id stringlengths 16 145 | text stringlengths 1 179k | title stringclasses 1
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cpp_utility/0eQsx6ip1DwJpli1_134_0.txt | But why are we stuck with the keyword? For object declarations I think
it makes perfect sense, even if a similar argument could be applied that
the compiler already knows a constant when it sees one. For functions,
though, it deceptively fails to fulfill its apparent (to the uninformed)
guarantee. | |
cpp_utility/76362_91_0.txt | Copy link | |
cpp_utility/0eQsx6ip1DwJpli1_248_0.txt | Daryle W. | |
cpp_utility/constexprarraysize_50_0.txt | We’d have to make the constraint something like the following (other
constraints omitted for brevity, like making sure the range is actually
contiguous and having the right underlying type): | |
cpp_utility/0eQsx6ip1DwJpli1_88_0.txt |
There's no rationale mentioned there. I can imagine it's in the interest
of standardization, that implementation divergence on this point defeats
the purpose of having a common standard in the first place. But it would
be good to have some kind of indication besides "it was debated and
opposite decision was made." | |
cpp_utility/0eQsx6ip1DwJpli1_204_0.txt | Reply to author | |
cpp_utility/constexprarraysize_67_0.txt |
All this ` constexpr ` machinery, and the best we can do is really only a
little bit better than C. | |
cpp_utility/CanIconstexpranstdar_33_0.txt | A constexpr variable’s initializer must be computable at compile time. The constexpr specifier insists to the compiler this be true. If the compiler cannot evaluate the variable’s initializer, i | |
cpp_utility/0eQsx6ip1DwJpli1_283_0.txt | Sign in to report message | |
cpp_utility/constexprarraysize_105_0.txt | Why were abbrev. lambdas rejected? | |
cpp_utility/constexprarraysize_84_0.txt | But _even then_ , we’re still stuck. We still have what I’m calling the vector
` push_back() ` / ` emplace_back() ` problem (I first pointed this out in
D2089). How can we make all of these work: | |
cpp_utility/0eQsx6ip1DwJpli1_56_0.txt | Delete | |
cpp_utility/76362_5_0.txt | * Product | |
cpp_utility/0eQsx6ip1DwJpli1_82_0.txt | Report message | |
cpp_utility/0eQsx6ip1DwJpli1_209_0.txt | You do not have permission to delete messages in this group | |
cpp_utility/0eQsx6ip1DwJpli1_14_0.txt | # Draft N3690 : Why is reference std::array::operator[] not constexpr ? | |
cpp_utility/0eQsx6ip1DwJpli1_129_0.txt | Show original message | |
cpp_utility/76362_81_0.txt | ### | |
cpp_utility/CanIconstexpranstdar_6_0.txt | The Royal family has been investing a portion o | |
cpp_utility/0eQsx6ip1DwJpli1_8_0.txt | [ Groups ](./my-groups "Groups") | |
cpp_utility/76362_56_0.txt | # constexpr std::array out-of-bounds array index access compiles without
warnings or errors #76362 | |
cpp_utility/76362_12_0.txt | By Solution | |
cpp_utility/cpp_classes_1_5.txt | nt link ](/mwiki/index.php?title=cpp/utility/tuple_size&oldid=152393 "Permanent link to this revision of the page")
* [ Page information ](/mwiki/index.php?title=cpp/utility/tuple_size&action=info)
* In other languages
* [ Deutsch ](http://de.cppreference.com/w/cpp/utility/tuple_size "cpp/utility/tuple size")
... | |
cpp_utility/0eQsx6ip1DwJpli1_36_0.txt | constexpr int baz ()
{
std :: array < int , 4 > i = { 1 , 2 , 3 , 4 };
i [ 0 ]= i [ 1 ]; // error reference operator[] is not constexpr
return i [ 0 ];
} | |
cpp_utility/0eQsx6ip1DwJpli1_28_0.txt | Report message | |
cpp_utility/0eQsx6ip1DwJpli1_145_0.txt | Sign in to forward | |
cpp_utility/76362_111_0.txt | Assignees | |
cpp_utility/0eQsx6ip1DwJpli1_213_0.txt | Show original message | |
cpp_utility/0eQsx6ip1DwJpli1_182_0.txt | ### Daryle Walker | |
cpp_utility/76362_93_0.txt | ### | |
cpp_utility/0eQsx6ip1DwJpli1_130_0.txt | Either email addresses are anonymous for this group or you need the view
member email addresses permission to view the original message | |
