convex functions have only one
minimum, which is global. Optimization criteria for neural networks are not convex, but in
practice even finding a local minimum su�ces.
Let’s see how gradient descent works.
4.2 Gradient Descent
In this section, I demonstrate how gradient descent finds the solution to a linear regression
problem1. I illustrate my description with Python source code as well as with plots that
show how the solution improves after some iterations of the gradient descent algorithm.
1
As you know, linear regression has a closed form solution. That means that gradient descent is not
needed to solve this specific type of problem. However, for illustration purposes, linear regression is a perfect
problem to explain gradient descent.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 3
I use a dataset with only one feature. However, the optimization criterion will have two
parameters: w and b. The extension to multi-dimensional training data is straightforward:
you have variables w(1), w(2), and b for two-dimensional data, w(1), w(2), w(3), and b for
three-dimensional data and so on.
Figure 1: The original data. The Y-axis corresponds to the sales in units (the quantity we
want to predict), the X-axis corresponds to our feature: the spendings on radio ads in M$.
To give a practical example, I use the real dataset with the following columns: the Spendings
of various companies on radio advertising each year and their annual Sales in terms of units
sold. We want to build a regression model that we can use to predict units sold based on
how much a company spends on radio advertising. Each row in the dataset represents one
specific company:
Company Spendings, M$ Sales, Units
1 37.8 22.1
2 39.3 10.4
3 45.9 9.3
4 41.3 18.5
.. .. ..
We have data for 200 companies, so we have 200 training examples. Fig. 1 shows all examples
on a 2D plot.
Remember that the linear regression model looks like this: f(x) = wx + b. We don’t know
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 4
what the optimal values for w and b are and we want to learn them from data. To do that,
we look for such values for w and b that minimize the mean squared error:
l = 1
N
Nÿ
i=1
(yi ≠ (wxi + b))2.
Gradient descent starts with calculating the partial derivative for every parameter:
ˆl
ˆw
= 1
N
Nÿ
i=1
≠2xi(yi ≠ (wxi + b));
ˆl
ˆb
= 1
N
Nÿ
i=1
≠2(yi ≠ (wxi + b)).
(1)
To find the partial derivative of the term (yi ≠ (wx + b))2 with respect to w we applied the
chain rule. Here, we have the chain f = f2(f1) where f1 = yi ≠ (wx + b) and f2 = f21 . To find
a partial derivative of f with respect to w we have to first find the partial derivative of f with
respect to f2 which is equal to 2(yi ≠ (wx + b)) (from calculus, we know that the derivative
ˆf
ˆx x
2 = 2x) and then we have to multiply it by the partial derivative of yi ≠ (wx + b) with
respect to w which is equal to ≠x. So overall ˆlˆw =
1
N
qN
i=1 ≠2xi(yi ≠ (wxi + b)). In a similar
way, the partial derivative of l with respect to b, ˆlˆb , was calculated.
We initialize2 w0 = 0 and b0 = 0 and then iterate through our training examples, each
example having the form of (xi, yi) = (Spendingsi, Salesi). For each training example, we
update w and b using our partial derivatives. The learning rate – controls the size of an
update:
wi Ω –
≠2xi(yi ≠ (wi≠1xi + bi≠1))
N
;
bi Ω –
≠2(yi ≠ (wi≠1xi + bi≠1))
N
,
(2)
where wi and bi denote the values of w and b after using the example (xi, yi) for the update.
One pass through all training examples is called an epoch. Typically, we need multiple
epochs until we start seeing that the values for w and b don’t change much; then we stop.
2
In complex models, such as neural networks, which have thousands of parameters, the initialization of
parameters may significantly a�ect the solution found using gradient descent. There are di�erent initialization
methods (at random, with all zeroes, with small values around zero, and others) and it is an important choice
the data analyst has to make.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 5
It’s hard to imagine a machine learning engineer who doesn’t use Python. So, if you waited
for the right moment to start learning Python, this is that moment. Below we show how to
program gradient descent in Python.
The function that updates the parameters w and b during one epoch is shown below:
def update_w_and_b(spendings, sales, w, b, alpha):
dl_dw = 0.0
dl_db = 0.0
N = len(spendings)
for i in range(N):
dl_dw += -2*spendings[i]*(sales[i] - (w*spendings[i] + b))
dl_db += -2*(sales[i] - (w*spendings[i] + b))
# update w and b
w = w - (1/float(N))*dl_dw*alpha
b = b - (1/float(N))*dl_db*alpha
return w, b
The function that loops over multiple epochs is shown below:
def train(spendings, sales, w, b, alpha, epochs):
for e in range(epochs):
w, b = update_w_and_b(spendings, sales, w, b, alpha)
# log the progress
if e % 400 == 0:
print("epoch:", e, "loss: ", avg_loss(spendings, sales, w, b))
return w, b
The function avg_loss in the above code snippet is a function that computes the mean
squared error. It is defined as:
def avg_loss(spendings, sales, w, b):
N = len(spendings)
total_error = 0.0
for i in range(N):
total_error += (sales[i] - (w*spendings[i] + b))**2
return total_error / float(N)
If we run the train function for – = 0.001, w = 0.0, b = 0.0, and 15000 epochs, we will see
the following output (shown partially):
epoch: 0 loss: 92.32078294903626
epoch: 400 loss: 33.79131790081576
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 6
epoch: 800 loss: 27.9918542960729
epoch: 1200 loss: 24.33481690722147
epoch: 1600 loss: 22.028754937538633
...
epoch: 2800 loss: 19.07940244306619
Epoch 0 Epoch 400 Epoch 800
Epoch 1200 Epoch 1600 Epoch 3000
Figure 2: The evolution of the regression line through gradient descent epochs.
You can see that the average loss decreases as the train function loops through epochs. Fig.
2 shows the evolution of the regression line through epochs.
Finally, once we have found the optimal values of parameters w and b, the only missing piece
is a function that makes predictions:
def predict(x, w, b):
return w*x + b
Try to execute the following code:
w, b = train(x, y, 0.0, 0.0, 0.001, 15000)
x_new = 23.0
y_new = predict(x_new, w, b)
print(y_new)
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 7
The output is 13.97.
The gradient descent algorithm is sensitive to the choice of the step –. It is also slow for large
datasets. Fortunately, several significant improvements to this algorithm have been proposed.
Stochastic gradient descent (SGD) is a version of the algorithm that speeds up the
computation by approximating the gradient using smaller batches (subsets) of the training
data. SGD itself has various “upgrades”. Adagrad is a version of SGD that scales – for
each parameter according to the history of gradients. As a result, – is reduced for very large
gradients and vice-versa. Momentum is a method that helps accelerate SGD by orienting
the gradient descent in the relevant direction and reducing oscillations. In neural network
training, variants of SGD such as RMSprop and Adam, are most frequently used.
Notice that gradient descent and its variants are not machine learning algorithms. They are
solvers of minimization problems in which the function to minimize has a gradient in most
points of its domain.
4.3 How Machine Learning Engineers Work
Unless you are a research scientist or work for a huge corporation with a large R&D budget,
you usually don’t implement machine learning algorithms yourself. You don’t implement
gradient descent or some other solver either. You use libraries, most of which are open
source. A library is a collection of algorithms and supporting tools implemented with stability
and e�ciency in mind. The most frequently used in practice open-source machine learning
library is scikit-learn. It’s written in Python and C. Here’s how you do linear regression in
scikit-learn:
def train(x, y):
from sklearn.linear_model import LinearRegression
model = LinearRegression().fit(x,y)
return model
model = train(x,y)
x_new = 23.0
y_new = model.predict(x_new)
print(y_new)
The output will, again, be 13.97. Easy, right? You can replace LinearRegression with some
other type of regression learning algorithm without modifying anything else. It just works.
The same can be said about classification. You can easily replace LogisticRegression algorithm
with SVC algorithm (this is scikit-learn’s name for the Support Vector Machine algorithm),
DecisionTreeClassifier, NearestNeighbors or many other classification learning algorithms
implemented in scikit-learn.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 8
4.4 Learning Algorithms’ Particularities
Here we outline some practical particularities that can di�erentiate one learning algorithm
from another. You already know that di�erent learning algorithms can have di�erent
hyperparameters (C in SVM, ‘ and d in ID3). Solvers such as gradient descent can also have
hyperparameters, like – for example.
Some algorithms, like decision tree learning, can accept categorical features. For example, if
you have a feature “color” that can take values “red”, “yellow”, or “green”, you can keep
this feature as is. SVM, logistic and linear regression, as well as kNN (with cosine similarity
or Euclidean distance metrics), expect numerical values for all features. All algorithms
implemented in scikit-learn expect numerical features. I show in the next chapter how to
convert categorical features into numerical ones.
Some algorithms, like SVM, allow the data analyst to provide weightings for each class.
These weightings influence how the decision boundary is drawn. If the weight of some class
is high, the learning algorithm tries to not make errors in predicting training examples of
this class (typically, for the cost of making an error elsewhere). That could be important if
instances of some class are in the minority in your training data, but you would like to avoid
misclassifying examples of that class as much as possible.
Some classification models, like SVM and kNN, given a feature vector only output the class.
Others, like logistic regression or decision trees, can also return the score between 0 and 1
which can be interpreted as either how confident the model is about the prediction or as the
probability that the input example belongs to a certain class3.
Some classification algorithms (like decision tree learning, logistic regression, or SVM) build the
model using the whole dataset at once. If you have got additional labeled examples, you have
to rebuild the model from scratch. Other algorithms (such as Naïve Bayes, multilayer percep-
tron, SGDClassifier/SGDRegressor, PassiveAggressiveClassifier/PassiveAggressiveRegressor
in scikit-learn) can be trained iteratively, one batch at a time. Once new training examples
are available, you can update the model using only the new data.
Finally, some algorithms, like decision tree learning, SVM, and kNN can be used for both clas-
sification and regression, while others can only solve one type of problem: either classification
or regression, but not both.
Usually, each library provides the documentation that explains what kind of problem each
algorithm solves, what input values are allowed and what kind of output the model produces.
The documentation also provides information on hyperparameters.
3
If it’s really necessary, the score for SVM and kNN predictions could be synthetically created using some
simple techniques.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 9
Andriy Burkov's
“All models are wrong, but some are useful.”
— George Box
The book is distributed on the “read first, buy later” principle.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft
5 Basic Practice
Until now, I only mentioned in passing some problems a data analyst can encounter when
working on a machine learning problem: feature engineering, overfitting, and hyperparameter
tuning. In this chapter, we talk about these and other challenges that have to be addressed
before you can type model = LogisticRegresion().fit(x,y) in scikit-learn.
5.1 Feature Engineering
When a product manager tells you “We need to be able to predict whether a particular
customer will stay with us. Here are the logs of customers’ interactions with our product for
five years.” you cannot just grab the data, load it into a library and get a prediction. You
need to build a dataset first.
Remember from the first chapter that).
The problem of transforming raw data into a dataset is called feature engineering. For
most practical problems, feature engineering is a labor-intensive process that demands from
the data analyst a lot of creativity and, preferably, domain knowledge.
For example, to transform the logs of user interaction with a computer system, one could
create features that contain information about the user and various statistics extracted from
the logs. For each user, one feature would contain the price of the subscription; other features
would contain the frequency of connections per day, week and year. Another feature would
contain the average session duration in seconds or the average response time for one request,
and so on. Everything measurable can be used as a feature. The role of the data analyst is to
create informative features: those would allow the learning algorithm to build a model that
predicts well labels of the data used for training. Highly informative features are also called
features with high predictive power. For example, the average duration of a user’s session
has high predictive power for the problem of predicting whether the user will keep using the
application in the future.
We say that a model has a low bias when it predicts well the training data. That is, the
model makes few mistakes when we try to predict labels of the examples used to build the
model.
5.1.1 One-Hot Encoding
Some learning algorithms only work with numerical feature vectors. When some feature in
your dataset is categorical, like “colors” or “days of the week,” you can transform such a
categorical feature into several binary ones.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 3
If your example has a categorical feature “colors” and this feature has three possible values:
“red,” “yellow,” “green,” you can transform this feature into a vector of three numerical
values:
red = [1, 0, 0]
yellow = [0, 1, 0]
green = [0, 0, 1]
(1)
By doing so, you increase the dimensionality of your feature vectors. You should not transform
red into 1, yellow into 2, and green into 3 to avoid increasing the dimensionality because that
would imply that there’s an order among the values in this category and this specific order is
important for the decision making. If the order of a feature’s values is not important, using
ordered numbers as values is likely to confuse the learning algorithm,1 because the algorithm
will try to find a regularity where there’s no one, which may potentially lead to overfitting.
5.1.2 Binning
An opposite situation, occurring less frequently in practice, is when you have a numerical
feature but you want to convert it into a categorical one. Binning (also called bucketing)
is the process of converting a continuous feature into multiple binary features called bins or
buckets, typically based on value range. For example, instead of representing age as a single
real-valued feature, the analyst could chop ranges of age into discrete bins: all ages between
0 and 5 years-old could be put into one bin, 6 to 10 years-old could be in the second bin, 11
to 15 years-old could be in the third bin, and so on.
For example, suppose in our feature j = 18 represents age. By applying binning, we replace
this feature with the corresponding bins. Let the three new bins, “age_bin1”, “age_bin2”
and “age_bin3” be added with indexes j = 123, j = 124 and j = 125 respectively. Now if
x(18)i = 7 for some example xi, then we set feature x
(124)
i to 1; if x
(18)
i = 13, then we set
feature x(125)i to 1, and so on.
In some cases, a carefully designed binning can help the learning algorithm to learn using
fewer examples. It happens because we give a “hint” to the learning algorithm that if the
value of a feature falls within a specific range, the exact value of the feature doesn’t matter.
1
When the ordering of values of some categorical variable matters, we can replace those values by numbers
by keeping only one variable. For example, if our variable represents the quality of an article, and the
values are {poor, decent, good, excellent}, then we could replace those categories by numbers, for example,
{1, 2, 3, 4}.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 4
5.1.3 Normalization
Normalization is the process of converting an actual range of values which a numerical
feature can take, into a standard range of values, typically in the interval [≠1, 1] or [0, 1].
For example, suppose the natural range of a particular feature is 350 to 1450. By subtracting
350 from every value of the feature, and dividing the result by 1100, one can normalize those
values into the range [0, 1].
More generally, the normalization formula looks like this:
x̄(j) = x
(j) ≠ min(j)
max(j) ≠ min(j)
,
where min(j) and max(j) are, respectively, the minimum and the maximum value of the
feature j in the dataset.
Why do we normalize? Normalizing the data is not a strict requirement. However, in practice,
it can lead to an increased speed of learning. Remember the gradient descent example from
the previous chapter. Imagine you have a two-dimensional feature vector. When you update
the parameters of w(1) and w(2), you use partial derivatives of the average squared error with
respect to w(1) and w(2). If x(1) is in the range [0, 1000] and x(2) the range [0, 0.0001], then
the derivative with respect to a larger feature will dominate the update.
Additionally, it’s useful to ensure that our inputs are roughly in the same relatively small
range to avoid problems which computers have when working with very small or very big
numbers (known as numerical overflow).
5.1.4 Standardization
Standardization (or z-score normalization) is the procedure during which the feature
values are rescaled so that they have the properties of a standard normal distribution with
µ = 0 and ‡ = 1, where µ is the mean (the average value of the feature, averaged over all
examples in the dataset) and ‡ is the standard deviation from the mean.
Standard scores (or z-scores) of features are calculated as follows:
x̂(j) = x
(j) ≠ µ(j)
‡(j)
.
You may ask when you should use normalization and when standardization. There’s no
definitive answer to this question. Usually, if your dataset is not too big and you have time,
you can try both and see which one performs better for your task.
If you don’t have time to run multiple experiments, as a rule of thumb:
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 5
• unsupervised learning algorithms, in practice, more often benefit from standardization
than from normalization;
• standardization is also preferred for a feature if the values this feature takes are
distributed close to a normal distribution (so-called bell curve);
• again, standardization is preferred for a feature if it can sometimes have extremely high
or low values (outliers); this is because normalization will “squeeze” the normal values
into a very small range;
• in all other cases, normalization is preferable.
Modern implementations of the learning algorithms, which you can find in popular libraries,
are robust to features lying in di�erent ranges. Feature rescaling is usually beneficial to most
learning algorithms, but in many cases, the model will still be good when trained from the
original features.
5.1.5 Dealing with Missing Features
In some cases, the data comes to the analyst in the form of a dataset with features already
defined. In some examples, values of some features can be missing. That often happens when
the dataset was handcrafted, and the person working on it forgot to fill some values or didn’t
get them measured at all.
The typical approaches of dealing with missing values for a feature include:
• Removing the examples with missing features from the dataset. That can be done if
your dataset is big enough so you can sacrifice some training examples.
• Using a learning algorithm that can deal with missing feature values (depends on the
library and a specific implementation of the algorithm).
• Using a data imputation technique.
5.1.6 Data Imputation Techniques
One technique consists in replacing the missing value of a feature by an average value of this
feature in the dataset:
x̂(j) = 1
N
x(j).
Another technique is to replace the missing value by the same value outside the normal range
of values. For example, if the normal range is [0, 1], then you can set the missing value equal
to 2 or ≠1. The idea is that the learning algorithm will learn what is it better to do when the
feature has a value significantly di�erent from other values. Alternatively, you can replace the
missing value by a value in the middle of the range. For example, if the range for a feature is
[≠1, 1], you can set the missing value to be equal to 0. Here, the idea is that if we use the
value in the middle of the range to replace missing features, such value will not significantly
a�ect the prediction.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 6
A more advanced technique is to use the missing value as the target variable for a regression
problem. You can use all remaining features [x(1)i , x
(2)
i , . . . , x
(j≠1)
i , x
(j+1)
i , . . . , x
(D)
i ] to form
a feature vector x̂i, set ŷi = x(j), where j is the feature with a missing value. Now we can
build a regression model to predict ŷ from the feature vectors x̂. Of course, to build training
examples (x̂, ŷ), you only use those examples from the original dataset, in which the value of
feature j is present.
Finally, if you have a significantly large dataset and just a few features with missing values,
you can increase the dimensionality of your feature vectors by adding a binary indicator
feature for each feature with missing values. Let’s say feature j = 12 in your D-dimensional
dataset has missing values. For each feature vector x, you then add the feature j = D + 1
which is equal to 1 if the value of feature 12 is present in x and 0 otherwise. The missing
feature value then can be replaced by 0 or any number of your choice.
At prediction time, if your example is not complete, you should use the same data imputation
technique to fill the missing features as the technique you used to complete the training data.
Before you start working on the learning problem, you cannot tell which data imputation
technique will work the best. Try several techniques, build several models and select the one
that works the best.
5.2 Learning Algorithm Selection
Choosing a machine learning algorithm can be a di�cult task. If you have much time, you
can try all of them. However, usually the time you have to solve a problem is limited. You
can ask yourself several questions before starting to work on the problem. Depending on
your answers, you can shortlist some algorithms and try them on your data.
• Explainability
Does your model have to be explainable to a non-technical audience? Most very accurate
learning algorithms are so-called “black boxes.” They learn models that make very few errors,
but why a model made a specific prediction could be very hard to understand and even
harder to explain. Examples of such models are neural networks or ensemble models.
On the other hand, kNN, linear regression, or decision tree learning algorithms produce
models that are not always the most accurate, however, the way they make their prediction
is very straightforward.
• In-memory vs. out-of-memory
Can your dataset be fully loaded into the RAM of your server or personal computer? If
yes, then you can choose from a wide variety of algorithms. Otherwise, you would prefer
incremental learning algorithms that can improve the model by adding more data
gradually.
• Number of features and examples
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 7
How many training examples do you have in your dataset? How many features does each
example have? Some algorithms, including neural networks and gradient boosting (we
consider both later), can handle a huge number of examples and millions of features. Others,
like SVM, can be very modest in their capacity.
• Categorical vs. numerical features
Is your data composed of categorical only, or numerical only features, or a mix of both?
Depending on your answer, some algorithms cannot handle your dataset directly, and you
would need to convert your categorical features into numerical ones by using some techniques
like one-hot encoding.
• Nonlinearity of the data
Is your data linearly separable or can it be modeled using a linear model? If yes, SVM with
the linear kernel, logistic regression or linear regression can be a good choice. Otherwise,
deep neural networks or ensemble algorithms, discussed in Chapters 6 and 7, might work
better for your data.
• Training speed
How much time is a learning algorithm allowed to use to build a model? Neural networks
are known to be slow to train. Simple algorithms like logistic and linear regression as well
as decision tree learning are much faster. Some specialized libraries contain very e�cient
implementations of some algorithms; you may prefer to do research online to find such
libraries. Some algorithms, such as random forests, benefit from the availability of multiple
CPU cores, so their model building time can be significantly reduced on a machine with
dozens of CPU cores.
• Prediction speed
How fast does the model have to be when generating predictions? Will your model be used in
production where very high throughput is required? Some algorithms, like SVMs, linear and
logistic regression, or some types of neural networks, are extremely fast at the prediction time.
Some others, like kNN, ensemble algorithms, and very deep or recurrent neural networks,
can be slower2.
If you don’t want to guess the best algorithm for your data, a popular way to choose one is
by testing it on the validation set. We talk about that below.
Alternatively, if you use scikit-learn, you could try their algorithm selection diagram shown
in fig. 1.
2
The prediction speeds of kNN and ensemble methods implemented in the modern libraries are still very
fast. Don’t be afraid of using these algorithms in your practice.
Andriy Burkov The Hundred-Page Machine Learning Book - Draft 8
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Andriy Burkov The Hundred-Page Machine Learning Book - Draft 9
5.3 Three Sets
Until now, I used the expressions “dataset” and “training set” interchangeably. However, in
practice data analysts work with three sets of labeled examples:
1) training set,
2) validation set, and
3) test set.
Once you have got your annotated dataset, the first thing you do is you shu�e the examples
and split the dataset into three subsets: training, validation, and test. The training set is
usually the biggest one, and you use it to build the model. The validation and test sets are
roughly the same sizes, much smaller than the size of the training set. The learning algorithm
cannot use examples from these two subsets to build a model. That is why those two sets are
often called hold-out sets.
There’s no optimal proportion to split the dataset into these three subsets. In the past, the
rule of thumb was to use 70% of the dataset for training, 15% for validation and 15% for
testing. However, in the age of big data, datasets often have millions of examples. In such
cases, it could be reasonable to keep 95% for training and 2.5%/2.5% for validation/testing.
You may wonder, what is the reason to have three sets and not one. Th | https://jp.b-ok.xyz/book/3676778/a61688 | CC-MAIN-2019-39 | refinedweb | 17,775 | 60.35 |
Introduction
To support interactive computing, fastai provides easy access to commonly-used external modules. A star import such as:
from fastai.basics import *
will populate the current namespace with these external modules in addition to fastai-specific functions and variables. This page documents these convenience imports, which are defined in fastai.imports.
Note: since this document was manually created, it could be outdated by the time you read it. To get the up-to-date listing of imports, use:
python -c 'a = set([*vars().keys(), "a"]); from fastai.basics import *; print(*sorted(set(vars().keys())-a), sep="\n")'
Names in bold are modules. If an object was aliased during its import, the original name is listed in parentheses. | https://docs.fast.ai/imports.html | CC-MAIN-2020-05 | refinedweb | 118 | 52.56 |
1 /* 2 * Copyright (c) 1998, 30 /** 31 * A class loader object from the target VM. 32 * A ClassLoaderReference is an {@link ObjectReference} with additional 33 * access to classloader-specific information from the target VM. Instances 34 * ClassLoaderReference are obtained through calls to 35 * {@link ReferenceType#classLoader} 36 * 37 * @see ObjectReference 38 * 39 * @author Gordon Hirsch 40 * @since 1.3 41 */ 42 @jdk.Exported 43 public interface ClassLoaderReference extends ObjectReference { 44 45 /** 46 * Returns a list of all loaded classes that were defined by this 47 * class loader. No ordering of this list guaranteed. 48 * <P> 49 * The returned list will include reference types 50 * loaded at least to the point of preparation and 51 * types (like array) for which preparation is 52 * not defined. 53 * 54 * @return a List of {@link ReferenceType} objects mirroring types 55 * loaded by this class loader. The list has length 0 if no types 56 * have been defined by this classloader. 57 */ 58 List<ReferenceType> definedClasses(); 59 60 /** 61 * Returns a list of all classes for which this class loader has 62 * been recorded as the initiating loader in the target VM. 63 * The list contains ReferenceTypes defined directly by this loader 64 * (as returned by {@link #definedClasses}) and any types for which 65 * loading was delegated by this class loader to another class loader. 66 * <p> 67 * The visible class list has useful properties with respect to 68 * the type namespace. A particular type name will occur at most 69 * once in the list. Each field or variable declared with that 70 * type name in a class defined by 71 * this class loader must be resolved to that single type. 72 * <p> 73 * No ordering of the returned list is guaranteed. 74 * <p> 75 * See 76 * <cite>The Java™ Virtual Machine Specification</cite>, 77 * section 5.3 - Creation and Loading 78 * for more information on the initiating classloader. 79 * <p> 80 * Note that unlike {@link #definedClasses()} 81 * and {@link VirtualMachine#allClasses()}, 82 * some of the returned reference types may not be prepared. 83 * Attempts to perform some operations on unprepared reference types 84 * (e.g. {@link ReferenceType#fields() fields()}) will throw 85 * a {@link ClassNotPreparedException}. 86 * Use {@link ReferenceType#isPrepared()} to determine if 87 * a reference type is prepared. 88 * 89 * @return a List of {@link ReferenceType} objects mirroring classes 90 * initiated by this class loader. The list has length 0 if no classes 91 * are visible to this classloader. 92 */ 93 List<ReferenceType> visibleClasses(); 94 } | http://checkstyle.sourceforge.net/reports/javadoc/openjdk8/xref/openjdk/jdk/src/share/classes/com/sun/jdi/ClassLoaderReference.html | CC-MAIN-2018-13 | refinedweb | 412 | 54.63 |
Is there any way to see how much memory/data it takes to define a particular geometry? For example, for me to see how much data is in a chair mode (which is an element of an architectural model)l, I have to copy it and paste it into a new file, and then save to see what the resultant file size is. Is there any way to select an object and find out how much data is in that object/geometry?
Model/geometry data size
Hi Lawrence - not in plain Rhino - I seem to remember seeing something like this in the Rhino Common SDK, but I can’t find it now so I was probably hallucinating. I’ll poke a bit more but I’m not too optimistic.
-Pascal
It’s a bit crude, but you could make a new file with nothing in it ans save it.
Record the file size. This is the file overhead.
Make another file with the object in it and save it.
Subtract the two to get a rough estimate of how much bigger the new file is.
Things like embedded images, render meshes, material assignment, etc. will greatly effect the file size.
I guess what I was hoping for was something more like the properties window. When you select a geometry, you can see its layer, material, type, etc. Why not the amount of data required to define the geometry as well?
The Audit3dmFile command breaks down the file size based on categories (not individual objects), but you might find what you need in that list.
@clement - yes, thanks that’s the chap! I could not find it again - thanks. Dunno if it is really useful here but maybe worth an experiment.
Did I do this right?
import Rhino import scriptcontext as sc import rhinoscriptsyntax as rs def test(): Id = rs.GetObject(preselect=True) if not Id: return x = sc.doc.Objects.Find(Id) print "Runtime memory use estimate:" ,str(round(x.MemoryEstimate()/1024,3)) , "k" test()
@lawrenceyy the above bit of python may tell you what you want to know - it is not the file size on disc but the runtime memory footprint that is estimated. I have no idea yet if or how things like materials and textures affect the estimate or if it counts render meshes (probably not). Wrong. It does appear to take render meshes into account.
Here it is as an actual py file (RunPythonScript).
ObjectMemoryEstimate.py (292 Bytes)
-Pascal
It sounds like what I’m looking for does not exist (displaying object data size in properties panel). Maybe this could make it into the next version of rhino? Sometimes when I open another person’s model, I can’t tell what is making the model slow or is making the file size so large. Being able to see the object data size would be really useful for auditing the model.
What could be really cool is if there was a shaded mode where data size was represented in color so you can see where there may be atypical objects that are using a lot of data. Or maybe like a infrared filter where high concentration of geometry and data results in a hotter color while areas of less geometry or data is cooler.
It may not be 100% accurate, but the most heavy part of your model would the in most cases the mesh or render mesh used to display your NURBS objects. So there is a relationship between how many triangles each object’s mesh has and how heavy the file is (well, with Block Instances it will count only once even if you have many of them). So, as mentioned above there is no automated way to preview your file in ‘heavy-filter’ (I like the idea though, should be doable via scripting) but if you want to check any particular objects, try _PolygonCount command. It will give you the # of triangles per-object or per-selection if many selected. Rule of thumb will be anything above 100,000 means ‘heavy’. There is probably close to linear increase in object ‘weight’ in file based on its polygon count. Most NURBS object definitions don’t take that much memory/disk space, since it is mostly math. It is the representing meshes that do. That’s why SaveSmall command makes files small - render meshes are discarded (files with mesh objects will not really get smaller).
I may take a stab at scripting the ‘infrared’ mode at some point since I like the idea. Unless someone gets at it first.
hth,
–jarek
@lawrenceyy, i too like the idea of some kind of display mode using hot cold colors, however it might be slow to draw all objects according to their memory estimate.
Below is a script which just selects the object (must be selectable PointCloud, Curve, Surface, PolySurface or Mesh) with the largest Memory estimate.
SelectLargestMemoryEstimate.py (1018 Bytes)
Note that an objects memory estimate or its polygon count are not necessarily what “slows down” a file, i could imagine having a 10Mio poly mesh shown without wireframe which navigates smoothly while a single cube having the isocurve density bumped up too high, influencing the display speed much more.
c.
Oh yeah ! You´re always faster
c.
Good point @clement lement, what usually would slow Rhino down is object count, not how heavy they are. You can have 1 object with 1,000,000 polygons running very fast vs. 10,000 light objects going very slow. Sounds like you bring geometry from other software - I have seen SKP or Revit files with a small shrub element slowing down entire building model because the block consisted of 10000s of sinle mesh triangle faces…
-j
Nice - finding the biggest one is probably more useful than per object query.
-Pascal
Hi Clement & Pascal, Thanks for these great scripts - very useful!
I have lots of items in blocks in my file. With @pascal’s script I get a nominal object size, presumably corresponding to the cost of an instance, not the unerlying geometry. With @clement’s script I get another object, not part of a block, and which I suspect to be smaller than some block objects.
Did either of you (or anyone else out there) do anything to handle blocks / block instances? I would like to be able to identify the objects, including blocks, which are increasing my file size.
Best regards,
Graham
Hi @Dancergraham, in this case you would need to recursively (in case of nested blocks) “explode” the block virtually and try if the method gives you memory sizes of the geometric objects inside the block. I have not done this yet because i use blocks only to reduce the memory footprint in case of many, many geometric instances, which i of course optimize before making them to a block.
_
c. | https://discourse.mcneel.com/t/model-geometry-data-size/29766 | CC-MAIN-2019-26 | refinedweb | 1,144 | 69.72 |
Creating weighing them.
For those familiar with gelcoat spraying, this is not a system with coupled gelcoat and peroxide pumps. But rather an external mixing spray gun where the peroxide is simply fed from a pressurized container to the spray gun.
Since we’re handling resins, solvents and peroxide, protective equipment including gloves is a must. That makes it cumbersome to whip out a smartphone to use it as a calculator to check the ratio. Since you don’t want to get gelcoat or peroxide on your expensive phone, you have to take off your gloves to handle it. This would have to be repeated several times.
So I decided to make a diagram where one could relatively easy read off the peroxide percentage given the quantities of both components. This can be printed and laminated between plastic to make it resistant against stains.
The whole thing can be found in a github repo.
Description
Such a diagram (basically a graphical analog computation device) is called a nomogram. The linked Wikipedia article gives and excellent overview.
Python and PostScript
Although PostScript is good at creating graphics, I find it cumbersome for calculations. So in this case, I’m using Python to do most of the calculations and have it generate PostScript commands for drawing.
Generating the nomogram
In this example I’m using two vertical axes for the input parameters, which are the measured quantities for the gelcoat and peroxide. The major ticks are spaced 10 mm apart for convenience. It is not a requirement to use similar spaced axes, it isn’t even necessary to use linear axes. Depending on the formula of the problem it could be advantageous to use logarithmic scales for one or both axes.
The heart of the program are two variables that hold the x-coordinates of the input axes, and two functions that convert the values of the axes into y-coordinates
# Axis locations xgel = 20 # mm xper = 80 # mm def ygel(g): """Calculates the y position for a given amount of gelcoat.""" return 10 + (g - 600) * 1 def yper(p): """Calculates the y position for a given amount of peroxide.""" return 100 + (p - 12) * -10 # mm
With this, we can draw the axes.
# Gelcoat axis with markings print(f'{xgel} mm {ygel(600)} mm moveto {xgel} mm {ygel(700)} mm lineto stroke') for k in range(600, 701): if k % 10 == 0: print(f'{xgel} mm {ygel(k)} mm moveto -5 mm 0 rlineto stroke') print(f'{xgel-10} mm {ygel(k)} mm moveto ({k}) align_center') elif k % 5 == 0: print(f'{xgel} mm {ygel(k)} mm moveto -2.5 mm 0 rlineto stroke') else: print('gsave') print('0.1 setlinewidth') print(f'{xgel} mm {ygel(k)} mm moveto -2 mm 0 rlineto stroke') print('grestore') # Peroxide axis with markings print(f'{xper} mm {yper(12)} mm moveto {xper} mm {yper(21)} mm lineto stroke') for k in range(120, 211): kk = k / 10 if k % 10 == 0: print(f'{xper} mm {yper(kk)} mm moveto 5 mm 0 rlineto stroke') print(f'{xper+10} mm {yper(kk)} mm moveto ({kk}) align_center') elif k % 5 == 0: print(f'{xper} mm {yper(kk)} mm moveto 2.5 mm 0 rlineto stroke') else: print('gsave') print('0.1 setlinewidth') print(f'{xper} mm {yper(kk)} mm moveto 2 mm 0 rlineto stroke') print('grestore')
The result (converted to PNG and scaled down) looks like the picture below.
When printed (from the generated PDF), the major ticks are exactly 10 mm apart and the horizontal distance between the vertical axes is 60 mm. For this gelcoat, between 2% and 3% of peroxide is used. So the range on the right axis runs from 2% of 600 to 3% of 700.
To draw the line that will have the ratio on it, we calculate 2% and 3% of 600 and 700 and draw the lines between those points on both axes. Their intersections define the limits of the axis for the ratios. The code for defining lines and calculating intersections is given below.
def line(p, q): """Create the line function passing through points P and Q. By solving py = a·px + b and qy = a·qx + b. Arguments: p: Point coordinates as a 2-tuple. q: Point coordinates as a 2-tuple. Returns: A 2-tuple (a, b) representing the line y = ax + b """ (px, py), (qx, qy) = p, q dx, dy = px - qx, py - qy if dx == 0: raise ValueError('y is not a function of x') a = dy / dx b = py - a * px return (a, b) def intersect(j, k): """Solve the intersection between two lines j and k. Arguments: j: 2-tuple (a, b) representing the line y = a·x + b. k: 2-tuple (c, d) representing the line y = c·x + d. Returns: The intersection point as a 2-tuple (x, y). """ (a, b), (c, d) = j, k if a == c: raise ValueError('parallel lines') x = (d - b) / (a - c) y = a*x + b return (x, y)
This code speaks for itself. The result is shown below. The lines for 2% are in red, and those for 3% are in blue. This should also make clear why the scale on the right axis in inverted. If not, the ratio axis would not lie between the two input axes.
How do we know that the third axis is a line? Basically because the relation between gelcoat, peroxide and ratio is linear. And because I used the same intersection method to calculate the locations of all the tick marks on the ratio axis. When I plotted them they all ended up on the previously drawn line.
Note that this calculation method always works. Even if the third axis is not a straight line.
The code for drawing the tick marks on the ratio axis is given below.
# Calculate the angle for the ratio labels p1 = (xgel, ygel(600)) p3 = (xgel, ygel(700)) p2 = (xper, yper(12)) p4 = (xper, yper(14)) # 2% ln1 = line(p1, p2) ln2 = line(p3, p4) intersect2 = intersect(ln1, ln2) # 3% p5 = (xper, yper(18)) p6 = (xper, yper(21)) ln3 = line(p1, p5) ln4 = line(p3, p6) intersect3 = intersect(ln3, ln4) print( f'{intersect2[0]} mm {intersect2[1]} mm moveto ' f'{intersect3[0]} mm {intersect3[1]} mm lineto stroke' ) dx = intersect2[0] - intersect3[0] dy = intersect2[1] - intersect3[1] dist = math.sqrt(dx * dx + dy * dy) angle = math.degrees(math.atan2(dy, dx)) - 90 # ratio axis markings for p in range(200, 301): pp = p / 100 A, B = (xgel, ygel(600)), (xper, yper(pp / 100 * 600)) C, D = (xgel, ygel(700)), (xper, yper(pp / 100 * 700)) l1 = line(A, B) l2 = line(C, D) ip = intersect(l1, l2) print('gsave') print(f'{ip[0]} mm {ip[1]} mm translate') print(f'{angle} rotate') if p % 10 == 0: print('0 0 moveto -5 mm 0 lineto stroke') val = f'{pp:.1f}'.replace('.', ',') print(f'-10 mm 0 moveto ({val} %) align_center') elif p % 5 == 0: print('0 0 moveto -2.5 mm 0 lineto stroke') else: print('gsave') print('0.1 setlinewidth') print('0 0 moveto -2 mm 0 lineto stroke') print('grestore') print('grestore')
Finally we add the headings for the axes, and an example of how to read the nomogram. The result is shown below.
