View source for Talk:Main Page/suggestions/archive 2

{{Aan}}

== std::inner_product description typo? ==

In the first sentence of the initial description of std::inner_product, I believe std::distance(first1, first2) should be std::distance(first1, last1).

[[User:NCSUMaxPower|NCSUMaxPower]] ([[User talk:NCSUMaxPower|talk]]) 08:44, 5 August 2024 (PDT)
: Fixed.{{done}} --[[User:Xmcgcg|Xmcgcg]] ([[User talk:Xmcgcg|talk]]) 17:47, 5 August 2024 (PDT)

== <type_traits> header page is missing reference_converts/constructs_from_temporary ==

Thanks for the great work of maintaining the website!

The "<type_traits> header page" (https://en.cppreference.com/w/cpp/header/type_traits) is missing the following entries:
* std::reference_converts_from_temporary: https://en.cppreference.com/w/cpp/types/reference_converts_from_temporary
* std::reference_constructs_from_temporary: https://en.cppreference.com/w/cpp/types/reference_constructs_from_temporary

The expected result is it has a similar "Supported operations" section as the "Metaprogramming library" (https://en.cppreference.com/w/cpp/meta)

Regards,
Zhao
:{{mark ok}} Done. --[[User:Fruderica|Fruderica]] ([[User talk:Fruderica|talk]]) 21:01, 25 July 2024 (PDT)

== Span's Defect reports has a type ==

Defect report LWG 3903 unn'''u'''cessary should be unn'''e'''cessary

[[Special:Contributions/82.75.229.3|82.75.229.3]] 10:25, 20 July 2024 (PDT) Hupie
:Fixed.{{done}} --[[User:Xmcgcg|Xmcgcg]] ([[User talk:Xmcgcg|talk]]) 02:34, 21 July 2024 (PDT)

== LegacyInputIterator requirements: wrong type / semantics for r ==

In the requirements summary for {{named req|InputIterator}}, the expression {{tt|r}} is introduced to have type {{tt|T&}}, namely a reference to {{tt|X}}'s value type (where {{tt|X}} is a supposed {{named req|InputIterator}}), and then is described to have iterator semantics, as evidenced by the following sample that appears in the table :  

{{c multi|1=T x = *r;|2=++r;|3=return x;}}

This doesn't make sense and is very puzzling to stumble upon. This used to be correct up until a revision on June 16th 2024: before then, r was described as an lvalue of type It, for which the above semantics made sense.

--[[User:Deqyra|Deqyra]] ([[User talk:Deqyra|talk]]) 00:37, 17 July 2024 (PDT)
: That's quite an oversight, thanks. Fixed and improved the names so this kind of thing should be harder to allow {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 03:38, 17 July 2024 (PDT)

== '}}' in page ==

there is a '}}' at the bottom of the page [[cpp/language/while]]

--[[User:Zyctree|Zyctree]] ([[User talk:Zyctree|talk]]) 05:10, 17 July 2024 (PDT)
: Fixed, thanks {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 05:58, 17 July 2024 (PDT)

{{Clear}}
== cpp/thread/jthread/stop suggested code change ==

I found the existing example somewhat misleading. I believe this change would better convey the intent.

{{source|1=
--- before.cpp  2024-04-22 13:31:41.118514403 -0600
+++ after.cpp   2024-04-22 13:33:05.353596405 -0600
@@ -29,13 +29,9 @@
     {
         std::mutex mutex;
         std::unique_lock lock(mutex);
-        std::condition_variable_any().wait(lock, stoken,
-            [&stoken] { return false; });
-        if (stoken.stop_requested())
-        {
-            std::cout << "Waiting worker is requested to stop\n";
-            return;
-        }
+        std::condition_variable_any().wait(lock, stoken, [] { return false; });
+        std::cout << "Waiting worker is requested to stop\n";
+        return;
     });

     // std::jthread::request_stop() can be called explicitly:
}}
{{unsigned|73.229.98.126|2024-04-22 13:31}}.

