Prolog maximum works like this: ?- R is max(3,4). R = 4 See below our versions. Which one do you prefer?
max(X,Y,X):- X >= Y. max(X,Y,Y):- Y > X. ?- max(5,3,R). R = 5 no
maxx(X,Y,X):- X >= Y. maxx(X,Y,Y). ?- maxx(3,5,R). R = 5 no ?- maxx(5,3,R). R = 5 R = 3
maxxx(X,Y,X):- X >= Y,!. maxxx(X,Y,Y). ?- maxxx(5,3,R). R = 5 no