// optional.h - v1.0.1
/* 
 * Copyright (c) 2008 Leigh Johnston.  All Rights Reserved.
 *
 * Permission to use, copy, modify and distribute this
 * software and its documentation for any purpose is hereby
 * granted, provided that the above copyright notice
 * appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation.
 * The author makes no representations about the
 * suitability of this software for any purpose. It is provided
 * "as is" without express or implied warranty.
 */

#ifndef LIB_OPTIONAL
#define LIB_OPTIONAL

#include <cassert>
#include "vecarray.h"

namespace lib
{
	template<typename T>
	class optional : private vecarray<T, 1>
	{
	public:
		typedef T value_type;
		typedef T* pointer;
		typedef const T* const_pointer;
		typedef T& reference;
		typedef const T& const_reference;
	private:
		typedef vecarray<T, 1> base;
	public:
		// construction
		optional() {}
		optional(const optional& rhs) : base(rhs) {}
		optional(const_reference value) : base(1, value) {}
		// state
		bool valid() const
		{
			return !base::empty();
		}
		bool invalid() const
		{
			return !valid();
		}
		operator bool() const 
		{ 
			return valid();
		}
		// element access
		reference get()
		{
			assert(valid()); return base::operator[](0); 
		}
		const_reference get() const
		{
			assert(valid()); return base::operator[](0); 
		}
		reference operator*() 
		{ 
			return get();
		}
		const_reference operator*() const 
		{ 
			return get();
		}
		pointer operator->() 
		{ 
			return &get(); 
		}
		const_pointer operator->() const 
		{ 
			return &get(); 
		}
		// modifiers
		void reset() 
		{ 
			base::clear(); 
		}
		optional& operator=(const optional& rhs) 
		{ 
			optional(rhs).swap(*this); 
			return *this;
		}
		optional& operator=(const_reference value) 
		{
			optional(value).swap(*this);
			return *this;
		}
		void swap(optional& rhs)
		{
			base::swap(rhs);
		}
	};
}

#endif // LIB_OPTIONAL