Add equality comparison for Variant

[libs/core.git] / source / core / meta.h

diff --git a/source/core/meta.h b/source/core/meta.h
index 923096517dba8132a873de68a79344ab6e2910b1..6998c5d1b8a712d69176a556e7c677bb745b9ec2 100644 (file)
--- a/source/core/meta.h
+++ b/source/core/meta.h
@@ -1,6 +1,8 @@
 #ifndef MSP_CORE_META_H_
 #define MSP_CORE_META_H_
 
+#include <cstddef>
+
 namespace Msp {
 
 template<typename T>
@@ -21,6 +23,11 @@ struct RemoveReference<T &>
 { typedef T Type; };
 
 
+template<typename T>
+struct RemoveConstReference
+{ typedef typename RemoveConst<typename RemoveReference<T>::Type>::Type Type; };
+
+
 template<bool c, typename R>
 struct EnableIf;
 
@@ -41,13 +48,28 @@ struct Sfinae
        struct Yes { char c[2]; };
        struct No { char c; };
 
-       template<size_t s>
+       template<typename T>
+       static No f(...);
+
+       template<typename C, typename T>
        struct Evaluate
        {
-               enum { value = (s==sizeof(Yes)) };
+               enum { value = (sizeof(C::template f<T>(0))==sizeof(Yes)) };
        };
 };
 
+
+struct CheckEqualityComparable: Sfinae
+{
+       static int &v;
+       template<typename T>
+       static Yes f(int (*)[sizeof(reinterpret_cast<const T &>(v)==reinterpret_cast<const T &>(v))]);
+       using Sfinae::f;
+};
+
+template<typename T>
+struct IsEqualityComparable: Sfinae::Evaluate<CheckEqualityComparable, T> { };
+
 } // namespace Msp
 
 #endif