operator-(ranges::zip_view::sentinel)
template< bool OtherConst >
requires (std::sized_sentinel_for<
ranges::sentinel_t</*maybe-const*/<Const, Views>>,
ranges::iterator_t</*maybe-const*/<OtherConst, Views>>> && ...)
friend constexpr
std::common_type_t<ranges::range_difference_t</*maybe-const*/<OtherConst, Views>>...>
operator-( const iterator<OtherConst>& x, const sentinel& y ); |
(1) | (since C++23) |
template< bool OtherConst >
requires (std::sized_sentinel_for<
ranges::sentinel_t</*maybe-const*/<Const, Views>>,
ranges::iterator_t</*maybe-const*/<OtherConst, Views>>> && ...)
friend constexpr
std::common_type_t<ranges::range_difference_t</*maybe-const*/<OtherConst, Views>>...>
operator-( const sentinel& y, const iterator<OtherConst>& x ); |
(2) | (since C++23) |
Computes the minimal distance between the underlying tuple of iterators of x and the underlying tuple of sentinels of y.
These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when zip_view::sentinel<Const> is an associated class of the arguments.
Parameters
| x | - | an iterator |
| y | - | a sentinel |
Return value
Let current_ denote the underlying tuple of iterators of x, and end_ denote the underlying tuple of sentinels of y.
Let DIST(x, y, i) be a distance calculated by expression equivalent to std::get<i>(x.current_) - std::get<i>(y.end_) for some integer i.
1) the value with the smallest absolute value among
DIST(x, y, i) of all
i in range
0 ≤ i < sizeof...(Views)
2)
-(x - y)
Example
#include <cassert>
#include <ranges>
#include <vector>
#include <deque>
#include <list>
int main() {
auto x = std::vector{1, 2, 3, 4};
auto y = std::deque{'a', 'b', 'c'};
auto z = {1.1, 2.2};
auto w = std::list{1, 2, 3};
auto p = std::views::zip(x, y, z);
assert(p.begin() - p.end() == +2);
assert(p.end() - p.begin() == -2);
[[maybe_unused]]
auto q = std::views::zip(x, y, w);
// The following code fires a compile-time error because std::list::iterator
// does not support operator- that is needed to calculate the distance:
// auto e = q.begin() - q.end();
}
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