%
% ELIZA reconstruction adapted from Sterling & Shapiro 1986, page 232
%
?- reconsult('library.pl').
eliza :-
  read_in(Input),
  eliza(Input), !.
%
eliza([bye]) :-
  reply([goodbye,i,hope,i,have,helped,you]).
eliza(Input1) :-
  pattern(Stimulus,Response),
  match(Stimulus,Dictionary,Input1),
  match(Response,Dictionary,Output1),
  reply(Output1),
  read_in(Input2),
  !, eliza(Input2).
%
match([N|Pattern],Dictionary,Target) :-
  integer(NP),
  lookup(N,Dictionary,LeftTarget),
  append(LeftTarget,RightTarget,Target),
  match(Pattern,Dictionary,RightTarget).
match([Word|Pattern],Dictionary,[Word|Target]) :-
  atom(Word),
  match(Pattern,Dictionary,Target).
match([],Dictionary,[]).
%
lookup(Key,[(Key,Value)|Dictionary],Value).
lookup(Key1,[(Key2,Value2)|Dictionary],Value1) :-
  Key1 /= Key2,
  lookup(Key1,Dictionary,Value1).
%
reply([Word|Words]) :-
  write(Word), write(' '), reply(Words).
reply([]) :-
  nl.
%
pattern([i,am,1],[how,long,have,you,been,1,?]).
pattern([1,you,2,me],[what,makes,you,think,i,2,you,?]).
pattern([i,like,1],[does,anyone,else,in,your,family,like,1,?]).
pattern([i,feel,1],[do,you,often,feel,that,way,?]).
pattern([1,X,2],[can,you,tell,me,more,about,X,?]) :-
  important(X).
pattern([1],[please,go,on]).
%
important(father).
important(sister).
important(mother).
important(brother).
important(son).
important(daughter).