NAME¶

std::front_insert_iterator - std::front_insert_iterator

Synopsis¶

Defined in header <iterator>
template< class Container >

class front_insert_iterator (until C++17)

: public std::iterator<std::output_iterator_tag, void, void,
void, void>
template< class Container > (since C++17)
class front_insert_iterator;

std::front_insert_iterator is a LegacyOutputIterator that prepends elements to a
container for which it was constructed. The container's push_front() member function
is called whenever the iterator (whether dereferenced or not) is assigned to.
Incrementing the std::front_insert_iterator is a no-op.

Member types¶

Member type Definition
iterator_category std::output_iterator_tag
value_type void
difference_type void (until C++20)
std::ptrdiff_t (since C++20)
pointer void
reference void
container_type Container

Member types iterator_category, value_type, difference_type, pointer
and reference are required to be obtained by inheriting from (until C++17)
std::iterator<std::output_iterator_tag, void, void, void, void>.

Member functions¶

constructor constructs a new front_insert_iterator
(public member function)
operator= inserts an object into the associated container
(public member function)
operator* no-op
(public member function)
operator++ no-op
operator++(int) (public member function)

Member objects¶

Member name Definition
container (protected) a pointer of type Container*

Example¶

// Run this code

#include <algorithm>
#include <deque>
#include <iostream>
#include <iterator>
#include <vector>

namespace stb
{
void println(auto, auto const& d)
{
std::ranges::copy(d, std::ostream_iterator<int>(std::cout, " "));
std::cout << '\n';
}
}

int main()
{
std::vector<int> v{1, 2, 3, 4, 5};
std::deque<int> d;

std::copy(v.begin(), v.end(),
std::front_insert_iterator<std::deque<int>>(d));
// or std::front_inserter(d)

stb::println("{}", d);
}

Output:¶

5 4 3 2 1

See also¶

creates a std::front_insert_iterator of type inferred from the
front_inserter argument
(function template)
back_insert_iterator iterator adaptor for insertion at the end of a container
(class template)
insert_iterator iterator adaptor for insertion into a container
(class template)