Creating PDF and PNG output
Both the PDF and PNG file are created from the Encapsulated PostScript generated by the python program.
To create tight-fitting PDF and PNG files, we need to know the bounding box of the generated PostScript code. This is done using ghostscript. Let’s look at some excerpts of the Makefile.
The fragment below specifies how to make an EPS file from a Python file. You should know that $< contains the name of the implied source (the Python file) and $@ represents the name of the output file.
.py.eps: Makefile python3 $< >body.ps echo '%!PS-Adobe-3.0 EPSF-3.0' >header.ps gs -q -sDEVICE=bbox -dBATCH -dNOPAUSE body.ps >>header.ps 2>&1 cat header.ps body.ps > $@ rm -f body.ps header.ps
First the Python code generates the body of the PostScript code. To make Encapsulated postscript, it has to have a header line and a BoundingBox. The header line is written to a file. Ghostscript is then used to calculate the bounding box for the body. This is then appended to the header. Finally, header and body are concatenated into the output file.
For converting the EPS file (now with BoundingBox) to PDF, ghostscript is used as well:
.eps.pdf: gs -q -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dEPSCrop \ -sOutputFile=$@ -c .setpdfwrite -f $<
The EPSCrop flag is used to produce a PDF file the size of the extents of the EPS file instead of a whole page.
Producing a PNG file is slightly more complicated. To produce a fitting figure, you need to know the extents of the EPS figure, and then combine that with the desired resolution to get a suitable size of the image in pixels. That information is fed into Ghostscript.
Initially, I put this in the Makefile. But then I realized this could be useful elsewhere. So I rewrote it into a POSIX shell-script called eps2png.sh. You can find that in my scripts repository on Github. The relevant parts of it is shown below. Note that $f is the name of the input file.
OUTNAME=${f%.eps}.png BB=`gs -q -sDEVICE=bbox -dBATCH -dNOPAUSE $f 2>&1 | grep %%BoundingBox` WIDTH=`echo $BB | cut -d ' ' -f 4` HEIGHT=`echo $BB | cut -d ' ' -f 5` WPIX=$(($WIDTH*$RES/72)) HPIX=$(($HEIGHT*$RES/72)) gs -q -sDEVICE=${DEV} -dBATCH -dNOPAUSE -g${WPIX}x${HPIX} \ -dTextAlphaBits=4 -dGraphicsAlphaBits=4 \ -dFIXEDMEDIA -dPSFitPage -r${RES} -sOutputFile=${OUTNAME} $f
Note that WIDTH and HEIGHT are in PostScript points, i.e. 1/72 inch. Together with the resolution ($RES, defaulting to 300) in pixels per inch they are used to calculate the image extents in pixels, which are used in the -g option. It is also important to know that the arithmetic expressions in the shell are limited to integers. So division implicitly rounds the result to an integer! Hence we multiply first and divide as the last operation. Otherwise there would be significant rounding errors. | http://rsmith.home.xs4all.nl/howto/creating-a-nomogram-with-python-and-postscript.html | CC-MAIN-2019-26 | refinedweb | 1,708 | 63.19 |
I have a UIControl (subclass of UIView), and when I create it and align it to the left side in my view controller, the "beginTrackingWithTouch" fails to get called when I touch the view. It will only get called when I release the touch. What is weird is that pointInside(point: CGPoint...) method gets called immediately when I touch the UIControl, and what is even weirder is that when I align this UIControl view on the right side of the view controller, it works fine--beginTrackingWithTouch is called immediately when the view is touched, not when released. In addition, beginTrackingWithTouch is called the same time endTrackingWithTouch is called. Through some testing, it works fine until the view is 20 px from the left side, then this strange issue occurs again.
Is there a reason why the UIControl continueTrackingWithTouch fails to register if it is put on the far left side of a view controller? Is this Apple's way of preventing left hand scroll? There is absolutely nothing on the left side which is blocking the UIControl.
//In public class CustomScrollBar : UIControl
//This method gets called everytime when UIControl (red area in picture) is touched
override public func pointInside(point: CGPoint, withEvent event: UIEvent?) -> Bool {
return CGRectContainsPoint(handleHitArea, point)
}
//Only gets called when UIControl is touched and let go. It will not get called until your finger lifts off the screen.
override public func beginTrackingWithTouch(touch: UITouch, withEvent event: UIEvent?) -> Bool {
self.scrollerLine.hidden = true
if let delegate = self.delegate {
delegate.beginTrackingWithTouch()
}
guard self.isHandleVisible else{
return false
}
self.lastTouchLocation = touch.locationInView(self)
self.isHandleDragged = true
self.setNeedsLayout()
return true
}
Navigation controller has a built in back gesture recognizer, set it to false. Make sure that it is set in viewDidAppear
self.navigationController!.interactivePopGestureRecognizer!.enabled = false | https://codedump.io/share/PjfMrOGUi3uA/1/uicontrol-touches-not-behaving-correctly-on-left-side-of-vc | CC-MAIN-2017-43 | refinedweb | 296 | 56.66 |
m
Functional library for Javascript
Changes a lot and not yet complete. Use Ramda to be safe.
Why only pipe
There is no structure difference between
pipe and
compose, both will use the same building blocks to get from A to B.
A series of transformations over an initial input can be written as
x -> f -> g -> result, piping, or as
result = g(f(x)), composing. The difference is only syntactic. Input is the same, transformations and order of application are the same, the result will be the same.
Syntax is the thing we look at, reason with and write ourselves everyday and is the difference between "Aah, right" and "Why is he doing -1 two times?".
There are reasons for why some use
compose notation and others
pipe. Math people will know more.
In Settings are evil, Mattias Petter Johansson makes the point of product decisions and why adding a toggle in the settings page just adds maintenance overhead and useless complexity. While a measly Twitter feature flag does not compare to Function Composition, choosing one might be helpful (just like "double quotes" over 'single quotes').
Having a set of functions/transformations/verbs, what is the best way of presenting them so that people with little to no knowledge of the overall context can understand it in the least amount of time and with smallest amount of cognitive overhead?
Given that:
- we read from left to right
- left/back is in the past, right/front is the future
- a lot of piping going on in your terminal
it makes sense to choose the syntactic more aligned with our intuition and context. The transformations are applied in a certain order with time as a medium -
input -> t0 -> t1 -> tn -> output. The way is forward.
const { sep } = require("path") const { pipe, compose, join, push, dropLast, split } = require("@codemachiner/m") // // Compose - g(f(x)) // const renameFile = newName => filePath => compose( join(sep), push(newName), dropLast, split(sep) )(filePath) // // Pipe - x -> f -> g // const renameFile = newName => filePath => pipe( split(sep), dropLast, push(newName), join(sep) )(filePath) // // When using the new pipeline operator, things are even more expressive // const renameFile = newName => filePath => filePath |> split(sep) |> dropLast |> push(newName) |> join(sep)
Links
Install
npm i --save-exact @codemachiner/m
Develop
git clone git@github.com:codemachiner/m.git && \ cd m && \ npm run setup # run tests (any `*.test.js`) once npm test # watch `src` folder for changes and run test automatically npm run tdd
Use
import { pipe, trim, split, dropLast, push, join } from "@codemachiner/m" const removeTrailingSlash = source => source[source.length - 1] === sep ? source.slice(0, -1) : source const renameFile = newName => pipe( removeTrailingSlash, split(sep), dropLast, push(trim(sep)(newName)), join(sep) )
Changelog
History of all changes in CHANGELOG.md | https://www.npmtrends.com/@codemachiner/m | CC-MAIN-2021-31 | refinedweb | 453 | 58.92 |
Redis
Component format
To setup Redis state store create a component of type
state.redis. See this guide on how to create and apply a state store configuration.
apiVersion: dapr.io/v1alpha1 kind: Component metadata: name: <NAME> namespace: <NAMESPACE> spec: type: state.redis version: v1 metadata: - name: redisHost value: <HOST> - name: redisPassword value: <PASSWORD> - name: enableTLS value: <bool> # Optional. Allowed: true, false. - name: failover value: <bool> # Optional. Allowed: true, false. - name: sentinelMasterName value: <string> # Optional - name: maxRetries value: # Optional - name: maxRetryBackoff value: # Optional - name: ttlInSeconds value: <int> # Optional
TLS: If the Redis instance supports TLS with public certificates it can be configured to enable or disable TLS
true or
false.
Failover: When set to
true enables the failover feature. The redisHost should be the sentinel host address. See Redis Sentinel Documentation
WarningThe above example uses secrets as plain strings. It is recommended to use a secret store for the secrets as described here.
If you wish to use Redis as an actor store, append the following to the yaml.
- name: actorStateStore value: "true"
Spec metadata fields
Setup Redis
Dapr can use any Redis instance - containerized, running on your local dev machine, or a managed cloud service. If you already have a Redis store, move on to the Configuration section.
A Redis instance is automatically created as a Docker container when you run
dapr init
We can use Helm to quickly create a Redis instance in our Kubernetes cluster. This approach requires Installing Helm.
Install Redis into your cluster. Note that we’re explicitly setting an image tag to get a version greater than 5, which is what Dapr’ pub/sub functionality requires. If you’re intending on using Redis as just a state store (and not for pub/sub), you do not have to set the image version. the:
metadata: - name: redisPassword value: lhDOkwTlp0
Note: this approach requires having an Azure Subscription.
- Open this link to start the Azure Cache for Redis creation flow. Log in if necessary.
- Fill out necessary information and check the “Unblock port 6379” box, which will allow us to persist state without SSL.
- Click “Create” to kickoff deployment of your Redis instance.
- Once your instance is created, you’ll need to grab the Host name (FQDN) and your access key.
- for the Host name navigate to the resources “Overview” and copy “Host name”
- for your access key navigate to “Access Keys” under “Settings” and copy your key.
- Finally, we need to add our key and our host to a
redis.yamlfile that Dapr can apply to our cluster. If you’re running a sample, you’ll add the host and key to the provided
redis.yaml. If you’re creating a project from the ground up, you’ll create a
redis.yamlfile as specified in Configuration. Set the
redisHostkey to
[HOST NAME FROM PREVIOUS STEP]:6379and the
redisPasswordkey to the key you copied in step 4. Note: In a production-grade application, follow secret management instructions to securely manage your secrets.
NOTE: Dapr pub/sub uses Redis Streams that was introduced by Redis 5.0, which isn’t currently available on Azure Managed Redis Cache. Consequently, you can use Azure Managed Redis Cache only for state persistence.
NoteThe Dapr CLI automatically deploys a local redis instance in self hosted mode as part of the
dapr initcommand.. | https://docs.dapr.io/reference/components-reference/supported-state-stores/setup-redis/ | CC-MAIN-2021-43 | refinedweb | 551 | 57.37 |
On Wed, Oct 26, 2011 at 6:50 AM, Nicolas George < nicolas.george at normalesup.org> wrote: > Le quartidi 4 brumaire, an CCXX, Marcus Nascimento a écrit : > > Please, check the answers bellow. > > That was more than perfect. Thanks. > > >. > > For now, it sounds quite straightforward. > > > The Manifest is just a XML file that provides some information regarding > > different streams and other information. > > Here is a basic example (modified parts of the original found here: > > > > > ): > > Do you know how much of the features of XML the manifest is allowed to use? > Writing a parser for well-balanced-tags-with-quoted-attributes is an easy > task, while supporting namespaces, external entities, processing > instructions, etc., is not. > > I have to check this out. For simplicity, I'll stick with a simple XML parser without namespaces, external entities and other stuff. It may be emproved in the future to be more correct about that. Something like: Let's make it work first. > >). > > Next it lists each fragment size. The first fragment would be referenced > as > > 0 (zero), and the others as a sum of previous fragments size. I'm not > sure > > exactly what those values mean. > > Next we have the same structure for audio description. > > Ok. > > >. > > I do not think you need to concern yourself with the heuristics for that: > that is for the application to decide, not the library implementing the > protocol. The library only needs to provide the information necessary to > make the decision. > > My concern here is how the application would know how long it took to get a fragment, to give an example. That would require a lot of interactions between ffmpeg and the application during playback. As everything else related to ffmpeg, I need to study a little first but I'll keep that in mind. > Other may disagree, but I believe that if you manage to implement anything > at all (for example reading the first, or the best stream of each type, or > maybe reading all streams while honoring the discard flag), that would be a > very good starting point. > > Perfect. Reading a single stream would be a huge progress. I'll aim to that. > >. > > > > I'm not sure how a decoder works, but I believe there is a way to > configure > > that in order to receive future "injected" data. > > > > If you get all the way here, I really thank you! > > I wonder how to fit all this into the ffmpeg structure. > > I will elaborate slightly on top of what Michael wrote. > > The "standard" scheme for ffmpeg has three completely separate layers: > > protocol -> demuxer -> codecs > > The protocol takes a string (an URL of some kind) and outputs a stream of > bytes. The most basic protocol is the file protocol, which takes a file > name > and just reads that file. Protocols can be nested (for example mmsh > internally uses http which internally uses TCP), but that is an > implementation detail that is not seen in the API (yet; there are plans to > do something for complex multistreams protocols). > > The demuxer reads a stream of bytes and then first populates a global data > structure, including one or several streams. Then it outputs a series of > packets. Packets are a sequence of bytes attached to a few simple > informations: size, timestamp, stream of attachment. > > The codecs decode the packets. There is normally one codec per stream, > except if that stream is ignored. The codec initialize itself with the data > in the stream data structure, then accepts packets and possibly outputs > video frames, audio PCM data or anything else (subtitles). > > AFAIK, in ffmpeg, the separation between demuxers and codecs has no real > exception. Which means that you should be able to ignore completely the > problem of codecs. > > On the other hand protocols and demuxer sometimes need to work hand in > hand. > > In your particular case, the problem may be as simple as getting your > protocol handler to resynthetize proper ISOM headers and concatenate the > data to obtain a valid non-seekable ISOM stream. > > At a later time, the ISOM demuxer could be adapted to be able to use the > seek-by-timestamp (read_seek) method that protocols can provide. > > But that is just random thoughts, and I do not know enough of the ISOM > particulars to know if that is workable. > > That helps a lot. Now I have a good idea on how things work. I'll dig into the code. > > I'm not that familiar with RTP but from what I've ready in the past few > > minutes it sounds similar. > > From what you described, RTP and SDP files are too simple to be of any use > by comparison. > > > Yes. I've seen something about it. It looks suitable for the case. > > It may be my starting point for studying. > > I believe that you can use the HTTP protocol handler directly as a backend, > like mmsh does. > > I'll check that. Thank you very much. > Good luck. > > Regards, > > -- > Nicolas George > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.11 (GNU/Linux) > > iEYEARECAAYFAk6nyeUACgkQsGPZlzblTJMG6ACeLxbpvgLJr/Nk3qPP9/i84j8U > D7kAoMpWtuiPAwVEqO3reaTmKfb0ETbh > =oDvU > -----END PGP SIGNATURE----- > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel at ffmpeg.org > > > -- Marcus Nascimento | http://ffmpeg.org/pipermail/ffmpeg-devel/2011-October/116120.html | CC-MAIN-2014-52 | refinedweb | 847 | 65.42 |
From: Daniel Mack <daniel@zonque.org>kdbus is a system for low-latency, low-overhead, easy to useinterprocess communication (IPC).The interface to all functions in this driver is implemented throughioctls on files exposed through the mount point of a kdbusfs. Thispatch>--- Documentation/kdbus.txt | 1837 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1837 insertions(+) create mode 100644 Documentation/kdbus.txtdiff --git a/Documentation/kdbus.txt b/Documentation/kdbus.txtnew file mode 100644index 000000000000..2bd7277ef179--- /dev/null+++ b/Documentation/kdbus.txt@@ -0,0 +1,1837 @@+D-Bus is a system for powerful, easy to use interprocess communication (IPC).+.++For the general D-Bus protocol specification, the payload format, the+marshaling, and the communication semantics, please refer to:+ a kdbus specific userspace library implementation please refer to:+ about D-Bus and kdbus:+. Terminology+===============================================================================++ Domain:+ A domain is created each time a kdbusfs is mounted. Each process that is+ capable to mount a new instance of a kdbusfs will have its own kdbus+ hierarchy. Each domain (ie, each mount point) offers its own "control"+ file to create new buses. Domains have no connection to each other and+ cannot see nor talk to each other. See section 5 for more details.++ Bus:+ A bus is a named object inside a domain. Clients exchange messages+ over a bus. Multiple buses themselves have no connection to each other;+ messages can only be exchanged on the same bus. The default entry point to+ a bus, where clients establish the connection to, is the "bus" file+ /sys/fs/kdbus/<bus name>/bus.+ Common operating system setups create one "system bus" per system, and one+ "user bus" for every logged-in user. Applications or services may create+ their own private named buses. See section 5 for more details.++ Endpoint:+ An endpoint provides the file to talk to a bus. Opening an endpoint+ creates a new connection to the bus to which the endpoint belongs.+ Inside the directory of the bus, every bus has a default endpoint+ called "bus". A bus can optionally offer additional endpoints with+ custom names to provide restricted access to the bus. Custom endpoints+ carry additional policy which can be used to create sandboxes with a+ locked-down, limited, filtered access to a bus. See section 5 for+ more details.++ Connection:+ A connection to a bus is created by opening an endpoint file of inside a+ bus' folder and becoming an active client with the HELLO exchange. Every+ connected client connection has a unique identifier on the bus and can+ address messages to every other connection on the same bus by using+ the peer's connection id as the destination.+ See section 6 for more details.++.++ Well-known Name:+ A connection can, in addition to its implicit unique connection id, request+ the ownership of a textual well-known name. Well-known names are noted in+ reverse-domain notation, such as com.example.service1. Connections offering+ a service on a bus are usually reached by its well-known name. The analogy+ of connection id and well-known name is an IP address and a DNS name+ associated with that address.++ Message:+ Connections can exchange messages with other connections by addressing+ the peers with their connection id or well-known name. A message consists+ of a message header with kernel-specific information on how to route the+ message, and the message payload, which is a logical byte stream of+ arbitrary size. Messages can carry additional file descriptors to be passed+ from one connection to another. Every connection can specify which set of+ metadata the kernel should attach to the message when it is delivered+ to the receiving connection. Metadata contains information like: system+ timestamps, uid, gid, tid, proc-starttime, well-known-names, process comm,+ process exe, process argv, cgroup, capabilities, seclabel, audit session,+ loginuid and the connection's human-readable name.+ See section 7 and 13 for more details.++ Item:+ The API of kdbus implements a notion of items, submitted through and+ returned by most ioctls, and stored inside data structures in the+ connection's pool. See section 4 for more details.++ Broadcast and Match:+ Broadcast messages are potentially sent to all connections of a bus. By+ default, the connections will not actually receive any of the sent+ broadcast messages; only after installing a match for specific message+ properties, a broadcast message passes this filter.+ See section 10 for more details.++ Policy:+ A policy is a set of rules that define which connections can see, talk to,+ or register a well-know name on the bus. A policy is attached to buses and+ custom endpoints, and modified by policy holder connection or owners of+ custom endpoints. See section 11 for more details.++ Access rules to allow who can see a name on the bus are only checked on+ custom endpoints. Policies may be defined with names that end with '.*'.+ When matching a well-known name against such a wildcard entry, the last+ part of the name is ignored and checked against the wildcard name without+ the trailing '.*'. See section 11 for more details.++ Privileged bus users:+ A user connecting to the bus is considered privileged if it is either the+ creator of the bus, or if it has the CAP_IPC_OWNER capability flag set.+++2. Control Files Layout+===============================================================================++The kdbus interface is exposed through files in its kdbusfs mount point+(defaults to /sys/fs/kdbus):++ /sys/fs/kdbus+ |-- control+ |-- 0-system+ | |-- bus+ | `-- ep.apache+ |-- 1000-user+ | `-- bus+ `-- 2702-user+ |-- bus+ `-- ep.app+++3. Data Structures and flags+===============================================================================++3.1 Data structures and interconnections+----------------------------------------++ +--------------------------------------------------------------------------++ | Domain (Mount Point) |+ | /sys/fs/kdbus/control |+ | +----------------------------------------------------------------------+ |+ | | Bus (System Bus) | |+ | | /sys/fs/kdbus/0-system/ | |+ | | +-------------------------------+ +--------------------------------+ | |+ | | | Endpoint | | Endpoint | | |+ | | | /sys/fs/kdbus/0-system/bus | | /sys/fs/kdbus/0-system/ep.app | | |+ | | +-------------------------------+ +--------------------------------+ | |+ | | +--------------+ +--------------+ +--------------+ +---------------+ | |+ | | | Connection | | Connection | | Connection | | Connection | | |+ | | | :1.22 | | :1.25 | | :1.55 | | :1.81 | | |+ | | +--------------+ +--------------+ +--------------+ +---------------+ | |+ | +----------------------------------------------------------------------+ |+ | |+ | +----------------------------------------------------------------------+ |+ | | Bus (User Bus for UID 2702) | |+ | | /sys/fs/kdbus/2702-user/ | |+ | | +-------------------------------+ +--------------------------------+ | |+ | | | Endpoint | | Endpoint | | |+ | | | /sys/fs/kdbus/2702-user/bus | | /sys/fs/kdbus/2702-user/ep.app | | |+ | | +-------------------------------+ +--------------------------------+ | |+ | | +--------------+ +--------------+ +--------------+ +---------------+ | |+ | | | Connection | | Connection | | Connection | | Connection | | |+ | | | :1.22 | | :1.25 | | :1.55 | | :1.81 | | |+ | | +--------------+ +--------------+ +--------------------------------+ | |+ | +----------------------------------------------------------------------+ |+ +--------------------------------------------------------------------------+++The above description uses the D-Bus notation of unique connection names that+adds a ":1." prefix to the connection's unique ID. kdbus itself doesn't+use that notation, neither internally nor externally. However, libraries and+other usespace code that aims for compatibility to D-Bus might.++3.2 Flags+---------++All ioctls used in the communication with the driver contain two 64-bit fields,+'flags' and 'kernel_flags'. In 'flags', the behavior of the command can be+tweaked, whereas in 'kernel_flags', the kernel driver writes back the mask of+supported bits upon each call, and sets the KDBUS_FLAGS_KERNEL bit. This is a+way to probe possible kernel features and make code forward and backward+compatible.++All bits that are not recognized by the kernel in 'flags' are rejected, and the+ioctl fails with -EINVAL.++.+++5. Creation of new domains, buses and endpoints+===============================================================================++The initial kdbus domain is unconditionally created by the kernel module. A+domain contains a "control" file which allows to create a new bus. New domains+(mount points) do not have any buses created by default.+++5.1 Buses+---------++Opening the control file returns a file descriptor which accepts the+KDBUS_CMD_BUS_MAKE ioctl to create a new bus. The control file descriptor needs+to be kept open for the entire life-time of the created bus, closing it will+immediately cleanup the entire bus and all its associated resources and+endpoints. Every control file descriptor can only be used once+to create a new bus; from that point, it is not used for any further+communication until the final close().++Each bus will generate a random, 128-bit UUID upon creation. It will be+returned to the creators of connections through kdbus_cmd_hello.id128 and can+be used by userspace to uniquely identify buses, even across different machines+or containers. The UUID will have its its variant bits set to 'DCE', and denote+version 4 (random).++Optionally, an item of type KDBUS_ITEM_ATTACH_FLAGS_RECV can be attached to+KDBUS_CMD_BUS_MAKE. In that, a set of required attach flags can be passed,+which is used as negotiation measure during connection creation.+++5.2 Endpoints+-------------++Endpoints are entry points to a bus. By default, each bus has a default+endpoint called 'bus'. The bus owner has the ability to create custom+endpoints with specific names, permissions, and policy databases (see below).++To create a custom endpoint, use the KDBUS_CMD_ENDPOINT_MAKE ioctl with struct+kdbus_cmd_make. Custom endpoints always have a policy database that, by+default, does not allow anything. Everything that users of this new endpoint+should be able to do has to be explicitly specified through KDBUS_ITEM_NAME and+KDBUS_ITEM_POLICY_ACCESS items.+++5.3 Domains+-----------++Each time a kdbusfs is mounted, a new kdbus domain is created, with its own+'control' file only. The lifetime of the domain ends once the user has+unmounted the kdbusfs.+++5.4 Creating buses and endpoints+--------------------------------+++ __u64 kernel_flags;+ Valid flags for this command, returned by the kernel upon each call.++ struct kdbus_item items[0];+ A list of items, only used for creating custom endpoints. Has specific+ meanings for KDBUS_CMD_BUS_MAKE and KDBUS_CMD_ENDPOINT_MAKE (see above).+};+++6. Connections+===============================================================================+++6.1 Connection IDs and well-known connection names+--------------------------------------------------++Connections are identified by their connection id, internally implemented as a+uint64_t counter. The IDs of every newly created bus start at 1, and every new+connection will increment the counter by 1. The ids are not reused.++In higher level tools, the user visible representation of a connection is+defined by the D-Bus protocol specification as ":1.<id>".++Messages with a specific uint64_t destination id are directly delivered to+the connection with the corresponding id. Messages with the special destination+id KDBUS_DST_ID_BROADCAST are broadcast messages and are potentially delivered+to all known connections on the bus; clients interested in broadcast messages+need to subscribe to the specific messages they are interested, though before+any broadcast message reaches them.++Messages synthesized and sent directly by the kernel will carry the special+source id KDBUS_SRC_ID_KERNEL (0).++In addition to the unique uint64_t connection id, established connections can+request the ownership of well-known names, under which they can be found and+addressed by other bus clients. A well-known name is associated with one and+only one connection at a time. See section 8 on name acquisition and the+name registry, and the validity of names.++Messages can specify the special destination id 0 and carry a well-known name+in the message data. Such a message is delivered to the destination connection+which owns that well-known name.++ +-------------------------------------------------------------------------++ | +---------------+ +---------------------------+ |+ | | Connection | | Message | -----------------+ |+ | | :1.22 | --> | src: 22 | | |+ | | | | dst: 25 | | |+ | | | | | | |+ | | | | | | |+ | | | +---------------------------+ | |+ | | | | |+ | | | <--------------------------------------+ | |+ | +---------------+ | | |+ | | | |+ | +---------------+ +---------------------------+ | | |+ | | Connection | | Message | -----+ | |+ | | :1.25 | --> | src: 25 | | |+ | | | | dst: 0xffffffffffffffff | -------------+ | |+ | | | | (KDBUS_DST_ID_BROADCAST) | | | |+ | | | | | ---------+ | | |+ | | | +---------------------------+ | | | |+ | | | | | | |+ | | | <--------------------------------------------------+ |+ | +---------------+ | | |+ | | | |+ | +---------------+ +---------------------------+ | | |+ | | Connection | | Message | --+ | | |+ | | :1.55 | --> | src: 55 | | | | |+ | | | | dst: 0 / org.foo.bar | | | | |+ | | | | | | | | |+ | | | | | | | | |+ | | | +---------------------------+ | | | |+ | | | | | | |+ | | | <------------------------------------------+ | |+ | +---------------+ | | |+ | | | |+ | +---------------+ | | |+ | | Connection | | | |+ | | :1.81 | | | |+ | | org.foo.bar | | | |+ | | | | | |+ | | | | | |+ | | | <-----------------------------------+ | |+ | | | | |+ | | | <----------------------------------------------+ |+ | +---------------+ |+ +-------------------------------------------------------------------------+++.++ Items of other types are silently ignored.+};+++6.3 Activator and policy holder connection+------------------------------------------++An activator connection is a placeholder for a well-known name. Messages sent+to such a connection can be used by userspace to start an implementor+connection, which will then get all the messages from the activator copied+over. An activator connection cannot be used to send any message.++A policy holder connection only installs a policy for one or more names.+These policy entries are kept active as long as the connection is alive, and+are removed once it terminates. Such a policy connection type can be used to+deploy restrictions for names that are not yet active on the bus. A policy+holder connection cannot be used to send any message.++The creation of activator, policy holder or monitor connections is an operation+restricted to privileged users on the bus (see section "Terminology").++.++In response to this call, a slice in the connection's pool is allocated and+filled with an object of type struct kdbus_info, pointed to by the ioctl's+'offset' field.++struct kdbus_info {+ __u64 size;+ The overall size of the struct, including all its items.++ __u64 id;+ The bus' ID++ __u64 flags;+ The bus' flags as specified when it was created.++ __u64 kernel_flags;+ Valid flags for this command, returned by the kernel upon each call.++ struct kdbus_item items[0];+ Metadata information is stored in items here.+};++Once the caller is finished with parsing the return buffer, it needs to call+KDBUS_CMD_FREE for the offset.+++6.6 Updating connection details+-------------------------------++Some of a connection's details can be updated with the KDBUS_CMD_CONN_UPDATE+ioctl, using the file descriptor that was used to create the connection.+The update command uses the following struct.++struct kdbus_cmd_update {+ __u64 size;+ The overall size of the struct, including all its items.++ struct kdbus_item items[0];+ Items to describe the connection details to be updated. The following item+ types are supported:++ KDBUS_ITEM_ATTACH_FLAGS_SEND+ Supply a new set of items that this connection permits to be sent along+ with messages.++ KDBUS_ITEM_ATTACH_FLAGS_RECV+ Supply a new set of items to be attached to each message.++ KDBUS_ITEM_NAME+ KDBUS_ITEM_POLICY_ACCESS+ Policy holder connections may supply a new set of policy information+ with these items. For other connection types, -EOPNOTSUPP is returned.+};+++6.6 Termination+---------------++A connection can be terminated by simply closing the file descriptor that was+used to start the connection. All pending incoming messages will be discarded,+and the memory in the pool will be freed.++An alternative way of closing down a connection is calling the KDBUS_CMD_BYEBYE+ioctl on it, which will only succeed if the message queue of the connection is+empty at the time of closing, otherwise, -EBUSY is returned.++When this ioctl returns successfully, the connection has been terminated and+won't accept any new messages from remote peers. This way, a connection can+be terminated race-free, without losing any messages.+++7. Messages+===============================================================================++Messages consist of a fixed-size header followed directly by a list of+variable-sized data 'items'. The overall message size is specified in the+header of the message. The chain of data items can contain well-defined+message metadata fields, raw data, references to data, or file descriptors.+++7.1 Sending messages+--------------------++Messages are passed to the kernel with the KDBUS_CMD_MSG_SEND ioctl. Depending+on the destination address of the message, the kernel delivers the message to+the specific destination connection or to all connections on the same bus.+Sending messages across buses is not possible. Messages are always queued in+the memory pool of the destination connection (see below).++The KDBUS_CMD_MSG_SEND ioctl uses struct kdbus_msg to describe the message to+be sent.++struct kdbus_msg {+ __u64 size;+ The overall size of the struct, including the attached items.++ __u64 flags;+ Flags for message delivery:++ KDBUS_MSG_FLAGS_EXPECT_REPLY+ Expect a reply from the remote peer to this message. With this bit set,+ the timeout_ns field must be set to a non-zero number of nanoseconds in+ which the receiving peer is expected to reply. If such a reply is not+ received in time, the sender will be notified with a timeout message+ (see below). The value must be an absolute value, in nanoseconds and+ based on CLOCK_MONOTONIC.++ For a message to be accepted as reply, it must be a direct message to+ the original sender (not a broadcast), and its kdbus_msg.reply_cookie+ must match the previous message's kdbus_msg.cookie.++ Expected replies also temporarily open the policy of the sending+ connection, so the other peer is allowed to respond within the given+ time window.++ KDBUS_MSG_FLAGS_SYNC_REPLY+ By default, all calls to kdbus are considered asynchronous,+ non-blocking. However, as there are many use cases that need to wait+ for a remote peer to answer a method call, there's a way to send a+ message and wait for a reply in a synchronous fashion. This is what+ the KDBUS_MSG_FLAGS_SYNC_REPLY controls. The KDBUS_CMD_MSG_SEND ioctl+ will block until the reply has arrived, the timeout limit is reached,+ in case the remote connection was shut down, or if interrupted by+ a signal before any reply; see signal(7).++ The offset of the reply message in the sender's pool is stored in+ in 'offset_reply' when the ioctl has returned without error. Hence,+ there is no need for another KDBUS_CMD_MSG_RECV ioctl or anything else+ to receive the reply.++ KDBUS_MSG_FLAGS_NO_AUTO_START+ By default, when a message is sent to an activator connection, the+ activator notified and will start an implementor. This flag inhibits+ that behavior. With this bit set, and the remote being an activator,+ -EADDRNOTAVAIL is returned from the ioctl.++ __u64 kernel_flags;+ Valid flags for this command, returned by the kernel upon each call of+ KDBUS_MSG_SEND.++ __s64 priority;+ The priority of this message. Receiving messages (see below) may+ optionally be constrained to messages of a minimal priority. This+ allows for use cases where timing critical data is interleaved with+ control data on the same connection. If unused, the priority should be+ set to zero.++ __u64 dst_id;+ The numeric ID of the destination connection, or KDBUS_DST_ID_BROADCAST+ (~0ULL) to address every peer on the bus, or KDBUS_DST_ID_NAME (0) to look+ it up dynamically from the bus' name registry. In the latter case, an item+ of type KDBUS_ITEM_DST_NAME is mandatory.++ __u64 src_id;+ Upon return of the ioctl, this member will contain the sending+ connection's numerical ID. Should be 0 at send time.++ __u64 payload_type;+ Type of the payload in the actual data records. Currently, only+ KDBUS_PAYLOAD_DBUS is accepted as input value of this field. When+ receiving messages that are generated by the kernel (notifications),+ this field will yield KDBUS_PAYLOAD_KERNEL.++ __u64 cookie;+ Cookie of this message, for later recognition. Also, when replying+ to a message (see above), the cookie_reply field must match this value.++ __u64 timeout_ns;+ If the message sent requires a reply from the remote peer (see above),+ this field contains the timeout in absolute nanoseconds based on+ CLOCK_MONOTONIC.++ __u64 cookie_reply;+ If the message sent is a reply to another message, this field must+ match the cookie of the formerly received message.++ __u64 offset_reply;+ If the message successfully got a synchronous reply (see above), this+ field will yield the offset of the reply message in the sender's pool.+ Is is what KDBUS_CMD_MSG_RECV usually does for asynchronous messages.++ struct kdbus_item items[0];+ A dynamically sized list of items to contain additional information.+ The following items are expected/valid:++ KDBUS_ITEM_PAYLOAD_VEC+ KDBUS_ITEM_PAYLOAD_MEMFD+ KDBUS_ITEM_FDS+ Actual data records containing the payload. See section "Passing of+ Payload Data".++ KDBUS_ITEM_BLOOM_FILTER+ Bloom filter for matches (see below).++ KDBUS_ITEM_DST_NAME+ Well-known name to send this message to. Required if dst_id is set+ to KDBUS_DST_ID_NAME. If a connection holding the given name can't+ be found, -ESRCH is returned.+ For messages to a unique name (ID), this item is optional. If present,+ the kernel will make sure the name owner matches the given unique name.+ This allows userspace tie the message sending to the condition that a+ name is currently owned by a certain unique name.+};++The message will be augmented by the requested metadata items when queued into+the receiver's pool. See also section 13.1 ("Metadata and namespaces").+++7.2 Message layout+------------------++The layout of a message is shown below.++ +-------------------------------------------------------------------------++ | Message |+ | +---------------------------------------------------------------------+ |+ | | Header | |+ | | size: overall message size, including the data records | |+ | | destination: connection id of the receiver | |+ | | source: connection id of the sender (set by kernel) | |+ | | payload_type: "DBusDBus" textual identifier stored as uint64_t | |+ | +---------------------------------------------------------------------+ |+ | +---------------------------------------------------------------------+ |+ | | Data Record | |+ | | size: overall record size (without padding) | |+ | | type: type of data | |+ | | data: reference to data (address or file descriptor) | |+ | +---------------------------------------------------------------------+ |+ | +---------------------------------------------------------------------+ |+ | | padding bytes to the next 8 byte alignment | |+ | +---------------------------------------------------------------------+ |+ | +---------------------------------------------------------------------+ |+ | | Data Record | |+ | | size: overall record size (without padding) | |+ | | ... | |+ | +---------------------------------------------------------------------+ |+ | +---------------------------------------------------------------------+ |+ | | padding bytes to the next 8 byte alignment | |+ | +---------------------------------------------------------------------+ |+ | +---------------------------------------------------------------------+ |+ | | Data Record | |+ | | size: overall record size | |+ | | ... | |+ | +---------------------------------------------------------------------+ |+ | +---------------------------------------------------------------------+ |+ | | padding bytes to the next 8 byte alignment | |+ | +---------------------------------------------------------------------+ |+ +-------------------------------------------------------------------------+++.++The caller is obliged to call KDBUS_CMD_FREE with the returned offset when+the memory is no longer.+++8. Name registry+===============================================================================++Each bus instantiates a name registry to resolve well-known names into unique+connection IDs for message delivery. The registry will be queried when a+message is sent with kdbus_msg.dst_id set to KDBUS_DST_ID_NAME, or when a+registry dump is requested.++All of the below is subject to policy rules for SEE and OWN permissions.