Question

当与患者（X）查询时，该程序直接返回错误

patient(X):-cancer(X);diabetes(X).

cancer(X):-pain(X).

diabetes(X):-sugar(X).

pain(X):-readPain(X)=='y'.
sugar(X):-readSugar(X)=='y'.


readPain(X):-write('is it painful?'),nl,read(X).
readSugar(X):-write('Do you have sugar problems?'),nl,read(X).

Answer 1

你写readPain(X)=='y'.。但Prolog将此解释为(==)(readPain(X),'y')。 Prolog将readPain(X)视为术语，不是作为谓词调用。

为了询问一个人是否有pain，您应该使用：

pain :-
    readPain(y).

现在它将查询用户，如果用户写入y.，谓词将成功。所以可以问：

patient :- cancer; diabetes.

cancer :- pain.

diabetes :- sugar.

pain :-
    readPain(y).
sugar:-
    readSugar(y).

readPain(X) :-
    write('is it painful?'),nl,read(X).
readSugar(X) :-
    write('Do you have sugar problems?'),nl,read(X).

read/1谓词向用户查询术语，解析该术语，并将该参数与该术语统一。这意味着在您调用readPain(X)之后，X将具有值y以防用户编写y.。通过与y进行统一，我们会检查是否确实如此。

该prolog程序不会询问用户的输入

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