HP Integrity NonStop H-Series - Manual (Page 97)

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©Copyright 1996 Rogue Wave Software
The map Data Abstraction
Other Names for Maps
A map is an indexed data structure, similar to a vector or a deque . However, maps differ from
vectors or deques in two important respects. First, in a map, unlike a vector or deque, the index
values (called the key values) need not be integer, but can be any ordered data type. For
example, maps can be indexed by real numbers, or by strings. Any data type for which a
comparison operator can be defined can be used as a key. As with a vector or deque, elements
can be accessed through the use of the subscript operator (although there are other techniques).
The second important difference is that a map is an ordered data structure. This means that
elements are maintained in sequence, the ordering being determined by key values. Because
they maintain values in order, maps can very rapidly find the element specified by any given
key (searching is performed in logarithmic time). Like a
list , maps are not limited in size, but
expand or contract as necessary as new elements are added or removed. In large part, a map can
simply be considered to be a
set that maintains a collection of pairs.
There are two varieties of maps provided by the standard library. The map data structure
demands unique keys. That is, there is a one-to-one association between key elements and their
corresponding value. In a map, the insertion of a new value that uses an existing key is ignored.
A
multimap , on the other hand, permits multiple different entries to be indexed by the same
key. Both data structures provide relatively fast (logarithmic time) insertion, deletion, and
access operations.
Pairs
Include files
Whenever you use a map or a multimap , you must include the map header file.
# include <map>