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

From cppreference.com
< cpp‎ | ranges‎ | adjacent view‎ | iterator
 
 
Ranges library
Range access
Range conversions
(C++23)

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(until C++23)(C++23)


 
 
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_)
    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.

Contents

[edit] Parameters

n - position relative to current location

[edit] Return value

1,3,5,6) *this
2,4) A copy of *this that was made before the change.

[edit] Example

#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)
    }
}

[edit] See also

performs iterator arithmetic
(public member function)