include/wx/meta/implicitconversion.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/meta/implicitconversion.h
   3 // Purpose:     Determine resulting type from implicit conversion
   4 // Author:      Vaclav Slavik
   5 // Created:     2010-10-22
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2010 Vaclav Slavik
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_META_IMPLICITCONVERSION_H_
  12 #define _WX_META_IMPLICITCONVERSION_H_
  13
  14 #include "wx/defs.h"
  15 #include "wx/meta/if.h"
  16
  17 // C++ hierarchy of data types is:
  18 //
  19 //   Long double (highest)
  20 //   Double
  21 //   Float
  22 //   Unsigned long int
  23 //   Long int
  24 //   Unsigned int
  25 //   Int (lowest)
  26 //
  27 // Types lower in the hierarchy are converted into ones higher up if both are
  28 // involved e.g. in arithmetic expressions.
  29
  30 namespace wxPrivate
  31 {
  32
  33 template<typename T>
  34 struct TypeHierarchy
  35 {
  36     // consider unknown types (e.g. objects, pointers) to be of highest
  37     // level, always convert to them if they occur
  38     enum { level = 9999 };
  39 };
  40
  41 #define WX_TYPE_HIERARCHY_LEVEL(level_num, type)        \
  42     template<> struct TypeHierarchy<type>               \
  43     {                                                   \
  44         enum { level = level_num };                     \
  45     };
  46
  47 WX_TYPE_HIERARCHY_LEVEL( 1, char);
  48 WX_TYPE_HIERARCHY_LEVEL( 2, unsigned char);
  49 WX_TYPE_HIERARCHY_LEVEL( 3, short);
  50 WX_TYPE_HIERARCHY_LEVEL( 4, unsigned short);
  51 WX_TYPE_HIERARCHY_LEVEL( 5, int);
  52 WX_TYPE_HIERARCHY_LEVEL( 6, unsigned int);
  53 WX_TYPE_HIERARCHY_LEVEL( 7, long);
  54 WX_TYPE_HIERARCHY_LEVEL( 8, unsigned long);
  55 #ifdef wxLongLong_t
  56 WX_TYPE_HIERARCHY_LEVEL( 9, wxLongLong_t);
  57 WX_TYPE_HIERARCHY_LEVEL(10, wxULongLong_t);
  58 #endif
  59 WX_TYPE_HIERARCHY_LEVEL(11, float);
  60 WX_TYPE_HIERARCHY_LEVEL(12, double);
  61 WX_TYPE_HIERARCHY_LEVEL(13, long double);
  62
  63 #if wxWCHAR_T_IS_REAL_TYPE
  64     #if SIZEOF_WCHAR_T == SIZEOF_SHORT
  65       template<> struct TypeHierarchy<wchar_t> : public TypeHierarchy<short> {};
  66     #elif SIZEOF_WCHAR_T == SIZEOF_INT
  67       template<> struct TypeHierarchy<wchar_t> : public TypeHierarchy<int> {};
  68     #elif SIZEOF_WCHAR_T == SIZEOF_LONG
  69       template<> struct TypeHierarchy<wchar_t> : public TypeHierarchy<long> {};
  70     #else
  71       #error "weird wchar_t size, please update this code"
  72     #endif
  73 #endif
  74
  75 #undef WX_TYPE_HIERARCHY_LEVEL
  76
  77 } // namespace wxPrivate
  78
  79 // Helper to determine resulting type of implicit conversion in
  80 // an expression with two arithmetic types.
  81 template<typename T1, typename T2>
  82 struct wxImplicitConversionType
  83 {
  84     typedef typename wxIf
  85             <
  86                 // if T2 is "higher" type, convert to it
  87                 (int)wxPrivate::TypeHierarchy<T1>::level < (int)wxPrivate::TypeHierarchy<T2>::level,
  88                 T2,
  89                 // otherwise use T1
  90                 T1
  91             >::value
  92             value;
  93 };
  94
  95
  96 template<typename T1, typename T2, typename T3>
  97 struct wxImplicitConversionType3 : public wxImplicitConversionType<
  98                         T1,
  99                         typename wxImplicitConversionType<T2,T3>::value>
 100 {
 101 };
 102
 103 #endif // _WX_META_IMPLICITCONVERSION_H_