cpp_utility/0eQsx6ip1DwJpli1_289_0.txt |
I'm a bit concerned, relaxed constrexpr was voted into the core language more
than one year ago, but library like std::array are not updated yet. | |
cpp_utility/constexprarraysize_23_0.txt | All of these compilers are actually correct to reject this example. The reason
is that in order for ` array_size(param) ` to work, we have to pass that
reference to ` param ` into ` array_size ` \- and that involves “reading” the
reference. The specific rule we’re violating is [ [expr.const]/5.12
](https://timsong-cpp.... | |
cpp_utility/76362_48_0.txt | [ Sign up for GitHub ](/signup?return_to=%2Fllvm%2Fllvm-
project%2Fissues%2Fnew%2Fchoose) | |
cpp_utility/76362_9_0.txt | * Solutions | |
cpp_utility/76362_6_0.txt | * [ Actions Automate any workflow ](https://github.com/features/actions)
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* [ Codespaces Instant dev environments ](https://github.com/features/codespace... | |
cpp_utility/0eQsx6ip1DwJpli1_126_0.txt | Copy link | |
cpp_utility/76362_88_0.txt | Sorry, something went wrong. | |
cpp_utility/constexprarraysize_49_0.txt |
How could we make this work? | |
cpp_utility/0eQsx6ip1DwJpli1_13_0.txt | [ Privacy ](https://policies.google.com/privacy?hl=en_US) • [ Terms
](https://policies.google.com/terms?hl=en_US) | |
cpp_utility/constexprarraysize_12_0.txt | **Update from 2022** : my proposal to address this problem, [ P2280
](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2280r4.html)
(Using unknown pointers and references in constant expressions ), has been
adopted for C++23. | |
cpp_utility/0eQsx6ip1DwJpli1_25_0.txt | Delete | |
cpp_utility/76362_17_0.txt | * [ GitHub Sponsors Fund open source developers ](https://github.com/sponsors) | |
cpp_utility/constexprarraysize_3_0.txt | * [ __ HOME ](/)
* [ __ TAGS ](/tags/)
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* [ __ ABOUT ](/about/) | |
cpp_utility/CanIconstexpranstdar_32_0.txt | Variables | |
cpp_utility/0eQsx6ip1DwJpli1_141_0.txt | Oct 13, 2013, 10:53:46 PM 10/13/13 | |
cpp_utility/cpp_classes_5_1.txt | alue_reference "cpp/types/is lvalue
reference") (C++11)
[ is_rvalue_reference ](/w/cpp/types/is_rvalue_reference "cpp/types/is rvalue
reference") (C++11)
[ is_member_pointer ](/w/cpp/types/is_member_pointer "cpp/types/is member
pointer") (C++11)
[ is_member_object_pointer ](/w/cpp/types/is_member_object_pointe... | |
cpp_utility/0eQsx6ip1DwJpli1_156_0.txt |
The Standards usually change only when someone makes a proposal,
champions it, convinces the committee, and it is adopted. | |
cpp_utility/CanIconstexpranstdar_7_0.txt | Profile photo for David Vandevoorde
David Vandevoorde
C++ committee and direction group memberAuthor has 1.2K answers and 11.1M answer views
·
Updated 3y
Related
How do I use the C++20 constexpr std::vector?
Originally Answered: How do I use the C++20 constexpr std: :vector?
Before I answer that let me remind you of tw... | |
cpp_utility/CanIconstexpranstdar_13_0.txt | Every team is different, so your team might not use Asana exactly like my team does. But every team can benefit from more clarity, coordination, and collaboration at work. Here are f | |
cpp_utility/0eQsx6ip1DwJpli1_193_0.txt | Sign in to report message | |
cpp_utility/0eQsx6ip1DwJpli1_15_0.txt | 571 views | |
cpp_utility/76362_4_0.txt | [ Sign in ](/login?return_to=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-
project%2Fissues%2F76362) | |
cpp_utility/0eQsx6ip1DwJpli1_267_0.txt | Thanks Daniel, | |
cpp_utility/0eQsx6ip1DwJpli1_131_0.txt | to std-dis...@isocpp.org | |
cpp_utility/76362_2_0.txt | Toggle navigation | |
cpp_utility/76362_105_0.txt | **[ dyumin ](/dyumin) ** commented Dec 27, 2023 | |
cpp_utility/CanIconstexpranstdar_8_0.txt | A constant expression: An expression that can be evaluated at compile time and whose value can then be used at run time.
