NAME¶

std::next - std::next

Synopsis¶

Defined in header <iterator>
template< class InputIt > (since C++11)
InputIt next( InputIt it, typename (until C++17)
std::iterator_traits<InputIt>::difference_type n = 1 );
template< class InputIt >

constexpr (since C++17)

InputIt next( InputIt it, typename
std::iterator_traits<InputIt>::difference_type n = 1 );

Return the n^th successor (or -n^th predecessor if n is negative) of iterator it.

Parameters¶

it - an iterator
n - number of elements to advance

Type requirements¶

-
InputIt must meet the requirements of LegacyInputIterator.

Return value¶

An iterator of type InputIt that holds the n^th successor (or -n^th predecessor if n
is negative) of iterator it.

Complexity¶

Linear.

However, if InputIt additionally meets the requirements of
LegacyRandomAccessIterator, complexity is constant.

Possible implementation¶

template<class InputIt>
constexpr // since C++17
InputIt next(InputIt it, typename std::iterator_traits<InputIt>::difference_type n = 1)
{
std::advance(it, n);
return it;
}

Notes¶

Although the expression ++c.begin() often compiles, it is not guaranteed to do so:
c.begin() is an rvalue expression, and there is no LegacyInputIterator requirement
that specifies that increment of an rvalue is guaranteed to work. In particular,
when iterators are implemented as pointers or its operator++ is
lvalue-ref-qualified, ++c.begin() does not compile, while std::next(c.begin()) does.

Example¶

// Run this code

#include <iostream>
#include <iterator>
#include <vector>

int main()
{
std::vector<int> v{4, 5, 6};

auto it = v.begin();
auto nx = std::next(it, 2);
std::cout << *it << ' ' << *nx << '\n';

it = v.end();
nx = std::next(it, -2);
std::cout << ' ' << *nx << '\n';
}

Output:¶

4 6
5

Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 2353 C++11 next required LegacyForwardIterator LegacyInputIterator allowed

See also¶

prev decrement an iterator
(C++11) (function template)
advance advances an iterator by given distance
(function template)
distance returns the distance between two iterators
(function template)
ranges::next increment an iterator by a given distance or to a bound
(C++20) (niebloid)