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

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< cpp‎ | ranges‎ | transform view‎ | sentinel

friend constexpr ranges::range_difference_t<Base> operator-( const /*iterator*/<Const>& x, const /*sentinel*/& y ) requires std::sized_sentinel_for<ranges::sentinel_t<Base>, ranges::iterator_t<Base>>; | (1) | (since C++20)
friend constexpr ranges::range_difference_t<Base> operator-( const /*sentinel*/& y, const /*iterator*/<Const>& x ) requires std::sized_sentinel_for<ranges::sentinel_t<Base>, ranges::iterator_t<Base>>; | (2) | (since C++20)

Computes the distance between the underlying iterator of `x` and the underlying sentinel of `y`.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when `transform_view::sentinel<Const>` is an associated class of the arguments.

### Parameters

x | - | an iterator
y | - | a sentinel

### Return value

Let `current_` denote the underlying iterator, `end_` denote the underlying sentinel.

1) x.current_ - y.end_
2) y.end_ - x.current_
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