A core constant expression: An expression that can be evaluated at compile time.
To understand the distinction, consider this example: | |
cpp_utility/76362_32_0.txt | ## Use saved searches to filter your results more quickly | |
cpp_utility/constexprarraysize_106_0.txt | ](/c++/2020/01/15/abbrev-lambdas/) [ | |
cpp_utility/CanIconstexpranstdar_1_0.txt | C++17 has so much functionality available at compile time that you don’t need template metaprogramming nearly so often. As long as you stick to recursion, tuples and parameter packs, concatenation, fold expressions and other compile-time constructs, you can do quite sophisticated things with the same template code that... | |
cpp_utility/cpp_classes_4_3.txt | /tuple_element&action=edit§ion=1
"Edit section: Member types") ] Member types
Member type | Definition
---|---
` type ` | ` T1 ` if ` I == 0 `
` T2 ` if ` I == 1 `
### [ [ edit
](/mwiki/index.php?title=cpp/utility/pair/tuple_element&action=edit§ion=2
"Edit section: Possible implementation") ]... | |
cpp_utility/0eQsx6ip1DwJpli1_210_0.txt | Copy link | |
cpp_utility/76362_95_0.txt | Undefined behavior is ill-formed in a constant expression context but in this
case ` return Array[3] ` does not force constant evaluation. The following
would tough: [ https://godbolt.org/z/8E75KcGsM
](https://godbolt.org/z/8E75KcGsM) | |
cpp_utility/0eQsx6ip1DwJpli1_75_0.txt | Reply to author | |
cpp_utility/0eQsx6ip1DwJpli1_200_0.txt |  | |
cpp_utility/76362_104_0.txt | ### | |
cpp_utility/0eQsx6ip1DwJpli1_162_0.txt | Reply to author | |
cpp_utility/constexprarraysize_39_0.txt | constexpr T* begin() const { return ptr; }
constexpr T* end() const { return ptr + size; }
constexpr size_t size() const { return size; }
}; | |
cpp_utility/0eQsx6ip1DwJpli1_235_0.txt | You do not have permission to delete messages in this group | |
cpp_utility/CanIconstexpranstdar_31_0.txt | Let’s examine some aspects of the three places constexpr can be used. | |
cpp_utility/0eQsx6ip1DwJpli1_113_0.txt |
Fast backward to 2003. When the notion of generalized constant
expression function was proposed, there was no keyword; I was confident
that none was needed as long as these functions were required to be
inline. However, various people -- implementers, in particular -- insisted
on a keyword to alert them in advance tha... | |
cpp_utility/constexprarraysize_107_0.txt | Implementing span's comparisons | |
cpp_utility/CanIconstexpranstdar_39_0.txt | Profile photo for Brian Bi
Brian Bi
software engineerAuthor has 4.7K answers and 59.4M answer views
·
5y
Related
Can someone help explain C++’s `constexpr`?
If a variable is declared constexpr, it means that the programmer agrees to accept certain restrictions to ensure that the compiler can evaluate the variable at co... | |
cpp_utility/0eQsx6ip1DwJpli1_112_0.txt |
I am not sure what you mean by this: (1) that you are unaware of how the
constexpr keyword came to be? or (2) that you know the history but you
just refuse to understand it? | |
cpp_utility/0eQsx6ip1DwJpli1_19_0.txt | unread, | |
cpp_utility/constexprarraysize_8_0.txt | # The constexpr array size problem | |
cpp_utility/0eQsx6ip1DwJpli1_223_0.txt | >> ` | |
cpp_utility/0eQsx6ip1DwJpli1_4_0.txt | Help | |
cpp_utility/cpp_tag_2_2.txt | on vocabulary types
| [ pair ](/w/cpp/utility/pair "cpp/utility/pair")
---
[ tuple ](/w/cpp/utility/tuple "cpp/utility/tuple") (C++11)
[ optional ](/w/cpp/utility/optional "cpp/utility/optional") (C++17)
[ any ](/w/cpp/utility/any "cpp/utility/any") (C++17)
[ variant ](/w/cpp/utility/variant "cpp/util... | |
cpp_utility/CanIconstexpranstdar_18_0.txt | constexpr auto sum = srd::accumulate( myConstArray.begin(), myConstArray.end(), 0); | |
cpp_utility/76362_94_0.txt | **[ shafik ](/shafik) ** commented Dec 27, 2023 | |
