24 Iterators library [iterators]

24.6 Stream iterators [stream.iterators]

24.6.2 Class template ostream_iterator [ostream.iterator]

1

ostream_iterator writes (using operator<<) successive elements onto the output stream from which it was constructed. If it was constructed with charT* as a constructor argument, this string, called a delimiter string, is written to the stream after every T is written. It is not possible to get a value out of the output iterator. Its only use is as an output iterator in situations like

while (first != last)
  *result++ = *first++;
2

ostream_iterator is defined as:

namespace std {
  template <class T, class charT = char, class traits = char_traits<charT>>
  class ostream_iterator {
  public:
    using iterator_category = output_iterator_tag;
    using value_type        = void;
    using difference_type   = void;
    using pointer           = void;
    using reference         = void;
    using char_type         = charT;
    using traits_type       = traits;
    using ostream_type      = basic_ostream<charT,traits>;

    ostream_iterator(ostream_type& s);
    ostream_iterator(ostream_type& s, const charT* delimiter);
    ostream_iterator(const ostream_iterator& x);
   ~ostream_iterator();
    ostream_iterator& operator=(const T& value);

    ostream_iterator& operator*();
    ostream_iterator& operator++();
    ostream_iterator& operator++(int);
  private:
    basic_ostream<charT,traits>* out_stream;  // exposition only
    const charT* delim;                       // exposition only
  };
}

24.6.2.1 ostream_iterator constructors and destructor [ostream.iterator.cons.des]

ostream_iterator(ostream_type& s);

1

Effects: Initializes out_stream with addressof(s) and delim with null.

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

2

Effects: Initializes out_stream with addressof(s) and delim with delimiter.

ostream_iterator(const ostream_iterator& x);

3

Effects: Constructs a copy of x.

~ostream_iterator();

4

Effects: The iterator is destroyed.

24.6.2.2 ostream_iterator operations [ostream.iterator.ops]

ostream_iterator& operator=(const T& value);

1

Effects: As if by: 

*out_stream << value;
if (delim != 0)
  *out_stream << delim;
return *this;

ostream_iterator& operator*();

2

Returns: *this.

ostream_iterator& operator++(); ostream_iterator& operator++(int);

3

Returns: *this.