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The pair class is used to house pairs of objects, such as might be stored in an associative container. It has this template specification:
template <class Ktype, class Vtype> struct pair { typedef Ktype first_type; typedef Vtype second_type; Ktype first; Vtype second; // constructors pair(); pair(const Ktype &k, const Vtype &v); template<class A, class B> pair(const<A, B> &ob); }
The value in first typically contains a key, and the value in second typically contains the value associated with that key.
The following operators are defined for pair: ==, !=, <, <=, >, and >=.
You can construct a pair using either one of pair’s constructors or by using make_pair( ), which constructs a pair object based upon the types of the data used as parameters. make_pair( ) is a generic function that has this prototype:
template <class Ktype, class Vtype>
pair<Ktype, Vtype> make_pair(const Ktype &k, const Vtype &v);
It returns a pair object consisting of values of the types specified by Ktype and Vtype. The advantage of make_pair( ) is that the types of the objects being stored are determined automatically by the compiler rather than being explicitly specified by you.
The pair class and the make_pair( ) function require the header <utility>.
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