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  1. num(X).
  2. odd(X) :- mod(X,2).
  3. ?- odd(X)
Compilation error #stdin compilation error #stdout 0s 0KB
stdin
?- num(10)
compilation info
prog.pl:1: warning: singleton variables [X] for num/1
prog.pl:3:4: syntax error: . or operator expected after expression
	1 error(s)
compilation failed
stdout
Standard output is empty