27 Iterators library [iterators]

27.6 Stream iterators [stream.iterators]

27.6.2 Class template ostream_­iterator [ostream.iterator]

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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++;
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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
  };
}

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

ostream_iterator(ostream_type& s);
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Effects: Initializes out_­stream with addressof(s) and delim with null.
ostream_iterator(ostream_type& s, const charT* delimiter);
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Effects: Initializes out_­stream with addressof(s) and delim with delimiter.
ostream_iterator(const ostream_iterator& x);
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Effects: Constructs a copy of x.
~ostream_iterator();
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Effects: The iterator is destroyed.

27.6.2.2 ostream_­iterator operations [ostream.iterator.ops]

ostream_iterator& operator=(const T& value);
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Effects: As if by: 
*out_stream << value;
if (delim != 0)
  *out_stream << delim;
return *this;
ostream_iterator& operator*();
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Returns: *this.
ostream_iterator& operator++(); ostream_iterator& operator++(int);
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Returns: *this.