message stringlengths 2 17.7k | message_type stringclasses 2
values | message_id int64 0 19 | conversation_id int64 0 1.03k |
|---|---|---|---|
So, students in Gryffindor are supposed to represent bravery. How does Neville represent bravery, to the point in being accepted into the house. I've always thought of his strongest traits being things like loyalty, willingness to work hard, etc, and these things would tend to put him in Hufflepuff. | instruction | 0 | 50 |
First of all, in the first 4 years, it isn't really shown that Neville is NOT brave - the only thing he's really afraid of is his Grandmother and maybe Snape during Potions. With good reason. :)
You may be confusing a lack of confidence/assertiveness with not being brave, but they are not the same (for a good in-univer... | output | 1 | 50 |
This claim was made popular by being said in the movie The Social Network. It exactly says:
> Did you know there are more people with genius IQs living in China than there are people of any kind living in the United States?
| instruction | 0 | 51 |
This claim can actually be tested very easily. Others have done it, e.g. Brian Dickerson: The perils of repeating political nonsense and came to the conclusion that the claim was wrong.
You just need the chance a random person from a large group has a genius level IQ, then multiply it with the number of people in Chin... | output | 1 | 51 |
I am trying to get my program to print out ```"banana"``` from the dictionary. What would be the simplest way to do this?
This is my dictionary:
```prices = {
"banana" : 4,
"apple" : 2,
"orange" : 1.5,
"pear" : 3
}
``` | instruction | 0 | 52 |
As of Python 3.7, insertion order is maintained, so you don't need an ```OrderedDict``` here. You can use the below approaches with a normal ```dict```
Changed in version 3.7: Dictionary order is guaranteed to be insertion order. This behavior was an implementation detail of CPython from 3.6.
source
Python 3.6 and e... | output | 1 | 52 |
Different coffee packets advertise different amounts of 'Robusta' and 'Arabica'? What do these terms refer to, and how does it affect the taste of the coffee? | instruction | 0 | 53 |
* One reason that the taste isn't as good for Robusta is that it has more caffeine compared to Arabica. Which may sound like a positive thing but caffeine carries a bitter taste which makes it an unpleasant drink. In fact the Robusta bean has 2.7% caffeine content, almost double the 1.5% of Arabica.
* Arabica contain... | output | 1 | 53 |
So whenever we want to shoot our flash before taking a photo. we have to charge it first.
What is the point of the charging our flashes? Aren't their power directly supplied by the battery of our camera?
Please answer for the built in flash on the 2000D and the traditional hot shoe Xenon flashes.
Perhaps these hot shoe... | instruction | 0 | 54 |
The peak power at work when a flash is being discharged is extreme.
Example: a classic Metz 45CT (a large but still handheld unit) on full manual power delivers around 90 watt-seconds of electrical output to the flash tube in 1/300s. That means there are 27000 watts at work for a short time.
A 27000 watt lightbulb (BTW... | output | 1 | 54 |
What are some strategies to maintain morale and productivity after massive layoffs? I am not in a managerial role, just a lead role, and am asking for myself and my fellow employees. | instruction | 0 | 55 |
The situation you're describing is tough. Layoffs have a very real impact on both the individuals that are let go and those that remain. I'm sorry you're experiencing this.
Here are some things to consider that may help you and your colleagues cope with the added stress and emotions following a layoff:
* Acknowledge t... | output | 1 | 55 |
Could you please clearly explain what is the difference between correlation and convolution that is done by a filter on an image?
I mean in terms of signal processing definition I know that convolution describes the output of an LTI system, that is if an LTI system produces an output due to convolution with an input s... | instruction | 0 | 56 |
Convolution is correlation with the filter rotated 180 degrees. This makes no difference, if the filter is symmetric, like a Gaussian, or a Laplacian. But it makes a whole lot of difference, when the filter is not symmetric, like a derivative.
The reason we need convolution is that it is associative, while correlati... | output | 1 | 56 |
24601 has developed into being an iconic part of both the Les Miserables book and musical. Was that number special to him, or was it simply a random number he chose (I doubt it)? | instruction | 0 | 57 |
Yes: it corresponds to the date of Hugo's conception.
