operator==,<=>(std::counted_iterator) - cppreference.com (original) (raw)
| template< std::common_with<I> I2 > friend constexpr bool operator==( const counted_iterator& x, const counted_iterator<I2>& y ); | (1) | (since C++20) |
|---|---|---|
| template< std::common_with<I> I2 > friend constexpr strong_ordering operator<=>( const counted_iterator& x, const counted_iterator<I2>& y ); | (2) | (since C++20) |
Compares the underlying lengths (i.e. distances to the end).
Checks if the underlying lengths are equal.
Compares the underlying lengths with operator
<=>.
The behavior is undefined if x and y do not point to elements of the same sequence. That is, there must exist some n such that std::next(x.base(), x.count() + n) and std::next(y.base(), y.count() + n) refer to the same element.
The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.
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 is an associated class of the arguments.
[edit] Parameters
[edit] Return value
x.count() == y.count()
y.count() <=> x.count()
[edit] Notes
Since the length counts down, not up, the order of the arguments of operator<=> in the underlying comparison expression is reversed, i.e. y is lhs, x is rhs.
[edit] Example
#include #include int main() { static constexpr auto v = {1, 2, 3, 4, 5, 6}; constexpr std::counted_iterator<std::initializer_list::iterator> it1{v.begin(), 5}, it2{v.begin(), 5}, it3{v.begin() + 1, 4}, it4{v.begin(), 0}; static_assert(it1 == it2); static_assert(it2 != it3); static_assert(it2 < it3); static_assert(it1 <= it2); static_assert(it3 != std::default_sentinel); static_assert(it4 == std::default_sentinel); // it2 == std::counted_iterator{v.begin(), 4}; // UB: operands do not refer to // elements of the same sequence }