package examples.fib;

import java.math.BigInteger;
import runtime.Logical;
import static util.arithmetics.primitives.intUtil.*;

public handler fib {
    solver runtime.EqualitySolver<BigInteger>;

    public constraint fib(int N, Logical<BigInteger> M);

    rules {
        fib(N,M1), fib(N,M2) <=> M1 = M2, fib(N, M1);

        fib(0,M) ==> M = 1;
    
        fib(1,M) ==> M = 1;

		local int N1, N2;
		local Logical<BigInteger> M1, M2;

        fib(N,M) ==> N > 1 | 
            N1 = dec(N),    fib(N1,M1),
            N2 = sub(N, 2), fib(N2,M2),
            M = M1.add(M2);
    }
}