This is part of a pattern of similarities between the character of Jean Valjean and the author himself: both are of similar age, have similar habits and similarly austere lifestyles, and even share the same dreams. This is according to David Bellos's The Novel of th... | output | 1 | 57 |
Why does Michael Crichton use US Customary measurements in hard sci-fi? | instruction | 0 | 58 |
Crichton used both imperial and metric, depending on the context.
In the course of one paragraph in The Sphere, he managed to use both!
> "Pacific coral grows two-and-a-half centimeters a year, and the object-- whatever it is-- is covered in about five meters of coral. That's a lot of coral. Of course, coral doesn't g... | output | 1 | 58 |
How can horns, most of which have only three buttons, play all their notes? | instruction | 0 | 59 |
Put as simply as possible, horns are tubes. Blowing in special ways makes certain notes sound from those tubes. By changing one's embouchure, those notes start at a fundamental, then gradually go up in harmonics. The first notes (in key C) would be C, G, C, E, G.Those notes are the ones we hear when a bugle is played -... | output | 1 | 59 |
I am a big fan of worldbuilding. A common sight in science fiction is that aliens pretend to be human (For example in Third Rock from the Sun). Obviously if the aliens are advanced enough to disguise themselves as another species, there are much easier, simpler and less expensive methods to destroy humanity, so why els... | instruction | 0 | 60 |
Aliens are alien, without a common background their motives may be incomprehensible.
If we assume that these aliens are Hollywood aliens (ie humans with odd-looking rubber bits stuck on their faces) then there are all of the reasons that humans from one culture spend time in another culture and try and learn to fit in:... | output | 1 | 60 |
I've taken a look at the list of surveys taken on scala-lang.org and noticed a curious question: "Can you name all the uses of “_”?". Can you? If yes, please do so here. Explanatory examples are appreciated. | instruction | 0 | 61 |
The following is an explanation of the uses of the underscore is Scala _ [underscore] magic.
Examples:
``` def matchTest(x: Int): String = x match {
case 1 => "one"
case 2 => "two"
case _ => "anything other than one and two"
}
expr match {
case List(1,_,_) => " a list with three element and the fi... | output | 1 | 61 |
My university usually asks that we book a flight via a travel agent, but the prices he gives me are about $50 higher than the prices I can get by online booking in the flight company's website. Why would a company want me to book a flight via a travel agent if it is more expensive? | instruction | 0 | 62 |
There are several reasons why such internal policies exist:
* Your institution may get a discount on certain services of the travel agent if it buys enough from the agent
* By having a contract with a reasonably-priced travel agent, they make sure that no employee books the flight with a very pricey agent or with a tr... | output | 1 | 62 |
Layman's explanation of encryption backdoors | instruction | 0 | 63 |
There are two somewhat orthogonal concepts in backdooring encryption algorithms:
* The backdoor can be explicit or implicit. An explicit backdoor is one that everybody knows it is there. An implicit backdoor strives at remaining undetected by the algorithm owners. Of course, when there is an explicit backdoor, people ... | output | 1 | 63 |
I have a page where a scroll bar containing table rows with divs in them is dynamically generated from the database. Each table row acts like a link, sort of like you'd see on a YouTube playlist next to the video player.
When a user visits the page, the option they are on is supposed to go to the top of the scrolling d... | instruction | 0 | 64 |
CSS ```scroll-margin``` and ```scroll-padding```
You might want to have a look at new CSS properties ```scroll-padding``` and ```scroll-margin```. You can use ```scroll-padding``` for the scrolling container (```html``` in this case), and ```scroll-margin``` for the element within the container.
For your example, you w... | output | 1 | 64 |
Suppose I have the geographic coordinates of "Saratoga, California, USA" as
```Latitude: 37°15.8298′ N
Longitude: 122° 1.3806′ W
```
I know from here that in the case of latitude ```1° ≈ 69 miles``` and that longitude varies:
```1° longitude = cosine (latitude) * length of degree (miles) at Equator.
```
How... | instruction | 0 | 65 |
It doesn't matter at what longitude you are. What matters is what latitude you are.
Length of ```1 degree of Longitude``` = ```cosine (latitude in radians) * length of degree (miles) at equator```.
