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

Click here to view the latest version of this page.
PrevUpHomeNext
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');

PrevUpHomeNext