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Unique Associative Container


Category: containers 
Component type: concept 
Description
A Unique Associative Container is an Associative Container with
the property that each key in the container is unique: no two elements
in a Unique Associative Container have the same key.
Refinement of
Associative Container
Associated types
None, except for those defined by Associative Container.
Notation
X

A type that is a model of Unique Associative Container

a

Object of type X

t

Object of type X::value_type

k

Object of type X::key_type

p, q

Object of type X::iterator

Definitions
Valid expressions
In addition to the expressions defined in
Associative Container, the
following expressions must be valid.
Name

Expression

Type requirements

Return type

Range constructor

X(i, j)
X a(i, j);

i and j are Input Iterators whose value type is convertible
to T [1]


Insert element

a.insert(t)


pair<X::iterator, bool>

Insert range

a.insert(i, j)

i and j are Input Iterators whose value type is convertible
to X::value_type. [1]

void

Count

a.count(k)


size_type

Expression semantics
Name

Expression

Precondition

Semantics

Postcondition

Range constructor

X(i, j)
X a(i, j);

[i,j) is a valid range.

Creates an associative container that contains all of the elements in the range [i,j)
that have unique keys.

size() is less than or equal to the distance from i to j.

Insert element

a.insert(t)


Inserts t into a if and only if a does not already contain an
element whose key is the same as the key of t. The return value
is a pair P. P.first is an iterator pointing to the
element whose key is the same as the key of t. P.second is
a bool: it is true if t was actually inserted into a, and
false if t was not inserted into a, i.e. if a already
contained an element with the same key as t.

P.first is a dereferenceable iterator. *(P.first) has the same
key as t. The size of a is incremented by 1 if and only if
P.second is true.

Insert range

a.insert(i, j)

[i, j) is a valid range.

Equivalent to a.insert(t) for each object t that is pointed to
by an iterator in the range [i, j). Each element is inserted into
a if and only if a does not already contain an element with
the same key.

The size of a is incremented by at most j  i.

Count

a.count(k)


Returns the number of elements in a whose keys are the same as k.

The return value is either 0 or 1.

Complexity guarantees
Average complexity for insert element is at most logarithmic.
Average complexity for insert range is at most O(N * log(size() + N)),
where N is j  i.
Invariants
Uniqueness

No two elements have the same key. Equivalently, this means that
for every object k of type key_type, a.count(k) returns either
0 or 1.

Models
Notes
[1]
At present (early 1998), not all compilers support
"member templates". If your compiler supports member
templates then i and j may be of any type that
conforms to the Input Iterator
requirements. If your compiler does not yet support member
templates, however, then i and j must be of type
const T* or of type X::const_iterator.
See also
Associative Container, Multiple Associative Container,
Unique Sorted Associative Container,
Multiple Sorted Associative Container
Copyright ©
1999 Silicon Graphics, Inc. All Rights Reserved.
TrademarkInformation