Convert your latitude into decimal degrees ~ 37.26383
Convert your decimal degrees into radians ~ 0.65038
Take the cosine ... | output | 1 | 65 |
I have read numerous times that some Norse warriors, upon death, would go in Fólkvangr, while some others would go to Valhalla. How was it decided which warrior would go to which place? Why did the need to have many "paradises" (whatever you many call it) exist?
Citing Wikipedia:
> In Norse mythology, Fólkvangr (Old ... | instruction | 0 | 66 |
The Norse mythological texts record three primary places where the dead were perceived to go: Helheim (Old Norse Helheimr, “the home of the goddess Hel“), Valhalla (Old Norse Valhöll, “the hall of the fallen”), and Folkvang (Old Norse Fólkvangr, “the field of the people” or “the field of warriors”).
But they're indisti... | output | 1 | 66 |
I noticed that there is a binary executable ```/bin/echo``` on my Ubuntu MATE 17.04 system.
I thought, that's odd, because
```$ type echo
echo is a shell builtin```
Cursory testing suggests that ```/bin/echo``` does the same sort of thing as the Bash builtin ```echo```:
```$ /bin/echo foo
foo
$ /bin/echo $USER
zanna
``... | instruction | 0 | 67 |
If you open up a ```bash``` prompt and type in an ```echo``` command, that uses a shell builtin rather than running ```/bin/echo```. The reasons it is still important for ```/bin/echo``` to exist are:
* You're not always using a shell. Under a variety of circumstances, you run an executable directly and not through a ... | output | 1 | 67 |
what's the difference between JavaScript objects, classes and functions? | instruction | 0 | 68 |
As you must already be aware by now there are no classes in JavaScript. Instead functions in JavaScript may be made to behave like constructors by preceding a function call with the ```new``` keyword. This is known as the constructor pattern.
In JavaScript everything is an object except for the primitive data types (bo... | output | 1 | 68 |
In most introductory algorithm classes, notations like $O$ (Big O) and $\Theta$ are introduced, and a student would typically learn to use one of these to find the time complexity.
However, there are other notations, such as $o$, $\Omega$ and $\omega$. Are there any specific scenarios where one notation would be prefer... | instruction | 0 | 69 |
You are referring to the Landau notation. They are not different symbols for the same thing but have entirely different meanings. Which one is "preferable" depends entirely on the desired statement.
$f \in \cal{O}(g)$ means that $f$ grows at most as fast as $g$, asymptotically and up to a constant factor; think of it a... | output | 1 | 69 |
Why is Gaia operating around Earth orbit? Why not send it to Neptune's orbit? | instruction | 0 | 70 |
Well, you thought about the spatial aspect of a parallax measurement, but not about the temporal one.
Gaia's intention is to measure 3D positions as well as 3D velocities. For the distance, you need accurate parallactic measurement, which come in with your orbital period.
For a typical Gaia-star with several measuremen... | output | 1 | 70 |
I have a string representing a unix timestamp (i.e. "1284101485") in Python, and I'd like to convert it to a readable date. When I use ```time.strftime```, I get a ```TypeError```:
```>>>import time
>>>print time.strftime("%B %d %Y", "1284101485")
Traceback (most recent call last):
File ... | instruction | 0 | 71 |
There are two parts here:
* Convert the unix timestamp ("seconds since epoch") to the local time
* Display the local time in the desired format.
A portable way to get the local time that works even if the local time zone had a different utc offset in the past and python has no access to the tz database is to use a ``... | output | 1 | 71 |
In Django, the convention is to put all of your static files (i.e css, js) specific to your app into a folder called static. So the structure would look like this:
```mysite/
manage.py
mysite/ --> (settings.py, etc)
myapp/ --> (models.py, views.py, etc)
static/
```
In ```mysite/settings.py``` I have... | instruction | 0 | 72 |
## Collect static files from multiple apps into a single path
A single Django project may use several apps, so while there you only have one ```myapp```, it may actually be ```myapp1```, ```myapp2```, etc
By copying them from inside the individual apps into a single folder, you can point your frontend web server (e.g.... | output | 1 | 72 |
I am used to thinking of finite-differences as a special case of finite-elements, on a very constrained grid. What are criteria to choose between finite-differences and finite-elements | instruction | 0 | 73 |
It is possible to write most specific finite difference methods as Petrov-Galerkin finite element methods with some choice of local reconstruction and quadrature, and most finite element methods can also be shown to be algebraically equivalent to some finite difference method. Therefore, we should choose a method based... | output | 1 | 73 |
How important is multithreading in the current software industry? | instruction | 0 | 74 |
It is extremely important.