+++8.1 Name validity+-----------------++A name has to comply to the following rules to be considered valid:++ - The name has two or more elements separated by a period ('.') character+ - All elements must contain at least one character+ - Each element must only contain the ASCII characters "[A-Z][a-z][0-9]_"+ and must not begin with a digit+ - The name must contain at least one '.' (period) character+ (and thus at least two elements)+ - The name must not begin with a '.' (period) character+ - The name must not exceed KDBUS_NAME_MAX_LEN (255)+++8.2 Acquiring a name+--------------------++To acquire a name, a client uses the KDBUS_CMD_NAME_ACQUIRE ioctl with the+following data structure.++struct kdbus_cmd_name {+ __u64 size;+ The overall size of this struct, including the name with its 0-byte string+ terminator.++ __u64 flags;+ Flags to control details in the name acquisition.++ KDBUS_NAME_REPLACE_EXISTING+ Acquiring a name that is already present usually fails, unless this flag+ is set in the call, and KDBUS_NAME_ALLOW_REPLACEMENT or (see below) was+ set when the current owner of the name acquired it, or if the current+ owner is an activator connection (see below).++ KDBUS_NAME_ALLOW_REPLACEMENT+ Allow other connections to take over this name. When this happens, the+ former owner of the connection will be notified of the name loss.++ KDBUS_NAME_QUEUE (acquire)+ A name that is already acquired by a connection, and which wasn't+ requested with the KDBUS_NAME_ALLOW_REPLACEMENT flag set can not be+ acquired again. However, a connection can put itself in a queue of+ connections waiting for the name to be released. Once that happens, the+ first connection in that queue becomes the new owner and is notified+ accordingly.++ __u64 kernel_flags;+ Valid flags for this command, returned by the kernel upon each call.++ struct kdbus_item items[0];+ Items to submit the name. Currently, one item of type KDBUS_ITEM_NAME is+ expected and allowed, and the contained string must be a valid bus name.+};+++8.3 Releasing a name+--------------------++A connection may release a name explicitly with the KDBUS_CMD_NAME_RELEASE+ioctl. If the connection was an implementor of an activatable name, its+pending messages are moved back to the activator. If there are any connections+queued up as waiters for the name, the oldest one of them will become the new+owner. The same happens implicitly for all names once a connection terminates.++The KDBUS_CMD_NAME_RELEASE ioctl uses the same data structure as the+acquisition call, but with slightly different field usage.++struct kdbus_cmd_name {+ __u64 size;+ The overall size of this struct, including the name with its 0-byte string+ terminator.++ __u64 flags;++ struct kdbus_item items[0];+ Items to submit the name. Currently, one item of type KDBUS_ITEM_NAME is+ expected and allowed, and the contained string must be a valid bus name.+};+++8.4 Dumping the name registry+-----------------------------++A connection may request a complete or filtered dump of currently active bus+names with the KDBUS_CMD_NAME_LIST ioctl, which takes a struct+kdbus_cmd_name_list as argument.++struct kdbus_cmd_name_list {+ __u64 flags;+ Any combination of flags to specify which names should be dumped.++ KDBUS_NAME_LIST_UNIQUE+ List the unique (numeric) IDs of the connection, whether it owns a name+ or not.++ KDBUS_NAME_LIST_NAMES+ List well-known names stored in the database which are actively owned by+ a real connection (not an activator).++ KDBUS_NAME_LIST_ACTIVATORS+ List names that are owned by an activator.++ KDBUS_NAME_LIST_QUEUED+ List connections that are not yet owning a name but are waiting for it+ to become available.++ __u64 offset;+ When the ioctl returns successfully, the offset to the name registry dump+ inside the connection's pool will be stored in this field.+};++The returned list of names is stored in a struct kdbus_name_list that in turn+contains a dynamic number of struct kdbus_cmd_name that carry the actual+information. The fields inside that struct kdbus_cmd_name is described next.++struct kdbus_name_info {+ __u64 size;+ The overall size of this struct, including the name with its 0-byte string+ terminator.++ __u64 owner_id;+ The owning connection's unique ID.++ __u64 conn_flags;+ The flags of the owning connection.++ struct kdbus_item items[0];+ Items containing the actual name. Currently, one item of type+ KDBUS_ITEM_OWNED_NAME will be attached, including the name's flags. In that+ item, the flags field of the name may carry the following bits:++ KDBUS_NAME_ALLOW_REPLACEMENT+ Other connections are allowed to take over this name from the+ connection that owns it.++ KDBUS_NAME_IN_QUEUE (list)+ When retrieving a list of currently acquired name in the registry, this+ flag indicates whether the connection actually owns the name or is+ currently waiting for it to become available.++ KDBUS_NAME_ACTIVATOR (list)+ An activator connection owns a name as a placeholder for an implementor,+ which is started on demand as soon as the first message arrives. There's+ some more information on this topic below. In contrast to+ KDBUS_NAME_REPLACE_EXISTING, when a name is taken over from an activator+ connection, all the messages that have been queued in the activator+ connection will be moved over to the new owner. The activator connection+ will still be tracked for the name and will take control again if the+ implementor connection terminates.+ This flag can not be used when acquiring a name, but is implicitly set+ through KDBUS_CMD_HELLO with KDBUS_HELLO_ACTIVATOR set in+ kdbus_cmd_hello.conn_flags.+};++The returned buffer must be freed with the KDBUS_CMD_FREE ioctl when the user+is finished with it.+++9. Notifications+===============================================================================++The kernel will notify its users of the following events.++ * When connection A is terminated while connection B is waiting for a reply+ from it, connection B is notified with a message with an item of type+ KDBUS_ITEM_REPLY_DEAD.++ * When connection A does not receive a reply from connection B within the+ specified timeout window, connection A will receive a message with an item+ of type KDBUS_ITEM_REPLY_TIMEOUT.++ * When a connection is created on or removed from a bus, messages with an+ item of type KDBUS_ITEM_ID_ADD or KDBUS_ITEM_ID_REMOVE, respectively, are+ sent to all bus members that match these messages through their match+ database.++ * When a connection owns or loses a name, or a name is moved from one+ connection to another, messages with an item of type KDBUS_ITEM_NAME_ADD,+ KDBUS_ITEM_NAME_REMOVE or KDBUS_ITEM_NAME_CHANGE are sent to all bus+ members that match these messages through their match database.++A kernel notification is a regular kdbus message with the following details.++ * kdbus_msg.src_id == KDBUS_SRC_ID_KERNEL+ * kdbus_msg.dst_id == KDBUS_DST_ID_BROADCAST+ * kdbus_msg.payload_type == KDBUS_PAYLOAD_KERNEL+ * Has exactly one of the aforementioned items attached+++10. Message Matching, Bloom filters+===============================================================================++10.1 Matches for broadcast messages from other connections+----------------------------------------------------------++A message addressed at the connection ID KDBUS_DST_ID_BROADCAST (~0ULL) is a+broadcast message, delivered to all connected peers which installed a rule to+match certain properties of the message. Without any rules installed in the+connection, no broadcast message or kernel-side notifications will be delivered+to the connection. Broadcast messages are subject to policy rules and TALK+access checks.++See section 11 for details on policies, and section 11.5 for more+details on implicit policies.++Matches for messages from other connections (not kernel notifications) are+implemented as bloom filters. The sender adds certain properties of the message+as elements to a bloom filter bit field, and sends that along with the+broadcast message.++The connection adds the message properties it is interested as elements to a+bloom mask bit field, and uploads the mask to the match rules of the+connection.++The kernel will match the broadcast message's bloom filter against the+connections bloom mask (simply by &-ing it), and decide whether the message+should be delivered to the connection.++The kernel has no notion of any specific properties of the message, all it+sees are the bit fields of the bloom filter and mask to match against. The+use of bloom filters allows simple and efficient matching, without exposing+any message properties or internals to the kernel side. Clients need to deal+with the fact that they might receive broadcasts which they did not subscribe+to, as the bloom filter might allow false-positives to pass the filter.++To allow the future extension of the set of elements in the bloom filter, the+filter specifies a "generation" number. A later generation must always contain+all elements of the set of the previous generation, but can add new elements+to the set. The match rules mask can carry an array with all previous+generations of masks individually stored. When the filter and mask are matched+by the kernel, the mask with the closest matching "generation" is selected+as the index into the mask array.+++10.2 Matches for kernel notifications+------------------------------------++To receive kernel generated notifications (see section 9), a connection must+install special match rules that are different from the bloom filter matches+described in the section above. They can be filtered by a sender connection's+ID, by one of the name the sender connection owns at the time of sending the+message, or by type of the notification (id/name add/remove/change).++10.3 Adding a match+-------------------++To add a match, the KDBUS_CMD_MATCH_ADD ioctl is used, which takes a struct+of the struct described below.++Note that each of the items attached to this command will internally create+one match 'rule', and the collection of them, which is submitted as one block+via the ioctl is called a 'match'. To allow a message to pass, all rules of a+match have to be satisfied. Hence, adding more items to the command will only+narrow the possibility of a match to effectively let the message pass, and will+cause the connection's user space process to wake up less likely.++Multiple matches can be installed per connection. As long as one of it has a+set of rules which allows the message to pass, this one will be decisive.++struct kdbus_cmd_match {+ __u64 size;+ The overall size of the struct, including its items.++ __u64 cookie;+ A cookie which identifies the match, so it can be referred to at removal+ time.++ __u64 flags;+ Flags to control the behavior of the ioctl.++ KDBUS_MATCH_REPLACE:+ Remove all entries with the given cookie before installing the new one.+ This allows for race-free replacement of matches.++ struct kdbus_item items[0];+ Items to define the actual rules of the matches. The following item types+ are expected. Each item will cause one new match rule to be created.++ KDBUS_ITEM_BLOOM_MASK+ An item that carries the bloom filter mask to match against in its+ data field. The payload size must match the bloom filter size that+ was specified when the bus was created.+ See section 10.4 for more information.++ KDBUS_ITEM_NAME+ Specify a name that a sending connection must own at a time of sending+ a broadcast message in order to match this rule.++ KDBUS_ITEM_ID+ Specify a sender connection's ID that will match this rule.++ KDBUS_ITEM_NAME_ADD+ KDBUS_ITEM_NAME_REMOVE+ KDBUS_ITEM_NAME_CHANGE+ These items request delivery of broadcast messages that describe a name+ acquisition, loss, or change. The details are stored in the item's+ kdbus_notify_name_change member. All information specified must be+ matched in order to make the message pass. Use KDBUS_MATCH_ID_ANY to+ match against any unique connection ID.++ KDBUS_ITEM_ID_ADD+ KDBUS_ITEM_ID_REMOVE+ These items request delivery of broadcast messages that are generated+ when a connection is created or terminated. struct kdbus_notify_id_change+ is used to store the actual match information. This item can be used to+ monitor one particular connection ID, or, when the id field is set to+ KDBUS_MATCH_ID_ANY, all of them.++ Other item types are ignored.+};+++10.4 Bloom filters+------------------++Bloom filters allow checking whether a given word is present in a dictionary.+This allows connections to set up a mask for information it is interested in,+and will be delivered broadcast messages that have a matching filter.++For general information on bloom filters, see++ size of the bloom filter is defined per bus when it is created, in+kdbus_bloom_parameter.size. All bloom filters attached to broadcast messages+on the bus must match this size, and all bloom filter matches uploaded by+connections must also match the size, or a multiple thereof (see below).++The calculation of the mask has to be done on the userspace side. The kernel+just checks the bitmasks to decide whether or not to let the message pass. All+bits in the mask must match the filter in and bit-wise AND logic, but the+mask may have more bits set than the filter. Consequently, false positive+matches are expected to happen, and userspace must deal with that fact.++Masks are entities that are always passed to the kernel as part of a match+(with an item of type KDBUS_ITEM_BLOOM_MASK), and filters can be attached to+broadcast messages (with an item of type KDBUS_ITEM_BLOOM_FILTER).++For a broadcast to match, all set bits in the filter have to be set in the+installed match mask as well. For example, consider a bus has a bloom size+of 8 bytes, and the following mask/filter combinations:++ filter 0x0101010101010101+ mask 0x0101010101010101+ -> matches++ filter 0x0303030303030303+ mask 0x0101010101010101+ -> doesn't match++ filter 0x0101010101010101+ mask 0x0303030303030303+ -> matches++Hence, in order to catch all messages, a mask filled with 0xff bytes can be+installed as a wildcard match rule.++Uploaded matches may contain multiple masks, each of which in the size of the+bloom size defined by the bus. Each block of a mask is called a 'generation',+starting at index 0.++At match time, when a broadcast message is about to be delivered, a bloom+mask generation is passed, which denotes which of the bloom masks the filter+should be matched against. This allows userspace to provide backward compatible+masks at upload time, while older clients can still match against older+versions of filters.+++10.5 Removing a match+--------------------++Matches can be removed through the KDBUS_CMD_MATCH_REMOVE ioctl, which again+takes struct kdbus_cmd_match as argument, but its fields are used slightly+differently.++struct kdbus_cmd_match {+ __u64 size;+ The overall size of the struct. As it has no items in this use case, the+ value should yield 16.++ __u64 cookie;+ The cookie of the match, as it was passed when the match was added.+ All matches that have this cookie will be removed.++ __u64 flags;+ Unused for this use case,++ __u64 kernel_flags;+ Valid flags for this command, returned by the kernel upon each call.++ struct kdbus_item items[0];+ Unused for this use case.+};+++11. Policy+===============================================================================++A policy databases restrict the possibilities of connections to own, see and+talk to well-known names. It can be associated with a bus (through a policy+holder connection) or a custom endpoint.++See section 8.1 for more details on the validity of well-known names.++Default endpoints of buses always have a policy database. The default+policy is to deny all operations except for operations that are covered by+implicit policies. Custom endpoints always have a policy, and by default,+a policy database is empty. Therefore, unless policy rules are added, all+operations will also be denied by default.++See section 11.5 for more details on implicit policies.+.+};++Policies are set through KDBUS_CMD_HELLO (when creating a policy holder+connection), KDBUS_CMD_CONN_UPDATE (when updating a policy holder connection),+KDBUS_CMD_ENDPOINT_MAKE (creating a custom endpoint) or+KDBUS_CMD_ENDPOINT_UPDATE (updating a custom endpoint). In all cases, the name+and policy access information is stored in items of type KDBUS_ITEM_NAME and+KDBUS_ITEM_POLICY_ACCESS. For this transport, the following rules apply.++ * An item of type KDBUS_ITEM_NAME must be followed by at least one+ KDBUS_ITEM_POLICY_ACCESS item+ * An item of type KDBUS_ITEM_NAME can be followed by an arbitrary number of+ KDBUS_ITEM_POLICY_ACCESS items+ * An arbitrary number of groups of names and access levels can be passed++uids and gids are internally always stored in the kernel's view of global ids,+and are translated back and forth on the ioctl level accordingly.+++11.2 Wildcard names+-------------------++Policy holder connections may upload names that contain the wildcard suffix+(".*"). That way, a policy can be uploaded that is effective for every+well-kwown name that extends the provided name by exactly one more level.++For example, if an item of a set up uploaded policy rules contains the name+"foo.bar.*", both "foo.bar.baz" and "foo.bar.bazbaz" are valid, but+"foo.bar.baz.baz" is not.++This allows connections to take control over multiple names that the policy+holder doesn't need to know about when uploading the policy.++Such wildcard entries are not allowed for custom endpoints.+++11.3 Policy example+-------------------++For example, a set of policy rules may look like this:++ KDBUS_ITEM_NAME: str='org.foo.bar'+ KDBUS_ITEM_POLICY_ACCESS: type=USER, access=OWN, id=1000+ KDBUS_ITEM_POLICY_ACCESS: type=USER, access=TALK, id=1001+ KDBUS_ITEM_POLICY_ACCESS: type=WORLD, access=SEE+ KDBUS_ITEM_NAME: str='org.blah.baz'+ KDBUS_ITEM_POLICY_ACCESS: type=USER, access=OWN, id=0+ KDBUS_ITEM_POLICY_ACCESS: type=WORLD, access=TALK++That means that 'org.foo.bar' may only be owned by uid 1000, but every user on+the bus is allowed to see the name. However, only uid 1001 may actually send+a message to the connection and receive a reply from it.++The second rule allows 'org.blah.baz' to be owned by uid 0 only, but every user+may talk to it.++.++If a policy database exists for a bus (because a policy holder created one on+demand) or for a custom endpoint (which always has one), each one is consulted+during name registry listing, name owning or message delivery. If either one+fails, the operation is failed with -EPERM.++For best practices, connections that own names with a restricted TALK+access should not install matches. This avoids cases where the sent+message may pass the bloom filter due to false-positives and may also+satisfy the policy rules.+++11.5 Implicit policies+----------------------++Depending on the type of the endpoint, a set of implicit rules might be+enforced. On default endpoints, the following set is enforced:++ * Privileged connections always override any installed policy. Those+ connections could easily install their own policies, so there is no+ reason to enforce installed policies.+ * Connections can always talk to connections of the same user. This+ includes broadcast messages.+ * Connections that own names might send broadcast messages to other+ connections that belong to a different user, but only if that+ destination connection does not own any name.++Custom endpoints have stricter policies. The following rules apply:++ * Policy rules are always enforced, even if the connection is a privileged+ connection.+ * Policy rules are always enforced for TALK access, even if both ends are+ running under the same user. This includes broadcast messages.+ * To restrict the set of names that can be seen, endpoint policies can+ install "SEE" policies.++.++ KDBUS_ATTACH_SECLABEL+ Attaches an item of type KDBUS_ITEM_SECLABEL, which contains the SELinux+ security label of the sending task. Access via kdbus_item->str.++ KDBUS_ATTACH_AUDIT+ Attaches an item of type KDBUS_ITEM_AUDIT, which contains the audio label+ of the sending taskj. Access via kdbus_item->str.++ KDBUS_ATTACH_CONN_DESCRIPTION+ Attaches an item of type KDBUS_ITEM_CONN_DESCRIPTION that contains the+ sender connection's current name in kdbus_item.str.++.+++14. Error codes+===============================================================================++Below is a list of error codes that might be returned by the individual+ioctl commands. The list focuses on the return values from kdbus code itself,+and might not cover those of all kernel internal functions.++For all ioctls:++ -ENOMEM The kernel memory is exhausted+ -ENOTTY Illegal ioctl command issued for the file descriptor+ -ENOSYS The requested functionality is not available++For all ioctls that carry a struct as payload:++ -EFAULT The supplied data pointer was not 64-bit aligned, or was+ inaccessible from the kernel side.+ -EINVAL The size inside the supplied struct was smaller than expected+ -EMSGSIZE The size inside the supplied struct was bigger than expected+ -ENAMETOOLONG A supplied name is larger than the allowed maximum size++For KDBUS_CMD_BUS_MAKE:++ -EINVAL The flags supplied in the kdbus_cmd_make struct are invalid or+ the supplied name does not start with the current uid and a '-'+ -EEXIST A bus of that name already exists+ -ESHUTDOWN The domain for the bus is already shut down+ -EMFILE The maximum number of buses for the current user is exhausted++For KDBUS_CMD_ENDPOINT_MAKE:++ -EPERM The calling user is not privileged (see Terminology)+ -EINVAL The flags supplied in the kdbus_cmd_make struct are invalid+ -EEXIST An endpoint of that name already exists++For KDBUS_CMD_HELLO:++ -EFAULT The supplied pool size was 0 or not a multiple of the page size+ -EINVAL The flags supplied in the kdbus_cmd_make struct are invalid, or+ an illegal combination of KDBUS_HELLO_MONITOR,+ KDBUS_HELLO_ACTIVATOR and KDBUS_HELLO_POLICY_HOLDER was passed+ in the flags, or an invalid set of items was supplied+ -ECONNREFUSED The attach_flags_send field did not satisfy the requirements of+ the bus+ -EPERM An KDBUS_ITEM_CREDS items was supplied, but the current user is+ not privileged+ -ESHUTDOWN The bus has already been shut down+ -EMFILE The maximum number of connection on the bus has been reached++For KDBUS_CMD_BYEBYE:++ -EALREADY The connection has already been shut down+ -EBUSY There are still messages queued up in the connection's pool++For KDBUS_CMD_MSG_SEND:++ -EOPNOTSUPP The connection is not an ordinary connection, or the passed+ file descriptors are either kdbus handles or unix domain+ sockets. Both are currently unsupported+ -EINVAL The submitted payload type is KDBUS_PAYLOAD_KERNEL,+ KDBUS_MSG_FLAGS_EXPECT_REPLY was set without a timeout value,+ KDBUS_MSG_FLAGS_SYNC_REPLY was set without+ KDBUS_MSG_FLAGS_EXPECT_REPLY, an invalid item was supplied,+ src_id was != 0 and different from the current connection's ID,+ a supplied memfd had a size of 0, a string was not properly+ nul-terminated+ -ENOTUNIQ The supplied destination is KDBUS_DST_ID_BROADCAST, a file+ descriptor was passed, KDBUS_MSG_FLAGS_EXPECT_REPLY was set,+ or a timeout was given for a broadcast message+ -E2BIG Too many items+ -EMSGSIZE The size of the message header and items or the payload vector+ is too big.+ -EEXIST Multiple KDBUS_ITEM_FDS, KDBUS_ITEM_BLOOM_FILTER or+ KDBUS_ITEM_DST_NAME items were supplied+ -EBADF The supplied KDBUS_ITEM_FDS or KDBUS_MSG_PAYLOAD_MEMFD items+ contained an illegal file descriptor+ -EMEDIUMTYPE The supplied memfd is not a sealed kdbus memfd+ -EMFILE Too many file descriptors inside a KDBUS_ITEM_FDS+ -EBADMSG An item had illegal size, both a dst_id and a+ KDBUS_ITEM_DST_NAME was given, or both a name and a bloom+ filter was given+ -ETXTBSY The supplied kdbus memfd file cannot be sealed or the seal+ was removed, because it is shared with other processes or+ still mmap()ed+ -ECOMM A peer does not accept the file descriptors addressed to it+ -EFAULT The supplied bloom filter size was not 64-bit aligned+ -EDOM The supplied bloom filter size did not match the bloom filter+ size of the bus+ -EDESTADDRREQ dst_id was set to KDBUS_DST_ID_NAME, but no KDBUS_ITEM_DST_NAME+ was attached+ -ESRCH The name to look up was not found in the name registry+ -EADDRNOTAVAIL KDBUS_MSG_FLAGS_NO_AUTO_START was given but the destination+ connection is an activator.+ -ENXIO The passed numeric destination connection ID couldn't be found,+ or is not connected+ -ECONNRESET The destination connection is no longer active+ -ETIMEDOUT Timeout while synchronously waiting for a reply+ -EINTR System call interrupted while synchronously waiting for a reply+ -EPIPE When sending a message, a synchronous reply from the receiving+ connection was expected but the connection died before+ answering+ -ECANCELED A synchronous message sending was cancelled+ -ENOBUFS Too many pending messages on the receiver side+ -EREMCHG Both a well-known name and a unique name (ID) was given, but+ the name is not currently owned by that connection.+ -EXFULL The memory pool of the receiver is full+ -EREMOTEIO While synchronously waiting for a reply, the remote peer+ failed with an I/O error.++For KDBUS_CMD_MSG_RECV:++ -EINVAL Invalid flags or offset+ -EAGAIN No message found in the queue+ -ENOMSG No message of the requested priority found+ -EOVERFLOW Broadcast messages have been lost++For KDBUS_CMD_MSG_CANCEL:++ -EINVAL Invalid flags+ -ENOENT Pending message with the supplied cookie not found++For KDBUS_CMD_FREE:++ -ENXIO No pool slice found at given offset+ -EINVAL Invalid flags provided, the offset is valid, but the user is+ not allowed to free the slice. This happens, for example, if+ the offset was retrieved with KDBUS_RECV_PEEK.++For KDBUS_CMD_NAME_ACQUIRE:++ -EINVAL Illegal command flags, illegal name provided, or an activator+ tried to acquire a second name+ -EPERM Policy prohibited name ownership+ -EALREADY Connection already owns that name+ -EEXIST The name already exists and can not be taken over+ -E2BIG The maximum number of well-known names per connection+ is exhausted+ -ECONNRESET The connection was reset during the call++For KDBUS_CMD_NAME_RELEASE:++ -EINVAL Invalid command flags, or invalid name provided+ -ESRCH Name is not found found in the registry+ -EADDRINUSE Name is owned by a different connection and can't be released++For KDBUS_CMD_NAME_LIST:++ -EINVAL Invalid flags+ -ENOBUFS No available memory in the connection's pool.++For KDBUS_CMD_CONN_INFO:++ -EINVAL Invalid flags, or neither an ID nor a name was provided,+ or the name is invalid.+ -ESRCH Connection lookup by name failed+ -ENXIO No connection with the provided number connection ID found++For KDBUS_CMD_CONN_UPDATE:++ -EINVAL Illegal flags or items+ -EOPNOTSUPP Operation not supported by connection.+ -E2BIG Too many policy items attached+ -EINVAL Wildcards submitted in policy entries, or illegal sequence+ of policy items++For KDBUS_CMD_ENDPOINT_UPDATE:++ -E2BIG Too many policy items attached+ -EINVAL Invalid flags, or wildcards submitted in policy entries,+ or illegal sequence of policy items++For KDBUS_CMD_MATCH_ADD:++ -EINVAL Illegal flags or items+ -EDOM Illegal bloom filter size+ -EMFILE Too many matches for this connection++For KDBUS_CMD_MATCH_REMOVE:++ -EINVAL Illegal flags+ -ENOENT A match entry with the given cookie could not be found.+++15. Internal object relations+===============================================================================++This is a simplified outline of the internal kdbus object relations, for+those interested in the inner life of the driver implementation.++From the a mount point's (domain's) perspective:++struct kdbus_domain+ |» struct kdbus_domain_user *user (many, owned)+ '» struct kdbus_node node (embedded)+ |» struct kdbus_node children (many, referenced)+ |» struct kdbus_node *parent (pinned)+ '» struct kdbus_bus (many, pinned)+ |» struct kdbus_node node (embedded)+ '» struct kdbus_ep (many, pinned)+ |» struct kdbus_node node (embedded)+ |» struct kdbus_bus *bus (pinned)+ |» struct kdbus_conn conn_list (many, pinned)+ | |» struct kdbus_ep *ep (pinned)+ | |» struct kdbus_name_entry *activator_of (owned)+ | |» struct kdbus_match_db *match_db (owned)+ | |» struct kdbus_meta *meta (owned)+ | |» struct kdbus_match_db *match_db (owned)+ | | '» struct kdbus_match_entry (many, owned)+ | |+ | |» struct kdbus_pool *pool (owned)+ | | '» struct kdbus_pool_slice *slices (many, owned)+ | | '» struct kdbus_pool *pool (pinned)+ | |+ | |» struct kdbus_domain_user *user (pinned)+ | `» struct kdbus_queue_entry entries (many, embedded)+ | |» struct kdbus_pool_slice *slice (pinned)+ | |» struct kdbus_conn_reply *reply (owned)+ | '» struct kdbus_domain_user *user (pinned)+ |+ '» struct kdbus_domain_user *user (pinned)+ '» struct kdbus_policy_db policy_db (embedded)+ |» struct kdbus_policy_db_entry (many, owned)+ | |» struct kdbus_conn (pinned)+ | '» struct kdbus_ep (pinned)+ |+ '» struct kdbus_policy_db_cache_entry (many, owned)+ '» struct kdbus_conn (pinned)+++For the life-time of a file descriptor derived from calling open() on a file+inside the mount point:++struct kdbus_handle+ |» struct kdbus_meta *meta (owned)+ |» struct kdbus_ep *ep (pinned)+ |» struct kdbus_conn *conn (owned)+ '» struct kdbus_ep *ep (owned)-- 2.1.3 | https://lkml.org/lkml/2014/11/21/10 | CC-MAIN-2017-51 | refinedweb | 7,647 | 53.21 |
What.
Steps to create a game
- 1. Have an idea for a game.
- 2. Draft up some scenarios on paper to resemble your vision and how will it look like.
- 3. Analyse the idea, iterate over a few versions by tweaking it and decide what the game will have in its initial version.
- 4. Pick a technology and start prototyping.
- 5. Start coding and creating the assets for the game.
- 6. Play-test, improve, and continuously make small steps towards finishing it.
- 7. Polish and release!
The Game Idea
Because this will be a one day project, there is very limited time at disposal and the goal is to learn the technology to make games, not the actual process. For this purpose I took the liberty to borrow ideas from other games and focus on the technical aspects of this process.
I will be borrowing heavily from a game called Star Guard. It’s a little gem made by Vacuum Flowers. Go get the game and check it out. A very simple shooter platformer with a simplistic style and old school arcade feel.
The idea is to guide our hero through the levels by killing enemies and and dodging everything that tries to kill us.
The controls are simple, the arrow keys move the hero to the left or right, Z jumps and X shoots the laser. The longer the jump button is held, the higher the hero jumps. He can change direction in the air and also shoot. We’ll see how we can translate these controls to Android later on.
The next steps (2 and 3) can be skipped over as we will already have this taken care of because of the functioning game.
Start your Eclipse
This is where we start. I will be using libgdx library to create the game. Why libgdx? It’s the best library (in my opinion) that makes developing games easy without knowing much about the underlying technology. It allows developers to create their games on the desktop and deploy it to Android without any modification. It offers all the elements to use it in games and hides the complexity of dealing with specific technologies and hardware. It will become more obvious as we go along.
Setting up the project
By following the instructions from libgdx’s documentation we have to first download the library.
Go to and download the
libgdx-nightly-latest.zip file and unpack it.
Create a simple java project in eclipse. I will call it
star-assault.
Leave the default settings and once the project was created, right click on it and select New->Folder and create a directory named
libs.
From the unpacked
libgdx-nighly-latest directory, copy the
gdx.jar file into the newly created
libs directory. Also copy the the
gdx-sources.jar file into the
libs directory. It is in the
sources sub-directory of the unpacked gdx directory. You can do this by simply dragging the jar files into your directories in eclipse. If you copy them using explorer, or finder or any other means, don’t forget to refresh your eclipse project after by pressing F5.
The structure should look like the following image:
Add
gdx.jar as a dependency to the project. Do this by right-clicking the project title and select Properties. On this screen pick Java Build Path and click onto the Libraries tab. Click Add JARs…, navigate to the
libs directory and select
gdx.jar, then click OK.
In order to have access to the gdx source code and to be able to debug our game easily, it’s a good idea to add the sources to the gdx.jar file. To do this, expand the
gdx.jar node, select Source attachment, click Edit…, then Workspace… and pick
gdx-sources.jar then OK until all the pop-up windows are closed.
The complete documentation for setting up projects with libgdx can be found on the official wiki.
This project will be the core project for the game. It will contain the game mechanics, the engine, everything. We will need to create two more projects, basically launchers for the 2 platforms we are targeting. One for Android and one for Desktop. These projects will be extremely simple and will contain only the dependencies required to run the game on the respective platforms. Think of them as the class containing the main method.
Why do we need separate projects for these? Because libgdx hides the complexity of dealing with the underlying operating system (graphics, audio, user input, file i/o, etc.), Each platform has a specific implementation and we will need to include only those implementations (bindings) that are required targeted. Also because the application life-cycle, the asset loading (loading of images, sounds, etc) and other common aspects of an application are heavily simplified, the platform specific implementations reside in different JAR files and only those need to be included that are required for the platform we are targeting.
The Desktop Version
Create a simple java project as in the previous step and name it
star-assault-desktop. Also follow the steps to create the
libs directory. This time the required
jar files from the downloaded
zip file are:
gdx-natives.jar,
gdx-backend-lwjgl.jar,
gdx-backend-lwjgl-natives.jar.
Also add these
jar files as dependencies to the project as in the previous project. (right click the project -> Properties -> Java Build Path -> Libraries -> Add JARs, select the three JARs and click OK.)
We also need to add the
star-assault project to the dependencies. To do this, click the Projects tab, click Add, check the
star-assault project and click OK.
Important! We need to make the
star-assault project a transitive dependency, meaning that dependencies for this project to be made dependencies of projects depending on this. To do this: right click on the main project -> Properties -> Java Build Path -> Order and Export -> check the gdx.jar file and click OK.
The Android Version
For this you will need the Android SDK installed.
Create a new Android project in eclipse: File -> New -> Project -> Android Project.
Name it
star-assault-android. For build target, check “Android 2.3?. Specify a package name
net.obviam or your own preference. Next to “Create Activity” enter
StarAssaultActivity. Click Finish.
Go to the project directory and create a sub-directory named libs (you can do this from eclipse). From the
nightly zip, place
gdx-backend-android.jar and the
armeabi and
armeabi-v7a directories in the newly created
libs directory.
In eclipse, right click the project -> Properties -> Java Build Path -> Libraries -> Add JARs, select
gdx-backend-android.jar and click OK.
Click Add JARs again, select gdx.jar under the main project (
star-assault) and click OK.
Click the Projects tab, click Add, check the main project and click OK twice.
This is how the structure should look like:
Important!
For ADT release 17 and newer, the
gdx jar files need to be explicitly marked to be exported.
To do this
Click on the Android Project
Select Properties
Select Java Build Path (step 1)
Select Order and Export (step 2)
Check all the references, e.g. the
gdx.jar, the
gdx-backend-android.jar, the main project etc. (step 3).
The following image shows the new state.
Also, more information on this issue here.
Sharing the Assets (images, sounds and other data)
Because the game will be identical on both desktop and Android but each version requires to be built separately from different projects, we want to keep the images, sounds and other data files in a shared location. Ideally this would be in the main project as it is included in both Android and desktop bu because Android has a strict rule on where to keep all these files, we will have to keep the assets there. It is in the automatically created
assets directory in the Android project. In eclipse there is the possibility to link directories as in symbolic links on linux/mac or shortcuts in windows. To link the
assets directory from the Android project to the desktop project do the following:
Right click the
star-assault-desktop project -> Properties -> Java Build Path -> Source tab -> Link Source… -> Browse… -> browse to the
asssets directory in the
star-assault-android project and click Finish. You can also extend the Variables… instead of browsing to the
assets directory. It is recommended as it makes the project file system independent.
Also make sure the
assets directory is included as a source folder. To do that, right click on the
assets directory in eclipse (the desktop project), select Build Path -> Use as Source Folder.
At this stage we are ready with the setup and we can go ahead to work on the game.
Creating the Game
A computer application is a piece of software that runs on a machine. It starts up, does something (even if that’s nothing) and stops in a way or another. A computer game is a specific type of application in which the “does something” part is filled with a game. The start and end is common to all applications. Also the game has a very straight forward architecture based around an continuous loop. You can find out more about the architecture and the loop here and here.
Thanks to libgdx our game can be pieced together as a staged play in a theatre. All you need to do is, to think of the game as a theatrical play. We will define the stages, the actors, their roles and behaviours, but we will delegate the choreography to the player.
So to set up our game/play we need to take the following steps:
- 1. Start application.
- 2. Load up all the images and sounds and store them in memory.
- 3. Create the stages for our play along with the actors and their behaviours (rules for interactions between them).
- 4. Hand the control to the player.
- 5. Create the engine that will manipulate the actors on the stage based on the input received from the controller.
- 6. Determine when the play ends.
- 7. End the show.
It looks quite simple and it really is. I will be introducing the notions and elements as they appear.
To create the Game we simply need just one class.
Let’s create
StarAssault.java in the
star-assault project. Every class will be created in this project with 2 exceptions.
package net.obviam.starassault; import com.badlogic.gdx.ApplicationListener; public class StarAssault implements ApplicationListener { @Override public void create() { // TODO Auto-generated method stub } @Override public void resize(int width, int height) { // TODO Auto-generated method stub } @Override public void render() { // TODO Auto-generated method stub } @Override public void pause() { // TODO Auto-generated method stub } @Override public void resume() { // TODO Auto-generated method stub } @Override public void dispose() { // TODO Auto-generated method stub } }
Just implement
ApplicationListener from
gdx and eclipse will generate the stubs for the methods needed to be implemented.
These are all the methods that we need to implement from the application lifecycle. It is very simple considering all the setup code needed for Android, or on desktop to initialise the OpenGL context and all those boring (and difficult) tasks.
The method
create() is called first. This happens when the application is ready and we can start loading our assets and create the stage and actors. Think of building the stage for the play in a theatre AFTER all the things have been shipped there and prepared. Depending on where the theatre is and how you get there, the logistic can be a nightmare. You can ship things by hand, or by plane or trucks…we don’t know. We’re inside and have the stuff ready and we can start to assemble it. This is what libgdx is doing for us. Shipping our stuff and delivering it regardless of the platform.
The method
resize(int width, int height) is called every time the drawable surface is resized. This gives us the chance to rearrange the bits before we go on to start the play. It happens when the window (if the game runs in one) is resized for example.
The heart of every game is the
render() method which is nothing more than the infinite loop. This gets called continuously until we decide that the game is over and want to terminate the program. This is the play in progress.
Note: For computers the game over is not equivalent of program over. So it’s just a state. The program is in a state of game over, but is still running.
Of course that the play can be interrupted bu pauses and they can be resumed. The
pause() method will be called whenever the application enters into the background on the desktop or Android. When the application comes to the foreground it resumes and the
resume() method is being called.
When the game is done and the application is being closed, the
dispose() is called and this is the time to do some cleanup. It’s similar when the play is over, spectators have left and the stage is being dismantled. No more coming back. More on the lifecycle here.
The Actors
Let’s start taking steps towards the actual game. The first mile-stone is to have a world in which our guy can move. The world is composed of levels and each level is composed of a terrain. The terrain is nothing more than some blocks through which our guy can’t go.
Identifying the actors and entities so far in the game is easy.
We have the guy (let’s call him Bob – libgdx has tutorials with Bob) and the blocks that make up the world.
