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Defined in header <ranges> | ||
Defined in header <iterator> | ||
inlinenamespace/* unspecified */{ inlineconstexpr/* unspecified */ ssize=/* unspecified */; | (since C++20) (customization point object) | |
Call signature | ||
template<class T> requires/* see below */ | (since C++20) | |
Calculates the number of elements int in constant time, and converts the result to a signed type.
Given thesubexpression of whicht denotes the (possiblymaterialized) result object asE:
Signed bemake-signed-like-t <decltype(ranges::size(t))>:Signed,ranges::ssize(E) isexpression-equivalent tostatic_cast<std::ptrdiff_t>(ranges::size(t)).Contents |
The nameranges::ssize denotes acustomization point object, which is a constfunction object of aliteralsemiregular class type. SeeCustomizationPointObject for details.
Ifranges::ssize(e) is valid for an expressione, the return type is asigned-integer-like type.
#include <array>#include <iostream>#include <ranges>#include <type_traits> int main(){std::array arr{1,2,3,4,5};auto s= std::ranges::ssize(arr); std::cout<<"ranges::ssize(arr) = "<< s<<'\n'<<"ranges::ssize is "<<(std::is_signed_v<decltype(s)>?"signed":"unsigned")<<'\n'; std::cout<<"reversed arr: "; for(--s; s>=0;--s)std::cout<< arr[s]<<' '; std::cout<<"\n""s = "<< s<<'\n';}
Output:
ranges::ssize(arr) = 5ranges::ssize is signedreversed arr: 5 4 3 2 1s = -1
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3403 | C++20 | ranges::size worked for some non-range types butranges::ssize did not | made work |
(C++20) | returns an integer equal to the size of a range (customization point object)[edit] |
(C++20) | specifies that a range knows its size in constant time (concept)[edit] |
(C++20) | returns the distance between an iterator and a sentinel, or between the beginning and end of a range (algorithm function object)[edit] |
(C++17)(C++20) | returns the size of a container or array (function template)[edit] |