What is more important though is to understand that multithreading is just one way to solve the asynchrony problem. The technical environment in which many people are now writing software differs from the historical software development environment (of monolithic applications performing batch... | output | 1 | 74 |
Is it true that the price of diamonds is based on a monopoly? And who actually runs/owns this supposed monopoly? Is this likely to affect diamond prices if I am interested in purchasing? | instruction | 0 | 75 |
Yes, the De Beers Group of Companies is a diamond cartel that had complete control of the diamond market for most of the 20th century. They still control a sizable portion of the market and their effort at marketing (particularly with the slogan "A Diamond is Forever") has done much to inflate the market for diamonds i... | output | 1 | 75 |
Normal filesystem images can be easily mounted:
```mount system.img /mnt
```
Examined, and modified. But when I try this with a Raspberry Pi system image (e.g. raspbian), I get:
```mount: unknown filesystem type '(null)'
```
And no matter what I try with ```-t```, it won't work. How can I mount this image? | instruction | 0 | 76 |
You can't mount the image as a whole because it actually contains two partitions and a boot sector. However, you can mount the individual partitions in the image if you know their offset inside the file. To find them, examine the image as a block device with ```fdisk -l whatever.img```. The output should include a t... | output | 1 | 76 |
How does immersion passively help with learning a language? | instruction | 0 | 77 |
There are a few reasons why immersion helps you learn a language without you actively trying:
* You encounter the language more often. When you are immersed in a language, you don't go to class and do homework for a few hours a week, but rather use the language the entire day. You depend on the language to survive—to... | output | 1 | 77 |
I have a script, that does not exit when I want it to.
An example script with the same error is:
```#!/bin/bash
function bla() {
return 1
}
bla || ( echo '1' ; exit 1 )
echo '2'
```
I would assume to see the output:
```:~$ ./test.sh
1
:~$
```
But I actually see:
```:~$ ./test.sh
1
2
:~$
```
Does the ```()``` comman... | instruction | 0 | 78 |
```()``` runs commands in the subshell, so by ```exit``` you are exiting from subshell and returning to the parent shell. Use braces ```{}``` if you want to run commands in the current shell.
From bash manual:
(list) list is executed in a subshell environment. Variable assignments and builtin commands that affect t... | output | 1 | 78 |
Adding a new swap file. How to edit fstab to enable swap after reboot? | instruction | 0 | 79 |
These ares the steps to create a swap on a file:
1. Create a large file e.g. with
```sudo mkdir -p /var/cache/swap/ # create a directory that holds the swap file
sudo dd if=/dev/zero of=/var/cache/swap/myswap bs=1M count=4096 # for 4 GByte
```
Of course any other method of creating a file of defined size would do.
... | output | 1 | 79 |
How do I add a validation to make sure the date string being passed to the method is in the ffg. format:
```'YYYY-MM-DD'
```
if it's not, method should raise some sort of error | instruction | 0 | 80 |
The Python ```dateutil``` library is designed for this (and more). It will automatically convert this to a ```datetime``` object for you and raise a ```ValueError``` if it can't.
As an example:
```>>> from dateutil.parser import parse
>>> parse("2003-09-25")
datetime.datetime(2003, 9, 25, 0, 0)
```
This raises a ```Val... | output | 1 | 80 |
When to use UICollectionView instead of UITableView? | instruction | 0 | 81 |
That depends on the requirements. How the application flows determines which type of UI to integrate into the application.
People mainly use the ```UICollectionview``` for creating types of UIs with multiple images shown in a grid. This would have complex logic using ```UITableView```, but with ```UICollectionview```, ... | output | 1 | 81 |
On my branch I had some files in .gitignore
On a different branch those files are not.
I want to merge the different branch into mine, and I don't care if those files are no longer ignored or not.
