at_key

Description

Returns the element associated with a Key from the sequence.

Synopsis

template <typename Key, typename Sequence>
typename result_of::at_key<Sequence, Key>::type
at_key(Sequence& seq);

template <typename Key, typename Sequence>
typename result_of::at_key<Sequence const, Key>::type
at_key(Sequence const& seq);

Parameters

Parameter	Requirement	Description
`seq`	Model of Associative Sequence	The sequence we wish to investigate.
`Key`	Any type	The queried key.

Expression Semantics

at_key<Key>(seq);

Return type: Returns a reference to the element associated with Key from the sequence seq if seq is mutable and e = o, where e is the element associated with Key, is a valid expression. Else, returns a type convertable to the element associated with Key.

Precondition: has_key<Key>(seq) == true

Semantics: Returns the element associated with Key.

Header

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

Example

set<int, char, bool> s(1, 'x', true);
assert(at_key<char>(s) == 'x');