: {{done}}, [[cpp/thread/jthread/request_stop#Example|updated]].) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 14:47, 22 April 2024 (PDT)

{{Clear}}
== wrong comment in example ==

In https://en.cppreference.com/w/c/language/operator_logical, in the first example, the comment says
{{example|code=
int n = isspace('a'); // zero if 'a' is a space, nonzero otherwise
}}, but it should be the other way around (see https://en.cppreference.com/w/c/string/byte/isspace, "Non-zero value if the character is a whitespace character, zero otherwise.")

[[User:Cvttsd2si|Cvttsd2si]] ([[User talk:Cvttsd2si|talk]]) 02:20, 23 April 2024 (PDT)
: Fixed, thanks {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 05:33, 23 April 2024 (PDT)

{{Clear}}
== Add code example for std::chrono::hh_mm_ss constructor ==

Add code example for https://en.cppreference.com/w/cpp/chrono/hh_mm_ss/hh_mm_ss

{{example
|code=
#include <chrono>
#include <iostream>

int main() {
    auto now = std::chrono::system_clock::now();
    std::chrono::hh_mm_ss time_of_days{now - std::chrono::floor<std::chrono::days>(now)};
    std::cout << "The time of day is: " << time_of_days;
}
|p=true
|output=
The time of the day is: 10:43:52.265396171
}}

: {{done|[[cpp/chrono/hh_mm_ss/hh_mm_ss#Example|Added]]}}, thanks.) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 05:28, 24 April 2024 (PDT)

{{Clear}}
== Update the libc++ URL with the current one ==

The current URL https://github.com/llvm-mirror/libcxx/blob/a12cb9d211019d99b5875b6d8034617cbc24c2cc/include/algorithm#L4219 for libc++ seems like quite a bit old. LLVM has moved their development tree from SVN to git about 5 years ago. Even though the logic is basically the same, it seems rather a good idea to link the current development tree.

Link: https://github.com/llvm/llvm-project/blob/8350d9c23d76fb95f42674a1563cbe8c32582dd5/libcxx/include/__algorithm/upper_bound.h#L35

Thanks.
: Thanks for the link, updated {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 14:48, 24 April 2024 (PDT)

{{Clear}}
== range_error copy constructor noexcept is since c++11 ==

In range_error page,

THIS:

3) Copy constructor. If *this and other both have dynamic type std::range_error then std::strcmp(what(), other.what()) == 0. No exception can be thrown from the copy constructor.(until C++11)

SHOULD BE:

3) Copy constructor. If *this and other both have dynamic type std::range_error then std::strcmp(what(), other.what()) == 0. No exception can be thrown from the copy constructor.(since C++11)


replace "until C++11" with "since C++11". noexept is added in C++11

[[Special:Contributions/64.125.32.42|64.125.32.42]] 13:48, 24 April 2024 (PDT)
: I'm actually not sure where this copy constructor comes from in the first place, noexcept or not, it doesn't seem to appear in the standard, at least not in the {{tt|[diagnostics]}} section... If it's the implicitly generated one, then I suppose we should add the move ctor too? But even then I don't see where the noexcept comes from --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 14:41, 24 April 2024 (PDT)
:: It comes from [http://eel.is/c++draft/exception#2 <nowiki>[exception]/2</nowiki>]: "Except where explicitly specified otherwise, each standard library class <tt>T</tt> that derives from class <tt>exception</tt> has the following publicly accessible member functions, each of them having a non-throwing exception specification: [...] copy constructor." --[[User:D41D8CD98F|D41D8CD98F]] ([[User talk:D41D8CD98F|talk]]) 05:23, 26 April 2024 (PDT)
::: Ah, thanks :) --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 03:55, 27 April 2024 (PDT)