Unfortunately I get this:
The following untracked working tree files would be overwritten by merge
How would I modify ... | instruction | 0 | 82 |
Safely remove/overwrite only bothersome files
When you want to ```merge```:
```git checkout -f donor-branch # replace bothersome files with tracked versions
git checkout receiving-branch # tracked bothersome files disappear
git merge donor-branch # merge works
```
When you want to ```pull```:
```git fetch
gi... | output | 1 | 82 |
Since long time ago I have been thinking in two problems that I have not been able to solve. It seems that one of them was recently solved. I have been thinking a lot about the motivation and its consequences. Mostly because people used to motivate one of them with some very interesting implications. My conclusion howe... | instruction | 0 | 83 |
The three-body problem is one of the most famous problems in the history of mathematics, which also has an important application in science: it was supposed to explain the Moon's motion, among other things. Enormous effort was spent on this problem by many famous mathematicians of the 18th and 19th centuries. Since New... | output | 1 | 83 |
How do GPS receivers communicate with satellites? | instruction | 0 | 84 |
The first thing to know is the communication is one-way. There's a satellite-to-receiver transmission, nothing going in the opposite direction. So your cell phone doesn't have to find the radio power to send a signal all the way to space!
(exceptions: The decommissioned Chinese BeiDou-1 system - and any products where ... | output | 1 | 84 |
Why is iceberg lettuce bad for rabbits? | instruction | 0 | 85 |
In short, iceberg lettuce is mostly water with little to no nutrient value. A rabbit can fill up on it (because of the bulk), but still need food because they didn't get enough calories, vitamins, minerals, etc.
If you look at the USDA's webpage on iceberg lettuce. You'll notice that water makes up just about 95% of th... | output | 1 | 85 |
How do I open the JavaScript console in different browsers? | instruction | 0 | 86 |
Chrome
Opening the “Console” panel of Chrome’s DevTools:
* Windows and Linux: Ctrl + Shift + J
* Mac OS: Cmd + Opt + J
Note: In addition to the “Console” panel, there also exists a smaller slide-up console which can be toggled via Esc while any of the other panels is active.
Firefox
Opening the “Console” panel in F... | output | 1 | 86 |
I have Ubuntu 10 as the guest OS on a Windows 7 machine. I have been trying to setup shares through VirtualBox, but nothing is working. First, I create the share in VirtualBox and point it to a Windows folder. Then I try to mount the drive in Linux, but I keep getting
```/sbin/mount.vboxsf: mounting failed with the ... | instruction | 0 | 87 |
In order to use shared folder functionality few prerequisites need to be met:
* Make sure that Guest Additions are properly installed on the guest OS.
* Users in a guest Ubuntu must be in the group ```vboxsf``` to be able to access shares.
* Define a directory on the host that will be used in the virtual machine using... | output | 1 | 87 |
What does %~dp0 mean, and how does it work?
I'd also like to know if it is a documented feature, or something prone to be deprecated. | instruction | 0 | 88 |
Calling `for /?` in the command-line gives help about this syntax (which can be used outside FOR, too, this is just the place where help can be found).
> In addition, substitution of FOR variable references has been enhanced. You can now use the following optional
syntax:
```%~I - expands %I removing any sur... | output | 1 | 88 |
Should a tester feel bad about finding too many defects/bugs in the product? | instruction | 0 | 89 |
If this is a medical application you are talking about it is serious stuff. What if the bugs affected real users? Developers would be much less happy if they put in life threat someone or if management has to retire a product or make public excuses. Nowadays it is pretty standard for software having minor bugs, but a m... | output | 1 | 89 |
Millions of colors in the visible spectrum can be generated by mixing red, green and blue - the RGB color system. Is there a basic set of smells that, when mixed, can yield all, or nearly all detectable smells ? | instruction | 0 | 90 |
There are about 100 (Purves, 2001) to 400 (Zozulya et al., 2001) functional olfactory receptors in man. While the total tally of olfactory receptor genes exceeds 1000, more than half of them are inactive pseudogenes. The combined activity of the expressed functional receptors accounts for the number of distinct odors t... | output | 1 | 90 |
Do you bleed to death after your penis is cut off? | instruction | 0 | 91 |
Assuming the person is not taking anticoagulants, it's actually quite difficult to bleed to death from dismemberment of small members (hands, feet, penis, ears, nose, etc). Even large members such as arms and legs are often survivable because the body is very good at protecting itself from blood loss. For example, tran... | output | 1 | 91 |
In Swift, is there a clever way of using the higher order methods on Array to return the 5 first objects?
