CODEWITHSUNDEEP
prolog
Snow White
Snow White

Reputation: 45

How to control user input in prolog?

I have this problem with my code in prolog.

It is about fashion stylist expert system that takes properties from the user and gives her the specified look.

Here is the code: 

main_level(2):- 
    write('Please enter weight (60s (1), 50s (2)): '), read(W),
    write('Please enter tall (more than 160 (1), less than 160 (2)): '), read(T),
    write('Please enter skin color (bronze (1), white (2), black (3)): '), read(S1),
    write('Please enter hair length (medium (1), short (2), long (3)): '), read(H1),
    write('Please enter hair color (brown (1), black (2), blond (3)): '), read(H2),
    write('Please enter event (wedding (1), fami party (2): '), read(E),

But how I can force the user to enter the correct answer, so the program will not complete until the user enters the correct answer?

I tried to do it by using recursive rule but It didn't work either!

Upvotes: 3

Views: 544

Answers (2)

Ahmad
Ahmad

Reputation: 9658

You can test if the answer is equal to the expected values, if not the rule fails, you can use a cut (!) after this check to show the error message as below.

main_level(2):- 
write('Please enter weight (60s (1), 50s (2)): '), 
read(W), (W == 1; W == 2),!,...

main_level(2):- write('Please enter a value according to the menu').

Upvotes: 1

CapelliC
CapelliC

Reputation: 60014

Basically, you could validate each input with this schema:

main_level(2):- 
    repeat, write('Please enter weight (60s (1), 50s (2)): '), read(W), (W == 1 ; W == 2),
    repeat, write('Please enter tall (more than 160 (1), less than 160 (2)): '), read(T), (T == 1 ; T == 2),
...

but I would suggest instead to code a simple menu, like

menu(Header, Choices, Choice) :-
  repeat,
  write(Header),
  forall(nth1(I,Choices,Value), format('~w (~d) ', [Value,I])),
  read(C),
  nth1(C, Choices, _). % validate index input

and call it with

main_level(2):- 
    menu('Please enter weight ',['60s','50s'], W),
    menu('Please enter tall ',['more than 160','less than 160'], T),
    ...

Upvotes: 1

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