operator-(std::counted_iterator)

 

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indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_output_iterator (C++20)	forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
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input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (C++17 中已棄用) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
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indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)	indirect_unary_predicate (C++20) indirect_binary_predicate (C++20)	indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
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reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter move_sentinel (C++20)	common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) make_const_iterator (C++23) make_const_sentinel (C++23)
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std::counted_iterator

成員函式

counted_iterator::counted_iterator

counted_iterator::operator=

counted_iterator::base

counted_iterator::count

counted_iterator::operator*counted_iterator::operator->

counted_iterator::operator[]

counted_iterator::operator++counted_iterator::operator++(int)counted_iterator::operator+counted_iterator::operator+=counted_iterator::operator--counted_iterator::operator--(int)counted_iterator::operator-counted_iterator::operator-=

非成員函式

operator==operator<=> (C++20)(C++20)

operator==(default_sentinel_t) (C++20)

operator+ (C++20)

operator- (C++20)

operator-(default_sentinel_t) (C++20)

iter_move (C++20)

iter_swap (C++20)

輔助類

iterator_traits<std::counted_iterator> (C++20)

 

template< std::common_with<I> I2 >     friend constexpr std::iter_difference_t<I2> operator-(         const counted_iterator& x, const counted_iterator<I2>& y );		(C++20 起)

計算兩個迭代器介面卡之間的距離。

如果 x 和 y 不指向同一序列的元素，則行為未定義。即，必須存在某個 n，使得 std::next(x.base(), x.count() + n) 和 std::next(y.base(), y.count() + n) 引用相同的元素。

此函式模板對於普通的非限定或限定查詢不可見，只能透過實參依賴查詢在 std::counted_iterator<I> 作為實參的關聯類時找到。

引數

x, y

-

要計算差異的迭代器介面卡

返回值

y.count() - x.count()

注意

由於“長度”是遞減而非遞增的，所以底層表示式中 operator- 的引數順序是反轉的，即 y 是左運算元，x 是右運算元。

示例

執行此程式碼

#include <initializer_list>
#include <iterator>
 
int main()
{
    static constexpr auto v = {1, 2, 3, 4, 5, 6};
    constexpr std::counted_iterator<std::initializer_list<int>::iterator>
        it1{v.begin(), 5},
        it2{it1 + 3},
        it3{v.begin(), 2};
 
    static_assert(it1 - it2 == -3);
    static_assert(it2 - it1 == +3);
//  static_assert(it1 - it3 == -3); // UB: operands of operator- do not refer to
                                    // elements of the same sequence
}

參閱

operator++operator++(int)operator+=operator+operator--operator--(int)operator-=operator-	遞增或遞減 counted_iterator (public member function)
operator+ (C++20)	前進迭代器 (function template)
operator-(std::default_sentinel_t) (C++20)	計算到末尾的帶符號距離 (function template)