Forward Iterator Forward Iterator Category: iterators Component type: concept Description A Forward Iterator is an iterator that corresponds to the usual intuitive notion of a linear sequence of values. It is possible to use Forward Iterators (unlike Input Iterators and Output Iterators) in multipass algorithms. Forward Iterators do not, however, allow stepping backwards through a sequence, but only, as the name suggests, forward. A type that is a model of Forward Iterator may be either mutable or immutable, as defined in the Trivial Iterators requirements. Refinement of Input Iterator, Output Iterator Associated types The same as for Input Iterator Notation X A type that is a model of Forward Iterator T The value type of X i, j Object of type X t Object of type T Definitions Valid expressions Forward Iterator does not define any new expressions beyond those defined in Input Iterator. However, some of the restrictions described in Input Iterator are relaxed. Name Expression Type requirements Return type Preincrement ++i   X& Postincrement i++   X Expression semantics Forward Iterator does not define any new expressions beyond those defined in Input Iterator. However, some of the restrictions described in Input Iterator are relaxed. Name Expression Precondition Semantics Postcondition Preincrement ++i i is dereferenceable i points to the next value i is dereferenceable or past-the-end. &i == &++i. If i == j, then ++i == ++j. [1] Postincrement i++ i is dereferenceable Equivalent to {X tmp = i; ++i; return tmp;} i is dereferenceable or past-the-end. [1] Complexity guarantees The complexity of operations on Forward Iterators is guaranteed to be amortized constant time. Invariants Models T* hash_set<T>::iterator Notes [1] The restrictions described in Input Iterator have been removed. Incrementing a forward iterator does not invalidate copies of the old value and it is guaranteed that, if i and j are dereferenceable and i == j, then ++i == ++j. As a consequence of these two facts, it is possible to pass through the same Forward Iterator twice. See also Input Iterator, Output Iterator, Bidirectional Iterator, Random Access Iterator, Iterator overview Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation