Question

Ok! last Prolog question for a long time!!

I’m trying to pick a response that is picked at random but all I can seem to do is pick the first one out of my tables of responses (see code)

I’m sure it’s done with Prologs “findall” and “random” but how?

pick_response(Sent, R) :-
    response(Sent, R), !.
pick_response(_,R) :-
    punt(R),!.

Answer 1

One way to do it with findall/3 and random/3 is:

% Responses for sentence 'sentence'
response(sentence, first).
response(sentence, second).
response(sentence, third).

% 1. Generate a list of all responses
% 2. Generate a random integer
% 3. Pick the response with the index of the integer from the list
random_response(Sentence, RandomResponse) :-
    findall(Response, response(Sentence, Response), List),
    length(List, Len),
    random(0, Len, RandomNumber),
    nth0(RandomNumber, List, RandomResponse).

Usage:

?- random_response(sentence, RandomResponse).
RandomResponse = third.

?- random_response(sentence, RandomResponse).
RandomResponse = first.

?- random_response(sentence, RandomResponse).
RandomResponse = second.

?- random_response(sentence, RandomResponse).
RandomResponse = second.

?- random_response(sentence, RandomResponse).
RandomResponse = second.

?- random_response(sentence, RandomResponse).
RandomResponse = third.