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diff --git a/src/moof/log.hh b/src/moof/log.hh
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+
+/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
+**]  All rights reserved.
+*
+* vi:ts=4 sw=4 tw=75
+*
+* Distributable under the terms and conditions of the 2-clause BSD license;
+* see the file COPYING for a complete text of the license.
+*
+**************************************************************************/
+
+#ifndef _MOOF_LOG_HH_
+#define _MOOF_LOG_HH_
+
+/**
+ * \file log.hh
+ * Functions related to logging the process.
+ * The logging functions are log_error(), log_warning(), and log_info(),
+ * listed from most critical to least critical.
+ */
+
+#include <cstdlib>		// exit
+#include <iostream>
+
+
+#undef ASSERT
+#if NDEBUG
+#define ASSERT(X)
+#else
+/**
+ * Macro which tests an assertion and issues a log_error() and exits if the
+ * assertion is false.
+ * \param X test to perform
+ */
+#define ASSERT(X) if (!(X)) moof::log_error \
+	<< "false assertion at " << __FILE__ << ":" << __LINE__ << ", " \
+	<< #X, exit(1)
+#endif
+
+
+namespace moof {
+
+
+class script;
+
+
+/**
+ * A class for handling a log priority.  There are two ways to log
+ * messages: by treating a log object as a function whose parameters are
+ * printed with default spacing, or by treating a log object as an output
+ * stream.  Either way, any object can be printed to the log as long as
+ * there is an override for the ostream insertion operator.
+ */
+class log
+{
+public:
+
+	/**
+	 * A type for the level or priority of a log message.
+	 */
+	enum level
+	{
+		none		= 0,		///< Disable all logging.
+		error		= 1,		///< Log only errors.
+		warning		= 2,		///< Log warnings and errors.
+		info		= 3,		///< Log everything.
+	};
+
+
+	/**
+	 * Set the lowest-priority log message that will be outputted to the
+	 * log.  Any logging with a lower priority will be ignored.
+	 * \param level The log level.
+	 */
+	static void level(level level);
+
+	/**
+	 * Get the current lowest-priority log level.  If unchanged, the
+	 * default level is info.
+	 * \return The log level.
+	 */
+	static enum level level();
+
+
+	/**
+	 * Import log functions to a script.
+	 * \param The script.
+	 */
+	static void import(script& script);
+
+
+	/**
+	 * Construct a log with a certain priority and prefix string.
+	 * \param level The log level.
+	 * \param prefix The string printed before each log message.
+	 */
+	log(enum level level, const char* prefix) :
+		level_(level),
+		prefix_(prefix) /* only pass literal strings */ {}
+
+
+	template <class A>
+	void operator () (const A& a)
+	{
+		*this << a << std::endl;
+	}
+
+	template <class A, class B>
+	void operator () (const A& a, const B& b)
+	{
+		*this << a << " " << b << std::endl;
+	}
+
+	template <class A, class B, class C>
+	void operator () (const A& a, const B& b, const C& c)
+	{
+		*this << a << " " << b << " " << c << std::endl;
+	}
+
+	template <class A, class B, class C, class D>
+	void operator () (const A& a, const B& b, const C& c, const D& d)
+	{
+		*this << a << " " << b << " " << c << " " << d << std::endl;
+	}
+
+	template <class A, class B, class C, class D, class E>
+	void operator () (const A& a,
+					  const B& b,
+					  const C& c,
+					  const D& d,
+					  const E& e)
+	{
+		*this << a << " "
+			  << b << " "
+			  << c << " "
+			  << d << " "
+			  << e << std::endl;
+	}
+
+
+private:
+
+	template <class T> friend std::ostream& operator << (log&, const T&);
+
+	static enum level	gLevel;
+
+	enum level			level_;
+	const char*			prefix_;
+};
+
+
+extern std::ostream&	log;
+extern std::ostream&	null_log;
+
+extern class log log_error;
+extern class log log_warning;
+extern class log log_info;
+
+
+template <class T>
+inline std::ostream& operator << (class log& log, const T& item)
+{
+	if (log::gLevel < log.level_) return null_log;
+	return moof::log << log.prefix_ << item;
+}
+
+
+} // namespace moof
+
+#endif // _MOOF_LOG_HH_
+