Added FindValue to more easily read optional keys in a map

include/nodeimpl.h

@@ -0,0 +1,65 @@
+#pragma once
+
+namespace YAML
+{
+	// implementation of templated things
+	template <typename T>
+	inline bool Node::Read(T& value) const {
+		std::string scalar;
+		if(!GetScalar(scalar))
+			return false;
+		
+		return Convert(scalar, value);
+	}
+	
+	template <typename T>
+	inline void operator >> (const Node& node, T& value) {
+		if(!node.Read(value))
+			throw InvalidScalar(node.m_line, node.m_column);
+	}
+	
+	template <typename T>
+	inline const Node *Node::FindValue(const T& key) const {
+		if(!m_pContent)
+			return 0;
+		
+		for(Iterator it=begin();it!=end();++it) {
+			T t;
+			if(it.first().Read(t)) {
+				if(key == t)
+					return &it.second();
+			}
+		}
+		
+		return 0;
+	}
+	
+	inline const Node *Node::FindValue(const char *key) const {
+		return FindValue(std::string(key));
+	}
+	
+	template <typename T>
+	inline const Node& Node::GetValue(const T& key) const {
+		if(!m_pContent)
+			throw BadDereference();
+		
+		for(Iterator it=begin();it!=end();++it) {
+			T t;
+			if(it.first().Read(t)) {
+				if(key == t)
+					return it.second();
+			}
+		}
+		
+		throw MakeTypedKeyNotFound(m_line, m_column, key);
+	}
+	
+	template <typename T>
+	inline const Node& Node::operator [] (const T& key) const {
+		return GetValue(key);
+	}
+	
+	inline const Node& Node::operator [] (const char *key) const {
+		return GetValue(std::string(key));
+	}
+}