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std::ranges::adjacent_view<V,N>::iterator<Const>::operator++,--,+=,-=

constexpr /iterator/& operator++();	(1)	(since C++23)
constexpr /iterator/ operator++( int );	(2)	(since C++23)
constexpr /iterator/& operator--() requires ranges::bidirectional_range<Base>;	(3)	(since C++23)
constexpr /iterator/ operator--( int ) requires ranges::bidirectional_range<Base>;	(4)	(since C++23)
constexpr /iterator/& operator+=( difference_type n ) requires ranges::random_access_range<Base>;	(5)	(since C++23)
constexpr /iterator/& operator-=( difference_type n ) requires ranges::random_access_range<Base>;	(6)	(since C++23)

Increments or decrements the iterator.

Let current_ be an underlying array of iterators.

1) Equivalent to:

for (auto& i : current_)
    std::ranges::next(i);
return *this;

The behavior is undefined if before the call the current_.back() is not incrementable.

2) Equivalent to:

auto tmp = *this;
++*this;
return tmp;

3) Equivalent to:

for (auto& i : current_)
    std::ranges::prev(i);
return *this;

The behavior is undefined if before the call the current_.front() is not decrementable.

4) Equivalent to:

auto tmp = *this;
--*this;
return tmp;

5) Equivalent to:

for (auto& i : current_)
    i += n;
return *this;

The behavior is undefined if before the call the current_.back() + n does not have well-defined behavior.

6) Equivalent to:

for (auto& i : current_)
    i -= n;
return *this;

The behavior is undefined if before the call the current_.front() - n does not have well-defined behavior.

Parameters

position relative to current location

Return value

1,3,5,6) *this

2,4) a copy of *this that was made before the change

Example

A link to test: Compiler Explorer/g++-13.

#include <cassert>
#include <list>
#include <ranges>
#include <utility>
#include <vector>
 
[[nodiscard]]
bool operator== (std::pair<int&, int&> x, std::pair<int, int> y)
{
    return x.first == y.first and x.second == y.second;
}
 
int main()
{
    {
        auto v = std::vector{0, 1, 2, 3, 4, 5};
        auto i = (v | std::views::pairwise).begin();
        assert((*i == std::pair{0, 1}));
        ++i;                            // overload (1)
        assert((*i == std::pair{1, 2}));
        --i;                            // overload (3)
        assert((*i == std::pair{0, 1}));
        i += 2;                         // overload (5)
        assert((*i == std::pair{2, 3}));
        i -= 2;                         // overload (6)
        assert((*i == std::pair{0, 1}));
    }
    {
        auto v = std::list{0, 1, 2, 3, 4, 5};
        auto i = (v | std::views::pairwise).begin();
        assert((*i == std::pair{0, 1}));
        ++i;                            // overload (1)
        assert((*i == std::pair{1, 2}));
        --i;                            // overload (3)
        assert((*i == std::pair{0, 1}));
//      i += 2; // Error: v is not a random_access_range; overload (5)
//      i -= 2; // Error: v is not a random_access_range; overload (6)
    }
}

std::ranges::adjacent_view<V,N>::iterator<Const>::operator++,--,+=,-=

Parameters

Return value

Example

See also