# std::experimental::ostream_joiner

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< cpp‎ | experimental

Defined in header `<experimental/iterator>` |  |
template< class DelimT, class CharT = char, class Traits = std::char_traits<CharT>> class ostream_joiner; |  | (library fundamentals TS v2)

`std::experimental::ostream_joiner` is a single-pass `OutputIterator` that writes successive objects into the std::basic_ostream object for which it was constructed, using `operator<<`, separated by a delimiter. The delimiter is written to the output stream between every two objects that are written. The write operation is performed when the iterator (whether dereferenced or not) is assigned to. Incrementing the `ostream_joiner` is a no-op.

In a typical implementation, the only data members of `ostream_joiner` are a pointer to the associated `std::basic_ostream`, the delimiter, and a `bool` member that indicates whether the next write is for the first element in the sequence.

Compared to std::ostream_iterator, `ostream_joiner` prints the delimiter sequence one fewer time, and is not templated on the type of the object to be printed.

### Member types

Member type | Definition
`char_type` | `CharT`
`traits_type` | `Traits`
`ostream_type` | std::basic_ostream<CharT, Traits>
`value_type` | void
`difference_type` | void
`pointer` | void
`reference` | void
`iterator_category` | std::output_iterator_tag

### Member functions

(constructor) | constructs a new `ostream_joiner` (public member function)
(destructor) (implicitly declared) | destructs an `ostream_joiner` (public member function)
operator= | writes a object to the associated output sequence (public member function)
operator* | no-op (public member function)
operator++operator++(int) | no-op (public member function)

### Non-member functions

make_ostream_joiner | creates a `ostream_joiner` object, deducing the template's type arguments from the function arguments (function template)

### Example

Run this code

    #include <algorithm>
    #include <experimental/iterator>
    #include <iostream>
    #include <iterator>

    int main()
    {
        int i[] = {1, 2, 3, 4, 5};
        std::copy(std::begin(i),
                  std::end(i),
                  std::experimental::make_ostream_joiner(std::cout, ", "));
    }

Output:

    1, 2, 3, 4, 5

### See also

ostreambuf_iterator | output iterator that writes to std::basic_streambuf (class template)
ostream_iterator | output iterator that writes to std::basic_ostream (class template)
istream_iterator | input iterator that reads from std::basic_istream (class template)

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