Having played Star Guard we can see that Bob has a few states. When we don’t touch anything, Bob is idle. He can also move (in both directions) and he can also jump. Also when he’s dead, he can’t do anything. Bob can be in only one of the 4 identified states at any given time. There are other states as well but we’ll leave them out for now.
The states for Bob:
- Idle – when not moving or jumping and is alive
- Moving – either left or right at a constant speed.
- Jumping – also facing left or right and high or low.
- Dead – he’s not even visible and respawning.
The Blocks are the other actors. For simplicity we have just blocks. The level consists of blocks placed in a 2 dimensional space. For simplicity we will use a grid.
Turn the start of Star Guard into a block and Bob structure, will look something like this:
The top one is the original and the bottom one is our world representation.
We have imagined the world but we need to work in a measure system that we can make sense of. For simplicity we will say that one block in the world is one unit wide and 1 unit tall. We can use meters to make it even simpler but because Bob is half a unit, it makes him half a meter. Let’s say 4 units in the game world make up 1 meter so Bob will be 2 meters tall.
It is important because when we will calculate the speed with which Bob runs for example, we need to know what we’re doing.
Let’s create the world.
Our main playable character is
Bob.
The
Bob.java class looks like this:
package net.obviam.starassault.model; import com.badlogic.gdx.math.Rectangle; import com.badlogic.gdx.math.Vector2; public class Bob { public enum State { IDLE, WALKING, JUMPING, DYING } static final float SPEED = 2f; // unit per second static final float JUMP_VELOCITY = 1f; static final float SIZE = 0.5f; // half a unit Vector2 position = new Vector2(); Vector2 acceleration = new Vector2(); Vector2 velocity = new Vector2(); Rectangle bounds = new Rectangle(); State state = State.IDLE; boolean facingLeft = true; public Bob(Vector2 position) { this.position = position; this.bounds.height = SIZE; this.bounds.width = SIZE; } }
Lines #16-#21 define the attributes of Bob. The values of these attributes define Bob’s state at any given time.
position – Bob’s position in the world. This is expressed in world coordinates (more on this later).
acceleration – This will determine the acceleration when Bob jumps.
velocity – Will be calculated and used for moving Bob around.
bounds – Each element in the game will have a bounding box. This is nothing more than a rectangle, in order to know if Bob ran into a wall, got killed by a bullet or shot an enemy and hit. It will be used for collision detection. Think of playing with cubes.
state – the current state of Bob. When we issue the walk action, the state will be
WALKING and based on this state, we know what to draw onto the screen.
facingLeft – represents Bob’s bearing. Being a simple 2D platformer, we have just 2 facings. Left and right.
Lines #12-#15 define some constants we will use to calculate the speed and positions in the world. These will be tweaked later on.
We also need some blocks to make up the world.
The
Block.java class looks like this:
package net.obviam.starassault.model; import com.badlogic.gdx.math.Rectangle; import com.badlogic.gdx.math.Vector2; public class Block { static final float SIZE = 1f; Vector2 position = new Vector2(); Rectangle bounds = new Rectangle(); public Block(Vector2 pos) { this.position = pos; this.bounds.width = SIZE; this.bounds.height = SIZE; } }
Blocks are nothing more than rectangles placed in the world. We will use these blocks to make up the terrain. We have one simple rule. Nothing can penetrate them.
libgdx note
You might have noticed that we are using the
Vector2 type from libgdx. This makes our life considerably easier as it provides everything we need to work with Euclidean vectors. We will use vectors to position entities, to calculate speeds, and to move thing around.
About the coordinate system and units
As the real world, our world has dimensions. Think of a room in a flat. It has a width, height and depth. We will make it 2 dimensional and will get rid of the depth. If the room is 5 meters wide and 3 meters tall we can say that we described the room in the metric system. It is easy to imagine placing a table 1 meter wide and 1 meter tall in the middle. We can’t go through the table, to cross it, we will need to jump on top of it, walk 1 meter and jump off. We can use multiple tables to create a pyramid and create some weird designs in the room.
In our star assault world, the world represents the room, the blocks the table and the unit, the meter in the real world.
If I run with 10km/h that translates to 2.77777778 metres / second ( 10 * 1000 / 3600). To translate this to Star Assault world coordinates, we will say that to resemble a 10km/h speed, we will use 2.7 units/second.
Examine the following diagram of representing the bounding boxes and Bob in the world coordinate system.
The red squares are the bounding boxes of the blocks. The green square is Bob’s bounding box. The empty squares are just empty air. The grid is just for reference. This is the world we will be creating our simulations in. The coordinate system’s origin is at the bottom left, so walking left at 10.000 units/hour means that Bob’s position’s X coordinate will decrease with 2.7 units every second.
Also note that the access to the members is package default and the models are in a separate package. We will have to create accessor methods (getters and setters) to get access to them from the engine.
Creating the World
As a first step we will just create the world as a hard-coded tiny room. It will be 10 units wide and 7 units tall. We will place Bob and the blocks following the image shown below.
The
World.java looks like this:
package net.obviam.starassault.model; import com.badlogic.gdx.math.Vector2; import com.badlogic.gdx.utils.Array; public class World { /** The blocks making up the world **/ Array<Block> blocks = new Array<Block>(); /** Our player controlled hero **/ Bob bob; // Getters ----------- public Array<Block> getBlocks() { return blocks; } public Bob getBob() { return bob; } // -------------------- public World() { createDemoWorld(); } private void createDemoWorld() { bob = new Bob(new Vector2(7, 2)); for (int i = 0; i < 10; i++) { blocks.add(new Block(new Vector2(i, 0))); blocks.add(new Block(new Vector2(i, 7))); if (i > 2) blocks.add(new Block(new Vector2(i, 1))); } blocks.add(new Block(new Vector2(9, 2))); blocks.add(new Block(new Vector2(9, 3))); blocks.add(new Block(new Vector2(9, 4))); blocks.add(new Block(new Vector2(9, 5))); blocks.add(new Block(new Vector2(6, 3))); blocks.add(new Block(new Vector2(6, 4))); blocks.add(new Block(new Vector2(6, 5))); } }
It is a simple container class for the entities in the world. Currently the entities are the blocks and Bob. In the constructor the blocks are added to the
blocks array and
Bob is created. It’s all hard-coded for the time being.
Remember that the origin is in the bottom left corner.
Reference: Getting Started in Android Game Development with libgdx – Create a Working Prototype in a Day – Tutorial Part 1 from our JCG partner Impaler at the Against the Grain blog.
I think you have an error in createDemoWorld()
it should be:
this.blocks.add(new Block(new Vector2(i, 6)));
instead of:
this.blocks.add(new Block(new Vector2(i, 7)));
I like the tutorial so far otherwise though :)
+1, nice find. Was wondering why my top row of blocks wasn’t visible.
Hi. I cannot find any straight contact to you so I’m writting here. Would you mind if I translate your tutorial into polish and publish on my site? I’ll put links to your side in translations.
I am getting this exception. I checked that android assets folder is a source folder of desktop but always get this error.
Exception in thread “LWJGL Application” com.badlogic.gdx.utils.GdxRuntimeException: File not found: imagestexturestextures.pack (Internal)
at com.badlogic.gdx.files.FileHandle.read(FileHandle.java:114)
at com.badlogic.gdx.graphics.g2d.TextureAtlas$TextureAtlasData.(TextureAtlas.java:100)
at com.badlogic.gdx.graphics.g2d.TextureAtlas.(TextureAtlas.java:216)
at com.badlogic.gdx.graphics.g2d.TextureAtlas.(TextureAtlas.java:211)
at com.badlogic.gdx.graphics.g2d.TextureAtlas.(TextureAtlas.java:201)
at net.obviam.starassault.view.WorldRenderer.loadTextures(WorldRenderer.java:65)
at net.obviam.starassault.view.WorldRenderer.(WorldRenderer.java:61)
at net.obviam.starassault.screens.GameScreen.show(GameScreen.java:25)
at com.badlogic.gdx.Game.setScreen(Game.java:59)
at net.obviam.starassault.StarAssault.create(StarAssault.java:11))
AL lib: ReleaseALC: 1 device not closed
Both Bob{ // … } and Block{ // … } need:
public Rectangle getBounds() {
return bounds;
}
// and
public Vector2 getPosition() {
return position;
}
methods added. That’s never discussed but it is referenced in the next section.
wow, the day I begin following this tutorial is also it’s first birthday. Happy Birthday :D
Hello, very nice tutorial. I just have one question(so far); if I use the LibGDX project setup (gdx-setup-ui) do I need to configure all the folders etc? I believe it does all that for me, but I wanted to be sure. Thanks. <– link to the setup ui.
Thank you for your tutorials, helped me develop my first game :
“Let’s say 4 units in the game world make up 1 meter so Bob will be 2 meters tall.”
I’m not understanding this part. If 4 units is 1 meter (1 unit = 1/4 a meter), and Bob is half a unit tall, that make him 1/8 a meter. Is it supposed to be 1 unit is 4 meters? Bob would then be 2 meters if that was the case. | http://www.javacodegeeks.com/2012/05/android-game-development-with-libgdx.html | CC-MAIN-2015-48 | refinedweb | 4,010 | 67.25 |
Steem Developer Portal
PY: Get Follower And Following List
Tutorial pulls a list of the followers or authors being followed from the blockchain then displays the result.
Full, runnable src of Get Follower And Following List can be downloaded as part of the PY tutorials repository.
This tutorial will explain and show you how to access the Steem blockchain using the steem-python library to fetch list of authors being followed or authors that a specified user is following.
Intro
We are using the
get_followers and
get_following functions that are built into the official library
steem-python. These functions allow us to query the Steem blockchain in order to retrieve either a list of authors that are being followed or a list of authors that are currently following a specified user. There are 4 parameters required to execute these functions:
- account - The specific user for which the follower(ing) list will be retrieved
- start follower(ing) - The starting letter(s) or name for the search query. This value can be set as an empty string in order to include all authors starting from “a”
- follow type - This value is set to
blogand includes all users following or being followed by the
user. This is currently the only valid parameter value for this function to execute correctly.
- limit - The maximum number of lines that can be returned by the query
Steps
- App setup - Library install and import
- Input variables - Collecting the required inputs via the UI
- Get followers/following Get the followers or users being followed
- Print output - Print results in output
1. App setup
In this tutorial we use 2 packages,
pick - helps us to select the query type interactively.
steem - steem-python library, interaction with Blockchain.
First we import both libraries and initialize Steem class
from pick import pick from steem import Steem s = Steem()
2. Input variables
We assign two of the variables via a simple input from the UI.
#capture username username = input("Username: ") #capture list limit limit = input("Max number of followers(ing) to display: ")
Next we make a list of the two list options available to the user,
following or
followers and setup
pick.
#list type title = 'Please choose the type of list: ' options = ['Follower', 'Following'] #get index and selected list name option, index = pick(options, title) print("List of " + option)
This will show the two options as a list to select in terminal/command prompt. From there we can determine which function to execute. We also display the choice on the UI for clarity.
3. Get followers/following
Now that we know which function we will be using, we can form the query to send to the blockchain. The selection is done with a simple
if statement.
if option=="Follower" : follow = s.get_followers(username, '', 'blog', limit) # for follower in follow: # lists.append(follower["follower"]) # print(*lists, sep='\n') else: follow = s.get_following(username, '', 'blog', limit) # for following in follow: # lists.append(following["following"]) # print(*lists, sep='\n')
The output is displayed using the same
if statement and will be discussed in the next step.
4. Print output
Next, we will print the result.
if option=="Follower" : # follow = s.get_followers(username, '', 'blog', limit) for follower in follow: lists.append(follower["follower"]) print(*lists, sep='\n') else: # follow = s.get_following(username, '', 'blog', limit) for following in follow: lists.append(following["following"]) print(*lists, sep='\n')
The query returns an array of objects. We use the
for loop to build a list of only the followers(ing) from that array and then display the list on the UI with line separators. This creates an easy to read list of authors.
We also do a check for when the list is empty to display the proper message.
#check if follower(ing) list is empty if len(lists) == 0: print("No "+option+" information available")
This is a fairly simple example of how to use these functions but we encourage you to play around with the parameters to gain further understanding of possible results.
To Run the tutorial
- review dev requirements
- clone this repo
cd tutorials/19_get_follower_and_following_list
pip install -r requirements.txt
python index.py
- After a few moments, you should see output in terminal/command prompt screen. | https://developers.steem.io/tutorials-python/get_follower_and_following_list | CC-MAIN-2018-47 | refinedweb | 698 | 53.71 |
A couple of years back I had a very surprising experience with a junior programmer, who had just joined our team. I had asked him to work on some code until there were no more JUnit errors. A few hours later he proudly showed there were no errors, and explained it was easier than he expected because he just commented out the tests! Then he paused, regarded my startled expression for a few seconds and quickly blushed deeply. Doh!
Poor old Alex Brown has been in and out of favour with the extreme anti-OOXML-ists (perhaps I should use a new acronym, such EAOOXMLista, to say for the hundred thousandth time that not every anti-OOXML person is extreme?) over the last few weeks. First, he didn’t somehow stop the DIS29500 BRM somehow (exactly how?) from doing its job. So he is bad. Then he works with SC34 to organize getting more improvements made to OOXML and ODF. Again, bad. Then he says ““The question behind the question, for a lot of the current OOXML debate, seems to be: can Microsoft really be trusted to behave? We shall see” which earned him the quote of the day on ConsortiumInfo. So presumably he is good.
Then he does a smoke test of validation conformance of Office and the various OOXMLs, and reported the validation errors he found. So he is deemed good. Now he has validated various versions of Open Office and ODF and reported the validation errors he found. And that makes him the devil again.
Unless there is some tussle between evil twins going on, I’d like to suggest that Alex is just trying to faithfuly fulfill his normal committee responsibilities, which include checking through standards. Alex has long been involved in Data Quality issues for publishing professionally, and has been very involved in the development of ISO DSDL at SC34 (which includes RELAX NG and Schematron.)
So what is it that Alex found about ODF that has caused the fuss? It is quite technical, but the gist is this, as I understand it: if a schema is not itself valid, no documents can be formally valid against it.
(When the invalid part of the schema is only detected at run-time when exercised by a particular instance document structure, and the document does not contain such a triggering instance, the implementation may report that the document is valid, but that is a false positive. And you make look at the schema and say “I know what was intended, and the false positive is in fact correct against the intent of the schema” but this is lucky accident, i.e. hacking, not formal validity.)
The particular issue is quite interesting because it relates to an area in a W3C Schema standard where the user requirements for XSD could not be supported by the facet model used, and where XSD fudges it. OASIS RELAX NG, also to an extent inherited this problem.
The problem is with attributes of type ID in the ODF schema. Alex Brown has provided a very simple fix, which I hope gets adopted into ODF 1.2.
The problem with IDs is this. XML inherits ID type attributes from SGML. They have various constraints, which include that they are XML names (tokens), that their values are unique within the document, and that an element can only have one ID attribute.
When XSD came to make its datatyping the XSD WG made a nice theoretical distinction between lexical space and value space: these are entirely context-free distinctions, which relate only the atomic values of the individual pieces of text. XSD also provided another mechanism to declare that certain data values should be unique. But the constraints that an ID attribute value must be document-unique and that an element may only have a single ID attribute are left out in the cold by this model, and are not directly in the XSD specs. Blink and you’ll miss them, there is a little handwaving going on but it is a good pragmatic workaround: the spec references the XML specification; that these non-facet constraints on IDs are intended is made explicit in the (non-normative) Primer which forms Part 0 of the spec:
the scope of an ID is fixed to be the whole document.
and, more importantly, the XSD Structures Spec Part 1 specifies the ID/IDREF table as part of the PSVI.
ODF uses RELAX NG, and ISO RELAX NG specifically allows (s. 9.3.8 data and value pattern) datatyping to validate using more than just the atomic string:
services may make use of the context of a string. For example, a datatype representing a QName would use the namespace map.
(This seems to be a difference from the original OASIS RELAX NG, which AFACS started with a more atomic view of datatypes. )
So when an ODF schema says an attribute is an ID type, we expect for full validation it will have all the XSD/XML semantics, and that for full validation of the schema conflicts would be pointed out. If you don’t want these semantics, you just use the base type
xs:ncName which has the lexical and value space but adds none of the other constraints.
So we come to the concrete problem that a couple of content models allow wildcarded attributes in any namespace, and many of the attributes in the namespaces in question have ID attributes. So the argument (which you can follow on Alex Brown and Rob Weir’s blog) is what class of error this should be: all the implementations of RELAX NG and Alex say this makes the schema invalid (in ISO Schematron I specifically included definitions for a “good schema” and a “correct schema” as well as a “valid schema” in order to make these nuances clearer); Rob thinks it shouldn’t be an error (”thinks” is too weak a term) and seems to think it should only be an error if a element actually has two ID attributes. I think this is also legitimate possible approach that the standards could take (but they don’t.).
Alex has found the fix for ODF, but I think RELAX NG and XSD could well have some extra clarifaction text (non-normative) to stop basic mistakes. If a schema, whether DTD, XSD or RELAX NG, says something is an ID, it has all the semantics of an XML ID.
So what was the point about the programmer turning off tests to make some code fault-free? That is Rob Weir’s suggestion on how to make the ODF documents valid: turn off ID testing! Brilliant! So what is the point of ODF 1.0 making these things IDs in the first place if that was not the intended semantics?
I suspect this is actually another example of where it would have been more satisfactory all around to have these constraints in Schematron. For example, not use ID type but xs:ncName (this is not real code, but to give the idea…you’d use a regex and this assumes a consistent naming convention in ODF and sub-vocabularies wrt attribute naming):
<sch:rule <sch:report There should not be more than one attribute called id. </sch:report> </sch:rule>
This seems to give the intended constraint against duplication, but makes it a run-time instance-driven problem, not a static schema error. Another assertion would handle uniqueness.
So my take: Alex is right that the schema has a flaw, and right to point it out and offer a fix; Rob is right that it is unnecessary for this to be a static error (which is the positive point I would infer from his over-reacting blog), but wrong that the way to fix it is to turn off validating that constraint.
My favourite citation is from the boys at noooxml.org, who have had this comment from me as their "quote of the day" for ages:
"'The tech community at large' should not be confused with a small subset of it who are vocal on blogs."
And must they think it's a score for them! Priceless!
- Alex.
Just Say NO To Thugs.
It's a phrase that I find ever more useful these days.
Jespers blog engine beats yours by a mile showing code in blog
And the speed of the Oreillynet servers is just terrible.
Of course if we had just one ISO standard and put the effort into it that has gone into the techno-wars we would be a lot further forward.
Ian, you're right - had all the effort gone into supporting ISO 8613 Open Document Architecture instead, we wouldn't have needed ODF or OOXML... ;)
Ian: But the decision on whether to work on the futile OOXML opposition rather than productive ODF promotion belonged to the individuals involved, not the sponsors of ODF or OOXML. Making OOXML as a standard need not have had any impact on ODF and the effort being put into improving it.
And, as is Patrick's comment, it is simplistic to think that ODF will not benefit from having an IS29500 under adequate maintenance.
Inigo: DSSSL would be a better choice that ODA. | http://www.oreillynet.com/xml/blog/2008/05/dont_show_me_problems_show_me.html | crawl-002 | refinedweb | 1,541 | 66.07 |
#include <streams.h>
Definition at line 537 of file streams.h.
Definition at line 552 of file streams.h.
Definition at line 554 of file streams.h.
Flush any unwritten bits to the output stream, padding with 0's to the next byte boundary.
Definition at line 582 of file streams.h.
This browser is not able to show SVG: try Firefox, Chrome, Safari, or Opera instead.
Write the nbits least significant bits of a 64-bit int to the output stream.
Data is buffered until it completes an octet.
Definition at line 562 of file streams.h.
Buffered byte waiting to be written to the output stream.
The byte is written buffer when m_offset reaches 8 or Flush() is called.
Definition at line 544 of file streams.h.
Number of high order bits in m_buffer already written by previous Write() calls and not yet flushed to the stream.
The next bit to be written to is at this offset from the most significant bit position.
Definition at line 549 of file streams.h.
Definition at line 540 of file streams.h. | https://doxygen.bitcoincore.org/class_bit_stream_writer.html | CC-MAIN-2020-24 | refinedweb | 182 | 77.53 |
‘@’] ‘_’ ‘*’ ‘)’ | ‘(’ [Patterns] ‘)’ | XmlPattern Patterns ::= Pattern {‘,’ Patterns}
A pattern is built from constants, constructors, variables and type tests. Pattern matching tests whether a given value (or sequence of values) has the shape defined by a pattern, and, if it does, binds the variables in the pattern to the corresponding components of the value (or sequence of values). The same variable name may not be bound more than once in a pattern. `:' TypePat | `_' `:'
Consider the following function definition:
def f(x: Int, y: Int) = x match { case y => ... }
Here,
y is a variable pattern, which matches any value.
If we wanted to turn the pattern into a stable identifier pattern, this
can be achieved as follows:
def f(x: Int, y: Int) = x match { case `y` => ... }
Now, the pattern matches the
y parameter of the enclosing function
f.
That is, the match succeeds only if the
x argument and the
y
argument of
f are equal.
Constructor Patterns
SimplePattern ::= StableId `(' [Patterns] `) ::= `(' [Patterns] `)' `(' [Patterns] `)'
The
Predef object contains a definition of an
extractor object
Pair:
object Pair { def apply[A, B](x: A, y: B) = Tuple2(x, y) def unapply[A, B](x: Tuple2[A, B]): Option[Tuple2[A, B]] = Some(x) }
This means that the name
Pair can be used in place of
Tuple2 for tuple
formation as well as for deconstruction of tuples in patterns.
Hence, the following is possible:
val x = (1, 2) val y = x match { case Pair(i, s) => Pair(s + i, i * i) }
Pattern Sequences
SimplePattern ::= StableId `(' [Patterns `,'] [varid `@'] `_' `*' `)'
Regular expression patterns have been discontinued in Scala from version 2.0.
Later version of Scala provide a much simplified version of regular
expression patterns that cover most scenarios of non-text sequence
processing. A sequence pattern is a pattern that stands in a
position where either (1) a pattern of a type
T which is
conforming to
Seq[A] for some
A is expected, or (2) a case
class constructor that has an iterated formal parameter
A*. A wildcard star pattern
_* in the
rightmost position stands for arbitrary long sequences. It can be
bound to variables using
@, as usual, in which case the variable will have the
type
Seq[A]._1$.
Types which are not of one of the forms described above are also accepted as type patterns. However, such type patterns will be translated to their erasure. The Scala compiler will issue an "unchecked" warning for these patterns to flag the possible loss of type-safety.
A type variable pattern is a simple identifier which starts with a lower case letter. type parameters $a_1 , \ldots , a_n$. These type parameters
are inferred in the same way as for the typed pattern
(_: $C[a_1 , \ldots , a_n]$).
Example
Consider the program fragment:
val x: Any x match { case y: List[a] => ... }
Here, the type pattern
List[a] is matched against the
expected type
Any. The pattern binds the type variable
a. Since
List[a] conforms to
Any
for every type argument, there are no constraints on
a.
Hence,
a is introduced as an abstract type with no
bounds. The scope of
a is right-hand side of its case clause.
On the other hand, if
x is declared as
val x: List[List[String]],
this generates the constraint
List[a] <: List[List[String]], which simplifies to
a <: List[String], because
List is covariant. Hence,
a is introduced with upper bound
List[String].
Example
Consider the program fragment:
val x: Any x match { case y: List[String] => ... }
Scala does not maintain information about type arguments at run-time,
so there is no way to check that
x is a list of strings.
Instead, the Scala compiler will erase the
pattern to
List[_]; that is, it will only test whether the
top-level runtime-class of the value
x conforms to
List, and the pattern match will succeed if it does. This
might lead to a class cast exception later on, in the case where the
list
x contains elements other than strings. The Scala
compiler will flag this potential loss of type-safety with an
"unchecked" warning message.
Example
Consider the program fragment
class Term[A] class Number(val n: Int) extends Term[Int] def f[B](t: Term[B]): B = t match { case y: Number => y.n }
The expected type of the pattern
y: Number is
Term[B]. The type
Number does not conform to
Term[B]; hence Case 2 of the rules above
applies. This means that
B is treated as another type
variable for which subtype constraints are inferred. In our case the
applicable constraint is
Number <: Term[B], which
entails
B = Int. Hence,
B is treated in
the case clause as an abstract type with lower and upper bound
Int. Therefore, the right hand side of the case clause,
y.n, of type
Int, is found to conform to the
function's declared result type,
Number.
Pattern Matching Expressions$. The guard expression is
evaluated if the preceding pattern in the case matches. If the guard
expression evaluates to
true, the pattern match succeeds as
normal. If the guard expression evaluates to
false, the pattern
in the case is considered not to match and the search for a matching
pattern continues.
In the interest of efficiency the evaluation of a pattern matching expression may try patterns in some other order than textual sequence. This might affect evaluation through side effects in guards. However, it is guaranteed that a guard expression is evaluated only if the pattern it guards matches.
If the selector of a pattern match is an instance of a
sealed class,
the compilation of pattern matching can emit warnings which diagnose
that a given set of patterns is not exhaustive, i.e. that there is a
possibility of a
MatchError being raised at run-time.
Example
Consider the following definitions of arithmetic terms:
abstract class Term[T] case class Lit(x: Int) extends Term[Int] case class Succ(t: Term[Int]) extends Term[Int] case class IsZero(t: Term[Int]) extends Term[Boolean] case class If[T](c: Term[Boolean], t1: Term[T], t2: Term[T]) extends Term[T]
There are terms to represent numeric literals, incrementation, a zero
test, and a conditional. Every term carries as a type parameter the
type of the expression it represents (either
Int or
Boolean).
A type-safe evaluator for such terms can be written as follows.
def eval[T](t: Term[T]): T = t match { case Lit(n) => n case Succ(u) => eval(u) + 1 case IsZero(u) => eval(u) == 0 case If(c, u1, u2) => eval(if (eval(c)) u1 else u2) }
Note that the evaluator makes crucial use of the fact that type parameters of enclosing methods can acquire new bounds through pattern matching.
For instance, the type of the pattern in the second case,
Succ(u), is
Int. It conforms to the selector type
T only if we assume an upper and lower bound of
Int for
T.
Under the assumption
Int <: T <: Int we can also
verify that the type right hand side of the second case,
Int
conforms to its expected type,
T.
Pattern Matching Anonymous Functions
BlockExpr ::= `{' CaseClauses `}'
An anonymous function can be defined by a sequence of cases
{ case $p_1$ => $b_1$ $\ldots$ case $p_n$ => $b_n$ }
which appear as an expression without a prior
match. The
expected type of such an expression must in part be defined. It must
be either
scala.Function$k$[$S_1 , \ldots , S_k$, $R$] for some $k > 0$,
or
scala.PartialFunction[$S_1$, $R$], where the
argument type(s) $S_1 , \ldots , S_k$ must be fully determined, but the result type
$R$ may be undetermined.
If the expected type is SAM-convertible
to
scala.Function$k$[$S_1 , \ldots , S_k$, $R$],
the expression is taken to be equivalent to the anonymous function:
($x_1: S_1 , \ldots , x_k: S_k$) => ($x_1 , \ldots , x_k$) match { case $p_1$ => $b_1$ $\ldots$ case $p_n$ => $b_n$ }
Here, each $x_i$ is a fresh name. As was shown here, this anonymous function is in turn equivalent to the following instance creation expression, where $T$ is the weak least upper bound of the types of all $b_i$.
new scala.Function$k$[$S_1 , \ldots , S_k$, $T$] { def apply($x_1: S_1 , \ldots , x_k: S_k$): $T$ = ($x_1 , \ldots , x_k$) match { case $p_1$ => $b_1$ $\ldots$ case $p_n$ => $b_n$ } }
If the expected type is
scala.PartialFunction[$S$, $R$],
the expression is taken to be equivalent to the following instance creation expression:
new scala.PartialFunction[$S$, $T$] { def apply($x$: $S$): $T$ = x match { case $p_1$ => $b_1$ $\ldots$ case $p_n$ => $b_n$ } def isDefinedAt($x$: $S$): Boolean = { case $p_1$ => true $\ldots$ case $p_n$ => true case _ => false } }
Here,
Here is a method which uses a fold-left operation
/: to compute the scalar product of
two vectors:
def scalarProduct(xs: Array[Double], ys: Array[Double]) = (0.0 /: (xs zip ys)) { case (a, (b, c)) => a + b * c }
The case clauses in this code are equivalent to the following anonymous function:
(x, y) => (x, y) match { case (a, (b, c)) => a + b * c } | http://www.scala-lang.org/files/archive/spec/2.11/08-pattern-matching.html | CC-MAIN-2016-36 | refinedweb | 1,497 | 67.89 |
Hi,
In short, here is my case:
I want to make a function to read XML file. In addition, I want to find a way to save as much memory for my application.
I don't know which ways is better for me:
Case 1:
Class XmlParser
{
//some kinds of parser
private Xml parser = null;
private static XmlParser instance;
public XmlParser()
{
parser = new Xml();
}
...
public static void getInstance()
{
if(instance == null) instance = new XmlParser();
return instance;
}
In this case, I create an instance to point to this class, so it won't be create again when I call the XmlParser
e.g XmlParser.getInstance().parse(fileUrl);
Whenever I need to use a parser, I just call a method in it and pass the file URL. It will create a new streamInput to pass to the parser;
Note: the "parser = new Xml()" is called only one time when the variable is created first time.
Case 2:
public class XmlParser
{
private Xml parser = null;
public XmlParser(String fileUrl)
{
//create input stream to the file and pass to the new parser
}
// some methods which can be called to start parsing
....
}
In this case, when I want to use the Parser, I must create a new instance of this class.
e.g XmlParser parser = new XmlParser("abc.xml");
An_Object a = parser.parse();
Could you please compare these two cases for me. Which one is the better way when I want to use the xml parser and want to save memory too (like optimization, maybe).
Note: I am using pull parser. About parsing xml in my application, the parser will be called when the app is started (only 1 time) and when a user changes the configuration of the app (e.g. he changes configuration of the app 1 times = 1 call to the parser, 2 time = 2 calls to the parser, etc.).
Thank you. | http://developer.nokia.com/Community/Discussion/showthread.php/164129-Memory-Usage-of-Variables-in-Java | CC-MAIN-2013-48 | refinedweb | 310 | 68.3 |
I intend to prepare a few blog entries that present the hotspot provider facilities as, I think the topic is too big for one blog entry. I have decided to break them up into functional groups. I am starting with the application method probes as this is the first place I start looking when I am looking for the cause of a slow application and then onto the method compilation probes.
In my opinion one of the best advances in Java, since generics, is the inclusion of the DTrace hotspot provider. This, while being a non GUI solution to profiling for the time being, could be the way we all do profiling in the future. In this blog entry I am going to discuss some of the cool things about the hotspot provider method tracing and how it can help us understand the application in question better.
I created a simple Java application for us to examine that creates a lockfile in /tmp, called myLock, then starts 5 threads that all check for the existance of this file then loop sleeping for a second wake up check for the file then sleep for again. When the file is deleted as the threads wake and detect this fact,they then exit. Quite simple and contrived but it is all we need to see the hotspot method probes in action.
Before we go any further I need to explain my environment. This article is based on the use of Mustang, (Java SE 6) build 84 and on OpenSolaris (Navada) build 40 for clarity I have provided the Java and OS versions I have used while developing this article. Please let me know if something does not work for you.
$ java -version
java version "1.6.0-beta2"
Java(TM) SE Runtime Environment (build 1.6.0-beta2-b84)
Java HotSpot(TM) Client VM (build 1.6.0-beta2-b84, mixed mode, sharing)
$ uname -a
SunOS squarepants 5.11 snv_40 i86pc i386 i86pc
We need start this by understanding the process I am using. I have found if you want to trace the whole Java life cycle or short lived programs the simplest solution is to use the -XX:+PauseAtStartup JVM switch. This initialses the JVM but does not start executing the Java program. It also creates a lock file of sorts in the current working directory named vm.paused.<PID> where <PID> is the proceess id. The examples in this article use this pid as an agument to the dtrace script. If you are not interested in JVM lifecycle probes there are easer ways of starting the application, like using the -c option when executing your dtrace script.
The arguments for these probes follow
To use the method probes you need one of the following JVM flags:
-XX:+ExtendedDTraceProbes (turns all of the application probes on).
-XX:+DTraceMethodProbes (turns on method probes).
Both of these flags can cause performace degredation in the VM so use with care. In order to use the -XX:+PauseAtStartup JVM switch flag another flag needs to be set -XX:+UnlockDiagnosticVMOptions. Here is the commandline I used to execute the Java application in order to trace the methods.
java -XX:+UnlockDiagnosticVMOptions -XX:+PauseAtStartup -XX:+DTraceMethodProbes dtracedemo.ThreadExample
We need a few terminal windows here in the first terminal I enter the command above, after I hit return the application appears to do nothing. In the second window, in the same CWD I can see the file vm.paused.1167. So I know that the pid that I need is 1167. In the third terminal I execute the dtrace script (./nv_app_track_time_depth.d -p 1167). At this point in the third terminal DTrace will report "BEGIN Java method entry/return tracing" We can now go back to the second terminal and remove the vm.paused.1167 file to allow the execution of the Java application to continue. Next, for this example, I remove the lock file (/tmp/myLock) and the application exits and dtrace reports the infomation gathered in the third terminal.
Here are the class names and methods of the ten methods that occupied the most time (ms) of the application run as produced by nv_app_track_time_depth.d.
37 java/io/File/<clinit>
37 java/io/FileSystem/getFileSystem
37 java/io/UnixFileSystem/<init>
39 java/lang/ClassLoader/loadClass
53 sun/misc/Launcher/<clinit>
53 sun/misc/Launcher/<init>
54 java/lang/ClassLoader/getSystemClassLoader
54 java/lang/ClassLoader/initSystemClassLoader
62 java/security/AccessController/doPrivileged
72 java/io/ExpiringCache/<init>
Another interesting statistic might be, what is the number of times each of these methods have been called?
nv_app_track_number.d.
402 java/util/HashMap/indexFor
439 java/lang/String/<init>
502 java/lang/String/hashCode
550 java/lang/Character/toLowerCase
554 java/lang/System/arraycopy
589 java/lang/StringBuilder/append
608 java/lang/AbstractStringBuilder/append
842 java/lang/String/indexOf
1460 java/lang/Object/<init>
5567 java/lang/String/charAt
At this point it would easy enough to see other interesting things we can do with this information. So how about how long did a particular method take to compile on the hotspot compiler?
Method Compilation Probes
Method compilation arguments
Output from nv_method_compile.d
Method compliled = java/lang/String/hashCode took 1493 us
Method compliled = java/lang/String/equals took 666 us
Method compliled = java/lang/String/indexOf took 1063 us
Method compliled = java/lang/String/charAt took 395 us
Method compliled = java/lang/String/lastIndexOf took 921 us
Method compliled = java/io/UnixFileSystem/normalize took 781 us
Method compliled = java/lang/String/indexOf took 1150 us
Method compliled = java/lang/Object/<init> took 251 us
Here is the simple Java application I wrote as an example we can use to examine the use of the hotspot method probes.
MyThread.java
package dtracedemo;
import java.io.*;
/*
* Use is subject to license terms.
*
* This is part of the Intro to Java DTrace developed by
* Damien Cooke (Damien.Cooke@Sun.COM)
*
*/
class MyThread extends Thread
{
public void run()
{
File thefile = new File("/tmp/myLock");
while(thefile.exists() == true)
{
try{this.sleep(1000);}catch(java.lang.InterruptedException ie){}
}
System.out.println("Thread "+ this.getId() +" exiting");
}
}
ThreadExample.java
package dtracedemo;
import java.io.*;
import java.util.Vector;
/*
* Use is subject to license terms.
*
* This is part of the Intro to Java DTrace developed by
* Damien Cooke (Damien.Cooke@Sun.COM)
*
*/
class ThreadExample
{
public static void main(String[] args)
{
Vector v = new Vector();
try
{
BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(new File("/tmp/myLock")));
bos.write(3);
bos.close();
for(int i = 0; i < 4; i++)
{
MyThread mt = new MyThread();
v.addElement((MyThread)mt);
System.out.println("Thread number "+v.size()+" created" );
}
for(int i = 0; i < 4; i++)
{
((MyThread)v.elementAt(i)).run();
}
}catch(IOException e){}
}
}
nv_app_track_time_depth.d
nv_app_track_number.d
nv_method_compile.d
Please let me know if there are any omissions or mistakes. I have tested them all but OpenSoalris (and Navada) are in development and Mustang in in beta. | http://blogs.sun.com/damien/category/Java | crawl-002 | refinedweb | 1,154 | 54.83 |
Logging
Eclipse ICE uses has two different standards for logging: logging in production source code and logging in tests. Logging in tests should be done using System.out and System.err since tests are not generally production code and are never distributed with the final product. Indeed, using a real logging service in the tests could make it harder to monitor test behavior.
Logging in production source code is done using SLF4J instead of shipping it to System.out or System.err. To be completely honest, we used System.out and System.err for over three years, but finally decided to put on our grown-up pants and use a real logging service. Logging to System.out and System.err was convenient, but it required that we always display a console and finding the log output was very confusing for users. Switching to a service allows us to simultaneously write to a file and to the Eclipse Error Log View.
There are lots of good examples of using the Logger in the source code, with a very simple one being our singleton for holding a reference to the Client service, the ClientHolder class.
SLF4J must be imported in the bundle's MANIFEST.mf file before if can be used.
