std::ostream_iterator

 

C++

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Iterator library

Iterator concepts
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)
Iterator primitives
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)
Algorithm concepts and utilities
Indirect callable concepts
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)
Utilities
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::ostream_iterator

Member functions

ostream_iterator::ostream_iterator

ostream_iterator::~ostream_iterator

ostream_iterator::operator=

ostream_iterator::operator*

ostream_iterator::operator++ostream_iterator::operator++(int)

 

Defined in header <iterator>
template< class T,           class CharT = char,           class Traits = std::char_traits<CharT>> class ostream_iterator : public std::iterator<std::output_iterator_tag,                                               void, void, void, void>

std::ostream_iterator is a single-pass output iterator that writes successive objects of type T into the std::basic_ostream object for which it was constructed, using operator<<. Optional delimiter string is written to the output stream after every write operation. The write operation is performed when the iterator (whether dereferenced or not) is assigned to. Incrementing the std::ostream_iterator is a no-op.

In a typical implementation, the only data members of std::ostream_iterator are a pointer to the associated std::basic_ostream and a pointer to the first character in the delimiter string.

When writing characters, std::ostreambuf_iterator is more efficient, since it avoids the overhead of constructing and destructing the sentry object once per character.

Member types

Member type	Definition
char_type	CharT
traits_type	Traits
ostream_type	std::basic_ostream<CharT, Traits>

Member functions

(constructor)	constructs a new ostream_iterator (public member function)
(destructor)	destructs an ostream_iterator (public member function)
operator=	writes an object to the associated output sequence (public member function)
operator*	no-op (public member function)
operator++operator++(int)	no-op (public member function)

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

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)

Example

Run this code

#include <iostream>
#include <sstream>
#include <iterator>
#include <algorithm>
#include <numeric>
 
int main()
{
    std::istringstream str("0.1 0.2 0.3 0.4");
    std::partial_sum(std::istream_iterator<double>(str),
                      std::istream_iterator<double>(),
                      std::ostream_iterator<double>(std::cout, " "));
}

Output:

0.1 0.3 0.6 1

See also

ostreambuf_iterator	output iterator that writes to std::basic_streambuf (class template)
istream_iterator	input iterator that reads from std::basic_istream (class template)