Boost C++ Libraries

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value_at_key

Description

Returns the actual element type associated with a Key from the Sequence.

Synopsis

template<
    typename Seq,
    typename Key>
struct value_at_key
{
    typedef unspecified type;
};

Table 1.34. Parameters

Parameter	Requirement	Description
`Seq`	A model of Associative Sequence	Argument sequence
`Key`	Any type	Key type

Expression Semantics

result_of::value_at_key<Seq, Key>::type

Return type: Any type.

Precondition: has_key<Seq, Key>::type::value == true (where Seq is not Unbounded Sequence)

Semantics: Returns the actual element type associated with key type Key in Seq.

Header

#include <boost/fusion/sequence/intrinsic/value_at_key.hpp>
#include <boost/fusion/include/value_at_key.hpp>

Example

typedef map<pair<int, char>, pair<char, char>, pair<double, char> > mymap;
BOOST_MPL_ASSERT((boost::is_same<result_of::value_at_key<mymap, int>::type, char>));