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Category: containers Component type: concept


A Pair Associative Container is an AssociativeContainer that associates a key with some other object. The value type of a Pair Associative Container is pair<const key_type, data_type>. [1]

Refinement of


Associated types

One new type is introduced, in addition to the types defined in the AssociativeContainer requirements. Additionally, Pair Associative Container introduces one new type restriction

Key type X::key_type The type of the key associated with X::value_type.
Data type X::data_type The type of the data associated with X::value_type. A Pair Associative Container can be thought of as a mapping from key_type to data_type.
Value type X::value_type The type of object stored in the container. The value type is required to be pair<const key_type, data_type>.


X A type that is a model of Pair Associative Container
a Object of type X
t Object of type X::value_type
d Object of type X::data_type
k Object of type X::key_type
p, q Object of type X::iterator


Valid expressions

None, except for those defined in the AssociativeContainer requirements.

Expression semantics

Complexity guarantees




[1] The value type must be pair<const key_type, data_type>, rather than pair<key_type, data_type>, because of the AssociativeContainer invariant of key immutability. The data_type part of an object in a Pair Associative Container may be modified, but the key_type part may not be. Note the implication of this fact: a Pair Associative Container cannot provide mutable iterators (as defined in the trivial requirements), because the value type of a mutable iterator must be Assignable, and pair<const key_type, data_type> is not Assignable. However, a Pair Associative Container can provide iterators that are not completely constant: iterators such that the expression (*i).second = d is valid.

See also

AssociativeContainer, SimpleAssociativeContainer

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