cpp_utility/76362_23_0.txt | # Search code, repositories, users, issues, pull requests... | |
cpp_utility/constexprarraysize_37_0.txt | constexpr T* begin() { return ptr; }
constexpr T* end() { return ptr + Extent; }
constexpr size_t size() const { return Extent; }
}; | |
cpp_utility/CanIconstexpranstdar_5_0.txt | But this $1 billion estate is nothing compared to the $10 billion that King Charles received tax free, thanks to a clever investment by the Queen into one of the world’s most exclusive asset classes … fine art. | |
cpp_utility/constexprarraysize_2_0.txt | Just a blog about C++ | |
cpp_utility/0eQsx6ip1DwJpli1_178_0.txt | It affects when a function template specialization is instantiated (constexpr
function template specializations may need to be instantiated if they're
called in unevaluated contexts; the same is not true for non-constexpr
functions since a call to one can never be part of a constant expression). If
we removed the meani... | |
cpp_utility/constexprarraysize_38_0.txt | // dynamic-extent: size is variable, needs to store
// both pointer and size
template <typename T>
struct span<T, dynamic_extent> {
T* ptr;
size_t size; | |
cpp_utility/0eQsx6ip1DwJpli1_266_0.txt | > The fact that std::array is applying constexpr to the const overloads
> alone is simply a consequence of the fact that the proposing paper was
> written at a time, where the rules were different and would not have
> allowed that. Fixing the inconsistent difference of constexpr
> non-static member functions versus... | |
cpp_utility/0eQsx6ip1DwJpli1_72_0.txt | ### David Krauss | |
cpp_utility/0eQsx6ip1DwJpli1_296_0.txt | Clear search | |
cpp_utility/constexprarraysize_4_0.txt | __ [ __ ](https://github.com/brevzin) [ __ ](https://twitter.com/BarryRevzin)
[ __ ](https://stackoverflow.com/users/2069064) [ __ ](/feed.xml) | |
cpp_utility/0eQsx6ip1DwJpli1_278_0.txt | Sign in to forward | |
cpp_utility/0eQsx6ip1DwJpli1_91_0.txt | The functions being marked as constexpr need to be evaluated on a
case-by-case basis and concrete requirements should be set. Common sense
rules can go into clause 17 [constexpr.functions], but cases such as the
tuple-like get() interface and even forward() and move() need more
elaboration. | |
cpp_utility/CanIconstexpranstdar_21_0.txt | Profile photo for Joe Zbiciak
Joe Zbiciak
I have been programming since grade schoolUpvoted by
Dmitriy Genzel
, PhD in CSAuthor has 5.8K answers and 50.2M answer views
·
4y
Related
In C++, can I pass an std::array with an unknown size and type to a function efficiently?
Without further context of what you’re trying to ... | |
cpp_utility/0eQsx6ip1DwJpli1_125_0.txt | You do not have permission to delete messages in this group | |
cpp_utility/constexprarraysize_103_0.txt | Share [ __
](https://twitter.com/intent/tweet?text=The+constexpr+array+size+problem -
Barry's C%2B%2B
Blog&url=https%3A%2F%2Fbrevzin.github.io%2Fc%2B%2B%2F2020%2F02%2F05%2Fconstexpr-
array-size%2F "Twitter") [ __
](https://www.reddit.com/r/cpp/submit?title=The+constexpr+array+size+problem -
Barry's C%2B%2B
Blog&url=ht... | |
cpp_utility/cpp_classes_3_1.txt | breakpoint "cpp/utility/breakpoint") (C++26)
[ Three-way comparison ](/w/cpp/utility#Three-way_comparison "cpp/utility")
[ three_way_comparable three_way_comparable_with
](/w/cpp/utility/compare/three_way_comparable "cpp/utility/compare/three way
comparable") (C++20) (C++20)
[ strong_ordering ](/w/cpp/utility/... | |
cpp_utility/constexprarraysize_86_0.txt | bunch_of_spans.emplace_back(c_array);
bunch_of_spans.emplace_back(cpp_array);
bunch_of_spans.emplace_back(dynamic_span); | |
cpp_utility/0eQsx6ip1DwJpli1_153_0.txt | to std-dis...@isocpp.org |
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