# operator-(ranges::zip_view::sentinel)

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< cpp‎ | 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

Run this code

    #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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