CODEWITHSUNDEEP
prolog
Collega
Collega

Reputation: 442

Compare user input to defined predicate

I am trying to create a "Who Is It" game (person guessing part).

I would like to check if user input equals the value/person that is saved in a predicate. Based on this, I would then return to the user if the value/person has been guessed or not.

The random person is chosen from a list called characters each time the menu is retuned to the user interface.

Which library do I need to use, or how would I achieve this kind of evaluation?

:- dynamic xxxxxxxxxxxx/1.

%characteristics of a person/character
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
male(bill).
male(alfred).

female(claire).  
female(anne).

bald(bill).
beard(bill).
beard(alfred).
blushes(bill).
redshirt(alfred).
hat(claire).
blond(claire).
dress(anne).
earrings(anne).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

chosen_character(_).

menu :-
    write('Possible characters to choose from:'),nl,
    characters(L), write(L),nl,
    read(Input),
    %CODE THAT COMPARES INPUT TO 'chosen_character' AND RETURNS NAME IF CORRECT ELSE GUESS AGAIN.
    menu.


character(L) :- findall(X, (male(X) ; female(X)), L).

new_character(Ans):-
    characters(L), 
    length(L, X), 
    R is random(X), 
    N is R+1, 
    random_between(L, N, Ans),
    chosen_character(Ans).

random_between([H|T],1,H).

random_between([H|T],N,E):-
    N1 is N-1,
    random_between(T,N1,E1),
    E=E1.

Upvotes: 0

Views: 301

Answers (1)

slago
slago

Reputation: 5509

Assuming you already have a list of names that can be chosen (defined by the predicate characters/1) and that you're using SWI-Prolog (since the question was originally tagged with swi-prolog), a possible solution is as follows:

characters([bill, alfred, claire, anne]).

guess :-
    characters(Names),
    random_member(Name, Names),
    guess(Name).

guess(Name) :-
    characters(Names),
    format(atom(Prompt), '\nChoose one of ~w: ', [Names]),
    prompt1(Prompt),
    read_line_to_string(user_input, String),
    atom_string(Atom, String),
    (   Atom = Name
    ->  format('Your guess is correct!\n')
    ;   format('Your guess is incorrect!\n'),
        guess(Name) ).

Note that SWI-Prolog already has some built-in predicates which are very useful for this application (random_member/2, format/3, prompt1/1, read_line_to_string/2, and atom_string/2).

Running example:

?- guess.

Choose one of [bill,alfred,claire,anne]: anne
Your guess is incorrect!

Choose one of [bill,alfred,claire,anne]: bill
Your guess is incorrect!

Choose one of [bill,alfred,claire,anne]: claire
Your guess is correct!
true.

Upvotes: 1

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