New ScanIterator class.

Not yet tested and only supporting the SCAN command for now, more to
come.
Also includes some refactoring that was needed to make everything work.

include/helpers/has_method.hpp

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2015 Michele "King_DuckZ" Santullo
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef idFBC29C5127784D35BE62F7BAC16E3687
+#define idFBC29C5127784D35BE62F7BAC16E3687
+
+#define define_has_method(method_name,pretty_name) \
+	template <typename T> \
+	struct Has ## pretty_name ## Method { \
+	private: \
+		struct TrueType { int a[2]; }; \
+		typedef int FalseType; \
+		template <typename C> static TrueType has_method ( decltype(&C::method_name) ); \
+		template <typename C> static FalseType has_method ( ... ); \
+	public: \
+		enum { value = sizeof(has_method<T>(0)) == sizeof(TrueType) }; \
+	}
+#define define_has_typedef(typedef_name,pretty_name) \
+	template <typename T> \
+	struct Has ## pretty_name ## Typedef { \
+	private: \
+		struct TrueType { int a[2]; }; \
+		typedef int FalseType; \
+		template <typename C> static TrueType has_typedef ( const typename C::typedef_name* ); \
+		template <typename C> static FalseType has_typedef ( ... ); \
+	public: \
+		enum { value = sizeof(has_typedef<T>(nullptr)) == sizeof(TrueType) }; \
+	}
+#define define_has_enum(enum_name,pretty_name) \
+	template <typename T> \
+	struct Has ## pretty_name ## Enum { \
+	private: \
+		struct TrueType { int a[2]; }; \
+		typedef int FalseType; \
+		template <typename C> static TrueType has_enum ( decltype(C::enum_name)* ); \
+		template <typename C> static FalseType has_enum ( ... ); \
+	public:\
+		enum { value = sizeof(has_enum<T>(nullptr)) == sizeof(TrueType) }; \
+	}
+
+#endif