handler gcd {

	class java.lang.Integer;
	class IntUtil;


	constraint gcd(java.lang.Integer);


	rules {

		variable java.lang.Integer M, N, L;


		// gcd(0) <=> true.
		{
			gcd(0)
		} <=> {
			true
		} simp;


		// gcd(N) \ gcd(M) <=> N=<M (guard) L is M-N, gcd(L).
		if(IntUtil.le(N, M)) {
			gcd(N) &\& gcd(M)
		} <=> {
			L = IntUtil.sub(M, N) && gcd(L)
		} newGCD;

	}//end of rules


	goal gcd_0 {
		 gcd(0)
	}//end of gcd_0


	goal gcd_0_3 {
		gcd(0) && gcd(3)
	}//end of gcd_0_3


	goal gcd_6_9 {
		gcd(6) && gcd(9)
	}//end of gcd_6_9


	goal gcd_120_9 {
		gcd(120) && gcd(9)
	}//end of gcd_120_9

}//end of handler gcd