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boost/multi_index/mem_fun.hpp

http://www.boost.org/LICENSE_1_0.txt)
 *
 * See http://www.boost.org/libs/multi_index for library home page.
 */

#ifndef BOOST_MULTI_INDEX_MEM_FUN_HPP
#define BOOST_MULTI_INDEX_MEM_FUN_HPP

#if defined(_MSC_VER)&&(_MSC_VER>=1200)
#pragma once
#endif

#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
#include <boost/mpl/if.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/utility/enable_if.hpp>

#if !defined(BOOST_NO_SFINAE)
#include <boost/type_traits/is_convertible.hpp>
#endif

namespace boost{

template<class T> class reference_wrapper; /* fwd decl. */

namespace multi_index{

/* mem_fun implements a read-only key extractor based on a given non-const
 * member function of a class.
 * const_mem_fun does the same for const member functions.
 * Additionally, mem_fun  and const_mem_fun are overloaded to support
 * referece_wrappers of T and "chained pointers" to T's. By chained pointer
 * to T we  mean a type P such that, given a p of Type P
 *   *...n...*x is convertible to T&, for some n>=1.
 * Examples of chained pointers are raw and smart pointers, iterators and
 * arbitrary combinations of these (vg. T** or auto_ptr<T*>.)
 */

/* NB. Some overloads of operator() have an extra dummy parameter int=0.
 * This disambiguator serves several purposes:
 *  - Without it, MSVC++ 6.0 incorrectly regards some overloads as
 *    specializations of a previous member function template.
 *  - MSVC++ 6.0/7.0 seem to incorrectly treat some different memfuns
 *    as if they have the same signature.
 *  - If remove_const is broken due to lack of PTS, int=0 avoids the
 *    declaration of memfuns with identical signature.
 */

template<class Class,typename Type,Type (Class::*PtrToMemberFunction)()const>
struct const_mem_fun
{
  typedef typename remove_reference<Type>::type result_type;

  template<typename ChainedPtr>

#if !defined(BOOST_NO_SFINAE)
  typename disable_if<
    is_convertible<const ChainedPtr&,const Class&>,Type>::type
#else
  Type
#endif

  operator()(const ChainedPtr& x)const
  {
    return operator()(*x);
  }

  Type operator()(const Class& x)const
  {
    return (x.*PtrToMemberFunction)();
  }

  Type operator()(const reference_wrapper<const Class>& x)const
  { 
    return operator()(x.get());
  }

  Type operator()(const reference_wrapper<Class>& x,int=0)const
  { 
    return operator()(x.get());
  }
};

template<class Class,typename Type,Type (Class::*PtrToMemberFunction)()>
struct mem_fun
{
  typedef typename remove_reference<Type>::type result_type;

  template<typename ChainedPtr>

#if !defined(BOOST_NO_SFINAE)
  typename disable_if<
    is_convertible<ChainedPtr&,Class&>,Type>::type
#else
  Type
#endif

  operator()(const ChainedPtr& x)const
  {
    return operator()(*x);
  }

  Type operator()(Class& x)const
  {
    return (x.*PtrToMemberFunction)();
  }

  Type operator()(const reference_wrapper<Class>& x)const
  { 
    return operator()(x.get());
  }
};

/* MSVC++ 6.0 has problems with const member functions as non-type template
 * parameters, somehow it takes them as non-const. mem_fun_explicit workarounds
 * this defficiency by accepting an extra type parameter that specifies the
 * signature of he member function. The workaround was found at:
 *   Daniel, C.:"Re: weird typedef problem in VC",
 *   news:microsoft.public.vc.language, 21st nov 2002, 
 *   http://groups.google.com/groups?
 *     hl=en&lr=&ie=UTF-8&selm=ukwvg3O0BHA.1512%40tkmsftngp05
 */

template<
  class Class,typename Type,
  typename PtrToMemberFunctionType,PtrToMemberFunctionType PtrToMemberFunction>
struct const_mem_fun_explicit
{
  typedef typename remove_reference<Type>::type result_type;

  template<typename ChainedPtr>

#if !defined(BOOST_NO_SFINAE)
  typename disable_if<
    is_convertible<const ChainedPtr&,const Class&>,Type>::type
#else
  Type
#endif

  operator()(const ChainedPtr& x)const
  {
    return operator()(*x);
  }

  Type operator()(const Class& x)const
  {
    return (x.*PtrToMemberFunction)();
  }

  Type operator()(const reference_wrapper<const Class>& x)const
  { 
    return operator()(x.get());
  }

  Type operator()(const reference_wrapper<Class>& x,int=0)const
  { 
    return operator()(x.get());
  }
};

template<
  class Class,typename Type,
  typename PtrToMemberFunctionType,PtrToMemberFunctionType PtrToMemberFunction>
struct mem_fun_explicit
{
  typedef typename remove_reference<Type>::type result_type;

  template<typename ChainedPtr>

#if !defined(BOOST_NO_SFINAE)
  typename disable_if<
    is_convertible<ChainedPtr&,Class&>,Type>::type
#else
  Type
#endif

  operator()(const ChainedPtr& x)const
  {
    return operator()(*x);
  }

  Type operator()(Class& x)const
  {
    return (x.*PtrToMemberFunction)();
  }

  Type operator()(const reference_wrapper<Class>& x)const
  { 
    return operator()(x.get());
  }
};

/* BOOST_MULTI_INDEX_CONST_MEM_FUN and BOOST_MULTI_INDEX_MEM_FUN resolve to
 * mem_fun_explicit for MSVC++ 6.0 and to [const_]mem_fun otherwise.
 */

#if defined(BOOST_MSVC)&&(BOOST_MSVC<1300)

#define BOOST_MULTI_INDEX_CONST_MEM_FUN(Class,Type,MemberFunName) \
::boost::multi_index::const_mem_fun_explicit<\
  Class,Type,Type (Class::*)()const,&Class::MemberFunName >
#define BOOST_MULTI_INDEX_MEM_FUN(Class,Type,MemberFunName) \
::boost::multi_index::mem_fun_explicit<\
  Class,Type,Type (Class::*)(),&Class::MemberFunName >

#else

#define BOOST_MULTI_INDEX_CONST_MEM_FUN(Class,Type,MemberFunName) \
::boost::multi_index::const_mem_fun< Class,Type,&Class::MemberFunName >
#define BOOST_MULTI_INDEX_MEM_FUN(Class,Type,MemberFunName) \
::boost::multi_index::mem_fun< Class,Type,&Class::MemberFunName >

#endif

} /* namespace multi_index */

} /* namespace boost */

#endif