Add equality comparison for Variant

Besides value comparison, it's also possible to check if two Variant
objects have the same type.

diff --git a/source/core/meta.h b/source/core/meta.h
index 8015f42370837e2ba6633acb0ee9b50a87ca9273..6998c5d1b8a712d69176a556e7c677bb745b9ec2 100644 (file)
--- a/source/core/meta.h
+++ b/source/core/meta.h
@@ -58,6 +58,18 @@ struct Sfinae
        };
 };
 
+
+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

diff --git a/source/core/variant.h b/source/core/variant.h
index 515350de6ae5543158e20b6e2c20d4ef786163fb..2dd9732fc60dd4faf1a692eef1be63d9c83328cd 100644 (file)
--- a/source/core/variant.h
+++ b/source/core/variant.h
@@ -24,6 +24,8 @@ private:
 
                virtual const std::type_info &type_id() const = 0;
                virtual StoreBase *clone() const = 0;
+               virtual bool type_equals(const StoreBase &) const = 0;
+               virtual bool value_equals(const StoreBase &) const = 0;
        };
 
        template<typename T>
@@ -35,6 +37,16 @@ private:
 
                virtual const std::type_info &type_id() const { return typeid(T); }
                virtual StoreBase *clone() const { return new Store<T>(data); }
+               virtual bool type_equals(const StoreBase &s) const { return dynamic_cast<const Store<T> *>(&s); }
+               virtual bool value_equals(const StoreBase &s) const { return value_equals_<T>(s); }
+
+               template<typename U>
+               typename EnableIf<IsEqualityComparable<U>::value, bool>::Yes value_equals_(const StoreBase &s) const
+               { const Store<T> *t = dynamic_cast<const Store<T> *>(&s); return (t && t->data==data); }
+
+               template<typename U>
+               typename EnableIf<IsEqualityComparable<U>::value, bool>::No value_equals_(const StoreBase &) const
+               { return false; }
        };
 
        StoreBase *store;
@@ -91,6 +103,15 @@ public:
                return dynamic_cast<Store<typename RemoveConst<T>::Type> *>(store)!=0;
        }
 
+       bool check_same_type(const Variant &v) const
+       { return store && v.store && store->type_equals(*v.store); }
+
+       bool operator==(const Variant &v) const
+       { return store && v.store && store->value_equals(*v.store); }
+
+       bool operator!=(const Variant &v) const
+       { return !(operator==(v)); }
+
        template<typename T>
        operator T() const
        { return value<T>(); }