Declaring and using a logger is straightforward. It requires two imports
import org.slf4j.Logger; import org.slf4j.LoggerFactory;
and can be declared as such
/** * Logger for handling event messages and other information. */ private static final Logger logger = LoggerFactory.getLogger(ClientHolder.class);
Messages can be log at multiple levels,
logger.info("This is information."); logger.error("This is an error."); logger.debug("This is information that should only show up when debugging.");
Loggers should be declared as shown above, in general, but there are special cases where declaring them differently is better. The ICEObject class is a good example of where a logger can be declared protected and final, but not static, so that it can be used by subclasses without explicitly declaring it them. | https://wiki.eclipse.org/index.php?title=Logging&oldid=388422 | CC-MAIN-2020-45 | refinedweb | 334 | 60.21 |
#include <itkMRASlabIdentifier.h>
Inheritance diagram for itk::MRASlabIdentifier< TInputImage >:
This class is templated over the type of image. In many cases, a 3D MR image is constructed by merging smaller 3D blocks (slabs) which were acquired with different settings such as magnetic settings and patient positions. Therefore, stripe like patterns with slabs can be present in the resulting image. Such artifacts are called "slab boundary".
For this identifier, a slice means 2D image data which is extracted from the input image along one of three axes (x, y, z). Users can specify the slicing axis using the SetSlicingDirection(int dimension) member. (0 - x, 1 - y, 2 - z).
The identification scheme used here is very simple. 1) Users should specify how many pixels per slice the identifier will sample. 2) For each slice, the identifier searches the specified number of pixels of which intensity values are greater than 0 and less than those of the other pixels in the slice 3) The identifier calculates the average for each slice and the overall average using the search results. 4) For each slice, it subtracts the overall average from the slice average. If the sign of the subtraction result changes, then it assumes that a slab ends and another slab begins.
Definition at line 65 of file itkMRASlabIdentifier.h. | http://www.itk.org/Doxygen16/html/classitk_1_1MRASlabIdentifier.html | crawl-003 | refinedweb | 216 | 54.93 |
I'm using the following function on two different computers. One one computer is running Ubuntu and the other OS X. The function works on OS X, but not Ubuntu.
#include <stdio.h>
#define MAXBUF 256
char *safe_strncat(char *dest, const char *src, size_t n) {
snprintf(dest, n, "%s%s", dest, src);
return dest;
}
int main(int argc, const char * argv[]){
char st1[MAXBUF+1] = "abc";
char st2[MAXBUF+1] = "def";
char* st3;
printf("%s + %s = ",st1, st2);
st3 = safe_strncat(st1, st2, MAXBUF);
printf("%s\n",st3);
printf("original string = %s\n",st1);
}
gcc concat_test.c -o concat_test
./concat_test
abc + def = def
original string = def
abc + def = abcdef
original string = abcdef
Your code invokes undefined behavior because you pass the destination buffer as one of the source strings of your
snprintf() format. This is not supported:
7.21.6.5 The
snprintffunction
Synopsis
#include <stdio.h> int snprintf(char * restrict s, size_t n, const char * restrict format, ...);
Description
The
snprintffunction is equivalent to
fprintf, except that the output is written into an array (specified by argument
s) rather than to a stream. If
nis zero, nothing is written, and
smay.
(emphasis mine).
The implementation of
snprintf differs between Ubuntu (glibc) and OS/X (Apple libc, based on BSD sources). The behavior differs and cannot be relied upon as it is undefined in all cases. | https://codedump.io/share/cbrvOAzew9e4/1/c-snprintf-used-to-concat-string | CC-MAIN-2017-43 | refinedweb | 224 | 64.41 |
Quoting David Howells (dhowells@redhat.com):> Randy Dunlap <rdunlap@xenotime.net> wrote:> > > > +Any task in or resource belonging to the initial user namespace will, to this> > > +new task, appear to belong to UID and GID -1 - which is usually known as> > > > that extra hyphen is confusing. how about:> > > > to UID and GID -1, which is> > 'which are'.> > DavidThis will hold some info about the design. Currently it containsfuture todos, issues and questions.Changelog: jul 26: incorporate feedback from David Howells. jul 29: incorporate feedback from Randy Dunlap.Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>Cc: Eric W. Biederman <ebiederm@xmission.com>Cc: David Howells <dhowells@redhat.com>Cc: Randy Dunlap <rdunlap@xenotime.net>--- Documentation/namespaces/user_namespace.txt | 107 +++++++++++++++++++++++++++ 1 files changed, 107 insertions(+), 0 deletions(-) create mode 100644 Documentation/namespaces/user_namespace.txtdiff --git a/Documentation/namespaces/user_namespace.txt b/Documentation/namespaces/user_namespace.txtnew file mode 100644index 0000000..b0bc480--- /dev/null+++ b/Documentation/namespaces/user_namespace.txt@@ -0,0 +1,107 @@+Description+===========++Traditionally, each task is owned by a user ID (UID) and belongs to one or more+groups (GID). Both are simple numeric IDs, though userspace usually translates+them to names. The user namespace allows tasks to have different views of the+UIDs and GIDs associated with tasks and other resources. (See 'UID mapping'+below for more.)++The user namespace is a simple hierarchical one. The system starts with all+tasks belonging to the initial user namespace. A task creates a new user+namespace by passing the CLONE_NEWUSER flag to clone(2). This requires the+creating task to have the CAP_SETUID, CAP_SETGID, and CAP_CHOWN capabilities,+but it does not need to be running as root. The clone(2) call will result in a+new task which to itself appears to be running as UID and GID 0, but to its+creator seems to have the creator's credentials.+.++When a task belonging to (for example) userid 500 in the initial user namespace.++Relationship between the User namespace and other namespaces+============================================================++Other namespaces, such as UTS and network, are owned by a user namespace. When+such a namespace is created, it is assigned to the user namespace of the task+by which it was created. Therefore, attempts to exercise privilege to+resources in, for instance, a particular network namespace, can be properly+validated by checking whether the caller has the needed privilege (i.e.+CAP_NET_ADMIN) targeted to the user namespace which owns the network namespace..++UID Mapping+===========+The current plan (see 'flexible UID mapping' at+) is:++The UID/GID stored on disk will be that in the init_user_ns. Most likely+UID/GID in other namespaces will be stored in xattrs. But Eric was advocating+(a few years ago) leaving the details up to filesystems while providing a lib/+stock implementation. See the thread around here:+ notes+=============+Capability checks for actions related to syslog must be against the+init_user_ns until syslog is containerized.++Same is true for reboot and power, control groups, devices, and time.++Perf actions (kernel/event/core.c for instance) will always be constrained to+init_user_ns.++Q:+Is accounting considered properly containerized with respect to pidns? (it+appears to be). If so, then we can change the capable() check in deferred some of commoncap.c. I'm punting on xattr stuff as they take+dentries, not inodes.++For drivers/tty/tty_io.c and drivers/tty/vt/vt.c, we'll want to (for some of+them) target the capability checks at the user_ns owning the tty. That will+have to wait until we get userns owning files straightened out.++We need to figure out how to label devices. Should we just toss a user_ns+right into struct device?++capable(CAP_MAC_ADMIN) checks are always to be against init_user_ns, unless+some day LSMs were to be containerized, near zero chance.++inode_owner_or_capable() should probably take an optional ns and cap parameter.+If cap is 0, then CAP_FOWNER is checked. If ns is NULL, we derive the ns from+inode. But if ns is provided, then callers who need to derive+inode_userns(inode) anyway can save a few cycles.-- 1.7.5.4 | http://lkml.org/lkml/2011/7/29/296 | CC-MAIN-2015-22 | refinedweb | 682 | 51.65 |
This article has been excerpted from book "Graphics Programming with GDI+".So far we have printed simple text and graphics items from the program itself. How about reading a text file and printing it from our program? We can make the editor open a text file and add print functionality to print the text file. In this section we will read a text file and print it.As usual, we create a Windows application and add a reference to the System.Drawing.Printing namespace. We then add a text box and four buttons to the form. We also change the Name and Text properties of the buttons controls. The final form looks like Figure 11.12. As you might guess, the Browse Text File button allows us to browse for text files.FIGURE 11.12: The form with text file printing optionsThe code for the Browse Text File button is given in Listing 11.21. This button allows you to browse a file and adds the selected file name to the text box. Clicking the Print Text File button prints the selected text file. We use an OpenFileDialog object to open a text file and set textBox1.Text as the selected file name. The functionality of the Print Text and Print Events buttons is obvious.LISTING 11.21: The Browse Text File button click event handler private void BrowseBtn_Click(object sender, System.EventArgs e) { //Create an OpenFileDialog object OpenFileDialog fdlg = new OpenFileDialog(); //Set its properties fdlg.Title = "C# Corner Open File Dialog"; fdlf.InitialDirectory = @"C:\"; fdlg.Filter = "Text files (*.txt | .txt | All files (*.*) | *.*"; fdlg.FilterIndex = 2; fdlg.RestoreDirectoty = true; //Show dialog and set the selected file name //as the text of the text box if (fldg.ShowDialog() == DialogResult.OK) { textBox1.Text = fdlg.FileName; } }Now let's add code for the Print Text File button click. First we add tow private variable to the application as follows: private Font verdana10Font; private StreamReader reader;Then we proceed as shown in Listing 11.22. The code is pretty simple. First we make sure that the user has selected a file name. Then we create a StreamReader object and read the file by passing the file name as the only argument. Next we create a font with font family Verdana and size 10. After that we create a PrintDocument object, and a PrintPage event handler, and call the Print method. The rest is done by the PrintPage event handler.Note: The StreamReader class is defined in the System.IO namespace.LISTING 11.22: The Print Text File button click event handler private void PrintTextFile_Click(object sender, System.EventArgs e) { //Get the file name string filename = textBox1.Text.TosTring(); //check if it's not empty if (filename.Equals(string.Empty)) { MessageBox.Show("Enter a valid file name"); textBox1.Focus(); return; } //Create a StreamReader object reader = new StreamReader(filename); //Create a Verdana font with size 10 verdana10Font = new Font("Verdana", 10); //Create a PrintDocument object PrintDocument pd = new PrintDocument(); //Add PrintPage event handler pd.PrintPage += new PrintPageEventHandler (this.PrintTextFileHandler); //Call Print Method pd.Print(); //Close the reader if (reader != null) reader.Close(); }The code for the PrintPage event handler PrintTextFileHandler is given in Listing 11.23. Here we read one line at a time from the text file, using the StreamReader.ReadLine method, and call DrawString, which prints each line until we reach the end of the file. To give the text a defined size, we use the verdana10Font.GetHegiht method.LISTING 11.23: Adding a print event handler private void PrintTextFileHandler(object sender, PrintPageEventArgs ppeArgs) { //Get the Graphics object Graphics g = ppeArgs.Graphics; float linesPerPage = 0; float yPos = 0; int count = 0; //Read margins from PrintPageEventArgs float leftMargin = ppeArgs.MarginBounds.Left; float topMargin = ppeArgs.MarginBounds.TOP; string line = null; //Calculate the lines per page on the basis of the height of the page and the height of the font linesPerPage = ppeArgs.MarginBounds.Height; verdana10Font.GetHeight(g); //Now read lines one by one, using StreamReader while (count < linesPerPage && ((line = reader.REadLine()) != null)) { //Calculate the starting position yPos = topMargin + (count * verdana10Font.GetHeight(g)); //Draw text g.DrawString(line, verdana10Font, Brushes.Black, leftMargin, yPose, new StringFormat()); //Move to next line count++; } //If PrintPageEventArgs has more pages to print if (line != null) ppeArgs.HasMorePages = true; else ppeArgs.HasMorePages = false; }You should be able to add code for the Print Text and Print Events buttons yourself. Their functionality should be obvious.Now run the application, browse a text file, and hit the Print Text File button, and you should be all set.Note: Using the same method, you can easily add printing functionality to the GDI+ editor. You can add a menu item called Print to the editor that will print an opened text file.ConclusionHope the article would have helped you in understanding Printing Text in GDI+. Read other articles on GDI+ on the website. | http://www.c-sharpcorner.com/uploadfile/mahesh/printing-text-in-gdi/ | CC-MAIN-2014-15 | refinedweb | 806 | 67.96 |
This article was originally posted as “Indexing and Search (C#)” on 15th June 2013 at Programmer’s Ranch. It has been slightly updated here. The source code is available at the Gigi Labs BitBucket repository.
This article is about indexing and search: what is it that allows you to search through thousands of documents in less than a second?
In order to understand how indexing works, we will use an example where we have the following three documents:
doc1.txt contains: The Three Little Pigs
doc2.txt contains: The Little Red Riding Hood
doc3.txt contains: Beauty And The Beast
Now, let’s say you want to find out which of these documents contain a particular word, e.g. “Little”. The easiest way to do this would be to go through each word in each document, one by one, and see if the word “Little” is in that document. Conceptually, we’re talking about this:
Doing this in C# is very easy:
string[] documents = { "doc1.txt", "doc2.txt", "doc3.txt" }; string keyword = Console.ReadLine(); foreach (string document in documents) { if (File.ReadAllText(document).Contains(keyword)) { Console.WriteLine(document); } } Console.ReadKey(true);
Remember to put in a
using System.IO; at the top, to be able to use
File. If you press F5 and test this program, you’ll see that it works:
However, this method isn’t good because it will take longer as the documents get larger (more words) and more numerous (more documents).
The proper way to process search requests quickly is to build an index. This would look something like this:
The index stores a list of all words, each with a list of documents that contain it. If you compare it with the first diagram, you’ll notice that we reversed the mapping of words and documents; this is why we call this an inverted index.
We can do this in C# by first building the index (remember to add
using System.Collections.Generic; at the top):
// Build the index string[] documents = { "doc1.txt", "doc2.txt", "doc3.txt" }; Dictionary<string, List<string>> index = new Dictionary<string, List<string>>(); foreach (string document in documents) { string documentStr = File.ReadAllText(document); string[] words = documentStr.Split(); foreach (string word in words) { if (!index.ContainsKey(word)) index[word] = new List<string>(); index[word].Add(document); } }
…and then using the index to search the documents quickly and efficiently:
// Query the index string keyword = Console.ReadLine(); if (index.ContainsKey(keyword)) { foreach (string document in index[keyword]) { Console.WriteLine(document); } } else Console.WriteLine("Not found!"); Console.ReadKey(true);
In this way, there is no need to search every document for the keyword each time the user wants to search for a word. The keyword is simply located in the index (if it exists), and a list of documents that contain it is immediately available:
This was a simple proof of concept of how indexing and search works, but here are a few additional notes:
- The index is usually built as documents are added to it, and then stored in one or more files (unlike in this program, where the index is rebuilt every time the program is run – that’s just to make the illustration easier).
- Words such as “and” and “the” which are very common are called stop words and are normally excluded from the index.
- It is common practice to make searches case insensitive, e.g. by converting indexed words and query keywords to lowercase.
This article presented the concept of indexing and how it is used to search for a single keyword. Although there are other techniques used in text search, indexing is definitely one of the most important, and has many applications including databases and text retrieval (e.g. search engines). A fundamental concept to remember is that the whole point of indexing is to make search fast! | https://gigi.nullneuron.net/gigilabs/2015/11/11/ | CC-MAIN-2020-05 | refinedweb | 638 | 63.49 |
In this blog post, we introduce the new window function feature that was added in Apache Spark 1.4. Window functions allow users of Spark SQL to calculate results such as the rank of a given row or a moving average over a range of input rows. They significantly improve the expressiveness of Spark’s SQL and DataFrame APIs. This blog will first introduce the concept of window functions and then discuss how to use them with Spark SQL and Spark’s DataFrame API.
What are Window Functions?
Before 1.4, there were two kinds of functions supported by Spark SQL that could be used to calculate a single return value. Built-in functions or UDFs, such as
substr or
round, take values from a single row as input, and they generate a single return value for every input row. Aggregate functions, such as
SUM or
MAX, operate on a group of rows and calculate a single return value for every group.
While these are both very useful in practice, there is still a wide range of operations that cannot be expressed using these types of functions alone. Specifically, there was no way to both operate on a group of rows while still returning a single value for every input row. This limitation makes it hard to conduct various data processing tasks like calculating a moving average, calculating a cumulative sum, or accessing the values of a row appearing before the current row. Fortunately for users of Spark SQL, window functions fill this gap.
At its core, a window function calculates a return value for every input row of a table based on a group of rows, called the Frame. Every input row can have a unique frame associated with it. This characteristic of window functions makes them more powerful than other functions and allows users to express various data processing tasks that are hard (if not impossible) to be expressed without window functions in a concise way. Now, let’s take a look at two examples.
Suppose that we have a productRevenue table as shown below.
We want to answer two questions:
- What are the best-selling and the second best-selling products in every category?
- What is the difference between the revenue of each product and the revenue of the best-selling product in the same category of that product?
To answer the first question “What are the best-selling and the second best-selling products in every category?”, we need to rank products in a category based on their revenue, and to pick the best selling and the second best-selling products based the ranking. Below is the SQL query used to answer this question by using window function
dense_rank (we will explain the syntax of using window functions in next section).
SELECT product, category, revenue FROM ( SELECT product, category, revenue, dense_rank() OVER (PARTITION BY category ORDER BY revenue DESC) as rank FROM productRevenue) tmp WHERE rank <= 2
The result of this query is shown below. Without using window functions, it is very hard to express the query in SQL, and even if a SQL query can be expressed, it is hard for the underlying engine to efficiently evaluate the query.
For the second question “What is the difference between the revenue of each product and the revenue of the best selling product in the same category as that product?”, to calculate the revenue difference for a product, we need to find the highest revenue value from products in the same category for each product. Below is a Python DataFrame program used to answer this question.
import sys from pyspark.sql.window import Window import pyspark.sql.functions as func windowSpec = \ Window .partitionBy(df['category']) \ .orderBy(df['revenue'].desc()) \ .rangeBetween(-sys.maxsize, sys.maxsize) dataFrame = sqlContext.table("productRevenue") revenue_difference = \ (func.max(dataFrame['revenue']).over(windowSpec) - dataFrame['revenue']) dataFrame.select( dataFrame['product'], dataFrame['category'], dataFrame['revenue'], revenue_difference.alias("revenue_difference"))
The result of this program is shown below. Without using window functions, users have to find all highest revenue values of all categories and then join this derived data set with the original productRevenue table to calculate the revenue differences.
Using Window Functions
Spark SQL supports three kinds of window functions: ranking functions, analytic functions, and aggregate functions. The available ranking functions and analytic functions are summarized in the table below. For aggregate functions, users can use any existing aggregate function as a window function.
To use window functions, users need to mark that a function is used as a window function by either
- Adding an OVER clause after a supported function in SQL, e.g.
avg(revenue) OVER (...); or
- Calling the over method on a supported function in the DataFrame API, e.g.
rank().over(...).
Once a function is marked as a window function, the next key step is to define the Window Specification associated with this function. A window specification defines which rows are included in the frame associated with a given input row. A window specification includes three parts:
- Partitioning Specification: controls which rows will be in the same partition with the given row. Also, the user might want to make sure all rows having the same value for the category column are collected to the same machine before ordering and calculating the frame. If no partitioning specification is given, then all data must be collected to a single machine.
- Ordering Specification: controls the way that rows in a partition are ordered, determining the position of the given row in its partition.
- Frame Specification: states which rows will be included in the frame for the current input row, based on their relative position to the current row. For example, “the three rows preceding the current row to the current row” describes a frame including the current input row and three rows appearing before the current row.
In SQL, the
PARTITION BY and
ORDER BY keywords are used to specify partitioning expressions for the partitioning specification, and ordering expressions for the ordering specification, respectively. The SQL syntax is shown below.
OVER (PARTITION BY ... ORDER BY ...)
In the DataFrame API, we provide utility functions to define a window specification. Taking Python as an example, users can specify partitioning expressions and ordering expressions as follows.
from pyspark.sql.window import Window windowSpec = \ Window \ .partitionBy(...) \ .orderBy(...)
In addition to the ordering and partitioning, users need to define the start boundary of the frame, the end boundary of the frame, and the type of the frame, which are three components of a frame specification.
There are five types of boundaries, which are
UNBOUNDED PRECEDING,
UNBOUNDED FOLLOWING,
CURRENT ROW,
<value> PRECEDING, and
<value> FOLLOWING.
UNBOUNDED PRECEDING and
UNBOUNDED FOLLOWING represent the first row of the partition and the last row of the partition, respectively. For the other three types of boundaries, they specify the offset from the position of the current input row and their specific meanings are defined based on the type of the frame. There are two types of frames, ROW frame and RANGE frame.
ROW frame
ROW frames are based on physical offsets from the position of the current input row, which means that
CURRENT ROW,
<value> PRECEDING, or
<value> FOLLOWING specifies a physical offset. If
CURRENT ROW is used as a boundary, it represents the current input row.
<value> PRECEDING and
<value> FOLLOWING describes the number of rows appear before and after the current input row, respectively. The following figure illustrates a ROW frame with a
1 PRECEDING as the start boundary and
1 FOLLOWING as the end boundary (
ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING in the SQL syntax).
RANGE frame
RANGE frames are based on logical offsets from the position of the current input row, and have similar syntax to the ROW frame. A logical offset is the difference between the value of the ordering expression of the current input row and the value of that same expression of the boundary row of the frame. Because of this definition, when a RANGE frame is used, only a single ordering expression is allowed. Also, for a RANGE frame, all rows having the same value of the ordering expression with the current input row are considered as same row as far as the boundary calculation is concerned.
Now, let’s take a look at an example. In this example, the ordering expressions is
revenue; the start boundary is
2000 PRECEDING; and the end boundary is
1000 FOLLOWING (this frame is defined as
RANGE BETWEEN 2000 PRECEDING AND 1000 FOLLOWING in the SQL syntax). The following five figures illustrate how the frame is updated with the update of the current input row. Basically, for every current input row, based on the value of revenue, we calculate the revenue range
[current revenue value - 2000, current revenue value + 1000]. All rows whose revenue values fall in this range are in the frame of the current input row.
In summary, to define a window specification, users can use the following syntax in SQL.
OVER (PARTITION BY ... ORDER BY ... frame_type BETWEEN start AND end)
Here,
frame_type can be either ROWS (for ROW frame) or RANGE (for RANGE frame);
start can be any of
UNBOUNDED PRECEDING,
CURRENT ROW,
<value> PRECEDING, and
<value> FOLLOWING; and
end can be any of
UNBOUNDED FOLLOWING,
CURRENT ROW,
<value> PRECEDING, and
<value> FOLLOWING.
In the Python DataFrame API, users can define a window specification as follows.
from pyspark.sql.window import Window # Defines partitioning specification and ordering specification. windowSpec = \ Window \ .partitionBy(...) \ .orderBy(...) # Defines a Window Specification with a ROW frame. windowSpec.rowsBetween(start, end) # Defines a Window Specification with a RANGE frame. windowSpec.rangeBetween(start, end)
What’s next?
Since the release of Spark 1.4, we have been actively working with community members on optimizations that improve the performance and reduce the memory consumption of the operator evaluating window functions. Some of these will be added in Spark 1.5, and others will be added in our future releases. Besides performance improvement work, there are two features that we will add in the near future to make window function support in Spark SQL even more powerful. First, we have been working on adding Interval data type support for Date and Timestamp data types (SPARK-8943). With the Interval data type, users can use intervals as values specified in
<value> PRECEDING and
<value> FOLLOWING for RANGE frame, which makes it much easier to do various time series analysis with window functions. Second, we have been working on adding the support for user-defined aggregate functions in Spark SQL (SPARK-3947). With our window function support, users can immediately use their user-defined aggregate functions as window functions to conduct various advanced data analysis tasks.
To try out these Spark features, get a free trial of Databricks or use the Community Edition.
Acknowledgements
The development of the window function support in Spark 1.4 is is a joint work by many members of the Spark community. In particular, we would like to thank Wei Guo for contributing the initial patch.
| https://databricks.com/blog/2015/07/15/introducing-window-functions-in-spark-sql.html | CC-MAIN-2019-47 | refinedweb | 1,830 | 52.39 |
Chapter 2
The Diverse Visual Class Structure
In the first chapter, we talked about how the construction of a framework like WPF is much like the construction of a house. If you don’t know why certain things are built the way they are, you are likely to use them improperly and break something.
This chapter is all about the tools you use when building your house. Every craftsman (including programmers!) knows that picking the right tool for the job is essential to the success of the project. If you use a tool that has too much power, you’re likely to break something or punch a hole through a wall. Go with something that doesn’t have enough power and you won’t be able to get the job done either.
WPF provides a rich and diverse set of classes that allow you to create everything from simple visuals to complex layered visuals and components. This is possible because of the precision with which the class structure of WPF was built. There are dozens of tools, but it is up to you to pick the right one for the job. Each class has a specific purpose and unique strengths that separate it from other classes. This allows us to mix and match classes to fit our particular needs.
Figure 2.1 shows the visual hierarchy of classes that we examine in detail in this chapter.
Introducing the Visual Classes
WPF has a rich, diverse set of building blocks and tools that you can use to create amazing interfaces. Knowing which tool to use and when to use it is absolutely invaluable to creating next-generation applications. What follows is a brief overview of the most important classes in WPF. These are the classes that you will use most often as you progress through this book and as you create your own applications.
The DispatcherObject Class
The DispatcherObject class can be found in the System.Windows.Threading namespace. It provides the basic messaging and threading capabilities for all WPF objects. The main property you will be concerned with on the DispatcherObject class is the Dispatcher property, which gives you access to the dispatcher the object is associated with. Just like its name implies, the dispatching system is responsible for listening to various kinds of messages and making sure that any object that needs to be notified of that message is notified on the UI thread. This class does not have any graphic representation but serves as a foundation for rest of the framework.
The DependencyObject Class
The DependencyObject class provides support for WPF’s dependency property system. The main purpose behind the dependency property system is to compute property values. Additionally, it also provides notifications about changes in property values. The thing that separates the WPF dependency property system from standard properties is the ability for dependency properties to be data bound to other properties and automatically recompute themselves when dependent properties change. This is done by maintaining a variety of metadata information and logic with the DependencyProperty.
DependencyObject also supports attached properties, which are covered in Chapter 6, “The Power of Attached Properties,” and property inheritance.
The DependencyObject class is part of the System.Windows namespace and has no graphic representation. It is a subclass of DispatcherObject.
The Visual and DrawingVisual Classes
The System.Windows.Media.Visual abstract class is the hub of all drawing-related activity in WPF. All WPF classes that have a visual aspect to their nature are descendants in some way from the Visual class. It provides basic screen services such as rendering, caching of the drawing instructions, transformations, clipping, and of course bounding box and hit-testing operations.
While the Visual class contains a tremendous amount of useful functionality, it isn’t until we get down to the DrawingVisual class in the hierarchy that we start seeing concrete implementations that we can work with. DrawingVisual inherits from ContainerVisual, a class that is designed to contain a collection of visual objects. This collection of child visuals is exposed through the Drawing property (of type DrawingGroup).
DrawingVisual is a lightweight class specifically designed to do raw rendering and doesn’t contain other high-level concepts such as layout, events, data binding, and so on. Keep in mind the golden rule of this chapter: Pick the right tool for the job. If you need to simply draw graphics and the extent of user interaction with that object is simple hit testing, you can save a lot on overhead by using DrawingVisual.
A great example of where DrawingVisuals would be an excellent choice is in a charting application. You can build a variety of charts by using the drawing primitives such as lines, beziers, arcs, and text and fill them with colors using a solid brush or even more advanced fills such as linear and radial gradients.
You might be wondering what to do for your charting application if you need the charts to be data bound. You see more about how to do this later, but remember that the output of processing a data template can be simple drawing visuals, allowing you to create data-bound charts that produce only the functionality you need.
Listing 2.1 shows an example of drawing a sector in a chart. In charting terms, a sector is a closed region that looks like a pizza slice. It has two straight lines that form the two sides of a triangle, but the last piece of the shape is closed by an arc rather than another straight line.
When rendered, the preceding class creates a visual that looks like the one shown in Figure 2.2.
Retained Mode Graphics
Remember that WPF is a retained-mode graphics system, which means all of the drawing instructions are cached and you do not need to call any kind of update graphics API to force a visual refresh, as in an immediate mode graphics system. Although the API around DrawingVisual and DrawingContext resembles something you find in an immediate mode graphics system, beware of using it like one. You should never have to call any kind of update-my-graphics API to force a visual to redraw.
If you have done any graphics programming for other platforms before, the concept behind the DrawingContext class should be pretty familiar to you. It is essentially an entry point into the conduit between your code and the actual rendered pixels on the user’s monitor. As WPF is a retained graphics system, it caches all the drawing instructions and renders them whenever a refresh is required. The DrawingContext is used as the cache from which these instructions are picked up. In the preceding code, we start by building the geometry of the sector using the StreamGeometryContext. We then use the DrawingVisual’s RenderOpen method to obtain a reference to the current DrawingContext instance and draw the geometry. The DrawingContext class contains methods for drawing lines, rectangles, geometry, text, video, and much more. Using these methods, you can build up a shape like the sector in Listing 2.1.
While the DrawingVisual class is ideally suited to scenarios in which you just need to do basic drawing and hit testing, it still needs a container that is responsible for placing those graphics on the screen. One such container is the FrameworkElement class.
The FrameworkElement Class
System.Windows.FrameworkElement derives from UIElement, which actually provides the core services such as layout, eventing, and user input that are used by rest of the framework. Although UIElement is a public class you would typically not derive from it. Instead, the FrameworkElement makes a better choice since it exposes the previous services (that is, layout, styles, triggers, data binding) in a user-customizable way.
FrameworkElement is also a lightweight container host for a set of visuals. Because it is a descendant of UIElement it is free to participate in the logical tree and can provide container support for more primitive visual elements (such as the DrawingVisual from the preceding example). The FrameworkElement class can be used in the following ways:
- Provide simple visual representations of data by overriding the OnRender method.
- Compose custom visual trees, making the FrameworkElement an excellent container class.
- Provide custom layout logic (sizing and positioning) for the contained visuals.
- A combination of the above.
For the pie slice control to be displayed onscreen, we need to build a container in which the SectorVisual class (refer to Listing 2.1) is the lone visual child, as shown in Listing 2.2.
The Spine
Inside the WPF team, a specific term is used for the set of classes comprised of DispatcherObject, DependencyObject, Visual, UIElement, and FrameworkElement. They call it the Spine and rightfully so. It is the backbone of WPF and provides the solid foundation to build more advanced functionality.
It is worth pointing out that the preceding VisualContainer class could also have been a subclass of UIElement instead of FrameworkElement, since it is not doing any custom layout. A FrameworkElement is best suited when you also want to provide custom sizing and positioning of elements, data binding, and styles.
The Shape Class
The Shape class provides yet another mechanism to enable primitive drawing in WPF applications. If we already have the DrawingVisual, which we have seen can be used to draw lines, arcs, and “pie slice” wedges, what do we need the Shape class for?
The Shape class actually provides a level of abstraction slightly above that of the DrawingVisual. Rather than using the primitives of the DrawingContext as we have already seen, instead we can use the concept of geometry to determine what is going to be drawn.
As a developer creating a custom shape, you use the DefiningGeometry property on your custom shape class. This geometry defines the raw shape of the class, and other properties such as the stroke, stroke thickness, and fill determine the rest of the information needed to render the shape. If you have ever used shapes, strokes, and fills in Adobe Photoshop or Illustrator, these concepts should already be familiar to you. Whatever you create using DefiningGeometry can also be done using the more primitive DrawingVisual class, but using the geometry allows your custom shape class to be inserted more easily into a logical tree, making it more flexible and more amenable to reuse and packaging.
Shape is a subclass of FrameworkElement, a base class used by most container-type classes such as Panel to render child elements. This lets Shape instances participate in the layout pass and allows for easier event handling. Shape also defines the Stretch property, which allows you to control how a shape’s geometry is transformed when the dimensions of the Shape object change.
Figure 2.3 illustrates a sector shape and how it can be transformed automatically using the Stretch property.
Taking the previous example of the sector and upgrading it this time to inherit from the Shape class, we end up with the code in Listing 2.3.
As you can see from the preceding code, the construction of the shape is exactly the same as constructing a visual-based sector. The difference here is that for a Shape we stop after creating the geometry and setting that to the DefiningGeometry property. With the SectorVisual, we must both construct the geometry and render it. The core difference is basically a difference in responsibilities. The Shape knows how to render itself in its container using the geometry defined in DefiningGeometry.
When creating a shape’s defining geometry, the most commonly used geometry classes are PathGeometry, StreamGeometry, GeometryGroup, or CombinedGeometry. You learn more about these types of geometry in more detailed examples later in the book.
The Text Classes
Developers often overlook fonts when they are digging in their toolbox for something to get the job done. WPF actually has robust support for drawing text, laying out text, and working with documents. Text can be displayed onscreen in multiple ways and ranges from simple text to text with complex layout and formatting support.
At the most primitive level, we have GlyphRuns and FormattedText. These can’t be used declaratively; rather, you need to use the DrawingContext to display them onscreen. This can be done using the DrawingContext.DrawGlyphRun and DrawingContext.DrawText APIs.
In today’s modern age of globalized applications, you need more than just the ability to blindly throw text onto the user interface. You need to be able to do things like display text that runs from right to left, display Unicode characters, and much more. For example, when you draw text into a drawing context, not only do you supply font information, but you also supply the text, text culture, flow direction, and the origin of the text:
drawingContext.DrawText( new FormattedText(“Hello WPF!”, CultureInfo.GetCultureInfo(“en-us”), FlowDirection.LeftToRight, new Typeface(“Segoe UI”), 36, Brushes.Black), new Point(10, 10));
Text can also be displayed declaratively and easily using the TextBlock and Label classes. TextBlocks (and Labels) are generally useful for a single line of text with fairly rich formatting and simple alignment support. For more complex text display, you can use the FlowDocument and FixedDocument classes that have more elaborate features to handle dynamic layouts, paragraphs, and mixing of rich media.
FlowDocument handles automatic layout and sizing of text and graphics as you resize the document. They are most useful for viewing newspaper-style text that can flow into columns and multiple pages. FixedDocuments are useful for programmatically generating a document with precise control over sizes of the textual elements, hence the name. These documents use two kinds of elements: blocks and inlines. Blocks are container elements that contain the more granular inline elements. Typical block-related classes include Paragraph, Section, List, and Table. Some of the common inline classes are Run, Span, Hyperlink, Bold, Italic, and Figure.
Although TextBlock, Label, FixedDocument, and FlowDocument are useful for displaying static text, WPF also provides interactive controls for editing text. These include the classic TextBox, which has limited formatting capabilities, and the RichTextBox, which as the name suggests has richer editing capabilities.
Most of these text-related classes expose properties to control alignment, fonts, font styles, and weights. Additionally, there is a class called Typography under the System.Windows.Documents namespace that has a rich set of properties to specifically control the various stylistic characteristics of OpenType fonts. They are available as attached properties, which can be set on text-related classes that use OpenType fonts. A sampling of the properties include Capitals, CapitalSpacing, Fraction, Kerning, and NumeralAlignment.
The Control Class
The Control class is pretty close to the top of the food chain of visual classes. It provides a powerful Template property (of type ControlTemplate) that can be used to change the entire look and feel of a control. Knowing that control templates can be changed during design time and at runtime can make for some amazingly powerful applications and compelling UIs. Designing with a Control allows developers and designers to quickly and easily define visual elements.
A rich set of classes that derive from the Control class provide specialized functionality and increasing complexity and level of abstraction. Choosing the right subclass of Control goes back to the analogy of choosing the right tool for the job. You need to make sure that you don’t take something overly complex as well as not picking something that is too simplistic and doesn’t offer the functionality you need. Choosing the wrong subclass can dramatically increase the amount of work you need to do.
For example, if you are building a control that needs to display a list of child items, you should start with ItemsControl or ListBox instead of starting with the comparatively low-level functionality of the Control class.
Unlike the earlier UI frameworks, the Control-related classes in WPF can be used directly without subclassing. Because of the powerful features such as Styles and Templates, you can customize the look and feel of a control declaratively. The subclasses of Control deal with the shape of the data rather than the appearance. A Button deals with singular data. ScrollBars, Sliders, and so on work with range data. ListBox and ListView work with collections. TreeView works with hierarchical data. It is up to the development team to decide how best to visually represent the data using these controls. In most cases, you do not have to subclass a control, rather you only have to change its Style and Template.
The ContentControl Class
The ContentControl class is ideal for displaying singular content, specified via the Content property. The content’s look and feel can be customized using its ContentTemplate property, which is of type DataTemplate. Remember back in Chapter 1, “The WPF Design Philosophy,” how plain data gets transformed into a visual representation through data templates.
The container that hosts the content can also be customized using the Template property of type ControlTemplate. This way you actually have two levels of customization available to you: You can customize the outer containing frame (via the Template property), and you can customize how the content within the frame is rendered (via the ContentTemplate property).
Controls derived from ContentControl are used to represent individual items that are displayed within list-based controls such as a ListBox, ItemsControl, ListView, and so on. The Template property is used for user interaction features such as showing selections, rollovers, highlights, and more. The ContentTemplate property is used for visually representing the data item associated with the individual element.
For example, if you have a list of business model objects of type Customer that you are displaying inside a ListBox, you can use its ItemTemplate property (of type DataTemplate) to define a visual tree that contains the customer’s picture, home address, telephone number, and other information. Optionally you can also customize the item container holding each Customer object. As mentioned, a ContentControl derived class is used for wrapping each item of a ListBox. We can customize this ContentControl derived container using its Template property, which is of type ControlTemplate.
