oddEven(X, RET) :- X > 0, V is mod(X,2), RET is V.
?- oddEven(2, RET).
GNU Prolog 1.3.1
By Daniel Diaz
Copyright (C) 1999-2009 Daniel Diaz
uncaught exception: error(syntax_error('user_input:1 (char:4) . or operator expected after expression'),read_term/3)