/*
	polynomial(Expression,X) :- 
		Expression is a polynomial in X.
*/
	polynomial(X,X).
	polynomial(Term,X) :- constant(Term).
	polynomial(Term1+Term2,X) :-
		polynomial(Term1,X), polynomial(Term2,X).
	polynomial(Term1-Term2,X) :-
		polynomial(Term1,X), polynomial(Term2,X).
	polynomial(Term1*Term2,X) :-
		polynomial(Term1,X), polynomial(Term2,X).
	polynomial(Term1/Term2,X) :-
		polynomial(Term1,X), constant(Term2).
	polynomial(Term ^ N,X) :-
		natural_number(N), polynomial(Term,X).

%	Program 3.29: Recognizing polynomials