#ifndef PREDICATE_HPP
#define PREDICATE_HPP

#include <boost/function.hpp>

template <typename ValueType>
class predicate
{
public:
	typedef boost::function1<bool, const ValueType&> type;

	struct and
	{
		and(const type &left, const type &right): left_(left), right_(right) {}
		bool operator()(const ValueType &value)
		{
			return left_(value) && right_(value);
		}
	private:
		type left_;
		type right_;
	};

	struct or
	{
		or(const type &left, const type &right): left_(left), right_(right) {}

		bool operator()(const ValueType &value)
		{
			return left_(value) || right_(value);
		}
	private:
		type left_;
		type right_;
	};
};

template <typename ValueType>
typename predicate<ValueType>::type operator &(const typename predicate<ValueType>::type &left,
											   const typename predicate<ValueType>::type &right)
{
	return typename predicate<ValueType>::and(left, right);
}

template <typename ValueType>
typename predicate<ValueType>::type operator |(const typename predicate<ValueType>::type &left,
											   const typename predicate<ValueType>::type &right)
{
	return typename predicate<ValueType>::or(*this, right);
}

#endif