{{done}} I removed the "until C++11" mark.
For the record, the non-throwing requirement was introduced by [https://cplusplus.github.io/LWG/issue471 LWG 471]. --[[User:D41D8CD98F|D41D8CD98F]] ([[User talk:D41D8CD98F|talk]]) 05:34, 26 April 2024 (PDT)

{{Clear}}
== Typo/small error in Class template argument deduction (CTAD) ==

In

Class template argument deduction (CTAD) > Deduction for class templates > Implicitly-generated deduction guides > 1st bullet point > 2nd bullet point,

there is a missing word "Fi". The sentence should read "the associated constraints of Fi are the conjunction of the associated constraints of C and the associated constraints of Ci"

[[Special:Contributions/174.138.232.125|174.138.232.125]] 06:06, 26 April 2024 (PDT)

: {{done|Fixed}} [[cpp/language/class_template_argument_deduction#Implicitly-generated_deduction_guides|here]]. Thank you indeed.) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 12:00, 26 April 2024 (PDT)

{{Clear}}
== Replace the part about multiple subscripts for {{c|operator[]}} with correct `rev begin/end` and `rev|until/since` block ==

{{rev begin}}
{{rev|until=c++23|
{{c|operator[]}}  can only take one subscript. In order to provide multidimensional array access semantics, e.g. to implement a 3D array access {{c|1=a[i][j][k] = x;}}, {{c|operator[]}} has to return a reference to a 2D plane, which has to have its own {{c|operator[]}} which returns a reference to a 1D row, which has to have {{c|operator[]}} which returns a reference to the element. To avoid this complexity, some libraries opt for overloading {{c|operator()}} instead, so that 3D access expressions have the Fortran-like syntax {{c|1=a(i, j, k) = x;}}.
}}
{{rev|since=c++23|
{{c|operator[]}} can take any number of subscripts. For example, an {{c|operator[]}} of a 3D array class declared as {{c|T& operator[](std::size_t x, std::size_t y, std::size_t z);}} can directly access the elements.
}}
{{rev end}}

: {{done}}. OK, [[cpp/language/operators#Array subscript operator|applied]], thanks.) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 12:26, 26 April 2024 (PDT)

cpp/container/map/try_emplace:

Under "Return value", replace "that was inserted or updated" with "whose key is equivalent to `k`".

Elements are never updated. The suggested replacement matches one in the standard wording.
: Addressed, thanks {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 12:49, 27 April 2024 (PDT)

{{Clear}}
== cpp/types/byte ==

Page: cpp/types/byte

Please add:

std::byte can only compared with other std::byte value.

Not possible:

    std::byte x = 2;        // Can't be assigned
    if (x == 3) {           // Can't be compared
        int A[] = { 1, 2, 4, 8 };
        int b   = A[x];     // Can't be used as an index
    }
: Done {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 07:15, 30 April 2024 (PDT)
: {{done|[[cpp/types/byte#Example|Added]]}}. --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 17:07, 1 May 2024 (PDT)

{{Clear}}
== in owner_hash in the member function the title is owner_less instead of owner_hash ==

just change the owner_less to owner_hash
{{unsigned|Shar-yashuv|12:55, 30 April 2024‎}}

{{done}} thx --[[User:Cubbi|Cubbi]] ([[User talk:Cubbi|talk]]) 06:13, 30 April 2024 (PDT)

{{Clear}}
== Add external links to Windows/Linux locales to the (std::)setlocale pages ==

The `std::locale` constructor page (https://en.cppreference.com/w/cpp/locale/locale/locale) has some seemingly useful external links to lists of locale names for Windows and Linux. I suggest adding these same links to the pages for `setlocale` (https://en.cppreference.com/w/c/locale/setlocale) and `std::setlocale` (https://en.cppreference.com/w/cpp/locale/setlocale).

