Amesos2_Meta.hpp

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#ifndef AMESOS2_META_HPP
#define AMESOS2_META_HPP

#include "Amesos2_config.h"


namespace Amesos2 {

  namespace Meta {

    template <class T, T val>
    struct integral_constant
    {
      typedef integral_constant<T, val>  type;
      typedef T                          value_type;
      static const T value;
    };

    /* Some compilers support initializing static const members alongside the
     * definition, but others do not, so we go we the safe method of external
     * initialization.
     */
    template <class T, T val>
    const T integral_constant<T,val>::value = val;

    typedef integral_constant<bool, true>  true_type;
    typedef integral_constant<bool, false> false_type;

    // Testing the same'ness of two types //

    template <typename, typename>
    struct is_same : public false_type
    {};

    template <typename T>
    struct is_same<T,T> : public true_type
    {};



    // Meta-functions for boolean operators //

    /* Must define these with the '_' suffix because they are
     * otherwise keywords in C++
     */

    template <bool b1, bool b2>
    struct or_ : public false_type {};

    template <bool b>
    struct or_<true,b> : public true_type {};

    template <bool b>
    struct or_<b,true> : public true_type {};


    template <bool b1, bool b2>
    struct and_ : public false_type {};

    template <>
    struct and_<true,true> : public true_type {};


    template <bool b>
    struct not_ {};

    template <>
    struct not_<true> : false_type {};

    template <>
    struct not_<false> : true_type {};


    // Evaluating to a conditional type //

    template <bool B, typename T1, typename T2>
    struct if_then_else {};

    template <typename T1, typename T2>
    struct if_then_else<true, T1, T2> {
      typedef T1 type;
    };

    template <typename T1, typename T2>
    struct if_then_else<false, T1, T2> {
      typedef T2 type;
    };


    // A meta-programming type-list structure //

    struct nil_t {};                // to denote an empty list

    template <typename Head, typename Tail>
    struct type_list {
      typedef type_list<Head,Tail> type;
      typedef Head head;
      typedef Tail tail;
    };

    template <typename T1>
    struct make_list1
      : type_list<T1,nil_t>
    { };

    template <typename T1, typename T2>
    struct make_list2
      : type_list<T1,type_list<T2,nil_t> >
    { };

    template <typename T1, typename T2, typename T3>
    struct make_list3
      : type_list<T1, type_list<T2, type_list<T3,nil_t> > >
    { };

    template <typename T1, typename T2, typename T3, typename T4>
    struct make_list4
      : type_list<T1, type_list<T2, type_list<T3, type_list<T4,nil_t> > > >
    { };

    template <typename T1, typename T2, typename T3, typename T4, typename T5>
    struct make_list5
      : type_list<T1, type_list<T2, type_list<T3, type_list<T4, type_list<T5,nil_t> > > > >
    { };

    template <typename T1, typename T2, typename T3, typename T4, typename T5, typename T6>
    struct make_list6
      : type_list<T1, type_list<T2, type_list<T3, type_list<T4, type_list<T5, type_list<T6,nil_t> > > > > >
    { };

    /* More declarations for larger type lists may be added if necessary */


    template <typename list, typename elem>
    struct type_list_contains {
      static const bool value;
    };

    // Base recursive case
    template <typename elem>
    struct type_list_contains<nil_t,elem> {
      static const bool value = false;
    };

    template <typename list, typename elem>
    const bool type_list_contains<list,elem>::value
    = if_then_else<is_same<typename list::head, elem>::value,
                   true_type,
                   type_list_contains<typename list::tail,elem> >::type::value;

  } // end namespace Meta

} // end namespace Amesos2

#endif  // AMESOS2_META_HPP