NAME¶

std::ranges::adjacent_view::iterator::operator++,--,+=,-= - std::ranges::adjacent_view::iterator::operator++,--,+=,-=

Synopsis¶

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

Increments or decrements the iterator.

Let current_ be an underlying array of iterators.

1) Equivalent to:

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

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

Parameters¶

n - 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¶

// Run this code

#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)
}
}

See also¶

operator+ performs iterator arithmetic
operator- (public member function)
(C++23)