===External links===
{{elink begin}}
{{elink|num=1|1=[https://ss64.com/locale.html List of Windows locale names].}}
{{elink|num=2|1=[https://lh.2xlibre.net/locales/ List of Linux locale names].}}
{{elink end}}

: {{done}} as you suggested.) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 10:27, 3 May 2024 (PDT)

{{Clear}}
== Allocator-aware copy constructor in AllocatorAwareContainer has wrong postcondition ==

Hi,

I have the feeling, that there is a mistake in 
[[https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer]]

The postcondition of

X u(t, m);

claims that

u.get_allocator() == A() must be true.


All C++ standards that I checked mention as postcondition that

u.get_allocator() == m must be true.


I therefore propose, that the postcondition of X u(t, m); is changed to:

u == t and u.get_allocator() == m are both true.

[[User:LittleHuba|LittleHuba]] ([[User talk:LittleHuba|talk]]) 08:10, 3 May 2024 (PDT)

: {{done|[[cpp/named_req/AllocatorAwareContainer#Statements|Fixed]]}} (per [https://eel.is/c++draft/container.alloc.reqmts#13 container.alloc.reqmts]). Good catch, thanks.) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 14:21, 3 May 2024 (PDT)

{{Clear}}
== Wrong return types of vector::rend and array::rend ==

{{c|iterator rend() noexcept;
const_iterator rend() const noexcept;
const_iterator crend() const noexcept;}}

The return types for these function is not correct. It should be:

{{c|reverse_iterator rend() noexcept;
const_reverse_iterator rend() const noexcept;
const_reverse_iterator crend() const noexcept;}}

--[[User:Nori0815|Nori0815]] ([[User talk:Nori0815|talk]]) 06:06, 5 May 2024 (PDT)

: {{done|Yep}}, affected pages {{ltt|cpp/container/vector/rend|vector::rend}}, {{ltt|cpp/container/array/rend|array::rend}} have been fixed. THX! --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 13:22, 5 May 2024 (PDT)

{{Clear}}
== ambiguities in https://en.cppreference.com/w/cpp/language/explicit_cast ==

Hello,

I believe the following statements from the page https://en.cppreference.com/w/cpp/language/explicit_cast (accessed at 6th of May, 2024) seem contradicting each other:

1)
 6,7) The auto specifier is replaced with the deduced type of the invented variable x declared with auto x(expression); (which is never interpreted as a function declaration) or auto x{expression};, respectively. The result is always a prvalue of an object type.

Such a statement means that, for C++23, in "auto(s)" the keyword auto is replaced by the type deduced from the expression 's'. It also reads "never interpreted as a function declaration".

Going on in the page, in the section "Ambiguous declaration statement",
there is:

2)
 However, if the outermost declarator in the ambiguous declaration statement has a trailing return type, the statement will only be treated as a declaration statement if the trailing return type starts with auto:

Let us now discuss the two example cases:

A)
"auto(s)()->M; // function declaration, equivalent to M s();"

B)
"S(s)()->M;    // expression"

According to the statements in (1), "auto(s)()->M" in case (A) should become "S(s)()->M", that is, equivalent to case (B), but the result is different (also experimented on godbolt with gcc 13.2 and option '-std=c++2b'), therefore the statement (1) should be refined.

Moreover, the statement (2) reads that the disambiguation in case of trailing return type selects a declaration only when such a type starts with auto. But, in case (A), such a type is 'M', not 'auto', against the fact that in case(A) we get a function declaration named 's'.

Finally, the statement (1) reads that with auto(expression) we should never get a declaration as result, but the case (A) proves the opposite.

Hope this helps to refine/improve the explanation in that page.

