Boost C++ Libraries

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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;
};

Table 1.34. Parameters

Parameter

Requirement

Description

Seq

A model of Associative 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.

Header
#include <boost/fusion/sequence/intrinsic/at_key.hpp>
#include <boost/fusion/include/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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