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operator-(ranges::zip_view::sentinel)

From cppreference.com
< cpp‎ | ranges‎ | zip view‎ | sentinel
 
 
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(C++23)

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(until C++23)(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 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.

[edit] Parameters

x - an iterator
y - a sentinel

[edit] 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).

[edit] Example

#include <cassert>
#include <deque>
#include <list>
#include <ranges>
#include <vector>
 
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();
}