std::istream_iterator::istream_iterator

 

C++

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Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Iterator library

Iterator primitives
iterator_traits
input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tag
iterator
Iterator adaptors
reverse_iterator move_iterator (C++11) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) back_inserter front_inserter inserter
Stream iterators
istream_iterator
ostream_iterator
istreambuf_iterator
ostreambuf_iterator
Iterator operations
advance
distance
prev (C++11)
next (C++11)
Range access
begincbegin (C++11)(C++14)
endcend (C++11)(C++14)
rbegincrbegin (C++14)(C++14)
rendcrend (C++14)(C++14)
Container access
size (C++17)
empty (C++17)
data (C++17)

 

std::istream_iterator

Member functions

istream_iterator::istream_iterator

istream_iterator::~istream_iterator

istream_iterator::operator*istream_iterator::operator->

istream_iterator::operator++istream_iterator::operator++(int)

Non-member functions

operator==operator!=

 

constexpr istream_iterator();	(1)
istream_iterator( istream_type& stream );	(2)
istream_iterator( const istream_iterator& other ) = default;	(3)

1) Constructs the end-of-stream iterator. This constructor is constexpr if std::is_trivially_default_constructible_v<T> is true .

2) Initializes the iterator, stores the address of stream in a data member, and performs the first read from the input stream to initialize the cached value data member.

3) Constructs a copy of other. If std::is_trivially_copy_constructible_v<T> is true , this copy constructor is a trivial copy constructor.

Parameters

stream	-	stream to initialize the istream_iterator with
other	-	another istream_iterator of the same type

Notes

The specification formally permits std::istream_iterator to delay the first read to take place when the first dereferencing is done. This was reaffirmed by lwg245, but contested by p0738 as unimplementable. All existing implementations perform the first read immediately, in the constructor.

Examples

Run this code

#include <iostream>
#include <iterator>
#include <algorithm>
#include <sstream>
int main()
{
    std::istringstream stream("1 2 3 4 5");
    std::copy(
        std::istream_iterator<int>(stream),
        std::istream_iterator<int>(),
        std::ostream_iterator<int>(std::cout, " ")
    );
}

Output:

1 2 3 4 5