std::istream_iterator<T,CharT,Traits,Distance>::istream_iterator

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, value-initializes the stored value. This constructor is constexpr if the initializer in the definition auto x = T(); is a constant initializer.

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

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
P0738R2	C++98	the first read may be deferred to the first dereferencing	the first read is performed in the constructor

Examples

#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

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