## Forward Iterators

    Iterator

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

### Summary

A forward-moving iterator that can both read and write.

### 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. Forward iterators are forward moving, and have the ability to both read and write data. These iterators satisfy the requirements listed below.

### Key to Iterator Requirements

The following key pertains to the iterator requirements listed below:

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

### Requirements for Forward Iterators

The following expressions must be valid for forward iterators:

`X u` | u might have a singular value
`X()` | X() might be singular
`X(a)` | copy constructor, `a == X(a)`
`X u(a)` | copy constructor, `u == a`
`X u = a` | assignment, `u == a`
`a == b, a != b` | return value convertible to `bool`
`*a` | return value convertible to `T&`
`a->m` | equivalent to `(*a).m`
`++r` | returns `X&`
`r++` | return value convertible to const `X&`
`*r++` | returns `T&`

Forward iterators have the condition that `a == b` implies `*a == *b`.

There are no restrictions on the number of passes an algorithm may make through the structure.

### See Also

Iterators, Bidirectional Iterators

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