Dogcows Code - chaz/yoink/blob - src/cml/core/meta/common.h

   1 /* -*- C++ -*- ------------------------------------------------------------
   2
   3 Copyright (c) 2007 Jesse Anders and Demian Nave http://cmldev.net/
   4
   5 The Configurable Math Library (CML) is distributed under the terms of the
   6 Boost Software License, v1.0 (see cml/LICENSE for details).
   7
   8  *-----------------------------------------------------------------------*/
   9 /** @file
  10  *  @brief
  11  */
  12
  13 #ifndef core_meta_common_h
  14 #define core_meta_common_h
  15
  16 namespace cml {
  17
  18 /** Type of a true statement. */
  19 struct true_type {};
  20
  21 /** Type of a false statement. */
  22 struct false_type {};
  23
  24 template<bool B> struct is_true {
  25     typedef false_type result;
  26 };
  27
  28 template<> struct is_true<true> {
  29     typedef true_type result;
  30 };
  31
  32 /** A "type pair". */
  33 template<typename T1, typename T2> struct type_pair {
  34     typedef T1 first;
  35     typedef T2 second;
  36 };
  37
  38 /** A "type quadruple". */
  39 template<typename T1, typename T2, typename T3, typename T4>
  40 struct type_quad {
  41     typedef T1 first;
  42     typedef T2 second;
  43     typedef T3 third;
  44     typedef T3 fourth;
  45 };
  46
  47 /** Match any type (for use with same_type<> and select_switch<>). */
  48 struct any_type {};
  49
  50 /** Determine if two types are the same.
  51  *
  52  * Defaults to false.
  53  */
  54 template<typename T, typename U> struct same_type {
  55     typedef false_type result;
  56     enum { is_true = false, is_false = true };
  57 };
  58
  59 /** Match the same type for both of same_type's template arguments. */
  60 template<typename T> struct same_type<T,T> {
  61     typedef true_type result;
  62     enum { is_true = true, is_false = false };
  63 };
  64
  65 /** Match a type and any_type. */
  66 template<typename T> struct same_type<T,any_type> {
  67     typedef true_type result;
  68     enum { is_true = true, is_false = false };
  69 };
  70
  71 /** Match a type and any_type. */
  72 template<typename T> struct same_type<any_type,T> {
  73     typedef true_type result;
  74     enum { is_true = true, is_false = false };
  75 };
  76
  77 /** Disambiguate pair of any_type's. */
  78 template<> struct same_type<any_type,any_type> {
  79     typedef true_type result;
  80     enum { is_true = true, is_false = false };
  81 };
  82
  83 } // namespace cml
  84
  85 #endif
  86
  87 // -------------------------------------------------------------------------
  88 // vim:ft=cpp