doit:-i, ii,iii.
i:- (f(W,W)=f(X,1),  write(  'I' ), nl,! ;  write(  'not I')), nl.
ii:- (f(W,W)=f(Y, g(Z)),  write(  'II' ), nl,! ;  write(  'not II')), nl.
iii:- (f(X,1)=f(Y, g(Z)),  write(  'III' ), nl,! ;  write(  'not III')), nl.