ostream_iterator

Library:  Iterators

ostream_iterator  iterator 

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Members

char_type operator*()

operator++() operator=()

ostream_iterator() ostream_type

traits_type

Stream iterators allow for use of iterators with ostreams and istreams. They allow generic algorithms to be used directly on streams.

#include <ostream>

namespace std {
  template <class T, class charT, 
            class traits = char_traits<charT> >
  class ostream_iterator;
}

Stream iterators use the standard iterator interface for input and output streams.

The class template ostream_iterator writes elements to an output stream. If you use the constructor that has a second argument, then that string is written after every element (the string must be null-terminated). Since an ostream iterator is an output iterator, it is not possible to dereference values through the iterator. You can only assign to it.

namespace std {

  template <class T, class charT = char, 
            class traits = char_traits<charT> >
  class ostream_iterator:  
    public iterator<output_iterator_tag,void,void,void,void> 
  {
    public:
    typedef T value_type;
    typedef charT char_type;
    typedef traits traits_type;
    typedef basic_ostream<charT,traits> ostream_type;

    ostream_iterator(ostream_type&);
    ostream_iterator(ostream_type&, const char_type*); 
    ostream_iterator(const ostream_iterator&);

    ostream_iterator& operator=(const T&);
    ostream_iterator& operator*() const;
    ostream_iterator& operator++();
    ostream_iterator  operator++(int);
  };
}

char_type; 

Type of character the stream is built on.

traits_type; 

Traits used to build the stream.

ostream_type; 

Type of stream this iterator is constructed on.

ostream_iterator (ostream_type& s);

Constructs an ostream_iterator on the given stream.

ostream_iterator (ostream_type& s, 
                  const char_type* delimiter);

Constructs an ostream_iterator on the given stream. The null terminated string delimiter is written to the stream after every element.

ostream_iterator (const ostream_iterator& x);

Copy constructor.

const T& 
operator= (const T& value);

Insert value into the associated output stream x by calling x << value.

const T& ostream_iterator& 
operator* ();
ostream_iterator&  
operator++();
ostream_iterator
operator++ (int);

These operators do nothing. They simply allow the iterator to be used in common constructs.

 #include <iterator>
 #include <numeric>
 #include <deque>
 #include <iostream>
 using namespace std;

 int main ()
 {
   //
   // Initialize a vector using an array.
   //
   int arr[4] = { 3,4,7,8 };
   int total=0;
   deque<int> d(arr+0, arr+4);
   //
   // stream the whole vector and a sum to cout
   //
   copy(d.begin(),d.end()-1,
        ostream_iterator<int,char>(cout," + "));
   cout << *(d.end()-1) << " = " <<
        accumulate(d.begin(),d.end(),total) << endl;
   return 0;
 }

istream_iterator, Iterators

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.5.2