poco/Foundation/include/Poco/Void.h

//
// Void.h
//
// $Id: //poco/1.4/Foundation/include/Poco/Void.h#1 $
//
// Library: Foundation
// Package: Core
// Module:  Void
//
// Definition of the Void class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_Void_INCLUDED
#define Foundation_Void_INCLUDED


#include "Poco/Foundation.h"


namespace Poco {


class Foundation_API Void
	/// A dummy class with value-type semantics, 
	/// mostly useful as a template argument.
	///
	/// This class is typically used together with ActiveMethod,
	/// if no argument or return value is needed.
{
public:
	Void();
		/// Creates the Void.

	Void(const Void& v);
		/// Creates the Void from another Void.
		///
		/// The philosophical aspects of this operation 
		/// remain undiscussed for now.
		
	~Void();
		/// Destroys the Void.

	Void& operator = (const Void& v);
		/// Assigns another void.

	bool operator ==(const Void& v) const;
		/// Will return always true due to Voids having no members.

	bool operator !=(const Void& v) const;
		/// Will return always false due to Voids having no members.
};


inline bool Void::operator ==(const Void& /*v*/) const
{
	return true;
}


inline bool Void::operator !=(const Void& /*v*/) const
{
	return false;
}


} // namespace Poco


#endif // Foundation_Void_INCLUDED