: Wording (1) is copied from {{stddoc|P0849R8}}, which is '''not''' adpoted into C++23 as-is. The editor report ({{stddoc|N4902}}) says:
 Poll LWG-8: The specification was subsequently simplified by reusing the term “placeholder type deduction”

: The inaccurate wording has been fixed based on the current wording in the working draft. --[[User:Xmcgcg|Xmcgcg]] ([[User talk:Xmcgcg|talk]]) 04:13, 6 May 2024 (PDT)

{{Clear}}
== max_align_t is not "usually" the largest scalar type ==

In the notes on the `max_align_t` page, it says that `max_align_t` is usually the largest scalar type on the platform, typically `long double`.  Since that is *not* the case for gcc, I don't think it's a fair comment.  In fact, readers should be alerted to the fact that, on gcc (using libc++), not only is `max_align_t` *not* a scalar type, it's `sizeof` is surprisingly larger than its `alignof`.  I consider this a bug in libc++ (a `struct` should have been a `union`), but the standard does not require that `max_align_t` be the *smallest* type having maximum alignment.
: Fixed, thanks. It wasn't a very interesting note anyway tbh {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 10:33, 7 May 2024 (PDT)

{{Clear}}
== Patterns, idioms, tips and tricks ==

[[User:Kediaaditi30|Kediaaditi30]] ([[User talk:Kediaaditi30|talk]]) 03:49, 10 May 2024 (PDT) Add in Patterns, idioms, tips and tricks
- C++ Cheat Sheet[https://programiz.pro/resources/cpp-cheat-sheet/]
: Not a suggestion. But I will leave a personal opinion: that cheat sheet sucks. I assume it's lazily copied from a python one, because C++ has no {{tt|**}} or {{tt|1=//=}} operator. {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 04:19, 10 May 2024 (PDT)
::[[User:Ybab321]] that was supposed to be {{not done}}, right? --[[Special:Contributions/109.178.139.220|109.178.139.220]] 16:52, 11 May 2024 (PDT)
::: Heh, yes, thank you :) --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 14:31, 12 May 2024 (PDT)

{{Clear}}
== cpp/language/reference says references to void are allowed ==

Just a small mistake in [[cpp/language/reference#Defect reports]]. "Allowed" should obviously be changed to "disallowed". [[Special:Contributions/109.178.139.220|109.178.139.220]] 16:48, 11 May 2024 (PDT)
:{{done}} yep --[[User:Cubbi|Cubbi]] ([[User talk:Cubbi|talk]]) 18:54, 11 May 2024 (PDT)

{{Clear}}
== std::println overload 4 looks wrong ==

[[cpp/io/println]]

4) Equivalent to std::println(stream, "\n").

std::println(stream, "\n") will print two newlines. Should be std::println(stream, "") or std::print(stream, "\n"). (Comments on the example say former.)

--[[Special:Contributions/98.128.166.54|98.128.166.54]] 05:31, 12 May 2024 (PDT)

: It should refer to {{tt|std::print}}, now fixed. {{done}} --[[User:Xmcgcg|Xmcgcg]] ([[User talk:Xmcgcg|talk]]) 08:46, 12 May 2024 (PDT)

{{Clear}}
== Wrong link to Transactional Memory TS ==

This diff should be reverted, it incorrectly updates from the Transactional Memory TS V2 paper to the *C++ Extensions for Concurrency V2* paper.

https://en.cppreference.com/mwiki/index.php?title=cpp/experimental&diff=157290&oldid=152301
: Corrected, thanks {{done}} --[[User:Ybab321|Ybab321]] ([[User talk:Ybab321|talk]]) 07:06, 13 May 2024 (PDT)

{{Clear}}
== Add in Patterns, idioms, tips and tricks ==

[[User:Aditikedia|Aditikedia]] ([[User talk:Aditikedia|talk]]) 23:15, 13 May 2024 (PDT)
Add in Patterns, idioms, tips and tricks
- C++ tricks[https://programiz.pro/resources/cpp-cheat-sheet/] by Programiz
: {{not done}} We heard you the [[#Patterns, idioms, tips and tricks|first time]]. Did you really need to make another account to say the same thing? --[[Special:Contributions/2A02:587:7E1E:1E00:7D68:2510:14C9:8672|2A02:587:7E1E:1E00:7D68:2510:14C9:8672]] 00:45, 14 May 2024 (PDT)

{{Clear}}
== fseek() return value is incorrect ==

The Return value description for fseek() is incorrect - https://en.cppreference.com/w/c/io/fseek

It should read:

File position indicator on success or {{c|-1L}} if failure occurs.

