database - prolog 数据库从终端读取输入并将其从当前数据库中收回

Question

在下面的代码中，我想找到一种首先读取字符的方法（通过用户输入“3.”，然后从 listCharacters 数据库
中删除/撤回该字符的数量

 :- dynamic listCharacters/1.  

 listCharacters(Joe).  
 listCharacters(Tom).  
 listCharacters(Peter).  

 :- write_ln('Type in the name of the character you have from the below list.    
  Example "Tom" '), write_ln('1. Joe'), write_ln('2. Tom'), write_ln('3. Peter'),   
  read(X), retract(listOfCharacters(X)).  

Answer 1

首先，您应该阅读列表中的元素，然后根据该内容构建菜单，例如

:- dynamic listCharacters/1.

listCharacters('Joe').
listCharacters('Tom').
listCharacters('Peter').

menu :-
    findall(Elem, listCharacters(Elem), L),

    format('Type in the index of the character you have from the below list.~n', []),
    forall(nth1(I,L,E), format('~d. ~q~n', [I, E])),

    read(X),
    (   nth1(X,L,E),
        retract(listCharacters(E))
    ->  true
    ;   format('cannot remove ~q', [X])
    ).

我已经介绍了一个menu程序，如果您坚持调用它，请:- menu.在文件底部添加咨询。一些测试：

?- menu.
Type in the index of the character you have from the below list.
1. 'Joe'
2. 'Tom'
3. 'Peter'
|: 2.
true.

?- menu.
Type in the index of the character you have from the below list.
1. 'Joe'
2. 'Peter'
|: 1.
true.