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:

• Ifranges::size(t) is ill-formed,ranges::ssize(E) is also ill-formed.
• Otherwise, letSigned bemake-signed-like-t <decltype(ranges::size(t))>:
  • Ifstd::ptrdiff_t is wider thanSigned,ranges::ssize(E) isexpression-equivalent tostatic_cast<std::ptrdiff_t>(ranges::size(t)).
  • Otherwise,ranges::ssize(E) is expression-equivalent tostatic_cast<Signed>(ranges::size(t)).

Customization point objects

The nameranges::ssize denotes acustomization point object, which is a constfunction object of aliteralsemiregular class type. SeeCustomizationPointObject for details.

[edit]Notes

Ifranges::ssize(e) is valid for an expressione, the return type is asigned-integer-like type.

[edit]Example

#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';}

ranges::ssize(arr) = 5ranges::ssize is signedreversed arr: 5 4 3 2 1s = -1

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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