On error, the {{c|errno}} variable is set to implementation-defined positive value.


----

Citations:
https://man7.org/linux/man-pages/man3/fseek.3p.htm

https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/fseek-fseeki64?view=msvc-170

: {{done}}. The POSIX requirements were appended to the [[c/io/fseek#Notes|Notes]] section. The C Standard only requires "nonzero value" on error.) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 01:16, 14 May 2024 (PDT)

{{Clear}}
== is_corresponding_member broken link ==

https://en.cppreference.com/w/cpp/types/is_corresponding_member

The "Standard layout" section in language/data_members was renamed to "Standard-layout", breaking the "common initial sequence" link at the top.

--[[Special:Contributions/155.4.128.189|155.4.128.189]] 02:48, 19 January 2024 (PST)

: {{done}}. The link's been [[cpp/types/is_corresponding_member|fixed]]. Thanks. --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 05:22, 19 January 2024 (PST)

{{Clear}}
== etalon, n. 1. A Fabry-Pérot interferometer. 2. ''archaic.'' An uncastrated male horse; a stallion. ==

Curiously, there once was even more obsolete meaning of ‘etalon’ that fell out of use by the Late Middle English period, probably in the early 14c: 3. A castrated male sheep; a wether.

I don't have a permission to modify the pages https://en.cppreference.com/w/cpp/memory/ranges/uninitialized_default_construct and https://en.cppreference.com/w/cpp/memory/ranges/uninitialized_default_construct_n.

I would really appreciate it if anyone blessed with edit access could replace {{c|etalon}} in the code example with e.g., {{c|letters}}, {{c|abcd}}, or anything else that you may find more appropriate. ‘Etalon’ is clearly not a meaningful identifier.&nbsp;— <span style='white-space:nowrap;padding:0 4px;border:none;border-radius:5px;background-image:linear-gradient(to right,#2553,#2551 60%,#A222,#EA23,#EA23,#EA24)'>⋖ [[Special:MyPage|Cy “kkm” K. N.]]  ∺  [[Special:mytalk|talk]] ⋗</span> 03:56, 19 January 2024 (PST)

: I've replaced the word {{c|etalon}} (one of the meaning &ndash; "standard of measurement", from early 20th century French ''étalon'') with more neutral {{c|sample}} which is close enough to the originally intended meaning. Will it be good enough)? Ah, thanks anyway.) {{done}} --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 06:11, 19 January 2024 (PST)

{{Clear}}
== Non-compiling exemple in alignas page ==

The page https://en.cppreference.com/w/cpp/language/alignas contains an example in which one of the lines is:

        << "alignof(cacheline) = " << alignof(alignas(64) char[64]) << '\n'

This line does not compile and if replaced by:

        << "alignof(cacheline) = " << alignof(cacheline) << '\n'

It is still a GNU extension (-Wgnu-alignof-extension)

Have a nice day

Joseph

[[Special:Contributions/195.68.40.4|195.68.40.4]] 05:56, 17 January 2024 (PST)

: {{done|Updated}} with [[cpp/language/alignas#Example|type alias]].) --[[User:Space Mission|Space Mission]] ([[User talk:Space Mission|talk]]) 14:00, 17 January 2024 (PST)

The type alias doesn't compile in Clang. From my understanding, alignas cannot be used in typedefs and usings. [[Special:Contributions/240E:391:EC1:E280:0:0:0:1000|240E:391:EC1:E280:0:0:0:1000]] 02:19, 21 July 2024 (PDT)