Stream iterators are useful when we need to read a sequence or print formatted data from a container:
// Data stream. Any number of various whitespace characters will be OK.
std::istringstream istr("1\t 2 3 4");
std::vector<int> v;
// Constructing stream iterators and copying data from stream into vector.
std::copy(
// Iterator which will read stream data as integers.
std::istream_iterator<int>(istr),
// Default constructor produces end-of-stream iterator.
std::istream_iterator<int>(),
std::back_inserter(v));
// Print vector contents.
std::copy(v.begin(), v.end(),
//Will print values to standard output as integers delimeted by " -- ".
std::ostream_iterator<int>(std::cout, " -- "));
The example program will print 1 -- 2 -- 3 -- 4 --
to standard output.