Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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at_key
Description

Returns the result type of at_key [8] .

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

Table1.30.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&>));


[8] 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


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