From c4b3b5e52e390e542c7dcda95effbc37544d676a Mon Sep 17 00:00:00 2001
From: beder <jbeder@gmail.com>
Date: Sun, 13 Nov 2011 16:05:42 -0600
Subject: [PATCH] Added (unspecified-type) bool conversions for Node (new API)

---
 include/yaml-cpp/node/detail/bool_type.h | 26 ++++++++++++++++++++++++
 include/yaml-cpp/node/impl.h             |  5 +++++
 include/yaml-cpp/node/node.h             |  6 ++++++
 test/new-api/nodetests.cpp               | 11 ++++++++++
 4 files changed, 48 insertions(+)
 create mode 100644 include/yaml-cpp/node/detail/bool_type.h

diff --git a/include/yaml-cpp/node/detail/bool_type.h b/include/yaml-cpp/node/detail/bool_type.h
new file mode 100644
index 0000000..80ed9a4
--- /dev/null
+++ b/include/yaml-cpp/node/detail/bool_type.h
@@ -0,0 +1,26 @@
+#ifndef NODE_DETAIL_BOOL_TYPE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
+#define NODE_DETAIL_BOOL_TYPE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
+
+#if defined(_MSC_VER) || (defined(__GNUC__) && (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ >= 4)) // GCC supports "pragma once" correctly since 3.4
+#pragma once
+#endif
+
+namespace YAML
+{
+	namespace detail
+	{
+		struct unspecified_bool {
+			struct NOT_ALLOWED;
+			static void true_value(NOT_ALLOWED*) {}
+		};
+		typedef void (*unspecified_bool_type)(unspecified_bool::NOT_ALLOWED*);
+	}
+}
+
+#define YAML_CPP_OPERATOR_BOOL()\
+operator YAML::detail::unspecified_bool_type() const\
+{\
+	return this->operator!() ? 0 : &YAML::detail::unspecified_bool::true_value;\
+}
+
+#endif // NODE_DETAIL_BOOL_TYPE_H_62B23520_7C8E_11DE_8A39_0800200C9A66
diff --git a/include/yaml-cpp/node/impl.h b/include/yaml-cpp/node/impl.h
index ac4089f..d562161 100644
--- a/include/yaml-cpp/node/impl.h
+++ b/include/yaml-cpp/node/impl.h
@@ -49,6 +49,11 @@ namespace YAML
 			m_pNode->set_null();
 		}
 	}
+	
+	inline bool Node::IsDefined() const
+	{
+		return m_pNode ? m_pNode->is_defined() : true;
+	}
 
 	inline NodeType::value Node::Type() const
 	{
diff --git a/include/yaml-cpp/node/node.h b/include/yaml-cpp/node/node.h
index 95df7cb..348b653 100644
--- a/include/yaml-cpp/node/node.h
+++ b/include/yaml-cpp/node/node.h
@@ -10,6 +10,7 @@
 #include "yaml-cpp/node/ptr.h"
 #include "yaml-cpp/node/type.h"
 #include "yaml-cpp/node/detail/iterator_fwd.h"
+#include "yaml-cpp/node/detail/bool_type.h"
 #include <stdexcept>
 
 namespace YAML
@@ -29,11 +30,16 @@ namespace YAML
 		~Node();
 		
 		NodeType::value Type() const;
+		bool IsDefined() const;
 		bool IsNull() const { return Type() == NodeType::Null; }
 		bool IsScalar() const { return Type() == NodeType::Scalar; }
 		bool IsSequence() const { return Type() == NodeType::Sequence; }
 		bool IsMap() const { return Type() == NodeType::Map; }
 		
+		// bool conversions
+		YAML_CPP_OPERATOR_BOOL();
+		bool operator!() const { return !IsDefined(); }
+		
 		// access
 		template<typename T> const T as() const;
 		const std::string& Scalar() const;
diff --git a/test/new-api/nodetests.cpp b/test/new-api/nodetests.cpp
index 37602fd..9b9bc2e 100644
--- a/test/new-api/nodetests.cpp
+++ b/test/new-api/nodetests.cpp
@@ -268,6 +268,16 @@ namespace Test
 			YAML_ASSERT(node[true].as<bool>() == false);
 			return true;
 		}
+		
+		TEST AutoBoolConversion()
+		{
+			YAML::Node node;
+			node["foo"] = "bar";
+			YAML_ASSERT(static_cast<bool>(node["foo"]));
+			YAML_ASSERT(!node["monkey"]);
+			YAML_ASSERT(!!node["foo"]);
+			return true;
+		}
 	}
 	
 	void RunNodeTest(TEST (*test)(), const std::string& name, int& passed, int& total) {
@@ -312,6 +322,7 @@ namespace Test
 		RunNodeTest(&Node::TempMapVariable, "temp map variable", passed, total);
 		RunNodeTest(&Node::TempMapVariableAlias, "temp map variable alias", passed, total);
 		RunNodeTest(&Node::Bool, "bool", passed, total);
+		RunNodeTest(&Node::AutoBoolConversion, "auto bool conversion", passed, total);
 
 		std::cout << "Node tests: " << passed << "/" << total << " passed\n";
 		return passed == total;