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Standard Template Library Programmer's Guide
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ostream_iterator<T>


Category: iterators	Component type: type

Description

An ostream_iterator is an Output Iterator that performs formatted output of objects of type T to a particular ostream. Note that all of the restrictions of an Output Iterator must be obeyed, including the restrictions on the ordering of operator* and operator++ operations.

Example

Copy the elements of a vector to the standard output, one per line.

vector<int> V;
// ...
copy(V.begin(), V.end(), ostream_iterator<int>(cout, "\n"));

Definition

Defined in the standard header iterator, and in the nonstandard backward-compatibility header iterator.h.

Template parameters

Parameter	Description	Default
`T`	The type of object that will be written to the `ostream`. The set of value types of an `ostream_iterator` consists of a single type, `T`.

Model of

Output Iterator.

Type requirements

T must be a type such that cout << T is a valid expression.

Public base classes

None.

Members

Member	Where defined	Description
`ostream_iterator(ostream&)`	`ostream_iterator`	See below.
`ostream_iterator(ostream&, const char* s)`	`ostream_iterator`	See below.
`ostream_iterator(const ostream_iterator&)`	Output Iterator	The copy constructor
`ostream_iterator& operator=(const ostream_iterator&)`	Output Iterator	The assignment operator
`ostream_iterator& operator=(const T&)`	Output Iterator	Used to implement the Output Iterator requirement `*i = t`. [1]
`ostream_iterator& operator*()`	Output Iterator	Used to implement the Output Iterator requirement `*i = t`. [1]
`ostream_iterator& operator++()`	Output Iterator	Preincrement
`ostream_iterator& operator++(int)`	Output Iterator	Postincrement
`output_iterator_tag iterator_category(const ostream_iterator&)`	iterator tags	Returns the iterator's category.

New members

These members are not defined in the Output Iterator requirements, but are specific to ostream_iterator.

Function	Description
`ostream_iterator(ostream& s)`	Creates an `ostream_iterator` such that assignment of `t` through it is equivalent to `s << t`.
`ostream_iterator(ostream& s, const char* delim)`	Creates an `ostream_iterator` such that assignment of `t` through it is equivalent to `s << t << delim`.

Notes

[1] Note how assignment through an ostream_iterator is implemented. In general, unary operator* must be defined so that it returns a proxy object, where the proxy object defines operator= to perform the output operation. In this case, for the sake of simplicity, the proxy object is the ostream_iterator itself. That is, *i simply returns i, and *i = t is equivalent to i = t. You should not, however, rely on this behavior. It is an implementation detail, and it is not guaranteed to remain the same in future versions.