## Output Iterators

    Iterator

- Summary
- Data Type and Member Function Indexes
- Description
- Key to Iterator Requirements
- Requirements for Output Iterators
- See Also

### Summary

A write-only, forward moving iterator.

### Data Type and Member Function Indexes
(exclusive of constructors and destructors)

None

### Description

> NOTE:For a complete discussion of iterators, see the Iterators section of this reference.

Iterators are a generalization of pointers that allow a C++ program to uniformly interact with different data structures. Output iterators are write-only, forward moving iterators that satisfy the requirements listed below. Note that unlike other iterators used with the standard library, output iterators cannot be constant.

### Key to Iterator Requirements

The following key pertains to the iterator requirements listed below:

`a and b` | values of type `X`
`n` | value of `distance` type
`u, Distance, tmp and m` | identifiers
`r` | value of type `X&`
`t` | value of type `T`

### Requirements for Output Iterators

The following expressions must be valid for output iterators:

`X(a)` | copy constructor, `a == X(a)`
`X u(a)` | copy constructor, `u == a`
`X u = a` | assignment, `u == a`
`*a = t` | result is not used
`++r` | returns `X&`
`r++` | return value convertible to const `X&`
`*r++ = t` | result is not used

The only valid use for the `operator *` is on the left-hand side of the assignment statement.

Algorithms using output iterators should be single pass algorithms. That is, they should not pass through the same iterator twice.

### See Also

Iterators, Input Iterators

Copyright (c) 1998, Rogue Wave Software, Inc.
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OEM Release, June 1998