predicates([even,odd,<]).
precedence( [even,odd,+,s,0,n,m] ).

0+X = X.
s(Y)+X = s(Y+X).
X+Y=Y+X.

even(0).
odd(0) -> [].
even(s(X))==odd(X).
odd(s(X))==even(X).

% forall X. even(X+X)
% induction hypothesis
even('$min'+'$min'). 
% base case + step case
even(0+0),even(s('$min')+s('$min')) -> []. 


:-sama([2]).