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% | Reference manual page: Handle_hash_function.tex
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% | 08.07.2001   Lutz Kettner
% | Package: Hash_map
% | 
\RCSdef{\RCSHandlehashfunctionRev}{$Id$}
\RCSdefDate{\RCSHandlehashfunctionDate}{$Date$}
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\begin{ccRefClass}{Handle_hash_function}

\ccDefinition
  
The class \ccRefName\ is a model for the \ccc{UniqueHasFunction}
concept.  It is applicable for all key types with pointer-like
functionality, such as handles, iterators, and circulators.
Specifically, for a \ccc{key} value the expression \ccc{&*key} must
return a unique address.

\ccInclude{CGAL/Handle_hash_function.h}

\ccIsModel

\ccRefConceptPage{UniqueHashFunction}

\ccCreation
\ccCreationVariable{hash}

\ccConstructor{Handle_hash_function();}{default constructor.}

\ccOperations

\ccMethod{template <class Handle>
          std::size_t operator()( const Handle& key);}{
    returns unique hash value for any \ccc{Handle}
    type for which \ccc{&*key} gives a unique address.
    \ccCommentHeading{Requirement} The type 
    \ccc{std::iterator_traits<Handle>::value_type} has to be defined
    (which it is already for pointers, handles, iterators, and 
    circulators).}

\ccSeeAlso

\ccRefIdfierPage{CGAL::Unique_hash_map<Key,Data,UniqueHashFunction>}

\ccImplementation

Plain type cast of \ccc{&*key} to \ccc{std::size_t} and devided
by the size of the \ccc{std::iterator_traits<Handle>::value_type} to
avoid correlations with the internal table size, which is a power of
two.

\end{ccRefClass}

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