Help with Prolog Here is my code fooXYZ Y 0 Z is X fooXYZ X

Help with Prolog:

Here is my code:

foo(X,Y,Z):- Y =< 0, Z is X.
foo(X,Y,Z):- X =< 0, Z is Y.
foo(X,Y,Z):- X >= Y, X1 is (X-2),
   Z is (X + foo(X1,Y)).
foo(X,Y,Z) :- X < Y, Y1 is (Y-3),
   Z is (Y + foo(X,Y1)).

I need to input foo(5,6) and return 18.

The problem is foo(x,y) = {

x if y<=0

y if x<=0

x + foo(x-2,y) if x>=y

y+foo(x,y-3) if x <y

I think my logic is good, I just don\'t know how to go to the next step and output the answer.

Solution

Try using the following for your foo predicate:

| ?-foo(5,6).

This should use foo and give result