View source for Talk:cpp/named req

== SeedSequence ==

I've removed SeedSequence which was on the list. I can't find it in standard papers -- [[User:Bazzy|Bazzy]] 16:08, 16 March 2012 (PDT)

: It's named as SSeq in the standard. -- [[User:P12|P12]] 04:57, 17 March 2012 (PDT)

== (C++11) ==

Why are some of the concepts marked as {{mark c++11}} ? None of the concepts were added before C++11, and they still aren't yet added to the standard. --- [[Undeterminant]] 17:28, 21 March 2012 (PDT)
: What this page is listing is properly called '''requirements'''. The 2003 revision of the C++ standard is defined in terms of requirements, such as ''CopyConstructible'', ''Assignable'', ''LessThanComparable'', etc. The 2011 revision adds many more requirements (some of which are detailed under §17.6.3[utility.requirements]). I think this is a great idea, since it makes it much easier to be precise in the rest of this wiki. --[[User:Cubbi|Cubbi]] 18:47, 21 March 2012 (PDT)
::Ah, okay. That makes more sense, then. --- [[Undeterminant]] 19:02, 21 March 2012 (PDT)

:: Is there a fundamental difference between "concepts" and "requirements"? As far as I remember, the committee used concepts to specify the constraints on templates throughout the draft paper in almost the same way as they now use requirements. To me it seems that direct language support is the only thing that these terms differ. Is there much ambiguity if we refer requirements by concepts, but also add an explanation in the page? -- [[User:P12|P12]] 11:38, 22 March 2012 (PDT)

:: After a further thought, I think that similarity doesn't mean anything if the terms are confusing. We could resolve this ambiguity easily by just replacing ''concepts'' with ''requirements'' or ''named requirements'' in {{tl|cpp/named req/title}}, {{tl|dcl list concept}} and several link names. -- [[User:P12|P12]] 14:07, 22 March 2012 (PDT)

::: I'm very slightly leaning towards renaming concepts => requirements.  But only slightly.  The current form, with the explanation as to what's going on, is tolerable and might save us some effort once concepts actually make it into the language. [[User:Nate|Nate]] 16:24, 22 March 2012 (PDT)

== UnaryPredicate ==

I can't find the UnaryPredicate concept, as used by std::find_if, on the page. Is it missing, or is it there under a different name? [[User:Vtable|Vtable]] 08:25, 22 March 2012 (PDT)
:I see ''Predicate'' and ''BinaryPredicate'' in the standard.
:They don't have many detailed requirements as the other concepts but maybe can be added here anyways.
:--[[User:Bazzy|Bazzy]] 09:07, 22 March 2012 (PDT)
::I've added those two to the list, but without any descriptive text yet.
::Would something like "A function or functor that takes a single argument and returns true or false." be ok as the brief description for Predicate? -- [[User:Vtable|Vtable]] 11:55, 22 March 2012 (PDT)
:::I've added a bit more precise description. Two things to note: the result doesn't need to be literally {{c|bool}}, only convertible to it. Also, the arguments are not modified. -- [[User:P12|P12]] 13:46, 22 March 2012 (PDT)

== Trivially copyable, POD etc. ==

Can these be considered concepts? --[[User:Bazzy|Bazzy]] 02:13, 24 March 2012 (PDT)
:I can't seem to find a specific place where they're mentioned on the wiki. It would make sense to include them here. --- [[Undeterminant]] 15:21, 24 March 2012 (PDT)
::Added as '''Class''' category --[[User:Bazzy|Bazzy]] 03:40, 25 March 2012 (PDT)
::: Note, that neither C++11, nor C++0x draft before the removal of concepts define these type properties as named concepts or requirements. They are defined in ''§3 Basic concepts'', so our usage is non-standard. There are a lot of other type properties, such as arithmetic, floating-point, reference, etc., so we probably want to ''very'' cautious with the wording (e.g. not "<...> must meet the requirements of {{named req|Trivial}}", but "<...> must be ''trivial'' (see {{named req|Trivial}})"), and put notes everywhere that these requirements are not defined as such in the standard. -- [[User:P12|P12]] 06:54, 25 March 2012 (PDT)
:::: I think it's worth listing all type categories (at least all categories standardized via type traits) here, if only to make it easy to explain things like the fourth overload of {{c|std::sqrt}}. We'd just link Integral to {{named req|Integral}}, which would explain which types are part of that category, and give a seealso to {{c|std::is_itegral}}. Incidentally, here's a chart I like that arranges those type categories neatly: http://home.roadrunner.com/~hinnant/TypeHiearchy.pdf , although it's missing a few other important categories: aggregate and literal, for example (although we kinda defined literal type at [[cpp/language/constexpr]], a link for aggregates would make explaining {{c|std::array}} and {{c|std::atomic}} easier. --[[User:Cubbi|Cubbi]] 07:13, 6 June 2012 (PDT)
::::: Agreed. A list with all our "custom" concepts and a note in corresponding pages should explain what we've done clearly enough. -- [[User:P12|P12]] 13:28, 6 June 2012 (PDT)

== Duplicated page ==

I noticed that [[cpp/iterator/concepts]] was added to the wiki a while ago. Its information should probably be consolidated into this section. --- [[Undeterminant]] 14:28, 2 April 2012 (PDT)
: I replaced it with redirect. The subpages of [[cpp/named req]] already have better explanations than [[cpp/iterator/concepts]]. -- [[User:P12|P12]] 13:34, 6 June 2012 (PDT)

== N3701 ==

Hello,
Maybe update article with new draft N3701 ? http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3701.pdf
Thanks
[[User:Guillaume Belz|Guillaume Belz]] 07:15, 9 August 2013 (PDT)
: Yes, that definitely should be mentioned. Updated.--[[User:Cubbi|Cubbi]] 08:40, 11 August 2013 (PDT)

== Rename? ==

How about we rename these 'library concepts' to something like 'library type requirements', now that we have actual concepts in C++20 and Ranges TS? --[[User:Cubbi|Cubbi]] ([[User talk:Cubbi|talk]]) 14:03, 9 August 2017 (PDT)
:I'm OK with that, especially since the library specification doesn't really use the word "concept" for these. [[User:T. Canens|T. Canens]] ([[User talk:T. Canens|talk]]) 17:09, 9 August 2017 (PDT)
:: The old STL called them "concepts", e.g. [https://www.sgi.com/tech/stl/LessThanComparable.html LessThanComparable] - maybe P12 got the idea from there. Okay, whoever finds the time first can rename. --[[User:Cubbi|Cubbi]] ([[User talk:Cubbi|talk]]) 18:41, 9 August 2017 (PDT)