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Returns a type convertible to bool
that evaluates to true if
the sequence contains an element associated with a Key, else, evaluates
to false.
template <typename Key, typename Sequence>
typename result_of::has_key<Sequence, Key>::type
has_key(Sequence const& seq);
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Parameter |
Requirement |
Description |
|---|---|---|
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Model of Associative Sequence |
The sequence we wish to investigate. |
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Any type |
The queried key. |
has_key<Key>(seq);
Return type: Convertible to bool.
Semantics: Evaluates to true if the sequence contains an element
associated with Key, else, evaluates to false.
#include <boost/fusion/sequence/intrinsic/has_key.hpp> #include <boost/fusion/include/has_key.hpp>
set<int, char, bool> s(1, 'x', true);
assert(has_key<char>(s) == true);