at_key

Description

Returns the result type of at_key ^[7] .

Synopsis

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

Table 1.30. Parameters

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

Expression Semantics

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

Return type: Any type.

Semantics: Returns the result of using at_key to access the element with key type Key in Seq.

/sequence/intrinsic/at_key.hpp>

Example

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

^[7] result_of::at_key reflects the actual return type of the function at_key. _sequence_s typically return references to its elements via the at_key function. If you want to get the actual element type, use result_of::value_at_key