get_answer( A ) :- 
	ratom( X ), name( X, String ),
        valid_resp( String, A ), !.

valid_resp( [H|T], A ) :- type_ans( H, A ).

type_ans( X, A ) :- ([X] = "y"; [X] = "Y"), A = yes.
type_ans( X, A ) :- ([X] = "n"; [X] = "N"), A = no.
type_ans( X, A ) :- ([X] = "w"; [X] = "W"), A = why.

?-print('\nYou can start animal by typing "help.<CR>"\n' ).

valid_resp( [], A ) :-
	print('\nPlease try to give me a yes or no answer.'),
	get_answer( A ), !.

valid_resp( [H|T], A ) :- valid_resp( T, A ).