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Concept ForwardIterator
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Concept ForwardIterator

ForwardIterator

Description

A forward iterator is an iterator that can read through a sequence of values. It is multi-pass (old values of the iterator can be re-used), and can be either mutable (data pointed to by it can be changed) or not mutable.

An iterator represents a position in a sequence. Therefore, the iterator can point into the sequence (returning a value when dereferenced and being incrementable), or be off-the-end (and not dereferenceable or incrementable).

Refinement of

Associated types

  • value_type

    std::iterator_traits<Iter>::value_type

    The value type of the iterator

  • category

    std::iterator_traits<Iter>::iterator_category

    The category of the iterator

Notation

Iter
A type playing the role of iterator-type in the ForwardIterator concept.
i, j
Objects of type Iter
x
Object of type value_type

Type expressions

Category tag

category must be derived from std::forward_iterator_tag.

Valid expressions

Name Expression Type Precondition Semantics Postcondition

Dereference

*i

const-if-not-mutable value_type &

i is incrementable (not off-the-end)

    

Member access

i->{member-name} (return type is pointer-to-object type)

const-if-not-mutable value_type *

i is incrementable (not off-the-end)

    

Preincrement

++i

Iter &

i is incrementable (not off-the-end)

    

Postincrement

i++

Iter

i is incrementable (not off-the-end)

Equivalent to {Iter j = i; ++i; return j;}

i is dereferenceable or off-the-end

Complexity

All iterator operations must take amortized constant time.

Invariants

Predecrement must return object

&i = &(++i)

Unique path through sequence

i == j implies ++i == ++j

Models

  • T *
  • std::hash_set<T>::iterator
Copyright © 2001, 2002 Indiana University
Copyright © 2000, 2001 University of Notre Dame du Lac
Copyright © 2000 Jeremy Siek, Lie-Quan Lee, Andrew Lumsdaine
Copyright © 1996-1999 Silicon Graphics Computer Systems, Inc.
Copyright © 1994 Hewlett-Packard Company

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

This product includes software developed at the University of Notre Dame and the Pervasive Technology Labs at Indiana University. For technical information contact Andrew Lumsdaine at the Pervasive Technology Labs at Indiana University. For administrative and license questions contact the Advanced Research and Technology Institute at 351 West 10th Street. Indianapolis, Indiana 46202, phone 317-278-4100, fax 317-274-5902.

Some concepts based on versions from the MTL draft manual and Boost Graph and Property Map documentation, the SGI Standard Template Library documentation and the Hewlett-Packard STL, under the following license:

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