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operator+,-(ranges::concat_view::iterator)

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Ranges library
Range adaptors
 
 
friend constexpr /*iterator*/
    operator+( const /*iterator*/& it, difference_type n )
        requires /*concat-is-random-access*/<Const, Views...>;
(1) (since C++26)
friend constexpr /*iterator*/
    operator+( difference_type n, const /*iterator*/& it )
        requires /*concat-is-random-access*/<Const, Views...>;
(2) (since C++26)
friend constexpr /*iterator*/
    operator-( const /*iterator*/& it, difference_type n )
        requires /*concat-is-random-access*/<Const, Views...>;
(3) (since C++26)
friend constexpr difference_type
    operator-( const /*iterator*/& x, const /*iterator*/& y )
        requires /*concat-is-random-access*/<Const, Views...>;
(4) (since C++26)
friend constexpr difference_type
    operator-( const /*iterator*/& x, std::default_sentinel_t )
        requires /* see description */;
(5) (since C++26)
friend constexpr difference_type
    operator-( std::default_sentinel_t, const /*iterator*/& x )
        requires /* see description */;
(6) (since C++26)

Increments or decrements the iterator.

1) Equivalent to auto t = it; t += n; return t;.
2) Equivalent to return it + n;.
3) Equivalent to auto t = it; t -= n; return t;.
4) Let Ix be x.it_ .index() and Iy be y.it_ .index():
  • If Ix > Iy is true, equivalent to difference_type result = ranges::distance(y.get-iter <Iy>(), y.get-end <Iy>());
    for (std::size_t I = Iy + 1; I < Ix; I++)
        result += ranges::distance(x.get-view <I>());
    return result + ranges::distance(x.get-begin <Ix>(), x.get-iter <Ix>());
    .
  • Otherwise, if Ix < Iy is true, equivalent to return -(y - x);.
  • Otherwise, equivalent to return x.get-iter <Ix>() - y.get-iter <Iy>();.
If x.it_ .valueless_by_exception() || y.it_ .valueless_by_exception() is true, the behavior is undefined.
5) Let Ix be x.it_ .index(), equivalent to difference_type result = ranges::distance(x.get-iter <Ix>(), x.get-end <Ix>());
for (std::size_t I = Ix + 1, count = sizeof...(Views); I < count; I++)
    result += ranges::distance(x.get-view <I>());
return -result;
.
Let Fs be the pack that consists of all elements of Views except the first element, the expression in the requires clause is equivalent to

(std::sized_sentinel_for<ranges::sentinel_t<maybe-const <Const, Views>>,
                         ranges::iterator_t<maybe-const <Const, Views>>> && ...) &&
    (ranges::sized_range<maybe-const <Const, Fs>> && ...)

.
If x.it_ .valueless_by_exception() is true, the behavior is undefined.
6) Equivalent to return -(x - std::default_sentinel);.
Let Fs be the pack that consists of all elements of Views except the first element, the expression in the requires clause is equivalent to

(std::sized_sentinel_for<ranges::sentinel_t<maybe-const <Const, Views>>,
                         ranges::iterator_t<maybe-const <Const, Views>>> && ...) &&
    (ranges::sized_range<maybe-const <Const, Fs>> && ...)

.
If x.it_ .valueless_by_exception() is true, the behavior is undefined.

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

Parameters

it, x, y - the iterators
n - a position relative to current location

Return value

As described above.

Example

See also

advances or decrements the underlying iterator
(public member function) [edit]