Increments or decrements begin_ :

• If I models bidirectional_iterator and n < 0 is true, decrements begin_ by -n elements.

Equivalent to: ranges::advance(begin_ , n);
if constexpr (StoreSize )
    size_ += to-unsigned-like (-n);
return *this;.

• Otherwise, increments begin_ by n elements, or until end_ is reached.

Equivalent to: auto d = n - ranges::advance(begin_ , n, end_ );
if constexpr (StoreSize )
    size_ -= to-unsigned-like (d);
return *this;.

According to the preconditions of ranges::advance, if n < 0 is true and begin_ cannot be decremented by -n elements, the behavior is undefined.

Parameters

Return value

*this

Example

#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <ranges>

void print(auto name, auto const sub)
{
    std::cout << name << ".size() == " << sub.size() << "; { ";
    std::ranges::for_each(sub, [](int x) { std::cout << x << ' '; });
    std::cout << "}\n";
};

int main()
{
    std::array arr{1, 2, 3, 4, 5, 6, 7};
    std::ranges::subrange sub{std::next(arr.begin()), std::prev(arr.end())};
    print("1) sub", sub);
    print("2) sub", sub.advance(3));
    print("3) sub", sub.advance(-2));
}

1) sub.size() == 5; { 2 3 4 5 6 }
2) sub.size() == 2; { 5 6 }
3) sub.size() == 4; { 3 4 5 6 }

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also