std::front_insert_iterator

 

C++

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indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_output_iterator (C++20)	forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
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input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (deprecated in C++17) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
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indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)	indirect_unary_predicate (C++20) indirect_binary_predicate (C++20)	indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20)	indirectly_copyable_storable (C++20)   indirectly_swappable (C++20) indirectly_comparable (C++20)	permutable (C++20) mergeable (C++20) sortable (C++20)
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indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
Iterator adaptors
reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter move_sentinel (C++20)	common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) make_const_iterator (C++23) make_const_sentinel (C++23)
Stream iterators istream_iterator    ostream_iterator istreambuf_iterator ostreambuf_iterator	Iterator customization points ranges::iter_move (C++20) ranges::iter_swap (C++20)
Iterator operations advance distance prev (C++11)   next (C++11) ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)	Range access begincbegin (C++11)(C++14) rbegincrbegin (C++14)(C++14)   endcend (C++11)(C++14) rendcrend (C++14)(C++14)   sizessize (C++17)(C++20) empty (C++17) data (C++17)

 

std::front_insert_iterator

Member functions

front_insert_iterator::front_insert_iterator

front_insert_iterator::operator=

front_insert_iterator::operator*

front_insert_iterator::operator++front_insert_iterator::operator++(int)

 

Defined in header <iterator>
template<class Container > class front_insert_iterator     :publicstd::iterator<std::output_iterator_tag, void, void, void, void>		(until C++17)
template<class Container > class front_insert_iterator;		(since C++17)

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 std::iterator<std::output_iterator_tag, void, void, void, void>.

(until C++17)

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++operator++(int)	no-op (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, autoconst& 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

front_inserter	creates a std::front_insert_iterator of type inferred from the 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)