Some of the most powerful tricks in WPF revolve around control templates, content controls, and content presenters, so it is well worth the effort of learning them in detail.
The ContentPresenter Class
The ContentPresenter class is the catalyst that brings a data template to life. It is the container that holds the visual tree of the data template. ContentPresenters are used inside the ControlTemplates of Control, ContentControl, or any other custom control that exposes a property of type DataTemplate. It may help to think of the role of the ContentPresenter as the class that is responsible for presenting the visual tree of a data template within its container.
Within the ControlTemplate, you associate the DataTemplate property of the template control with the ContentTemplate property of the ContentPresenter. You might do this in XAML (eXtensible Application Markup Language) this way:
<ContentPresenter ContentTemplate={TemplateBinding ContentTemplate} />
In the preceding snippet, we are template binding the ContentTemplate property of the ContentPresenter to the ContentControl’s ContentTemplate property.
In general, you can think of a presenter element as a shell or container for the actual content. It instantiates the template tree and applies the content to it. As you may recall from Chapter 1, you can think of the content as being a piece of cookie dough, the template is the cookie cutter, and the presenter pushes down on the dough and presents the end result of a nicely shaped cookie.
The ItemsControl Class
As this class’s name suggests, the ItemsControl class is ideally suited to displaying a list of items. More specifically, those items are interactive controls.
Not so long ago, when the main framework for building Windows applications was Windows Forms using .NET, controls were almost always too specialized. A ComboBox would display a drop-down list of items, but those items were always text, unless you rolled up your sleeves and did some serious work. This same problem occurred in virtually every place where Windows Forms displayed a list of items-the type and display of each item in a list was fixed unless you practically rewrote the control.
With WPF, the ItemsControl allows you to present a list of items that can have any visual representation you choose and can be bound to any list-based data you want. Finally we have both the flexibility we have always wanted and the power we have always needed.
Frequently used derivations of the ItemsControl class include the ListBox, ListView, and TreeView. The ItemsControl class exposes a wide variety of properties for customizing the look of the control and also of its contained items. Because these properties are exposed as DependencyProperties, they can be data-bound to other properties. These properties include the following:
- ItemsPanel-The ItemsControl needs a panel to lay out its children. We specify the panel using an ItemsPanelTemplate. The ItemsPanelTemplate is then applied to an ItemsPresenter.
- ItemTemplate-The ItemTemplate is the DataTemplate for the items being displayed. This template may be applied to a ContentPresenter or a ContentControl.
- ItemContainerStyle-This property indicates the style for the UI container for each individual item. Note that an ItemControl wraps each data item within a UI container such as a ContentPresenter or a ContentControl-derived class.
- Template-This defines the ControlTemplate for the ItemsControl itself.
If this seems like a lot to take in, don’t worry. The concepts behind content controls, presenters, and data templates can seem daunting at first, but we use them so extensively throughout this book that their use will quickly become second nature to you. We cover the ItemsControl in greater detail in Chapter 5, “Using Existing Controls,” and Chapter 8, “Virtualization.”
The UserControl Class
The UserControl class is a container class that acts as a “black box” container for a collection of related controls. If you need a set of three controls to always appear together and be allowed to easily talk to each other, then a likely candidate for making that happen is the UserControl class.
Creating your own UserControl is an easy first start at creating your own custom controls. It provides the familiar XAML + Code-Behind paradigm that you can use to define your control’s appearance and associated logic. The UserControl class derives from ContentControl and makes a few additions to ContentControl’s stock dependency properties.
The first thing you may notice about a user control is that the control itself cannot receive keyboard focus nor can it act as a Tab stop. This is because in the static constructor for UserControl, the UIElement.Focusable DependencyProperty and the KeyboardNavigation.IsTabStop property have been set to false.
This makes complete sense when you think about the idea that the primary function of a UserControl is to wrap a set of related controls and not act as an interactive control on its own.
To make things more clear, let’s take a look at an example. Suppose that you have to create a search bar for your application that looks something like the one in Figure 2.4.
The search bar in Figure 2.4 is comprised of a TextBox and a Button. When a user types a keyword or set of keywords and then presses the Enter key, the search functionality is invoked. The same functionality is invoked if the user types in a keyword and clicks the Search button.
While you can place these two controls individually in your window, their purpose and functionality are so interconnected that you would never really use them separately. This makes them ideal candidates for being placed inside a UserControl.
To further enhance the encapsulation, you could write your UserControl such that it doesn’t tell the hosting container when the user presses Enter or when the user clicks the Search button; it simply exposes a single event called SearchInvoked. Your window could listen for that event and, in an ideal Model-View-Controller world, pass the search request on to a search controller for processing.
Note
Customizing UserControls
A UserControl doesn’t allow customization of its look and feel because it does not expose properties for templates, styles, or triggers. You will have the best luck with UserControls if you think of them as faceless containers for logically and functionally related controls.
Within the UserControl, you have the ability to improve the look and feel of that single element without affecting the UI definition of the window and enabling your control for reuse in multiple locations throughout your application. Additionally, wrapping a set of related controls and giving them a purpose-driven name such as SearchBar makes your XAML and your code easier to read, maintain, and debug.
Similar to the way refactoring allows you to incrementally improve your C# code to make it more understandable, maintainable, and testable, refactoring the UI provides the same benefits and is much easier to do within the bounds of a UserControl. This is often called view refactoring.
The Panel Class
The Panel class is an element that exists solely to provide the core layout functionality in WPF. Powerful, dynamic layout capability has always been something that was missing in Windows Forms, and now that WPF has dynamic layout features, the world is a much happier place.
Think of the Panel as a “layout brain” rather than something that actually produces its own UI. Its job is to size the child elements and arrange them in the allocated space, but it has no UI of its own. WPF ships with a powerful set of panels that handle many of the common layout scenarios that developers run into on a daily basis. These include the Grid, StackPanel, DockPanel, and the WrapPanel. The following is a brief description of each layout pattern (don’t worry, you see plenty more of these classes in the code samples throughout the book):
- Grid-Provides a row/column paradigm for laying out child controls.
- StackPanel-Child controls are laid out in horizontal or vertical stacks.
- DockPanel-Child controls are docked within the container according to the preferences specified by each child control.
- WrapPanel-Child controls in this panel wrap according to the specified wrapping preferences.
Another panel called the Canvas provides static, absolute coordinate-based layout. Panels can be nested within each other to create more complex layouts. Layout in WPF is handled using the two-phased approach of measure and arrange.
During the measure phase, the parent requests that each of its children supply their minimum-required dimensions. The parent then applies additional requirements such as margins, alignment, and padding.
Once each child has been measured, the parent panel then performs the arrange phase. During this phase, the parent panel places each child control in its actual position in the final dimensions. The final position and size of the child element may not be what the child element requested. In these scenarios, the parent panel is the final authority on where the child controls are and how much space they take up.
Panels also have some extra functionality that you might not want to supersede, such as built-in ability to work with ItemsControls and the ability to dynamically change the z-order of a child element with the Panel.SetZIndex method.
The Decorator Class
A Decorator class is responsible for wrapping a UI element to support additional behavior. It has a single Child property of type UIElement, which contains the content to be wrapped. A Decorator can be used to add simple visual decoration, such as a Border, or more complex behavior such as a ViewBox, AdornerDecorator, or the InkPresenter.
When you subclass a Decorator, you can expose some useful DependencyProperties to customize it. For example, the Border class exposes properties like BorderBrush, BorderThickness, and CornerRadius that all affect how the border is drawn around its child content.
The Adorner Class
If we already have an additive decoration class in the form of the Decorator, why do we need an Adorner class? As mentioned earlier, every single class in the class hierarchy that makes up WPF has a specific purpose. While a Decorator is responsible for drawing decoration around the outside of a piece of child content, the Adorner class allows you to overlay visuals on top of existing visual elements. An easy way to think of adorners is that they are secondary interactive visuals that provide additional means to interact with the primary visual. That might seem complex, but think about widgets such as resizing grips that appear on elements in a typical diagramming program. Those are a secondary visual that sit on top of the elements that they are adorning and provide additional functionality and interaction. By clicking and dragging the resizing-handles, the user can resize the underlying control.
Adorner classes work in conjunction with the AdornerDecorator, which is an invisible surface on which the adorners rest. To be part of the visual tree, adorners have to have a container. The AdornerDecorator acts as this container.
AdornerDecorators are generally defined at the top of the visual tree (such as the ControlTemplate for the Window control). This makes all adorners sit on top of all of the Window content. We explore the use of adorners throughout the book, but you see them specifically in Chapter 6, “The Power of Attached Properties,” and Chapter 9, “Creating Advanced Controls and Visual Effects.”
The Image Class
You might be a little surprised to see the Image class mentioned here among all of the other highly interactive visual controls. In most frameworks, images contain just enough functionality to display rasterized (nonvector) images and maybe support reading and writing streams of image data, but that’s about it.
Image classes can actually provide control-like capabilities for some specific scenarios. Image derives from FrameworkElement, so it can be composed in logical trees and has rich support for event handling and layout. It encapsulates the functionality to render an instance of an ImageSource, specified via the Source property. The ImageSource class can represent a vector image like DrawingImage or a raster/bitmap image like the BitmapSource.
Images can be useful when you want to visualize a large amount of data for which you have limited interaction. Some situations where this might come in handy are when you are visualizing high-volume graphs or network monitoring tools that are visualizing thousands of network nodes. In cases like this, even DrawingVisuals become extremely expensive because each data item is a separate visual and consumes CPU and memory resources. Using an image, and knowing that each data point doesn’t need to be interactive, you can visualize what you need without bringing the host computer to its knees.
Since the Image class also has event handling support, we can attach handlers for mouse events that can query the pixel at the mouse’s current coordinates and report information about that data item. With a little bit of creativity and forethought, the class can be a powerful tool in any developer’s toolbox.
The Brushes
The Brush-related classes in WPF represent a powerful way of drawing simple to complex graphics with extreme ease of use. A brush represents static noninteractive graphics that serve mostly as backgrounds on visual elements. You can use a basic brush like SolidColorBrush, which only draws solid colors like Red, Blue, LightGray, and so on, and also gradient brushes like a LinearGradientBrush and RadialGradientBrush. The gradient brushes have additional properties to control the style of drawing the gradient. Figure 2.5 shows you various kinds of gradient brushes.
Although solid and gradient brushes are available in previous UI technologies, the real power comes with the TileBrush classes such as ImageBrush, DrawingBrush, and VisualBrush. An ImageBrush as the name suggests allows you to create a Brush out of an image. This is useful since it allows you to use an image without using the Image class. Since it is a brush, you can use it wherever a Brush type property is expected.
DrawingBrush gives you the power of defining complex graphics as a simple brush. Using DrawingGroups and GeometryDrawings, you can define nested graphics that can provide elegant backgrounds to your visuals. In Figure 2.6, you can see a nested set of graphic elements to create the final DrawingBrush. With clever use of DrawingBrushes, you can simplify the way you define some ControlTemplates.
A VisualBrush gives you a live snapshot of a rendered element from the visual tree. We see many uses of VisualBrushes in later chapters, such as using VisualBrush as a texture on a 3D model or creating reflections.
The TileBrush can also be stretched and tiled to fill the bounds of the visual. You can also cut out a rectangular section of the brush using the Viewport and ViewBox properties. Just like regular visuals, you can also apply transforms. Brushes have two kinds of transform properties: RelativeTransform and Transform. The RelativeTransform property scales the brush using the relative coordinates of the visual ([0,0] to [1,1]). It is useful if you want to transform the brush without knowing the absolute bounds of the visual on which it is applied. The Transform property works after brush output has been mapped to the bounds of the visual-in other words, after the RelativeTransform is applied.
The DataTemplate, ControlTemplate, and ItemsPanelTemplate Classes
WPF has a set of template classes that are used to represent visual trees. Templates are never actually rendered directly; rather, they are applied to other container classes like a ContentPresenter, ItemsPresenter, or a Control.
Each template class derives from the FrameworkTemplate class. These include the DataTemplate, ControlTemplate, and ItemsPanelTemplate classes. There is also a HierarchicalDataTemplate that is used for representing hierarchical data. It takes a little getting used to, but once you are, it is an invaluable tool for representing multilevel or tiered data. HierarchicalDataTemplates are used for controls such as the TreeView.
Each of these three templates contains a visual tree that can be greater than one level. The exception here is that the ItemsPanelTemplate can only contain a Panel-derived class as the root (there is a hint to this exception in the name of the template class itself).
The Viewport3D Class
So far every class that we have discussed so far has been a flat, two-dimensional control. WPF also gives developers unprecedented power and accessibility into the world of 3D programming. The Viewport3D class (see Figure 2.7) gives developers the ability to work in three dimensions without having to deal with complex game-oriented frameworks such as Direct3D or OpenGL.
The Viewport3D class is a container for a 3D world that is comprised of 3D models, textures, cameras, and lights. Viewport3D derives from the FrameworkElement class instead of Control. This makes a good deal of sense because FrameworkElement works great as a visual container, and the Viewport3D class is a visual container for an interactive 3D scene.
The Viewport3D class also has no background. As a result, you can place a 3D viewport on top of 2D elements and create stunning effects by mixing and matching 2D and 3D visual elements. Just keep in mind that the 3D world must reside in a completely different container. For example, you can use a VisualBrush to take a 2D visual and apply it to the surface of a 3D model as a material. The .NET Framework 3.5 introduced additional classes that allow you to have live, interactive 2D visuals on a 3D surface. For example, you can place a Button visual as a material for a Sphere and interact with it like a regular button, even if the Sphere is spinning and being dynamically lit by a light source.
The MediaElement Class
Many of today’s modern applications are more than just static controls and grids and buttons. Many of them contain multimedia such as sounds, music, and video. WPF not only lets you play audio and video, but gives you programmatic control of the playback.
WPF gives you this multimedia programming experience with the MediaElement class. You indicate the source of the media using the Source property. You can control the media playback using the Play, Pause, and Stop methods. You can even control the volume and skip to a specific time in the playback using the Position property.
Figure 2.8 shows a simple WPF application that contains a media element and some controls for manipulating the video.
The InkCanvas
The Tablet PC introduced a more widespread use of the stylus as a means to interact with the applications. The strokes created using the stylus were treated as ink, which could also be mapped to application-specific gestures. Although the stylus is treated as the default device, a mouse makes a good substitute.
WPF has the InkCanvas class that provides most of the features available on the Tablet PC. In fact the InkCanvas becomes the slate on which we can scribble either with the mouse or with the stylus. InkCanvas can be created declaratively and exposes a variety of events related to strokes. It also has built-in gesture recognition for some standard gestures. By overlaying an InkCanvas on some UI elements, you can add some interesting features to an application. For example, for a photo-viewing application, you can overlay an InkCanvas on a photo to annotate parts of the picture, as shown in Figure 2.9.
Summary
With the diverse range of classes available to use within WPF, we can see that WPF is a great toolset for creating interesting, compelling, and visually stunning interfaces and controls.
Understanding and respecting this diversity and knowing which is the best tool for any given situation will make your development experience more rewarding and enjoyable and will ultimately improve the quality of your applications.
Table 2.1 presents a summary of the classes discussed in this chapter.
In the next chapter, we discuss creating controls and some best practices for approaching control creation. We build on the foundations from this chapter and the previous chapter as we venture into the world of creating exciting, modern interfaces with WPF. | http://www.codemag.com/article/100023 | CC-MAIN-2014-42 | refinedweb | 6,337 | 52.6 |
Opened 3 years ago
Closed 2 years ago
#6064 closed change (fixed)
Put C++ code into a configurable namespace
Description
Background
In order to avoid conflicts with already existing C++ code when one tries to use it natively we should put all our C++ code into a namespace. However it still can make sense to not use a namespace when it's compiled to JS in order to avoid additional dealing with name mangling.
What to change
- introduce base.h which should be included as the first our header in every our header.
- introduce ABP_USER_CONFIG which is a path to a header file included by base.h and representing options which may be configured by a user. If it's not defined then use user.h.
- add defines ABP_NS, ABP_NS_BEGIN, ABP_NS_END and ABP_NS_USING into user.h and add corresponding usage of them into all headers and C++ files.
Change History (4)
comment:1 Changed 3 years ago by sergz
comment:2 Changed 3 years ago by fhd
- Cc trev removed
comment:3 Changed 2 years ago by abpbot
comment:4 Changed 2 years ago by sergz
- Resolution set to fixed
- Status changed from reviewing to closed
Note: See TracTickets for help on using tickets.
A commit referencing this issue has landed:
Issue 6064 - Put C++ code into a configurable namespace | https://issues.adblockplus.org/ticket/6064 | CC-MAIN-2020-29 | refinedweb | 220 | 69.01 |
I was messing around with a DI container comparision with weld-se, Guice, PicoContainer and Spring and I ran across an issue with weld-se.
What I want to do is have the DI framework repeatedly instantiate a POJO, with no dependencies (no injection points). This will serve as the first phase of the benchmark, as I'll add injection points later. This was very easy to do in Guice and PicoContainer, somewhat of a chore in Spring, but in Weld SE I was having a little trouble. Anyway, I finally got weld to instantiate the POJO like this:
WeldContainer weld = new Weld().initialize(); weld.event().select(ContainerInitialized.class).fire(new ContainerInitialized()); Instance<TestBean> instance = weld.instance().select(TestBean.class); TestBean bean = null; for (int i = 0 ; i < 100000; i++) { bean = instance.get(); }
The TestBean interface and implementation are very ordinary. The implementation uses some singleton counters to count the number of instances the container creates:
public interface TestBean { void action(); } public class NoDepsImpl implements TestBean { public NoDepsImpl() { Counters.getInstance().incrementClient(); } public void action() { } }
In the other containers, this works fine, as the unreferenced beans are cleaned up by the GC fairly quickly. Is there something hanging on to the instances of TestBean? Is this the right way to repeatedly instantiate a POJO?
It looks like the 'creationalContext' inside the Instance object is adding each object to some sort of internal collection, and that collection is never cleared. The example ends up using the 'dependent context', so I'm not sure what the behavior ought to be.
Off the top of my head I'd say that Instance.get() in this case has a pretty severe memory leak. Seems related to WELD-920, IMO. | https://developer.jboss.org/thread/180089 | CC-MAIN-2018-17 | refinedweb | 284 | 55.84 |
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TurboTaxes vaction contest not recognizing my order #
TurboTaxes vaction contest not recognizing my order #
When I put in my TurboTaxes order # from my confirmation email from my 2012 federal tax return (from TurboTaxes) it says it is invalid even though from the help button I am seeing that I am using the correct Order # and not making any typos as I've even tried copy and pasting this.
- Hi Joe,
Thanks for messaging us. Can you email us at support@saveup.com with your order number and a screenshot of your email confirmation?
Thanks for your patience.
Best,
JeanComment | https://getsatisfaction.com/saveup/topics/turbotaxes_vaction_contest_not_recognizing_my_order | CC-MAIN-2014-15 | refinedweb | 113 | 52.9 |
#include <LgiClasses.h>
Inherits GAppI, and OsApplication.
This should be the first class you create, passing in the arguments from the operating system. And once your initialization is complete the 'Run' method is called to enter the main application loop that processes messages for the life time of the application.
Construct the object.
References AppWnd, GTypeFace::Bold(), GFont::Create(), GFontType::Create(), GetOption(), GFontType::GetSystemFont(), MB_OK, SetAppArgs(), SystemBold, SystemNormal, and GTypeFace::Transparent().
Exits the event loop with the code specified.
Gets the MIME type of a file
References GArray< Type >::Length(), LGI_PATH_SEPARATOR, GStringPipe::NewStr(), and GProcess::Run().
Get a system metric.
References LGI_MET_DECOR_CAPTION, LGI_MET_DECOR_X, and LGI_MET_DECOR_Y.
Gets the application name, by default it will be generated from the mime type, but can also be set by calling GApp::SetName
Parses the command line for a switch.
References GetOption().
Parses the command line for a switch.
References IsOk(), and GArray< Type >::Length().
Referenced by GApp(), and GetOption().
Enters the message loop.
Set the application name. This is currently used to generate the leaf folder for LSP_APP_ROOT | http://www.memecode.com/lgi/docs/classGApp.html | CC-MAIN-2016-30 | refinedweb | 174 | 52.56 |
Plone Viewlets First Contact
In this tutorial we will learn how to add elements to our plone pages, making something like this appear in your site:
There are a number of things we will not learn about viewlets - but we will get somewhere to start.
Files needed
Only need three files are needed to do this:
__init__.py configure.zcml skins/myviewlet_footer.pt
__init__.py
The __init__.py-file only contains a comment. This can be considered good practice since it is otherwise easy for a user to remove blank files.
skins/myviewlet_footer.pt
This is a typical Plone page template (as seen in for example: Plone Archetypes View Template Modifications) and contains nothing fancy:
<p> This page is <b tal:URL</b> </p>
As you can see we print the url of the present file and then a link to the Plone Cms page in my blog.
configure.zcml
The configure.zcml file contains the real action. It hooks zope and the page template together.
First let's see the important contents and then we will slowly walk through:
<configure ... > <browser:viewlet </configure>
As we can see we define a browser:viewlet (so we need the browser namespace). These are the following attributes:
- name="myviewlet.myviewlet_footer", meaning that we call this viewlet myviewlet.myviewlet_footer.
- for="*", meaning that we display it for everything (hopefully I'll elaborate on that in a later tutorial).
- manager="plone.app.layout.viewlets.interfaces.IPortalFooter", this line tells us that our viewlet belongs in the IPortalFooter viewlet manager.
- template="skins/myviewlet_footer.pt", defines the page template file we use.
- permission="zope.Public", means that this viewlet can be viewed by anyone.
Limitations
Things we might want to be able to control that are not covered in this tutorial include:
- Turning the viewlet on and off by installing and uninstalling an Add-on product.
- Only viewing the viewlet for special pages.
- Executing Python code that affects out viewlets.
- More... ?
See also: Plone Cms
This page belongs in Kategori Programmering | http://pererikstrandberg.se/blog/index.cgi?page=PloneViewletsFirstContact | CC-MAIN-2017-39 | refinedweb | 333 | 65.42 |
<Andy_Carr@tertio.com> asked
> I have written an XML schema (that makes use of the standard XML
Schema
> definitions) but am having zero success in getting the parser to find
my
> schema definition file.
>
> The top of my XML file looks like:
>
> <?xml version="1.0" ?>
> <GMI xmlns="">
> <ServiceTag>CSO</ServiceTag>
> ...etc...
I don't know how Xerces finds schemas, but a namespace declaration does
not have anything to do with assigning schemas or anything else. It
only gives you a way to distinguish names that might otherwise be taken
to be the same. You definitely don't want something as changeable as a
file location on your own machine to be a namespace designator.
Tom Passin | http://mail-archives.apache.org/mod_mbox/xml-general/200009.mbox/%3C002e01c01825$9673c540$38a3f1ce@mitretek.org%3E | CC-MAIN-2017-04 | refinedweb | 117 | 61.46 |
You probably have used mathematical functions in algebra class, but they all had calculated values associated with them. For instance if you defined
F(x)=x2
then it follows that F(3) is 32 = 9, and F(3)+F(4) is 32 + 42 = 9 + 16 = 25.
Function calls in expressions get replaced during evaluation by the value of the function.
The corresponding definition and examples in C# would be the
following, taken from example program
return1.cs. Read
and run:
using System; class Return1 { static int F(int x) { return x*x; } static void Main() { Console.WriteLine(F(3)); Console.WriteLine(F(3) + F(4)); } }
The new C# syntax is the return statement, with the word
return followed by an expression. Functions that return values
can be used in expressions, just like in math class. When an
expression with a function call is evaluated, the function call is
effectively replaced temporarily by its returned value. Inside the
C# function, the value to be returned is given by the
expression in the
return statement.
Since the function returns data, and all data in C# is typed,
there must be a type given for the value returned. Note that the
function heading does not start with
static void.
In place of
void is
int. The
void in earlier function headings
meant nothing was returned. The
int here means that a value is
returned and its type is
int.
After the function
F
finishes executing from inside
Console.WriteLine(F(3));
it is as if the statement temporarily became
Console.WriteLine(9);
and similarly when executing
Console.WriteLine(F(3) + F(4));
the interpreter first evaluates F(3) and effectively replaces the call by the returned result, 9, as if the statement temporarily became
Console.WriteLine(9 + F(4));
and then the interpreter evaluates F(4) and effectively replaces the call by the returned result, 16, as if the statement temporarily became
Console.WriteLine(9 + 16);
resulting finally in 25 being calculated and printed.
C# functions can return any type of data, not just numbers, and
there can be any number of statements executed before the return
statement. Read, follow, and run the example program
return2.cs:
Many have a hard time following the flow of execution with functions. Even more is involved when there are return values. Make sure you completely follow the details of the execution:
firstName = "Benjamin";
lastName = "Franklin"
separatorthe value
", "
resultthe value of
lastName + separator + firstNamewhich is
"Franklin" + ", " + "Benjamin", which evaluates to
"Franklin, Benjamin"
"Franklin, Benjamin"
Console.WriteLine("Franklin, Benjamin");, so print it.
firstName = "Andrew";
lastName = "Harrington"
"Harrington, Andrew"
"Harrington, Andrew"
Compare return2/return2.cs and addition1/addition1.cs,
from the previous
section. Both use functions. Both print, but where the printing is
done differs. The function
SumProblem prints directly inside
the function and returns nothing. On the other hand
LastFirst does not print anything but returns a string. The
caller gets to decide what to do with the returned string, and above it is
printed in
Main.
In general functions should do a single thing. You can easily combine a sequence of functions, and you have more flexibility in the combinations if each does just one unified thing. The function SumProblem in addition1/addition1.cs does two thing: It creates a sentence, and prints it. If that is all you have, you are out of luck if you want to do something different with the sentence string. A better approach is to have a function that just creates the sentence, and returns it for whatever further use you want. After returning that value, printing is one possibility, done in addition2/addition2.cs:
using System; class Addition2 { static string SumProblemString(int x, int y) { int sum = x + y; string sentence = "The sum of " + x + " and " + y + " is " + sum + "."; return sentence; } static void Main() { Console.WriteLine(SumProblemString(2, 3)); Console.WriteLine(SumProblemString(12345, 53579)); Console.Write("Enter an integer: "); int a = int.Parse(Console.ReadLine()); Console.Write("Enter another integer: "); int b = int.Parse(Console.ReadLine()); Console.WriteLine(SumProblemString(a, b)); } }
This example constructs the sentence using the string
+ operator.
Generating a string with substitutions using a format string
in
Console.Write is neater, but
we are forced to directly print the string,
and not remember it for later arbitrary use.
It is common to want to construct and immediately print a string,
so having
Console.Write is definitely handy when we want it.,
However it is an example of combining two separate steps! Sometimes
(like here) we just want to have the resulting string, and do something else
with it. We introduce
the C# library function
string.Format, which does just what we want:
The parameters
have the same form as for
Console.Write, but the formatted string is
returned.
Here is a revised version of the function
SumProblemString,
from example addition2a/addition2a.cs:
static string SumProblemString(int x, int y) // with string.Format { int sum = x + y; return string.Format("The sum of {0} and {1} is {2}.", x, y, sum); }
The only caveat with
string.Format is that
there is no special function corresponding to
Console.WriteLine,
with an automatic terminating newline.
You can generate a newline with string.Format: Remember the
escape code
"\n". Put it at the end to go on to a new line.
In class recommendation: Improve example painting/painting.cs
with a function used for repeated similar operations.
Copy it to a file
painting_input.cs in your
own project and modify it.
Write a program by that accomplishes the same thing as
Interview Exercise/Example, but introduce a function
InterviewSentence that takes name
and time strings as parameters and returns the interview sentence string.
For practice use
string.Format in the function.
With this setup you can manage input from the user and output to the
screen entirely in
Main, while using
InterviewSentence to generate
the sentence that you want to later print.
(Here we are having you work on getting used to function syntax while keeping the body of your new function very simple. Combining that with longer, more realistic function bodies is coming!)
If you want a further example on this idea of returning something first and then using the result, or if you want to compare your work to ours, see our solution, interview2/interview2.cs.
Create
quotient_return.cs by modifying
quotient_prob.cs in
Quotient Function Exercise so that the program accomplishes the same
thing, but everywhere:
QuotientStringthat merely returns the string rather than printing the string directly.
Mainprint the result of each call to the
QuotientStringfunction.
Use
string.Format to create the sentence that you return. | http://books.cs.luc.edu/introcs-csharp/functions/funcreturn.html | CC-MAIN-2019-09 | refinedweb | 1,098 | 58.99 |
On the Process of Effecting Mass
Zonk posted more than 6 years ago | from the lots-of-it-to-move dept.
Dean Takahashi, of the San Jose Mercury News, has up a lengthy interview with Mass Effect project director Casey Hudson on the almost four-year-long development of the title. The two men go into some detail on BioWare's approach to game creation, as well as discussing the numerous technical and storytelling leaps they made with the game. "Hudson said, 'One thing I'm hoping people see in it is how much more there is for a player to make decisions on. It makes it really hard for us to develop, given the customization that we make possible in the game. For example, from the beginning, you are not pre-made as a character. You can play Commander Shepard. But you can also create your own character, male or female. You can choose your special abilities. Those are ways to make your game different and unique. These are things that make it much harder for us to make the game so that it is consistent all the way through, given your choices.'"
decisions decisions... (1)
OleMoudi (624829) | more than 6 years ago | (#21480003)
I'm kind of an old school gamer and I always thought in time games would evolve not only to provide better realistic graphics but also to increase the freedom you have in them. When a game really touches you, you automatically get trapped withing its unique universe, and your experience is so much better when you really feel that "I can do almost everything" feeling.
It's a shame current state-of-the-art games usually just focus their appeal on graphics and pre-scripted sequences that only look great the first time you get to them. And even if you are not planning to play again the game after finishing it, a scripted scene always has that feeling of having nothing to do with the actions you just performed, or more importantly, that it has not happened because you *choose* it to happen.
Call of Duty 4 is a perfect example of this. Sure, the game looks great, definitely top-notch fps gameplay. However the game stinks of immutability. There is no freedom available on how to complete missions. There is only one way to do them. Maybe it is just too well designed to appeal casual and hardcore gamers at the same time. Maybe they just tried to make the game approachable for the big audience. They probably succeeded in that but they left freedom out in the process.
Take Half-Life 2 as a counter-example. When I played this game for the first time I really had bad times figuring out gameplay mechanics. Nobody in the game tells you can use flammable barrels as grenades with your gravity gun. Nobody tells you a lot of things in that game. You just figure them out as you play, in a way maybe intended by developers, but perfectly dressed to make you believe you actually come with the solution by yourself. The sense of accomplishment in this game is absolutely brilliant. Maybe it's not perfect, but it definitely points in the right direction while CoD4 doesn't. GTA is another great example of that kind of freedom illusion games should offer nowadays.
I haven't picked up Mass Effect yet, but I'm really looking forward. Seems like an oasis in the desert of immutable games flooding us lately.
Re:decisions decisions... (1)
LingNoi (1066278) | more than 6 years ago | (#21480379)
A better example would be nethack. Complete freedom.
Re:decisions decisions... (1)
Harlockjds (463986) | more than 6 years ago | (#21480737)
Re:decisions decisions... (2, Interesting)
TheThiefMaster (992038) | more than 6 years ago | (#21481063)
Portal. That game is designed around coercing the player into figuring things out themself. Play it through, then play it again with the commentary on and see how many times they taught you how to do something without you even noticing.
Re:decisions decisions... (1)
PopeJM (956574) | more than 6 years ago | (#21486865)
You mean "affect" (3, Funny)
Tetsujin (103070) | more than 6 years ago | (#21480009)
Re:You mean "affect" (1)
avalean (1176333) | more than 6 years ago | (#21480047)
Re:You mean "affect" (1)
bonkeydcow (1186443) | more than 6 years ago | (#21480139)
Well, that's the real problem (3, Insightful)
Moraelin (679338) | more than 6 years ago | (#21480639)
The problem is that, until someone invents an AI GM that can at least pass the Turing test, what you ask is simply not feasible. Someone has to design and code all those states you changed.
I mean, let's pretend we design a game where each quest truly changes the game's world.
E.g., you can decide that instead of saving Bastila on KOTOR, you capture her and sell her to the Sith. (Sure, _Malak_ would probably kill you if you ran into him face to face, but there's no reason you couldn't go be the dark apprentice of some Sith who's never anywhere near Malak.) And the game branches from there. Taris is never destroyed. You never get the Ebon Hawk, even, since the Sith lift the blockade and Canderous doesn't need you to get off the planet. You never fly to Dantooine to become a Jedi. Etc. Let's say the whole story can fork like that at any point.
Well, now let's say we allow only 3 solutions to each such point: good, evil, don't do it. (After all, it's unrealistic that I _must_ do something at any point in the game.)
After the first such quest, there are 3 possible paths. The next one multiplies them to 9. Then 27. Then 81. Then 243.
Sounds good, right?
Well, it would, if the devs had infinite funds. In practice you can look at it more realistically like this: they'd have to code 243 outcomes and 1+3+9+27+81=121 quests, just to give you... a chain of exactly 5 quests. And you'd think "gee, this game sucked, it had a whole 5 quests."
Alternately, if they made it a completely linear game, you could see all 121 quests. And probably think, "bestest game evar! It had more quests than KOTOR 1+2 combined."
For the same development money, the linear solution will actually be the better game.
The problem with that branching is _literally_ that the chain you see is a logarithm of the total number of quests they have to code. Which gets shittier with each level you add to that pyramid. Adding a 6'th quest to the chain seen by the player, in a truly branching game would raise the number of quests you need to code by another 243. It's a mammoth cost and effort just so the player sees a total of 6, no matter what kind of character they play..
That, in a nutshell, is why everyone avoids branching like the plague.
KOTOR didn't truly branch either. Heck, even in Oblivion or Morrowind, open-ended as they are, the story doesn't really branch. The world, in fact, doesn't change much as a result of your actions.
What good designers really do is
A) contain the effects. Sure, they might tell you that you just got the Republic kicked off Manaan, but it won't influence the rest of the game at all. Yeah, you just got told that you gave the Sith a major advantage, but it's not like now they'll finish the conquest before you reach the Star Forge.
B) create an illusion of having some consequence. Sure, you'll get an alignment number, NPC's talking about you like you're Mother Teresa or Jack The Ripper, etc, but that's all an illusion that doesn't influence anything else.
Basically that way they can give you all the quests and a number of ways to solve each, without the possibilities exploding out of control. The trick is to keep it all an illusion.
Re:Well, that's the real problem (1)
magical_mystery_meat (1042950) | more than 6 years ago | (#21481077).
And you'd have to support all of the munchkins that have to do everything that's possible in a game. "I killed Plotz, Gary, and saved Clyde, but now I can't get the Pwnage Crystal. Gamefaqs says I'm supposed to get it if my alignment is
Having an immutable main quest and X number of "optional" side quests seems to be the best bang for the buck. It wasn't the main quest that made KOTOR great. It was the side quests and the characters.
Re:Well, that's the real problem (2)
tricorn (199664) | more than 6 years ago | (#21482637)
There are lots of ways to prune the tree, though. Make ones where you are inconsistent just end up killing you or stranding you somewhere (in an obvious way), forcing you to go back to an earlier level (e.g. you make some "evil" choices, you make some "good" choices, both sides are now pissed at you and you die). Perhaps even auto-save your status at each decision point in the tree so it is always available to undo, even if you didn't save it as a "save game".
You can also merge branches; figure out 16 different ways you can get to the same major game point, and give 4 intermediate choices (where only 2 of the choices at each one advance you, others kill you or strand you or move you into a different minor or major branch, or skip a decision point). The auto-save points for the intermediate branches could be dropped as soon as you get to the next major branch point. You can nest this type of sub-branch pruning to many levels, thus giving lots of choices and lots of potential reasonable paths through the decision points.
The only thing the game designers really need to make sure of is that you can't get WAY past a decision point where you screwed up and didn't get some item or ability or cause some event to happen that is critical at some future point. Make sure you can return (even if it is difficult) to an earlier point if you allow the player to advance much beyond that point without making it obvious that they screwed up and will have to restore from an earlier saved game status; nothing worse than pointlessly replaying a a large chunk because you didn't realize you'd need to do something for later. If the player DOES need to return, make sure that getting back AND returning to the current point is actually a new fun sequence just for screw-ups like yourself (if you make it so you can ONLY go through that sequence if you didn't take the previous action, you've now added a new way to progress through the game!)...
Re:Well, that's the real problem (1)
Dahamma (304068) | more than 6 years ago | (#21482927)
Ugh, that's a horrible solution. It makes things even MORE arbitrary than not giving you a choice at all. The whole point of providing choice is to let the player feel like the world is not all black and white, right and wrong. If you want to die every time you make the "wrong choice", go play Dragon's Lair...
Re:Well, that's the real problem (1)
tricorn (199664) | more than 6 years ago | (#21484267)
No, making it so that one single choice kills you would be bad, I'm saying that you prune a tree when a player makes several bad choices. What, you want a world where there are no consequences?
It's also possible to make choices that affect the future game play, but not the main story line. Such choices can change the state of things in the future in ways that make it easier or more difficult (but not impossible) to accomplish something.
My real preference is for emergent behavior, with some sort of monitor process to herd the resultant state so that it is consistent with (the/a) story line. There are plenty of ways to do that without building everything totally scripted.
Sounds like Wing Commander 1 (1)
Moraelin (679338) | more than 6 years ago | (#21485935)
And, yes, more than half the paths led to "you lost the game". Take too many arcs to the left, and nothing could save the outcome any more.
