?-is_odd(4).
?-is_even(4).
?-is_odd(15).
?-is_even(15).

GNU Prolog 1.3.1
By Daniel Diaz
Copyright (C) 1999-2009 Daniel Diaz
uncaught exception: error(syntax_error('user_input:1 (char:3) . or operator expected after expression'),read_term/3)
uncaught exception: error(syntax_error('user_input:2 (char:3) . or operator expected after expression'),read_term/3)
uncaught exception: error(syntax_error('user_input:3 (char:3) . or operator expected after expression'),read_term/3)
uncaught exception: error(syntax_error('user_input:4 (char:3) . or operator expected after expression'),read_term/3)