The obj-c way of doing it was saving an index, and for-loop through the array incrementing index until it was 5 and returning the new array. Is there a way to do this with ```filter```, ```map``` or ```reduce```? | instruction | 0 | 92 |
With Swift 5, according to your needs, you may choose one of the 6 following Playground codes in order to solve your problem.
#1. Using ```subscript(_:)``` subscript
```let array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
let arraySlice = array[..<5]
//let arraySlice = array[0..<5] // also works
//... | output | 1 | 92 |
What's the simplest way to get an environment variable from a docker container that has not been declared in the Dockerfile?
For instance, an environment variable that has been set through some ```docker exec container /bin/bash``` session?
I can do ```docker exec container env | grep ENV_VAR```, but I would prefer som... | instruction | 0 | 93 |
The downside of using ```docker exec``` is that it requires a running container, so ```docker inspect -f``` might be handy if you're unsure a container is running.
Example #1. Output a list of space-separated environment variables in the specified container:
```docker inspect -f \
'{{range $index, $value := .Config.... | output | 1 | 93 |
I am confused about the use cases for both ```InputStream``` and ```OutputStream```.
Please include a snippet of code to go along with your explanation. | instruction | 0 | 94 |
InputStream is used for reading, OutputStream for writing. They are connected as decorators to one another such that you can read/write all different types of data from all different types of sources.
For example, you can write primitive data to a file:
```File file = new File("C:/text.bin");
file.createNewFile();
Data... | output | 1 | 94 |
What is the difference between:
```npm install [package_name]
```
and:
```npm install [package_name] --save
```
and:
```npm install [package_name] --save-dev
```
What does this mean? And what is really the effect of ```--save``` and ```-dev``` keywords? | instruction | 0 | 95 |
The difference between ```--save``` and ```--save-dev``` may not be immediately noticeable if you have tried them both on your own projects. So here are a few examples...
Let's say you were building an app that used the moment package to parse and display dates. Your app is a scheduler so it really needs this package t... | output | 1 | 95 |
pod install -bash: pod: command not found | instruction | 0 | 96 |
Please follow the following steps to install Pod:
1. Open terminal and type:
```sudo gem install cocoapods
```
Gem will get installed in Ruby inside the System library. Or try on 10.11 Mac OSX El Capitan, type:
```sudo gem install -n /usr/local/bin cocoapods
```
If there is an error "activesupport requires Ruby v... | output | 1 | 96 |
I read in the Essential C# 3.0 and .NET 3.5 book that:
GetHashCode()’s returns over the life of a particular object should be
constant (the same value), even if the object’s data changes. In many
cases, you should cache the method return to enforce this.
Is this a valid guideline?
I have tried a couple built-in... | instruction | 0 | 97 |
The answer is mostly, it is a valid guideline, but perhaps not a valid rule. It also doesn't tell the whole story.
The point being made is that for mutable types, you cannot base the hash code on the mutable data because two equal objects must return the same hash code and the hash code has to be valid for the lifetim... | output | 1 | 97 |
Especially in blitz or bullet games, it is possible that a player makes an illegal move, for example castles through check.
* If the opponent does notice the illegal move, then as far as I know the first player is obliged to make a legal move with the same piece, if one exists. What if there are no legal moves?
* Wh... | instruction | 0 | 98 |
This only really applies to over the board games (since online chess servers prevent illegal moves).
In a standard time control game, under USCF rules, when the illegal move is noticed by one of the players, a few things happen. First, the illegal move must have been made within the last 10 moves. If not, then the cu... | output | 1 | 98 |
How to set button click effect in Android? | instruction | 0 | 99 |
It is simpler when you have a lot of image buttons, and you don't want to write xml-s for every button.
Kotlin Version:
```fun buttonEffect(button: View) {
button.setOnTouchListener { v, event ->
when (event.action) {
MotionEvent.ACTION_DOWN -> {
v.background.setColorFilter(-0x1f... | output | 1 | 99 |
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