Sounds like sorta what you're proposing. The same idea _could_ be applied to good/evil choices.
Well... don't get me wrong, WC was a good game. I will say however that there must have been a reason why they dropped the idea in WC2. If I'm allowed to take wild guesses, I'd say:
1. Any player would see far fewer missions than the game contained. No matter if you're top ace or quadriplegic, you'll see only one arc. Ditto for applying the idea to good vs evil. Mr Pure or Darth Sidious, you'll see only a square root of the number of nodes. That's wasted programming and design effort.
Think in KOTOR terms. Let's say each node is a planet, and you want to visit 6 planets during the game. You start on Taris, and on the good side the next planets would be Dantooine, Tatooine, Manaan, Korriban and finally the Rakata world + starforge. That kind of a graph with 6 levels, would still contain 1+2+3+4+5+6=21 planets. Out of which you see 6. That's a major waste of money and talent.
I'll get to pruning them later.
2. It still doesn't scale well. If you want to lengthen the game, each level just adds disproportionately more worlds out of which only 1 will be present in any given campaign. E.g., adding a 7'th level makes it 7 planets seen out of 28. It increased the waste from 15 worlds to 21 worlds. And percentage-wise from 71.4% to 75%.
3. And again, it's actually worse than it sounds, because most people just reloaded until they won all battles even if they sucked at the game. There were disproportionately fewer people who saw the planets and story along the "lose" arcs.
It would be slightly more balanced if it were "win for the good" and "win for the evil" arcs, instead of "win" and "lose". But not by much. Basically now almost everyone will see the left and right edges of that triangle, but almost noone will see the centre.
4. The fact remains that, by your idea and Origin's too, a lot of paths will lead to a "lose" state. Whether you kill the player early or let him play to the end of the "you lost" arc, it's still giving people a camouflaged "shoot yourself in the foot" option. Which tends to be less fun than it sounds.
5. Especially killing off the player, you have to realize that it's just making the game linear again, only this time in a non-fun way. You've just turned the triangle into a pair of trousers, so to speak, instead of just one tube. Decisions taken early on will force him down one leg or the other, which is linear again. And being killed for not following the tube is one of the least fun ways to be forced along the tracks.
Some of the principles of good game design, at least according to Brian Reynolds [gamespy.com] (the author of Alpha Centauri) include:
- "bang, you're dead" choices are _not_ fun. If chosing the "good" answer will just get a previously evil player killed, with no recourse, that's just not fun. Even if you have to have an arc that leads to bad consequences, there should be ample warning and a possibility to take counter-measures at each step along that arc.
- choices along the lines of "a piano falls on top of you, jump to the side? (1)Yes, (2) No" are not really choices at all. If you expect everyone to pick option 1 or get squashed if they take option 2, then that's not really a choice at all. You shouldn't have them in a game in the first place.
Choices make sense only if there's some good reason to pick either. E.g., option 1 gets you some money and evil points, option 2 gets you some amulet and good points. That's a choice.
So basically the choices you describe aren't even really choices. The player _is_ pushed down a tube, with no real choice. Only this time in a nasty way. Big improvement, eh?
Re:Sounds like Wing Commander 1 (1)
mcvos (645701) | more than 6 years ago | (#21516509)
If you want to prevent this triangle or "trousers" (somehow I seem to recall the phrase "trousers of fate", but I have no idea where I heard that), what you could do is make it 3 paths with lots of choices to jump from one path to another. One path could represent "good", one is "evil" and one is "undecided", and the decisions where you jump from one to the other are repenting, falling to the dark side, etc.
So instead of:
...
You'd get: ...
1
|\
2 3
|\|\
4 5 6
|\|\|\
1
|\
2 3
|\|\
4 5 6
|X|X|
7 8 9
|X|X|
A B C
You can also do this with only two paths, ofcourse. But at least this way people can have a really different experience when they play "good", "evil", "undecided", "switch from good to evil", "choose evil, then repent", etc.
Re:Well, that's the real problem (1)
mcvos (645701) | more than 6 years ago | (#21516293)
In Vampire Bloodlines, for example, there are 5 different endings possible, but they all consist of pretty much the same set of elements except for some differences in dialogue and a different cutscene at the end. And for some ending you may not have to do some particular quests.
But which endings you can choose, is determined by your behaviour during earlier quests. Were you nice to the Anarchs and fulfill their quests? Then you can choose the Anarch ending. Did you always obey LaCroix? Then you can do his ending. If you do a faction's quests, you can do their ending, unless you screwed them over.
Something I'd also love to see is quests where you play on a different side of the quest. If you side with faction A at some point, you get the "Steal The MacGuffin for Faction A" quest. Do you side with faction B, you get the "Steal The MacGuffin for Faction B" quest. Are you independent, you can still steal it but decide later who to give/trade/sell it to. It should be possible to reuse cleverly designed quests this way.
Ofcourse the holy grail would be a game where high-quality quests are generated dynamically depending on all soorts of subtle balanced in the game, and where your performance during that quest has an impact on those balances. This idea of mine goes back to when I played Elite/Frontier. Some worlds were (according to their description) on the brink of civil war. If you decide to smuggle 100 tons of weapons to that planet, that should have some impact, right? Especially if you can decide to sell it to the rebels. I want a game that takes that sort of thing into account, and if nobody else is going to write it, I will. Some day.
Re:You mean "affect" (1)
Aladrin (926209) | more than 6 years ago | (#21480351)
Learn what words really mean before you try to be a grammar nazi.
Re:You mean "affect" (2, Insightful)
Tetsujin (103070) | more than 6 years ago | (#21480997)
Learn what words really mean before you try to be a grammar nazi.
whoosh....
Re:You mean "affect" (1)
Aladrin (926209) | more than 6 years ago | (#21481801)
Maybe you were a bit too subtle. Sometimes the difference between subtle and oblivious is indistinguishable on the net.
Re:You mean "affect" (1)
Jackmn (895532) | more than 6 years ago | (#21493669)
Re:You mean "affect" (1)
im_thatoneguy (819432) | more than 6 years ago | (#21488351)
The full title for "Mass Effect" should be:
"The resulting Effect of Advanced Space Technology(tm) manipulating the Mass of a given object is people with super powers and an excuse for spaceships to fly around the galaxy faster than the speed of light... by Bioware the company who made Knights of the Old Republic and operates out of Alberta... that's in Canada for you Americans who don't know where that is...Buy it."
I guess someone in marketing decided that the print costs would be too high on all promotional material which charges by the word and just dropped out everything else.
Re:You mean "affect" (1)
FooAtWFU (699187) | more than 6 years ago | (#21480417)
Think of it this way, if you're so inclined: Effecting a reduction in carbon emissions is likely to affect global warming.
Get old school on them (1)
orclevegam (940336) | more than 6 years ago | (#21480277)
Re:Get old school on them (1)
seebs (15766) | more than 6 years ago | (#21480399))
orclevegam (940336) | more than 6 years ago | (#21481289))
seebs (15766) | more than 6 years ago | (#21484141)
Re:Get old school on them (1)
orclevegam (940336) | more than 6 years ago | (#21484385)
DM: uh... what? WHY?!
Player: I don't like the way he's looking at me, and I'm chaotic neutral.
DM: But... he hasn't finished giving you your quest yet.
Player: so?
A new DM would refuse to let him do it, or let him then panic as the campaign falls apart. A seasoned DM would figure out someway to get the players back to where he wanted them (all while acting cool and collected even though he's panicking inside), and a really really good DM planned for it already.
For a good laugh as well as a great illustration of this check out this comic [feartheboot.com], and the following one [feartheboot.com]
Dean Takahashi is a Microsoft mouthpiece (0, Insightful)
Anonymous Coward | more than 6 years ago | (#21480371)
Ending suprise (0)
Anonymous Coward | more than 6 years ago | (#21480557)
Re:Ending suprise (1)
tepples (727027) | more than 6 years ago | (#21480915)
Re:Ending suprise (1)
bWareiWare.co.uk (660144) | more than 6 years ago | (#21516285)
Shoulda Coulda (1)
ShawnCplus (1083617) | more than 6 years ago | (#21480701)
It's been done (1)
Moraelin (679338) | more than 6 years ago | (#21480881)
The trick is that basically people seem to not mind it much if their name only appears in the subtitles. The subtitle can say "I thank you Master Jedi Shawn Cplus, saviour of the universe" while the voice over just says "I thank you Master Jedi, saviour of the universe." Noone seemed to mind it that much.
But as a counterpoint, you could even pull a Gothic 1, where noone asked for your name at all. IIRC the opening conversation with Diego went something like,
Me: "Hi, I'm..."
Diego: "I'm not interested in who you are."
And that was that
Re:It's been done (1)
ShawnCplus (1083617) | more than 6 years ago | (#21480965)
Re:It's been done (1)
Tetsujin (103070) | more than 6 years ago | (#21481651)
Re:It's been done (1)
WobindWonderdog (1049538) | more than 6 years ago | (#21485949)
Suprisingly intelligent science and physics (3, Interesting)
elrous0 (869638) | more than 6 years ago | (#21480739)
I don't know who wrote all these codex entries, but they must have put quite a bit of effort into them. Unfortunately, this isn't always matched with the rest of the game. For example, one of the weapons entries explains the "unlimited ammo" aspect of the game by the nature of the guns themselves. Rather than fire "bullets" as we think of them, the complex computers in each weapon actually shave an appropriate small mass of metal off a large solid block "cartridge," with its mass based on the velocity it will be fired at, the desired effect, the range to the target, and adjusting for other factors like wind, gravity, and planetary conditions. It's a pretty clever way of explaining a lame game convention. Unfortunately, the other game designers must not have gotten the memo about this, because in the equipment section the ammo is shown and treated exactly as if it were conventional bullets in conventional shell casings (the ammo graphics all show bullets and the text all refers to "rounds").
Re:Suprisingly intelligent science and physics (1)
Gravatron (716477) | more than 6 years ago | (#21481323)
Re:Suprisingly intelligent science and physics (2, Interesting)
orclevegam (940336) | more than 6 years ago | (#21481503)
Re:Suprisingly intelligent science and physics (1)
WuphonsReach (684551) | more than 6 years ago | (#21486423)
Her space battles are chaotic, pretty realistic, and deal with the issue that velocity = power. A ship moving at a fraction of the speed of light can do a lot of damage to a ship that is stuck at dock or that has just undocked.
Re:Suprisingly intelligent science and physics (1)
AHumbleOpinion (546848) | more than 6 years ago | (#21498025)
No fancy ass rail guns needed either. Just head towards the target, open a hatch, and have the cook dump some trash.
Re:Suprisingly intelligent science and physics (1)
Pranadevil2k (687232) | more than 6 years ago | (#21482513)
Inherent problem with RPGs (2, Interesting)
Leo Sasquatch (977162) | more than 6 years ago | (#21481637)
But how do you handle level progression when you're supposed to start the game as a fully trained whatever-it-is? In Mass Effect, you start out as a highly-trained uber-warrior who's supposed to be hard as nails, yet you can't shoot straight, your weapons are ineffectual shit, and you'll get beat down by just about anybody until you put some points into your combat skills. Bioware had the same problem with Jade Empire - 15 years in a martial arts school as their star pupil in the pre-game scene-setting, but weedy as hell in the actual game until you spent some points. At least KOTOR and KOTOR2 had reasons in game why you didn't have, or couldn't remember your actual abilities.
It's just that everyone's going on about the brilliant story, and yet completely missing the fact that in order to shoehorn it into a traditional RPG engine, they've had to bend it all out of shape. Why would you make your elite troops buy their own guns with their own money? Because hoarding gold and trading it for stuff has been a mainstay of D&D since pencil and paper days. Why would you issue special forces soldiers with guns that overheat after firing three rounds? Because shitty starter weapons are generic to the classic RPG advancement-based structure. Doesn't fit the storyline at all, but it's a tired old staple of the genre, so just make the player do it.
Even being given the option of having all the character-design points at the start of the game would have been a good idea. Once your character's created, that's who and what he's going to be until the end of the game, because that's who he's become in the last 15 years of special forces training. The events of the game last about a week in game time - tops. What are you going to learn in one week that's going to override everything else you've ever learned?
The actual plot and characterisation, and the sheer scope of the game is fantastic - showing what they can do with a KOTOR-style game when not tied to the Star Wars universe. But the overall framework of the story makes no sense at all, and that just rankles. I'm sure that due to the massive financial success of the game and all their others, they're perhaps not too worried about one gamer's opinion, but everybody else seems to be queueing up to suck Bioware's corporate cock over this damn game, and I feel like the only person who's spotted that nobody could have heard Kane say Rosebud...
Re:Inherent problem with RPGs (1)
Moraelin (679338) | more than 6 years ago | (#21482075)
Go after even tougher guys, and become even better trained.
Fact is, in most armies you'll have an inherent difference between recruits trained back at some boot camp, and guys who've already survived an enemy shelling and assault. Half of the latter will probably wake up screaming for the rest of their life, but be better soldiers while they're on the front line anyway.
You can see the same in all eras, really. From the Roman legions to Napoleon's guard regiment to WW2, there was always a distinction between veteran and fully trained recruits. When Germany in WW1 wanted to make a last ditch effort, it handpicked its best veterans for the special units, they didn't just fully train some new recruits.
So it seems to me that there's always room to evolve and grow.
In a RL firefight, involving highly trained professionals (e.g., SWAT), about 80% of the rounds miss, and some by a wide margin.
Why would you issue your special forces soldiers different ammo than what the gun was designed for, and have it jam? It happened IRL.
Why would you give your troops a bolt action rifle when you know how to make a SMG? WW2 Germany, anyone? Because production capacity wasn't there.
Why would you give your squads a shitty BAR when you know how to make a machinegun? WW2 USA this time? Doctrines, that's why.
Why would you withhold AP ammo from your fucking tanks? WW2 USA again. Doctrines, that's why.
Why would your special troops have shitty one-shot rifles when even savages have repeaters? That's how Custer died.
Re:Inherent problem with RPGs (1)
flitty (981864) | more than 6 years ago | (#21482077)
You create the game you are insisting on, and you no longer have an rpg, you have Doom. A supersoldier who can use any weapon/item/armor, at any time, as long as you find it on the ground.
Re:Inherent problem with RPGs (1)
orclevegam (940336) | more than 6 years ago | (#21482891)
Re:Inherent problem with RPGs (1)
orclevegam (940336) | more than 6 years ago | (#21483195)
After thinking about this a bit more I think there's as much or more potential in this style of game than in a traditional RPG style (game in this case being computer of video, as opposed to pen and paper). Originally the whole idea behind character progression in pen and paper RPGs was to give the player a constantly moving goal. If you set a fixed point (I.E. you only get say 5 levels) once the player reaches that point that's it, they have very little drive to progress unless you give them some sort of reward, and what good is a reward if they don't really have anything to use it on? Sure they may have some uber sword that one hits everything, but what's the fun in that, and how often can you give them uber-sword++ before they start to wonder how it is that there always seems to be some sword out there just a bit better than the last one you gave them and told them was the greatest sword every made.
The original solution of course was to make a character progression chart with effectively no upper bound, that way the goal is always just "get better", effectively allowing infinite play time. This is great in a pen and paper setting in which you can always bring in new campaigns and modules and weave them into your existing campaigns, but somewhat less so in a modern game with a fixed storyline (MMOs being the exception to this). In a video game the players goal is always to ultimately finish the game. It doesn't matter if they do it at level 10, or level 60, ultimately they get to the end, the credits roll, and they get to brag how they did it with such and such completion percent or other. Honestly what's the point of the level grind then? Why even bother? Just give them the points, and let them get to the end however they see fit. I think that style of game, maybe with a nice awards system as has become fashionable as of late, would be an excellent design, and provide plenty of incentive to play.
This style of play would be particularly enticing I think on a game with a really strong back story such as Mass Effect. The goal then being to reach the end, and possibly to receive various endings based on player choices throughout the game.
Re:Inherent problem with RPGs (1)
flitty (981864) | more than 6 years ago | (#21484041)
Of course, my POV is coming from playing probably a total of 15 rpg's (picking from the "critically acclaimed" mostly) and no RP'ing to speak of, so I'm definately not as worn out on the formula as many other fans of RPG's are, and I can see how the Skill-less baffoon becoming the hero of the day is a tired gameplay mechanic.
Re:Inherent problem with RPGs (1)
Rolgar (556636) | more than 6 years ago | (#21483615)
That said, I'd love to see games get away from characters who start puny, which is usually only an excuse to add hours of low level content to avoid being labeled short. A Morrowind or Oblivion that didn't need leveling would still be a great game, because there was so much content, and quests steer the player toward visiting the different locations so they don't miss any of the good stuff. But hours of repetitively using a skill or even paying for lessons which could still take worthless minutes of effort instead of having an option to level up 5 or 10 levels in one visit is just a waste of time and and not fun.
I would also love to drop the use of HP in RPG games, especially in something like KOTOR where one swipe of a light saber or shot with a blaster should kill everyone in the game, regardless of level. Instead, make the weapon either kill or cripple, which gives the player a better chance of a lethal strike on the next attack. Since combat would be more deadly with less chance to correct for getting hit, you have to, within reason, make hits rarer without making them impossible. This would add the illusion of untouchable characters (PC and NPC) that are so good they're impossible to hit and kill, if portrayed correctly, and the winner must have been really good for succeeding in landing the decisive blow.
Re:Inherent problem with RPGs (1)
orclevegam (940336) | more than 6 years ago | (#21483915)
I've actually done this in the past. We decide we wanted to play around with some of the templates and make a band of misfits so to speak, but part of the challenge is making hybrid characters essentially added 5 "virtual" levels to our characters. In order to pull it off we had to scale a level 4 encounter up to a level 6 (level 1 characters, with 5 extra levels due to the racials from the templates). All in all it went off pretty well until we reached the last encounter of the dungeon. Well, the final encounter we went up against a ghost that kept possessing members of our party, and since none of us had anything that could hurt a ethereal it just slaughtered our entire party. It was an example of a good idea that failed to scale properly. Going up against an actual level 6 party it would be likely they would have some magical equipment that would have been useful, but our group had beginning equipment, and it was only the racials that made us more powerful than normal, so we were ill-equiped for this particular situation even though by our calculated level we should have been able to handle it. That being said in a campaign actually designed around the characters rather then having them shoe-horned into it I'm sure that wouldn't have been a problem.
As for the more realistic weaponry, it's interesting in theory, and maybe in the right game would be fun, but for most games would just really frustrate the players. The problem is that in most current games combat is to important an aspect of the game to make it that deadly. Think about how often in modern RPGs your have fights. Now imagine that every time you got into one of those fights there was at least a 50% chance you were going to die. Players would quickly give up and leave. Not to say that I don't see it having a place, but much like our band of misfits, the game would have to be designed around the mechanic in order for it to be playable. It would be excellent in a game that emphasized more realistic actions for example. Do something like start a shoot-out in the middle of the street and in 10 minutes you've got a van of SWAT coming after you. It would provide more incentive to find alternative ways of accomplishing things, such as talking with NPCs to negotiate what you want rather than just shooting anything in your way. Or perhaps leading you to work more on your stealth skills as opposed to just trying to beef up your armor.
Re:Inherent problem with RPGs (1)
Leo Sasquatch (977162) | more than 6 years ago | (#21484925)
The role-playing aspect of it could remain effectively unchanged - you talk to characters, make conversational choices, follow the clues, or miss them if you don't have the skills. Levelling up does not equal role-playing.
As for the time aspect of this - yes you can have a game which focusses on significant events in a character's life - generally that's the point of most media. Your character can become a Spectre within a few hours of play time, but he didn't get there by mailing in his boxtops. This is the culmination of years of training and experience, all of which is laid out in the backstory, but not represented in the character you get given to play with.
Re:Inherent problem with RPGs (1)
mcvos (645701) | more than 6 years ago | (#21516681)
Starting as a badass does in no mean require your stats to be maxed out. In a well-designed system, there should be plenty of room to advance from "badass" to "better badass", "even bigger badass", and "badass with more diversity". Plenty of paper RPGs do that. Why can't CRPGs? Because the creators are only familiar with CRPGs or at best D&D, that's why.
How about a super soldier who's an expert with his preferred firearm, but has only limited experience with random weapons he finds on the ground? What about someone who is competent enough to do (and have done) some really hard missions, yet is still capable of failing them?
Re:Inherent problem with RPGs (0)
Anonymous Coward | more than 6 years ago | (#21483893)
However, I think some of it is at least somewhat plausible. Regarding equipment, look at how many American soldiers' families had to chip in to purchase body armor for their loved ones. Even in one of the wealthiest nations, soldiers are buying their own gear.
And, my dad was a veteran. He lived in Korea for about 2 years between 1951 and 1953. During that time, he was only killing people for a small part of it. Yet, the rest of his life was shaped by those specific few experiences (nightmares, explosive rages of violence, inability to be part of society, fearlessness towards police and authority).
In Mass Effect, the main character is a war hero, yes. But, he's going beyond participation in a pitched battle, now. He's taking on some of the most evil badasses in the galaxy under the mandate of an interstellar confederation. He is not like other men anymore. He's an uber mensche who will experience constant fighting against overwhelming odds. Heck, it takes a few hours to get "Spectre" status, and I think it's fine in the context of the fantasy world.
Re:Inherent problem with RPGs (2, Funny)
nutshell42 (557890) | more than 6 years ago | (#21485423)
Re:Inherent problem with RPGs (1)
mcvos (645701) | more than 6 years ago | (#21516623)
And all that while there are plenty of excellent pen & paper RPGs that do not require you to start as weak nobodies with crappy equipment. In GURPS, for example, it's not uncommon to start your fresh character as a highly trained specialist with excellent equipment. And yet there's still lots of room for improvement.
The problem is that many CRPG experience systems have very coarse granularity and a low ceiling, and try to emulate the Star Wars/LotR-style from farmboy to hero story. Which is fine when the story is about a farmboy who becomes a hero. But if the story is about highly trained professionals who get even better at what they're already good at, you need more diversity and more room to improve even very good skills, and not make each level-up turn you into a superman compared to the monsters that could easily kill you just a moment ago. In other words: a shallower power curve. | http://beta.slashdot.org/story/93699 | CC-MAIN-2014-15 | refinedweb | 7,042 | 75.74 |
Your Account
by M. David Peterson!
And while I understand not wanting to break existing clients, if you want to take advantage of Feed Threads, known precedence problems arise when clients support all present extensions.
Of course, Dare is a client developer, and as such, he’s understandably going to be grumpy every time someone creates something new that his code will need to support… but I think in the case of Feed Threads, the intermittent breakage is worthwhile.
This is a multi-pronged issue, and you can’t really take any singular stance about it.
Thanks for providing your insite. I recognize the fact multi-pronged issues can and easily do exist. And I DEFINITELY understand and agree... The Feed Thread Extension has been thought through from beginning to end, discussed in the community via public forums, and the result is that it provides a MUCH better overall interface for providing a way to communicate, and to keep track of that communication for a given topic/thread.
I'm not sure I know what all of the issues involved here are, and in fact I can say for certain that I don't based on the above post. While its probably enough to state "there's more here than meets the eye" if you have a chance and can provide any extended information, I'm sure quite a few folks, including myself, would appreciate the extended information provided.
Either way, thanks for taking the time to comment!
wfw:comment - provides a link to the comments for the entry.
FTE - provides a link to one or more sets of comments to an entry, these sets could be alternate representations of the same comments, or different sets of comments, you'll have to guess.
slash:comments - provides a count of the number of comments to an entry
FTE - provides a count of one or more sets of comments to an entry, problems as above. This count attribute doesn't use Atom extensibility points, so is liable to be dropped by Atom infrastructure (Windows Feed Platform is a concrete example), but apparently people won't mind the data-loss
wfw+slash - fits the Atom extensibility model, despite pre-dating it.
FTE - doesn't fit the Atom extensibility model, despite being designed around it.
To be fair, thr:in-reply-to is ok.
Does this all boil down to which approach has the fewest (boo! hiss!) namespaces? The XML community would get a lot more done if they spent more time thinking about interoperability, and less about subjective aesthetics, but I suspect that this is the risk of XML having no real-world model behind a document. In OO, RDBMs, and RDF people can have reasoned debates about design. XML design is like watching adults play with Fuzzy Felt.
Lets see if I can stop laughing about the fuzzy felt comment long enought to follow-up your comment. :D
I must admit that the points you have brought out seem pretty painful to the "FTE is better" argument. Of course, I did see the tail end of the discussion on the Atom list, and it *seemed* to end with good vibes based on some last second adjustments based on community preferences of the usage of the @ref and @id attributes (if I'm remembering correctly... would need to check the archives to be certain as to if it was these two attributes for sure.) I guess maybe the good vibes were not as wide spread as I assumed.
I need to stop doing that (assuming :)
So then this conversation gets more interesting. And it seems to me that if there are problems with WTE, then maybe discussing them in the more wide open blog-based "forums" here on OReillyNet/XML.com will certainly allow for folks who would otherwise not participate in the mailing list to participate in a place that might feel a little more neutral. Not that I have anything wrong with the mailing list, but when you know who the folks are that your message is being sent to it can sometimes be a bit intimidating. Not the bad, intentional type intimidation, just the kind that makes you think twice about posting to the list.
Of course, this has never stopped me from sharing my own views on various matters, but there are times where I certainly wish it would... Such is life for a punk a$$ hacker with an attitude such as myself. :D
Ultimatelly my hope is that if problems exist, they simply get fixed. Life is simple when we live in bubbles.
But bubbles have a tendency to pop... Not always a good thing.
Thanks for your additional insite!
Anyone else care to take it from here?
wfw:commentRss
thr:in-reply-to
wfw:commentRss allows you to associate a feed for comments with an entry. That means your comments must be a flat list, and it also means that you need to poll one feed per weblog post, so it’s infeasible to stay current with all threads on a weblog that has had hundreds of posts over a couple of years. Theoretically, you can implement nested comment threads with wfw:commentRss – if each of the posts in the comment feeds has a comment of its own. Can you say combinatorial explosion? I have often wondered what the guy who wrote that spec was thinking; how could anyone have missed the obvious scalability problem of that approach? Basically wfw:commentRss has exactly one use case.
In contrast, the FTE allows you to have a single comment feed that contains the replies to all of your entries while still associating each comment with the right entry – or, in the case of nested threads, with the right entry-or-comment. You can even put both your entries and your comments in a single feed. You can also continue doing the per-entry comment feed thing. Or you can do several of those at once. You can do it pretty much any way you want, because the granularity of thr:in-reply-to is entry-to-entry, not entry-to-feed.
Robert was vociferous about the thr:count attributes for the comment feed links, but if you consider that an entry may have any number of replies distributed among any number of resources, and any of these replies may appear in any number of these resources (a case which can be disambiguated using the Atom ID on the replies – this is Atom, remember?), then it makes a lot of sense. This thing allows for a lot more use cases than just blogs with flat comment list – you can go so far as to completely replicate the semantics of Usenet, distributed news feeds and all, which takes us full circle, but anyway, let’s not veer into that.
thr:count
Okay, so in Dare’s post I just saw he mentioned annotate:reference. I had never heard of that one before. How many clients support that? And how much work will it be to convince any single client developer who has no support for any of these to support just the FTE (and all of it), vs convincing them to support slash plus wfw plus annotate (and then you’re still not covering all of the semantics the FTE allows) without quitting half-way through?
annotate:reference
slash
wfw
annotate
This is pointless reinvention on the same level on which Atom was pointless reinvention of RSS.
I don't think I could argue against your points even if this was my all out intention (to argue for the sake of arguing)... which its not.
It all seems pretty straight forward to me that this is something that needs to happen.
From a personal perspective, there are two things I hope to see happen:
1) Atom become the primary data feed for anything that goes beyond just simple, one way syndication, and even then I think there are enough issues just with this portion of RSS 2.0 to warrant promoting Atom as the defacto base standard in which RSS feeds can implement atom:element* to fix the areas that are broken, without breaking those in which have built their brand against the RSS name (which I personally have my own feelings how to gain the best of both worlds in this regard, but its not something worth pushing as in the end its the quality of feed that matters most) There are certainly enough reasons and references to make this a pretty straight forward process.
2) Have the same group of folks that built Atom use the proven process of getting the right people into the right "room" in which anyone with internet access can join in (just like it is now) and build the necessary extensions that will cover the areas specifically and intentially left out of the Atom spec (like the Feed Thread portion) such that there can be one core base of primary extensions that cover a 95+% use case scenario such that within a years time the vendors can build in support for these extensions and feel confident that in doing so they won't be faced with problems down the road when its suddenly discovered "oh, this won't work for that, so now we need to break our apps again to implement a proper fix."
To me, the reason I attached myself to the use of Atom was because it was pulled together to fix problems by folks with a proven history of fixing problems and building great software.
If that same group is willing to employ their services, once again at no cost, to work on the extension areas that need work...
Well then its obvious to me its time for folks to simply get out of the way, and let them do their job.
I'll update this post, to mention both your comments, as well as James comments as MUST READ.
Thanks for adding all of this additional insite!
Thanks again for helping me, and hopefully others as well, gain this understanding!
My apologies! I meant to add a follow-up to your comments to the same comment box as that in which I responded to Aristotle.
Your point regarding the importance of the specification process, as well as the final result of that process is absolutely spot on. It seems absolutely NUTTS to me when I hear people make comments that a well written, well developed specification is not something that is all that important. But, as made obvious in a post to my personal blog last August > < that's exactly the attitude that permeates the tech landscape by people who simply don't understand that a specification isn't something designed to bind, limit, or in other ways hold back the ability for any given entity (personal, corporate, sector, etc...) to make progress. As you point out:
>> For many potential implementors, a stable spec published via an organization with clearly defined IPR rules and community review processes is not just a convenience, it is a requirement <<
Real progress, growth, innovation, etc... comes when folks have the ability to minimize the risks involved with EXTENSIVE investment into new areas of technology. The way to minimize the risk, of course, comes in the form of a specification, in which they can use to build software, hardware, or other tangible items against a common interface which ensures a certain level of interop, and at very least enough common ground such that the overall costs of building the base foundation for these technologies can be "shared" across a larger base of manufactures.
Of course the long term reduction in cost of goods can be measured with much greater precision when well understood formulas can be implemented because of an understanding that "with every increase in production of X units, the overall cost of goods will be reduced by Y". With a specification, the increase of X is in FAR GREATER proportion than without.
With all of this said... I don't think I could agree with your point more than I already do. Of all the variables that go into the formula that quantifies the rate of potential progress in any given sector/society, the existence of a well written and designed specification in which contains input by ALL parties who plan to work against this spec is the final multiplier of a complex equation in which the lack of a specification is ~0, the presence of a specification [range 1-n] where n represents the commitment of parties to build against this same said spec.
Why people don't get this, I will NEVER understand!
Thanks for taking the time to add your additional (and obviously, authoritative) insite to the overall conversation!
The issue of whether or not it is good for interoperability to re-implement (and extend) the features of wfw+slash with FTE is interesting, but I am more interested in discussing the quality of FTE itself:
Why is replies implemented as an atom:link with non-standard attributes, when thr:in-reply-to is implemented as an extension element? Using non-standard attributes on atom:link is an interoperability issue that can be fixed simply by replacing the element with an extension element. I don't see any costs in doing this. Is atom:link used just because of subjective prettiness; does this trump interoperability? I refer back to my Fuzzy Felt quip.
I feel strongly about this. Using non-standard XML attributes on Atom elements is even more damaging to Atom, than QNames in content is to XML. mnot's quote: "Putting QNames into your XML content is like using TCP packets as delimiters in an application protocol.", describes the problem well. It binds Atom entries, feeds, links, and authors to the XML document that they were found in and prevents applications, APIs and frameworks from working with these concepts at a useful level of abstraction.
>> Anyone want to take this and run with it?
Hopefully someone will pick this up and we'll see where it goes from there.
I don't have the time to search the archives right at this moment, but if you happen to have a link or two in regards to this discussion I would certainly appreciate it as this seems like something that certainly justifies a deeper understanding as to the reasoning behind this particular decision, which to be honest I didn't realize was the case. (note: I need to read the spec again, but are the attributes in their own namespace? If yes, if not mistaken this is perfectly legal, if not looked upon as something to avoid if at all possible.)
That said, I would hesitate to suggest that the reasoning goes beyond something that could be considered reasonable, given the folks in whom I am aware of that were involved with the development. But as mentioned previously, I only witnessed the very tail end of the discussion, and in no way participated as I was too far out of the loop to be able to even comment, much less join in the debate.
Of course, (again, as previously mentioned) that hasn't been true in ALL cases... I tend not to worry too much about jumping in head first into any given conversation, but generally speaking this will take place only when the topic at hand it something that I do have a reasonable amount of experience with and/or overall understanding, even if the overall subject matter is part of an ongoing discussion in which I've arrived a bit late to gain full context, something thats bitten me more than enough times to suggest maybe I should avoid such things if at all possible. Then again, there are times when the context is the problem in and of itself, so the bites and the bites back tends to even themselves out over time.
What this has to with anything... to be honest... I'm not really sure. I guess I'll leave it, but this is obviously not something to connect with the overall conversation.
Ironically, the primary reason for using link for "replies" is because it makes very little sense to duplicate the function of the link element. I considered a thr:replies element. Ultimately, it would have looked and acted darn near identical to the atom:link element (with attributes like type, href, hreflang, etc). One needs to consider whether or not it makes sense to introduce a new namespaced extension element that duplicates the basic function of atom:link just to support the addition of two *optional* and *purely advisory* attributes.
The way I read the spec, Atom has two levels of extensibility. The first is defined by Section 6 of RFC4287. The second is defined by XML. RFC4287 allows undefined attributes and undefined content on the link element. This means that unknown attributes and elements MAY appear but aren't covered by Section 6. Pure RFC4287 implementations may or may not choose to support such extensions. RFC4287 implementations that also claim to support the Feed Thread Extensions should likely be expected to support 'em. Publishers that choose to use FTE need to be aware that not all clients will be able to do anything with the thr:count and thr:when attributes. That's ok.
While I have heard others suggest that adding namespaced attributes is something you should avoid, and instead use a completely new namespaced element, I have found that the arguments have leaned more towards "just cuz' I prefer to work with elements whos attributes all belong to the same namespace of the containg element" instead of performance related issues, or other equally valid concerns. While I can recognize that a it doesn't always look 'pleasing to the eye' this tends to be the case when someone chooses to implement a namespace extension that contradicts what would look pleasing all by itself on a plane white sheet of paper, much less contained within the opening and closing angle brackets of an element.
I'll leave plenty of room for someone who feels theres more to it than this to provide extended reasoning, but for now I would have to side with you on this as it takes less processing code to handle the additional two attributes to then use the existing atom:link code as is, than it would be to add in the extended code base to process the exact same thing -- which would, of course, require definining a link element as part of the FTE spec, which when you think about all of the constructs and rulesets that apply to atom:link, theres obviously a significant amount of overhead just to handle something thats already within scope of the containing atom document.
Of course, dependent on the processing language used, the actual amount of code needed to handle the addition of a namespaced element or attribute is not really all that much, but the spec piece of this alone is enough to justify this, regardless of the fact that the additional code necessary to handle the processing would be minimal.
I'd be interested to see if others have strong opinions that suggest that a namespaced attribute that differs from the namespace of its containing element holds more potential problems than I am allowing credit for, but if anyone does take up the challenge, instead of using theory, use code. My guess is that if the code suggests performance problems, between myself, and various 'friends of the family' we can find ways to fix that problem in a jiffy :D
Oh, and Javascript code that walks the DOM doesn't count. If this were to be your 'proof', your problem has nothing to do with namespaced attributes, and everything to do with your insistence that the code presented even qualifies as code, much less something that highlights the problems of using namespaced attributes.
Regarding the 'wfw+slash'; I realize that this may sound like a silly thing, but to me the use of the slash namespace is the problem. When you're working with production systems in a competitive marketplace, using a 'brand name' within a code base in which your customers both can and more than likely will actually look at from time to time, using 'brand name extensions', especially if you just so happen to consider slashdot a competitor, which given the primary focus of slashdot in general, can be just about anybody they decide to trash-n-bash on any given day. Of course, just as much praise can be found their as well, but my guess is that there are enough folks that have been slammed by the slashdot crew to suggest that in and of itself is going to cause people to frown upon its usage in a production system that their name is attached to.
Again, this probably sounds a bit ridiculous, but my guess is the reality is probably something close to this, if not spot on for a lot of different companies out there.
NOTE: To be honest, I cant even say for sure if the slash extension is related to slashdot, although it seems to me that last time I looked through the various docs the connection was obvious. Even still, theres an association thats made regards of any actual connection. So unfortunately, no matter how you look at it, the adoption rate as web feeds continue to move even further away from the early adopting slashdot crowd, is going to decrease for seemingly silly, yet very real reasons.
Forgetting the specifics of FTE for a moment, I'll just answer your question, and explain my problems with namespaced attributes in Atom:
In Mark Nottingham's post about the XML Infoset, he describes 3 approaches to using XML. I strongly prefer staying away from the complexity of the Infoset (approach #1), and instead basing applications around a reusable model that can be converted to and from XML (approach #2). This way people can work with Atom entries in terms of Java classes, database tables, or whatever, rather than always be required to work with the XML. One of my goals in participating in the Atom WG, was to ensure that the spec was clear enough that Atom (including extensions) could be represented in some form other than Atom XML without any data loss.
Atom doesn't require a document to be valid according to a schema or DTD, and in any case, foreign namespaced attributes are specifically allowed on any atom: elements by the RNG, they are just "undefined".
