/*  A simple sentence alterer. 
    Helen Pain (from Clocksin and Mellish)  26.2.85

    To use the program, first consult this file and then
    type:
        ?- alter([i,write,a,sentence],X).
    Another sentence will be output, with a number of the
    words in the input sentence changed.

*/
alter([],[]).
alter([H|T],[X|Y]):-
    change(H,X),
    alter(T,Y).

change(we,you).
change(are,[are,not]).
change(french,german).
change(do,no).
change(you,we).
change([are,not],are).
change(yes,no).
change(i,you).
change(am,[am,not]).
change(X,X).