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Forward Container


Category: containers 
Component type: concept 
Description
A Forward Container is a Container whose
elements are arranged in a definite order: the ordering will not
change spontaneously from iteration to iteration. The requirement of
a definite ordering allows the definition of elementbyelement
equality (if the container's element type is
Equality Comparable) and of
lexicographical ordering (if the container's element type is
LessThan Comparable).
Iterators into a Forward Container satisfy the
forward iterator requirements;
consequently, Forward Containers support multipass algorithms and
allow multiple iterators into the same container to be active at the
same time.
Refinement of
Container,
EqualityComparable,
LessThanComparable
Associated types
No additional types beyond those defined in
Container. However, the requirements for
the iterator type are strengthened: the iterator type must be a model
of Forward Iterator.
Notation
X

A type that is a model of Forward Container

a, b

Object of type X

T

The value type of X

Definitions
Valid expressions
In addition to the expressions defined in
Container,
EqualityComparable, and
LessThanComparable, the following
expressions must be valid.
Expression semantics
Semantics of an expression is defined only where it is not defined in
Container,
EqualityComparable, or
LessThanComparable, or where there
is additional information.
Name

Expression

Precondition

Semantics

Postcondition

Equality

a == b


Returns true if a.size() == b.size() and if each element of a
compares equal to the corresponding element of b. Otherwise
returns false.


Less

a < b


Equivalent to lexicographical_compare(a,b)


Complexity guarantees
The equality and inequality operations are linear in the
container's size.
Invariants
Ordering

Two different iterations through a forward container will access
its elements in the same order, providing that there have been
no intervening mutative operations.

Models
Notes
See also
The iterator overview,
Forward Iterator,
Sequence
Copyright ©
1999 Silicon Graphics, Inc. All Rights Reserved.
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