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std::counted_iterator<I>:: count

From cppreference.net
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
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(C++17) (C++20)
(C++17)
(C++17)
std::counted_iterator
constexpr std:: iter_difference_t < I > count ( ) const noexcept ;
(C++20 起)

返回底层 长度 ，即到末尾的距离。

目录

参数

(无)

返回值

底层的 长度 。

示例

运行此代码 
#include <cassert>
#include <iostream>
#include <iterator>
int main()
{
    constexpr static auto il = {1, 2, 3, 4, 5};
    constexpr std::counted_iterator i1{il.begin() + 1, 3};
    static_assert(i1.count() == 3);
    auto i2{i1};
    for (; std::default_sentinel != i2; ++i2)
        std::cout << "*i2: " << *i2 << ", count(): " << i2.count() << '\n';
    assert(i2.count() == 0);
}

输出： 

*i2: 2, count(): 3
*i2: 3, count(): 2
*i2: 4, count(): 1

参见

访问底层迭代器
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