operator- (std::counted_iterator<I>, std::default_sentinel_t)

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C++
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Range access
(C++11) (C++14)
(C++14) (C++14)
(C++11) (C++14)
(C++14) (C++14)
(C++17) (C++20)
(C++17)
(C++17)
std::counted_iterator
friend constexpr std:: iter_difference_t < I > operator - (
const counted_iterator & x, std:: default_sentinel_t ) ;
(1) (since C++20)
friend constexpr std:: iter_difference_t < I > operator - (
std:: default_sentinel_t , const counted_iterator & y ) ;
(2) (since C++20)
1) Returns the negative distance to the end.
2) Returns the positive distance to the end.

This function template is not visible to ordinary unqualified or qualified lookup , and can only be found by argument-dependent lookup when std::counted_iterator<I> is an associated class of the arguments.

Parameters

x, y - iterator adaptors to compute the difference of

Return value

1) - x. count ( )
2) y. count ( )

Example

Run this code 
#include <initializer_list>
#include <iterator>
 
int main()
{
    constexpr static auto v = {1, 2, 3, 4};
    constexpr std::counted_iterator<std::initializer_list<int>::iterator>
        it{v.begin(), 3};
    constexpr auto d1 = it - std::default_sentinel;
    static_assert(d1 == -3); // (1)
    constexpr auto d2 = std::default_sentinel - it;
    static_assert(d2 == +3); // (2)
}

See also

(C++20)
advances or decrements the iterator
(public member function)
(C++20)
advances the iterator
(function template)
(C++20)
computes the distance between two iterator adaptors
(function template)
(C++20)
default sentinel for use with iterators that know the bound of their range
(class)
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