Increments or decrementsbegin_ :

• IfI modelsbidirectional_iterator andn<0 istrue, decrementsbegin_ by-n elements.

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

• Otherwise, incrementsbegin_ byn elements, or untilend_ is reached.

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

According to the preconditions ofranges::advance, ifn<0 istrue andbegin_ 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,autoconst 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

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