std::ranges::subrange<I,S,K>::advance

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.

[edit] Parameters

[edit] Return value

*this

[edit] 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 }

[edit] Defect reports

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

[edit] See also