Dogcows Code - chaz/yoink/blob - src/moof/cml/core/meta/switch.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 meta_switch_h
  14 #define meta_switch_h
  15
  16 #include <cml/core/meta/common.h>
  17 #include <cml/core/meta/if.h>
  18
  19 namespace cml {
  20
  21 struct NilCase {};      /* For terminating the case list. */
  22 struct Default {};      /* For indicating the default result. */
  23
  24 /* The working parts of the meta-switch go into namespace meta: */
  25 namespace meta {
  26
  27 /* "Interior" case statements: */
  28 template<typename Case, typename Result, typename NextCase>
  29 struct select_case
  30 {
  31     template<typename Find> struct match {
  32         typedef typename select_if<
  33             same_type<Find,Case>::is_true,
  34             Result,
  35             typename NextCase::template match<Find>::result
  36         >::result result;
  37     };
  38 };
  39
  40 /* Default case, returned when no match is found in a previous case: */
  41 template<typename Result>
  42 struct select_case<Default,Result,NilCase>
  43 {
  44     template<typename Find> struct match {
  45         typedef Result result;
  46     };
  47 };
  48
  49 /* The last case statement (if no match until now, the result is 'void'): */
  50 template<typename Case, typename Result>
  51 struct select_case<Case,Result,NilCase>
  52 {
  53     template<typename Find> struct match {
  54         typedef typename select_if<
  55             same_type<Find,Case>::is_true,
  56             Result,
  57             void
  58         >::result result;
  59     };
  60 };
  61
  62 } // namespace meta
  63
  64 /** Return the matched type (like a switch/case statement).
  65  *
  66  * This is a convenience wrapper to avoid having to explicitly type out
  67  * select_case for each case in the list of types to match against.
  68  */
  69 template<typename Find
  70 , typename T1,           typename R1
  71 , typename T2 = NilCase, typename R2 = void
  72 , typename T3 = NilCase, typename R3 = void
  73 , typename T4 = NilCase, typename R4 = void
  74 , typename T5 = NilCase, typename R5 = void
  75 , typename T6 = NilCase, typename R6 = void
  76 , typename T7 = NilCase, typename R7 = void
  77 , typename T8 = NilCase, typename R8 = void
  78 , typename T9 = NilCase, typename R9 = void
  79 , typename T10 = NilCase, typename R10 = void
  80 , typename T11 = NilCase, typename R11 = void
  81 , typename T12 = NilCase, typename R12 = void
  82 , typename T13 = NilCase, typename R13 = void
  83 , typename T14 = NilCase, typename R14 = void
  84 , typename T15 = NilCase, typename R15 = void
  85 , typename T16 = NilCase, typename R16 = void
  86 > struct select_switch
  87 {
  88     typedef typename
  89           meta::select_case< T1,R1
  90         , meta::select_case< T2,R2
  91         , meta::select_case< T3,R3
  92         , meta::select_case< T4,R4
  93         , meta::select_case< T5,R5
  94         , meta::select_case< T6,R6
  95         , meta::select_case< T7,R7
  96         , meta::select_case< T8,R8
  97         , meta::select_case< T9,R9
  98         , meta::select_case< T10,R10
  99         , meta::select_case< T11,R11
 100         , meta::select_case< T12,R12
 101         , meta::select_case< T13,R13
 102         , meta::select_case< T14,R14
 103         , meta::select_case< T15,R15
 104         , meta::select_case< T16,R16
 105         , NilCase
 106         > > > > > >     /* 6 */
 107         > > > > > > > > > >     /* 10 */
 108         ::template match<Find>::result result;
 109 };
 110
 111 } // namespace cml
 112
 113 #endif
 114
 115 // -------------------------------------------------------------------------
 116 // vim:ft=cpp