比较事实和输出结果

Question

我是Prolog的新手，我正试图做一个测验，用户被给予3个问题和每个问题3个选项。每个问题问完后，会显示3种可能的答案选择。用户键入该问题的答案，就会显示下一个问题，然后继续进行测试，直到问完所有3个问题并给出答案。

接下来我要做的是将每个用户的答案与该问题的正确答案进行比较，并输出用户是对的、错的还是跳过了一个问题。我认为我需要将数据库知识中的事实与静态事实进行比较是正确的。我知道这不是一个真正的问题，但如果有人能给我建议，如何最好地实现我的目标，我将不胜感激。我只是有点困惑。如有需要，我们将提供更多信息。

question(1,'What is the fifth planet of our Solar System?').
question(2,'In what year was George Best born?').
question(3,'What is the capital of Austraila?').
possibleAns(1,[mars,jupiter,saturn]).
possibleAns(2,[1945,1946,1948]).
possibleAns(3,[sydney,canberra,melbourne]).
rightAns(1,jupiter).
rightAns(2,1946).
rightAns(3,canberra).
skip(s).
%Confused as to how best to achieve the comparing and output
check_answer(AnsNo,userChoice):-
    rightAns(AnsNo,Choice),
    userAnswer(AnsNo,userChoice)    
getChoice(ChoiceNo,ChoiceList):-
    write('Choose from'),nl,
    write(ChoiceList),nl,
    read(Choice),
    (member(Choice,ChoiceList);skip(Choice)),
    %userAnswer will compare with rightAnswer
    assert(userAnswer(ChoiceNo,Choice)).
getChoice(ChoiceNo,ChoiceList):-
    writeln('Illegal Choice'),
    getChoice(ChoiceNo,ChoiceList).
//check if the question has been asked
//if not, write question
//get users choice and move to next question
get_question(PreviousAsked):-
    question(QNum,Text),
    + member(QNum,PreviousAsked),
    write(Text),nl,
    possibleAns(QNum,ChoiceList),
    getChoice(QNum,ChoiceList),
    get_question([QNum|PreviousAsked]).
get_question(_).
start_quiz:-
    get_question([]).

---

Updated
getChoice(ChoiceNo,ChoiceList):-
    write('Choose from'),nl,
    write(ChoiceList),nl,
    read(Choice),
    (member(Choice,ChoiceList);skip(Choice)),
    assert(userAnswer(ChoiceNo,Choice)).
    (   rightAns(ChoiceNo,Choice)
    ->   write('Right!'),nl;
    write('Wrong,'),nl).

Answer 1

在可能的情况下，我们应该避免断言和收回，通常我们会得到更简单的程序，更容易理解和调试。

在您的示例中，您可以首先收集问题Qs列表

findall(Q, question(Q,_), Qs)

，然后运行一个循环，直到Qs为空。当用户选择问题并且以适当的方式回答时，仅删除问题。

编辑我只保留了question/2,possible/2,rightAns/2，并与此代码

show(Q) :-
    question(Q, T),
    possibleAns(Q, As),
    format('~d: ~s ~w~n', [Q, T, As]).
loop([]).
loop(Qs) :-
    maplist(show, Qs),
    (   (read((Q,Y)),
         select(Q, Qs, Rs),
         rightAns(Q, Y)
        ) -> loop(Rs) ; loop(Qs)
    ).
quiz :-
    findall(Q, question(Q,_), Qs),
    loop(Qs).

我

?- quiz.
1: What is the fifth planet of our Solar System? [mars,jupiter,saturn]
2: In what year was George Best born? [1945,1946,1948]
3: What is the capital of Austraila? [sydney,canberra,melbourne]
|: 1,mars.
1: What is the fifth planet of our Solar System? [mars,jupiter,saturn]
2: In what year was George Best born? [1945,1946,1948]
3: What is the capital of Austraila? [sydney,canberra,melbourne]
|: 1,jupiter.
2: In what year was George Best born? [1945,1946,1948]
3: What is the capital of Austraila? [sydney,canberra,melbourne]
|: 2,1946.
3: What is the capital of Austraila? [sydney,canberra,melbourne]
|: 3,canberra.
true .

Answer 2

既然您已经在数据库中定义了rightAns/2，我建议您像这样比较getChoice中的结果:

getChoice(ChoiceNo,ChoiceList):-
    write('Choose from'),nl,
    write(ChoiceList),nl,
    read(Choice),
    (member(Choice,ChoiceList);skip(Choice)),
    (   rightAns(ChoiceNo,Choice)
    ->  write('Right!'),nl
    ;   write('Wrong.'),nl).

如果你不喜欢比较getChoice/2内部的答案的想法(因为你想保持你的谓词的意义尽可能纯净)，你可以创建一个简单的规则:

check_answer(AnsNo,userChoice)
    (   rightAns(AnsNo,userChoice)
    ->  write('Right!'),nl
    ;   write('Wrong.'),nl).

我还建议您在测试结束时使用cut (!)或任何其他机制来防止回溯。