Namespaced elements on the other hand are regarded as extension points to Atom: properties of the feed, entry, or person depending on where they appear.
When you start adding undefined attributes to an Atom document, you get something that can only be represented in XML, and can't be represented in the simpler entry/feed abstraction anymore. So you basically prevent everyone from working with nice Atom APIs, and from storing these attributes in their database schema. The abstraction is made to leak, and everybody suffers.
Enough of the theory: imagine an Atom consumer (such as an Atom Protocol server, or an Atom parsing API), that stores entries in Java classes, database tables, a legacy CMS, or anything else that isn't the exact XML file that the entry was received as. A basic implementation might be expected to do some sort of competent job of preserving core Atom properties such as atom:title, and atom:content; a better implementation might preserve some specific extension elements that it knows of; a better implementation might generically preserve extension elements as blocks of XML; but it is really asking a lot for the implementation to preserve the XML document identically to the one that was received.
Windows Feed Platform is a real-life example of an Atom implementation that does try to preserve core elements, and extension elements, but makes no attempt to preserve undefined mark-up, such as foreign namespaced attributes.
Atom doesn't actually define conformance levels for preservation of extensions, so implementations are permitted to do whatever they want, but realistically implementations will preserve Atom mark-up with varying levels of fidelity. The less fidelity that is required to preserve the extension, the more interoperable the extension will be. It would be nice if every APP client, APP server, Atom feed, Atom intermediary, Atom parsing API, Atom storage backend, and Atom aggregator supported every extension as soon as it was conceived, but this "boil the ocean" approach isn't going to happen. I think extensions are an important part of Atom, so the alternative: having as many bits of the infrastructure as possible, provide some generic support for arbitrary extension elements (just as most of the HTTP infrastructure provides generic support for arbitrary HTTP headers), is a better option.
I am away from my office at the moment (@coffee after catching up on some errands real quick) so I didn't see the notification regarding your comment, and am just noticing this now after logging in to the system to write Yet Another Follow-Up based on the Atom syntax mailing list conversation that I just finished reading.
I had actually been "writing" the post in my head while I was running my errands based on your most recent post, only to discover that Aristotle's follow-up which only strengthened what I plan to write. I *HOPE* to keep it short and simple. We'll see how I do :D
I'll post the link to the list when it's ready.
Thanks for the follow-up!
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All trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners. | http://archive.oreilly.com/pub/post/if_its_not_broken_dont_fix_it.html | CC-MAIN-2017-26 | refinedweb | 4,309 | 53.24 |
* Fred L. Drake, Jr. | | 1. Create a new package in the standard library, with the following | structure: | | xml/ | dom/ | __init__ # provides parse(), parseFile(), | # and Document | minidom # Paul's basic DOM 1 + namespaces | # implementation | ??? # driver to load a DOM from a SAX parser? Should be there, I think. Little point in having a DOM implementation that can't load from XML documents. | parsers/ | expat # Python Expat wrapper with namespace | # support IMHO we should use the namespace support that is built-in to expat. Anything else is bound to slow us down. | sax/ | __init__ # provides parse(), parseFile(), and | # some classes from the handler module Whoops! parseFile() no longer exists! We now use the InputSource class instead. | saxutils # pretty much the same as now Probably not. There's a lot of SAX 1.0 legacy there now. That would need to be removed. The basic structure looks good to me, however. --Lars M. | https://mail.python.org/pipermail/xml-sig/2000-June/002841.html | CC-MAIN-2016-30 | refinedweb | 150 | 77.84 |
In this post, we will use React Native, Serverless framework and Upstash to develop a mobile application for viewing and updating a leaderboard.
We will use React Native to develop the mobile application backed by the Serverless framework, which consists of Python functions running on AWS Lambda.
1 - Using Upstash Redis
In a typical leaderboard app, user information and scores belonging to users are needed to be stored. Since all of these data should be sorted by scores, using Redis is one of the best possible solutions.
“Sorted Set”, which is supported by Redis is a sorted data type that enables users to do storing, adding, removing and querying by range operations in a very fast manner.
Sorted set is exactly the thing that is needed for storing, updating and displaying a sorted leaderboard.
1.1 - Getting Started with Upstash
Upstash provides a serverless database for Redis. For more detailed information about how Redis works, please check Redis documentation.
Here are some of the advantages that led us to use Upstash Redis in our example:
Pay as you go pricing system, Pricing
Free tier for storing and operations
Very easy implementation
No need for detailed configuration
In our case, the first step is creating an Upstash account Console. Secondly, create an Upstash database as you wish. Then, it is ready to go!
To get familiar, we can do some operations in CLI, which is provided in the Upstash console.
First, we can start our database by adding a new user with a score to the sorted set, which we set its name as Leaderboard.
ZADD Leaderboard <Score> <User>
Then we can display all user information with its score.
ZRANGE Leaderboard 0 -1 WITHSCORES
We can do these operations on AWS Lambda functions with Serverless Framework to connect Redis to the backend of the app.
2 - Create Functions with Serverless Framework
Serverless is a framework which allows us to work with serverless functions of cloud providers such as AWS, Azure, Google Cloud etc. It is a very powerful tool to implement and manage serverless functions from the user side.
Let’s start by installing and configuring Serverless Framework for AWS. Visit and follow the steps Serverless quick start.
After installation, we have handler.py and serverless.yml.
serverless.yml
In this file, we will define the functions that we will implement. In our case, we will only need to add new users and get the leaderboard to display. Therefore, defining “addScore” and “getLeaderboard” functions should be enough.
functions:
addScore:
handler: handler.addScore
events:
- httpApi: 'POST /add'
getLeaderboard:
handler: handler.getLeaderboard
events:
- httpApi: 'GET /getLeaderboard'
handler.py
In this file, we will implement the functions, which are the codes that will be executed in the backend when a http request is sent by a mobile app as defined in serverless.yml file.
First, we need to import and configure redis, which is the only dependency we have. To add redis dependency to the serverless framework, we need to add the “Serverless Python Requirements” plugin. Run the command,
serverless plugin install -n serverless-python-requirements
Then ensure that the plugin is added to serverless.yml as below.
plugins:
- serverless-python-requirements
For further detail, please visit serverless-python-requirements.
As the last step, we need to create the requirements.txt file in the same directory as serverless.yml. Add the redis dependency to the requirements.txt file as below
redis==4.0.2
Now we can configure our Upstash Redis in handler.py.
import json
import redis
r = redis.Redis(
host= 'YOUR_REDIS_ENDPOINT',
port= 'YOUR_REDIS_PORT',
password= 'YOUR_REDIS_PASSWORD',
charset="utf-8",
decode_responses=True)
After we have finished the Redis configuration, we can prepare our functions that will be called by users.
We have two functionalities.
First one is adding new users and scores to the leaderboard. This is a POST request. Users will send their information inside the body of the HTTP request.
{"score": 15,"firstname": "Jack","lastname": "Thang"}
The function can be implemented as below.
def addScore(event, context):
info = json.loads(event["body"])
leaderboard = "Leaderboard"
score = info["score"]
player_name = info["firstname"] + "_" + info["lastname"]
r.zadd(leaderboard, {player_name: score})
body = {
"message": "Score added successfully!",
}
response = {"statusCode": 200, "body": json.dumps(body)}
return response
We can parse the score and user information from the event parameter, which is provided by AWS Lambda.
By using the zadd function of redis, we can add users and score to the sorted set “Leaderboard”. Example:
Request body: {"score": 15,"firstname": "Jack","lastname": "Thang"}
Response body: {"message": "Score added successfully!"}
Our second function is getLeaderboard. This function accepts GET requests from users and it returns the leaderboard in descending order, which is read from Redis.
def getLeaderboard(event, context):
leaderboard = "Leaderboard"
score_list = r.zrange(leaderboard, 0, -1, withscores=True, desc=True)
body = {
"message": "Leaderboard returned successfully!",
"leaderboard": score_list
}
response = {"statusCode": 200, "body": json.dumps(body)}
return response
Example:
Response body: {"message": "Leaderboard returned successfully!", "leaderboard": [["Jack_Thang", 15.0], ["Omer_Aytac", 12.0]]}
Finally, we can deploy our functions by running
serverless deploy -v
You will see Service Information while deploying. Save endpoints to somewhere to use them again later.
endpoints:
GET -
Now the serverless backend is ready.
3 - Developing Mobile App with React Native
React Native is a framework, which allows us to develop mobile applications for multiple platforms by writing code in Javascript.
To develop mobile applications with React Native, we have to set up our environment and create the project. Please follow the steps to create your first mobile application environment-setup.
In our mobile application, there will be two screens. The first one is the screen where users add a new score with user information.
For the sake of simplicity, we will only request first name, last name and score from the user.
Screen which users submit scores looks like below.
In this screen, when a user enters a score, the application will send a HTTP request to our serverless endpoint
which we saved while deploying serverless functions. The function used in this example is
async addScore(){
if(isNaN(this.state.score)){
Alert.alert("Error", "Please enter a valid score.");
return;
}
if(this.state.firstname == "" || this.state.lastname == "" || this.state.score == null){
Alert.alert("Error", "Please fill in the blanks.");
return;
}
await fetch('', {
method: 'POST',
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
},
body: JSON.stringify({
firstname: this.state.firstname,
lastname: this.state.lastname,
score: parseInt(this.state.score)
}),
})
.then(response => response.json())
.then(data => {
if(data.message == "Score added successfully!"){
Alert.alert("Done!", "Score added successfully!");
}
else{
Alert.alert("Error", "Please try again later.");
}
})
.catch(err => {
console.error(err)
Alert.alert("Error", "Please try again later.");
});
}
As you can see, the POST request body contains “firstname”, “lastname”, “score” keys and corresponding values that we get from users.
If the response that is sent from the backend contains "Score added successfully!", then this means that the request we sent is received and the score is added successfully.
Now, we will design a very simple leaderboard screen. The user can be navigated to the leaderboard screen by clicking the “Go to Leaderboard” button.
Leaderboard screen will look like this.
Sending an HTTP POST request to the following endpoint is the most important thing on this screen.
when the screen opens at the beginning. For this purpose, we can send this request in the componentDidMount function which is invoked immediately after a component is mounted as follows.
async componentDidMount() {
await fetch('',{
method: 'GET',
headers: {
Accept: 'application/json',
'Content-Type': 'application/json'
}
})
.then(response => response.json())
.then(data => {
console.log(data);
userlist = data.leaderboard;
this.setState({reRender: !this.state.reRender});
})
.catch(err => console.error(err));
}
Complete source code of the application is available upstash-react-native-project
Conclusion
In this post, we developed a mobile application for the leaderboard which is backed by Python functions running on AWS Lambda through Serverless Framework. We stored our leaderboard inside Upstash Redis.
There are so many things that can be done with Upstash. Building a leaderboard application using Redis is just one of them.
I hope this post helps you all! | https://blog.upstash.com/serverless-react-native | CC-MAIN-2022-05 | refinedweb | 1,338 | 58.89 |
An Introduction to Python's Collections module
An overview of 5 important container objects from the collections module.
Python provides a lot of built-in data structures, such as
list,
set,
dict, and
tuple. The collections module provides a set of special containers that extends the functionalities of these basic data structures.
Let’s look into some of the important container objects from the collections module.
Table of Contents
1. NamedTuple
Python tuples contain a list of immutable values. The namedtuple() function is used to create a NamedTuple, where the values are attached to a key.
Let’s see how to create a named tuple.
from collections import namedtuple Employee = namedtuple('Employee', 'id name role') john = Employee(id=10, name='John', role='Software Engineer') # Employee(id=10, name='John', role='Software Engineer') print(john)
We can access named tuple values via index as well as by key name.
# 10 print(john.id) # John print(john.name) # John print(john[1]) # Software Engineer print(john[2])
Just like tuples, named tuples are also immutable. Let’s see what happens when we try to change the values of a named tuple.
# AttributeError: can't set attribute john.name='John Doe'
When should I use NamedTuple?
When your tuple object has a lot of elements, using NamedTuple is advisable because you can access elements through their key, which is less confusing than accessing elements with index numbers.
Another case would be when you want to have an object similar to a dictionary but immutable - NamedTuple would be perfect in that scenario.
2. OrderedDict
The OrderedDict extends the functionality of dict. It maintains the order of insertion, so that the elements are retrieved in the same order.
If we insert an item with an existing key, the value is updated but the insertion position remains unchanged.
from collections import OrderedDict employees = OrderedDict({1: 'John', 2: 'David'}) # OrderedDict([(1, 'John'), (2, 'David')]) print(employees) # 1 John # 2 David for id, name in employees.items(): print(id, name) # adding a new item employees[3] = 'Lisa' # updating an existing key employees[1] = 'Mary' # OrderedDict([(1, 'Mary'), (2, 'David'), (3, 'Lisa')]) print(employees) # 1 Mary # 2 David # 3 Lisa for id, name in employees.items(): print(id, name)
When should I use OrderedDict?
Sometimes, we want to process dictionary items in a certain order. OrderedDict is useful for iterating the
dict elements in the order of their insertion.
3. Counter
The Counter object allows us to count the keys in a sequence. It’s a subclass of dict where the key is the sequence elements and value are their count.
from collections import Counter nums = [1, 2, 3, 2, 2, 4, 5, 1] c = Counter(nums) # Counter({2: 3, 1: 2, 3: 1, 4: 1, 5: 1}) print(c)
When should I use Counter?
When you quickly want to get some idea about the elements in the sequence. For example, how many unique elements there are, which element is present most number of times, etc.
4. Deque
deque is a double-ended queue implementation that supports adding and removing elements from both ends.
We can pass an iterable object to the
deque() method to populate the deque.
from collections import deque nums = deque('12345') # deque(['1', '2', '3', '4', '5']) print(nums) nums.append(6) # deque(['1', '2', '3', '4', '5', 6]) print(nums) nums.appendleft(0) # deque([0, '1', '2', '3', '4', '5', 6]) print(nums) # 7 print(len(nums)) # 6 print(nums.pop()) # 0 print(nums.popleft()) # deque(['1', '2', '3', '4', '5']) print(nums) nums.reverse() # deque(['5', '4', '3', '2', '1']) print(nums)
When should I use Deque?
Whenever you need a double-ended queue data structure created from a sequence, you can use Deque. For example: if you are creating a playing cards game where the players can pick cards from either the top or the bottom of the deck.
5. ChainMap
A ChainMap object allows us to create a group from multiple dict-like objects. It’s useful when we have to work with multiple dicts. The ChainMap contains the maps in a list and they are backed by the original maps. So, if the value in the underlying map change, then the ChainMap value will also change.
When searching for an element, ChainMap searches for the key in all the maps and returns the first found value.
from collections import ChainMap d1 = {1: "One", 2: "Two"} d2 = {1: "ONE", 2: "TWO", 3: "THREE"} cm = ChainMap(d1, d2) # ChainMap({1: 'One', 2: 'Two'}, {1: 'ONE', 2: 'TWO', 3: 'THREE'}) print(cm) # List of Keys: [1, 2, 3] print(f'List of Keys: {list(cm)}') # One print(cm[1]) # THREE print(cm[3])
When should I use ChainMap?
When you are working with multiple dictionaries and you have to search for elements from them, you should use ChainMap instead of writing multiple lines of code to look through the dicts one-by-one.
Author Bio: Pankaj has over 14 years of IT experience and loves working in Python. You can follow him on Twitter to get in touch with him, or learn more by going through his Python tutorials. | https://victorzhou.com/posts/python-collections-module/ | CC-MAIN-2020-29 | refinedweb | 856 | 63.49 |
Daily Coding Problem #2
Ivan
Nov 25 '18
・1 min read
Seeing the first post gained some popularity, here is the second problem
For #2
This problem was asked?
My solution
using System; using System.Linq; namespace Task02 { public class Program { public static void Main(string[] args) { var input = Console.ReadLine() .Split(' ') .Select(int.Parse) .ToArray(); var result = new int[input.Length]; for (int i = 0; i < result.Length; i++) { result[i] = 1; for (int j = 0; j < result.Length; j++) { if (j != i) { result[i] *= input[j]; } } } Console.WriteLine(string.Join(' ', result)); } } }
Explanation
Here I could not think of any better than the naive solution, which works in O(n2) time and you never like square complexity.
Basically for every item in the result array, foreach the input array and check if the index is different from the item's. If they are, multiply the current value of the item times the current input item.
(open source and free forever ❤️)
Why Software Testing is a good career option?
Vikas Arora - Feb 14
Open question. Is it really possible to keep a big project code clean?
David Ibáñez - Feb 14
Given A Row Of Product Cards, Should The Whole Card Be A Link?
Jack Harner - Feb 11
In python 2.7, no division, O(n) time. The tradeoff is using a bunch of memory, if the list is very long.
Or this.
Or with no additional space required:
Nice find :-)
For the first problem I'd loop over the array twice. The first time to compute the total product and the second time to fill in the output array, dividing out each element of the input array from the total product for the corresponding output element.
I'm guessing that your solution is for the follow-up question though :-). If you have logarithms you could use them to convert multiplication and division to addition and subtraction. This is a common trick when working over finite fields.
stackblitz.com/edit/js-xqagwj
I did something very similar to this. I realised quickly that if any of the numbers in the array are repeated, the totals don’t come out right. I had to explicitly remove the element from the input array and then use the reduce function to calculate the product.
HTH
Here's my TypeScript version.
This approach works in O(n) by dividing the product of all elements by
x[i].
O(n) with division, in C#
Solution in Python without division, still in O(n²), but inner loop is only executed n²/2 times:
JavaScript O(n) but with division:
Here is
O(N)without division:
The idea is to calculate opposite partial products and then reduce them. In a language that has a proper
map_reducefunction implemented on enumerables (like Elixir,) that might be done in one step without intermediate variables.
Simple Rust solution:
For follow-up question:
Without being aware of possible constraints on the input numbers, a solution with division is most efficient as it conserves both memory (2 array allocations: input and output) and cpu (2 enumerations of the the array, O(2n) ~= O(n)). This was described by @severinson . Here it is in F#.
To consider a solution without division, understand that we are using division here to reverse a multiplication. An alternative is to choose not to multiply in the first place. But in order to do that, we move to an O( n2 ) solution where we shape each element of the output array as we process the input. Then we can choose to selectively skip multiplication.
Note: This function is "pure", despite using mutation internally.
Part 2 solution, slightly better than O(n2), using a copy to initialize the array, and the inner loop runs 2 fewer times than the outer.
Don't know if the use of Parallel.ForEach is legit, but here's my take using C# and Linq
Javascript solution, no division, O(n) time.
The idea is basically two steps:
I also do a 3rd step to map from that object to the subproducts, but that could be spared if we created a new array during step 1, but still that step would still keep it O(n)
I like the idea, I will be joining it daily. Thanks! | https://dev.to/cwetanow/daily-coding-problem-2-21pj | CC-MAIN-2019-09 | refinedweb | 711 | 63.8 |
> I don't know how you infer any of those from what I said, nor > from the process of introducing features in Python. None of > what you say there rings at all true with anything I've > experienced in Python's core or the attitudes surrounding > development if the language; indeed, quite the opposite. That has been my experience as well, which is why this particular action seems surprising and out of character. > Speaking of irony, you're complaining about namespace > conflicts with a -two character identifier- you've chosen. > Here's a hint: choose better names. Hey, come on now -- developers working on top of an existing language bear nowhere near the responsibility as the language & implementation maintainers. Also, note that the fields of math and science are filled with short identifiers with well-defined meanings -- brevity doesn't mean ambiguous within a given application domain! But regardless, our scripts use "as" in the same way as Python -- to change the effective appearance of an object, albeit in a representational rather than naming space. So if we're wrong in our choice, then so is Python. In addition, note that my choice of a concise method identifier affects only my users. Python's introduction of a new keyword affects the entire Python world code base, so perhaps you should be directing your "choose better names" criticism in another direction? > To match your honesty, I'm somewhat tired with the trend of > some people to hit -one- issue with Python and suddenly lash > out like children over all the same old tired crap. Have you > even looked at multiprocessing? Have you contributed to any > projects working on GIL- less implementations? Or are you > just regurgitating the same bullet points we've heard time > and time again? Multiprocessing solves some problems, but it is unsuitable for high-frequency handoffs of large (in memory) objects between many independent threads/processes -- the HPC object/data flow parallelization model in a nutshell. Furthermore, not every coder has the compsci chops to work on language & VM implementations (my PhD involved programming DNA and directing evolution in a test tube, not parse trees and state machines). But that isn't to say I didn't try: at one point I even sketched out a possible TLS-based GIL workaround for handling the issue without breaking the existing C/API. It was of course shunned by those who knew better...for performance reasons IIRC. > For chrissake, if you cannot do ANYTHING but BITCH about a > change, then you've no damn right to consider yourself a > programmer. Real programmers find solutions, not excuses. Though I have certainly bitched about the threading issue multiple times on mailing lists including baypiggies and python-dev, bitching is not the only thing I've done. Having come to grips with my own coding limitations, I also offered to contribute financial resources from my own Python-enhanced business in support of GIL-removal -- before Python 3.0 was finalized. Unfortunately, no one responded to my offer. Even today, I am indirectly proposing the solution of "as" not being a reserved keyword since it has worked just fine for years without it. Yes that's late, but I didn't see this particular trainwreck coming (since it is not actually our current code which breaks, but rather, quantities of code created years ago but which must still run with fidelity into the far off future). Installing a Python macro preprocessor is another after-the-fact possible solution which may bear further investigation... Also today, I am proposing a pragmatic general solution for projects like ours in addressing both the 2.6/3.0 compatibility and threading situations. Specifically: deliberate migration away from C/Python and on to alternate VMs which happen to support Python syntax. Obviously none of my past efforts yielded fruit -- but it is wrong and unfair of you to assume and accuse me of not trying to come up with solutions. Solutions are virtually the entire game! > > And if so, then thank you all for so many wonderful years of effort > > and participation! > > You're welcome. Don't let the door hit you on the ass on your way out. But who's leaving who exactly? Surely a language as beautiful as Python will easily transcend the limitations of its flagship implementation (if or to the extent that such an implementation cannot keep pace with the times). That's all well and good -- it may even end up being the next great leap forward for the language. I believe Guido has even said as much himself. Warren | https://mail.python.org/pipermail/python-list/2008-December/473184.html | CC-MAIN-2014-15 | refinedweb | 767 | 61.46 |
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With „ATV Quadracer Vol.2“ you can show your skills on different terrains.
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Simulates 3D vehicle turning maneuvers on surface and mesh object terrains.
CoastalWare Freeware
It can build huge terrains, add roads and foilage.
Tricky Software 140 Shareware
You have to guide Armado safely through dangerous terrains.
1 iCube R&D Group 62 Commercial
3DS Max plugin to generate topographically accurate terrains.
Non-reviewed
Reallusion Inc. 7
Reallusion Inc. 2
Reallusion Inc. 1
Articles of interest› All articles | http://softwaretopic.informer.com/import-terrains-to-iclone/ | CC-MAIN-2018-17 | refinedweb | 287 | 51.65 |
ofTheGetting Started
Let’s go through how to add server-side rendering to a basic client rendered React app with Babel and webpack. Our app will have the added complexity of getting the data from a third-party API.
Editor’s note: This post was from a CMS company, and I got some rather spammy emails from them which I consider highly uncool, so I’m removing all references to them in this article and replacing with generic “CMS” terminology.
import React from 'react'; import cms from 'cms'; const content = cms('b60a008584313ed21803780bc9208557b3b49fbb'); var Hello = React.createClass({ getInitialState: function() { return {loaded: false}; }, componentWillMount: function() { contentAdding Server Side Rendering
Next, we’ll implement server-side rendering so that fully generated HTML is sent to the browser.Fetching data before rendering
To fix this, we need to make sure the API request completes before the
Hello component is rendered. This means making the API request outside of React’s component rendering cycle and fetching data before we render the component. cms from 'cms' import Transmit from 'react-transmit'; const content = cms( contentGoing.
Just wanted to point out that technically, the user will still see a “white page.” When they hit your domain the user still has to wait for the request to be made to your server, and then for your server to make the request to the API, then the data gets sent back to the user. The user sees nothing on their screen during this time. If the request to the 3rd party api is slow, I think it would actually be a better experience to return your application code from a CDN so your empty UI can be shown as soon as possible, and then at least you can show a spinner to the user while you wait for the 3rd party API.
I agree, by the way if the concerned api is on the same server the request might be very fast, which is a good point for server rendering :)
The problem of your solution is the empty UI which is pretty bad for SEO.
I think on app with many API requests with heterogeneous response time we must make a mixin of server side requests and client side request, with priority to requests that are essentials to the SEO and/or UI’s top layer in server rendering.
If you’re concerned about the extra round trip for the server to return data from a 3rd party service, you can always render the UI on the client first sans the 3rd party component (possibly with a temp spinner). Defer a client request for DOMContentLoaded or the onload event to request the server to do the transaction. There’s no getting around network delays (unless you don’t use the network, which would be my answer for this use case ;), but I can’t see why you can’t shuffle them so they occur at any point you like.
Episode 15 of Front End Center (paid only) has a video called “The Hidden Costs of Client-Side Rendering” that goes into all this as well, with a different React-based lib for static HTML rendering. Fascinating topic and I’m glad people are taking it seriously and taking it on from different angles.
SEO is always a prime reason to perform server-side rendering. However, if the load time is a concern would it not be beneficial to employ a form of client-side caching for your application data? Service Workers address this issue in addition to saving data bandwidth by not requiring all the application data on each initial page load.
Even though iOS has been slow to the party for Service Workers, the server-side rendering would still give you a bit of a speed boost, while Android and PC users would see a significant boost to the response times. In addition, Service Workers would open the door to the offline use of an application as well as enhanced native mobile functionality.
Just a note but you should not be calling an API in the componentWillMount ..if your call would return an error you would have a hell lot of fun :)
Hi chaps, screw all that work and go with a service which does it all for you:
Pre-render
Host
Smile
I was part of the beta, and I know the guy would be so please if the community took hold of this and ran with it!!
SPAs are an atrocity to the Web. SSR if you like but you’re just adding complexity to your codebase when you should’ve been building with PJAX to begin with. Teehee. | https://css-tricks.com/server-side-react-rendering/ | CC-MAIN-2022-40 | refinedweb | 773 | 61.4 |
C
Controls Styling
Customizing a Control
Sometimes you'll want to create a "one-off" look for a specific part of your UI, and use a complete style everywhere else. Perhaps you're happy with the style you're using, but there's a certain button that has some special significance.
The first way to create this button is to simply define it in-place, wherever it is needed. For example, perhaps you're not satisfied with the default style's Button having square corners. To make them rounded, you can override the background item and set the radius property of Rectangle:
import QtQuick 2.15 import QtQuick.Controls 2.15 Rectangle { id: root color: "#d7d1df" readonly property int leftMargin: 10 readonly property int rowSpacing: 14 Button { id: button text: qsTr("A Special Button") background: Rectangle { implicitWidth: 100 implicitHeight: 40 color: button.down ? "#d6d6d6" : "#f6f6f6" radius: 4 } } }
The second way to create the button is good if you plan to use the above button in several places.
For this approach, you have to create a
MyButton.qml file with the content
import QtQuick 2.15 import QtQuick.Controls 2.15 Button { id: btn background: Rectangle { implicitWidth: 100 implicitHeight: 40 color: btn.down ? "#d6d6d6" : "#f6f6f6" radius: 4 } }
To use the control in your application, refer to it by its filename:
Item{ Rectangle { id: root color: "#d7d1df" readonly property int leftMargin: 10 readonly property int rowSpacing: 14 MyButton { id: button text: qsTr("A Special Button") } } }
The third way to create the button is a bit more structured, both in terms of where the file sits in the file system and how it is used in QML. Create the file as above, but this time name it
Button.qml and put it into a subfolder in your project named (for example)
controls. To use the control, first import the folder into a namespace:
import QtQuick 2.15 import QtQuick.Controls 2.15 import "controls" as MyControls Rectangle { id: root color: "#d7d1df" readonly property int leftMargin: 10 readonly property int rowSpacing: 14 MyControls.Button { id: button text: qsTr("A Special Button") } }
As you now have the
MyControls namespace, you can name the controls after their actual counterparts in the Qt Quick Controls module. You can repeat this process for any control that you wish to add.
Creating a Custom Style
Qt Quick Ultralite in general follows the Qt Quick approach to defining custom style.
Differences in styling between Qt5 and Qt Quick Ultralite
- Qt Quick Ultralite currently provides only default style.
- Qt Quick Ultralite supports only compile-time styling.
- Default controls without style used to define a styled controls are located in
QtQuick.Templates.
QUL_CONTROLS_STYLECMake target property must be set to your custom style module's uri
- The style module must be linked to the application CMake target
Default style for controls
To use the default style for the controls, follow these steps:
- Link `Qul::QuickUltraliteControlsStyleDefault` library to your CMake project (see: target_link_libraries).
- Import QtQuick.Controls in the .qml file.
Custom style for controls
To create a custom style for controls, follow these steps:
- Implement custom components for the style based on QtQuick.Templates.
The components in the Templates module have useful baseline functionality and make it easier to create components that end up interchangable with the default style controls.
- Create a QML module for the custom style.
The module consists of .qml/.h source and generated files, a qmldir file and a library. Example:
MyControlsStyle.a MyControlsStyle/ MyControlsStyle/qmldir MyControlsStyle/Button.qml (source file) MyControlsStyle/Button.h (generated file from qmltocpp) MyControlsStyle/Helper.h (source file) MyControlsStyle/Helper.qml (generated file from qmlinterfacegenerator) ...
To use a custom style for controls:
- Link your custom style library to the CMake project (see: target_link_libraries).
- Ensure the custom style QML module is found in the include path (see: target_include_directories).
Note that it should be set to the path containing the module's directories, not to the path containing the qmldir file. If you have
<path>/My/Style/qmldirand want the module uri to be
My.Stylethen set the include path to
<path>.
- Set the
QUL_CONTROLS_STYLECMake target property to your custom style module's uri to make it provide QtQuick.Controls.
In the above example one would use
QUL_CONTROLS_STYLE=My.Style.
- Import QtQuick.Controls in the .qml file.
See `styling` example for reference.
Available under certain Qt licenses.
Find out more. | https://doc.qt.io/archives/QtForMCUs-1.5/qtul-controls-styling.html | CC-MAIN-2021-31 | refinedweb | 723 | 56.96 |
18 May 2010 10:55 [Source: ICIS news]
LONDON (ICIS news)--BP Refining and Petrochemicals (BPRP) has declared force majeure on propylene (C3) supplies from its PCK Schwedt, Germany, and Nerefco Rotterdam, Netherlands refineries, a company source said on Tuesday.
“The forces majeures were declared on Monday (17 May)” the source said.
In a letter to its customers, BPRP said that a gas leak and resulting fire on 15 May had forced it to declare force majeure for the rest of May 2010 to its customers supplied from its PCK Schwedt fluid catalytic cracker (FCC).
The FCC had been down for planned maintenance since 7 April and had been due to restart around 6 May.
In ?xml:namespace>
The PCK Schwedt refinery FCC has the capacity to produce 250,00 tonnes/year of propylene and is key to the inland
The FCC at the Nerefco refinery produces around 150,000 tonnes/year refinery grade propylene, according to the source.
The propylene market in
Spot prices were being assessed at around contract value - €1,000/tonne ($1,240/tonne) CIF (cost insurance freight) NWE (northwest Europe) in the week ending 14 May, according to global chemical market intelligence service ICIS pricing, but were widely expected to firm.
June contract discussions were due to get under way this week; the May contract settled at €1,000/tonne FD (free delivered) NWE.
($1 = €0.81)
For more on propylene visit ICIS chemical intelligence | http://www.icis.com/Articles/2010/05/18/9360312/bprp-declares-c3-forces-majeures-at-schwedt-rotterdam-units.html | CC-MAIN-2015-06 | refinedweb | 240 | 51.21 |
How to add a Custom Cursor in NextJS Application?
What will we build?
We will add a Custom Cursor to our NextJS application. I will be using the custom index file provided by NextJS and add the custom cursor to it, but you can add the cursor to any file by following the same steps.
NextJS Custom Cursor Demo.mp4
Store photos and docs online. Access them from any PC, Mac or phone. Create and work together on Word, Excel or…
1drv.ms
You can find the live demo over here.
Let’s cursor) in the root directory.
This is how your final directory should look:
Next create a file named Cursor.js in your components directory and export a default function based component returning a div with className = ‘cursor’.
Now we will give some styling to this element in our styles/global.css directory:
.cursor {
width: 20px;
height: 20px;
border: 1px solid white;
border-radius: 50%;
position: absolute;
pointer-events: none;
}.cursor::after {
content: "";
width: 20px;
height: 20px;
position: absolute;
border: 2px solid blue;
border-radius: 50%;
opacity: .5;
top: -8px;
left: -8px;
}@keyframes cursorAnim {
0% {
transform: scale(1);
}
50% {
transform: scale(5);
}
100% {
transform: scale(1);
opacity: 0;
}
}.expand {
animation: cursorAnim .5s forwards;
}
In this file the things to note are that on click of the element, we have added a custom class named “expand” to the element so that it gives us an effect on click which you can notice in the demo. All the other attributes of the CSS are self-explanatory.
But now comes the main part, how will we track the mouse and shift our element according to it?
For that we will use the react useRef hook to reference the element and the useEffect hook to add the logic for changing the position of the element and add the CSS class “expand” onClick.
Here is the code to it:
export default function CustomCursor() {
const cursorRef = useRef(null)
useEffect(() => {if (cursorRef.current == null || cursorRef == null)
return;
document.addEventListener('mousemove', e => {
if (cursorRef.current == null)
return;
cursorRef.current.setAttribute("style", "top: " + (e.pageY) + "px; left: " + (e.pageX) + "px;")
})document.addEventListener('click', () => {
if (cursorRef.current == null)
return;
cursorRef.current.classList.add("expand");
setTimeout(() => {
if (cursorRef.current == null)
return;
cursorRef.current.classList.remove("expand");
}, 500)
})
}, [])return (
<div className='cursor' ref={cursorRef}>
</div>
)
}
The things to note here are that everytime we are checking whether the “cursorRef” is null or not. This is because, whenever we use this component in different pages the useEffect hook is run again, which is why we need to discard all the requests made by any null reference of the “cursorRef”. Next thing to note is that we are using a set timeout to remove the expand class again from the element. This is because if we don’t do it, the “expand” class will continously append over the element, resulting in errors, therefore we are removing this class every time our animation gets completed. All the other code is basic JS and self-explanatory.
So now, that we have our custom cursor’s component ready, the next step is to add this component in our index.js file.
The process is same as importing any other component.
First import the component, and then use it the main element:
import CustomCursor from ‘../components/Cursor’
Now add it into the main element of our file:
<main className={styles.main}>
<CustomCursor />
<h1 className={styles.title}>
Welcome to <a href=”">Next.js!</a>
</h1>
.................
Congratulations 🥳, you have successfully added the cursor to your NextJS application.
Conclusion
You can now use this CustomCursor component in any page and add your custom cursor. This way you can add more customization to your pages and make them feel more attractive. The GitHub repository for the code is here.
What Next?
We have just made a simple cursor but you can add a lot of customization to your Cursor and make them look more attractive like adding a delay and infinite heart beating css etc.
Happy Coding :) | http://rushankshah65.medium.com/how-to-add-a-custom-cursor-in-nextjs-application-bd7564cd7b54?responsesOpen=true&source=---------0---------------------------- | CC-MAIN-2021-21 | refinedweb | 667 | 58.38 |
GENLIB_LOSIG.3alc - Man Page
declare an internal logical signal, or a vector of internal logical signals
Synopsis
#include <genlib.h> void GENLIB_LOSIG(name) char ∗name;
Parameters
- name
Name of a signal to be declared
Description
LOSIG creates the internal signal, or the set of internal signals corresponding to a vector description, represented by name. See BUS(3) and ELM(3) for more details on vectors.
The need for declaring signal is mostly felt when one wants to create a consistent vector declaration, for file formats that do not allow partial or multiple declarations, like vhdl. This way, a user can create a vector and access its member the way he wants, but still having an internal consistent form.
- Warning
If a signal is declared with LOSIG, but not used, the resulting file will have an internal node floating. This is not an error from a genlib point of view, so the user must be aware of it.
Example
#include <genlib.h> main() { /∗ Create a figure to work on ∗/ GENLIB_DEF_LOFIG("cell"); /∗ Define interface ∗ GENLIB_LOCON(... /∗ declare buses ∗/ GENLIB_LOSIG("grum[23:0]"); GENLIB_LOSIG("iconection[0:7]"); /∗ Place an instance ∗/ GENLIB_LOINS("no2_y" ,"no3" ,"grum[12]" ,"a9_s" ,"new_no3_s" ,"vdd" ,"vss" ,0); GENLIB_LOINS("no2_y" ,"no4" ,"a12_s" ,"grum[6]" ,"no4_s" ,"vdd" ,"vss" ,0); GENLIB_LOINS("a2_y" ,"a22" ,"no3_s" ,"grum[15]" ,"a22_s" ,"vdd" ,"vss" ,0); /∗ Save all that on disk ∗/ GENLIB_SAVE_LOFIG(); }
See Also
genlib(1), GENLIB_LOINS(3), GENLIB_LOCON(3), GENLIB_BUS(3), GENLIB_ELM(3).
Referenced By
genlib.1alc(1), GENLIB_LOCON.3alc(3). | https://www.mankier.com/3/GENLIB_LOSIG.3alc | CC-MAIN-2020-24 | refinedweb | 242 | 51.68 |
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