c++11 checker composition

compose.cpp

template <typename T>
using Checker = std::function<bool(T)>;

template <typename T>
class Param {
public:
	Param(std::string, Checker<T>) {
	}
	Param(std::string) {
	}
};

class Regex {
public:
	Regex(std::string regex)
			: regex_{regex} {
	}
	bool operator()(std::string) {
		return true;
	}

private:
	const std::string regex_;
};

template <typename T>
class All {
public:
	All();
};

template <typename T>
class Max {
public:
	Max(T max)
			: max_{max} {
	}
	bool operator()(T value) {
		return value < max_;
	}

private:
	const T max_;
};

template <typename T>
class Min {
public:
	Min(T min)
			: min_{min} {
	}
	bool operator()(T value) {
		return value > min_;
	}

private:
	const T min_;
};

template <typename T>
Checker<T> operator+(Checker<T> l, Checker<T> r) {
	return [l, r](T value) {
		return l(value) && r(value);
	};
}

template <typename T>
Checker<T> all(Checker<T> l, Checker<T> r) {
	return [l, r](T value) {
		return l(value) && r(value);
	};
}

TEST(XXX, YYY) {
	/* senza checker */
	Param<std::string>("ciao");

	/* con lambda */
	auto checker = [](std::string toBeChecked) { return toBeChecked == "foo"; };
	Param<std::string>("ciao", checker);

	/* con callable */
	Param<std::string>("ciao", Regex(".*"));

	Param<int>("foo.bar", all<int>(Min<int>(5), Max<int>(9)));
}