Prolog，使用大写字母 [英] Prolog, working with capital letter

问题描述

我正在 SWI-Prolog 中进行数据库项目.问题是我想使用我从输入中读取的运动员的名字.我需要用大写字母保存他们的名字，但 prolog 将这些解释为变量.任何想法如何解决这个问题?

I am working on database project in SWI-Prolog. Problem is that i want to work with names of Sportsmen which i read from input. I need to save their names with capital letters, but prolog interprets these as variables. Any ideas how to fix this?

推荐答案

我会使用 code_type/2 来确保任何输入的名称都以大写字母开头.

I would use code_type/2 to ensure that any entered name starts with a capital letter.

由于您希望用户输入带有小写或大写字母的名称，因此我对使用 read_line_to_codes/2 读取的代码列表进行了大小写转换.

Since you want to allow a user to enter a name with a letter that is either lower- or uppercase, I do the case conversion on the codes list that I read with read_line_to_codes/2.

由于您想将名称存储在数据库中，因此我使用 dynamic/1 声明我将添加一些 sportsname/1 条目，并且我使用 assert/1 将特定名称添加到数据库中.

Since you want to store the names in a database, I use dynamic/1 to declare that I will be adding some sportsname/1 entries, and I use assert/1 to add a specific name to the database.

代码如下:

:- dynamic(sportsname/1).

:- initialization(input).

input:-
  repeat,
  format(user_output, 'Please enter a name (or type `quit`):\n', []),
  read_line_to_codes(user_input, Codes1),
  (
    atom_codes(quit, Codes1)
  ->
    !, true
  ;
    capitalize(Codes1, Codes2)
  ->
    atom_codes(Name, Codes2),
    assert(sportsname(Name)),
    format(current_output, 'Sportsname ~a writen to database.\n', [Name]),
    fail
  ;
    fail
  ).

capitalize([], []).
capitalize([H1|T], [H2|T]):-
  code_type(H2, to_upper(H1)).

使用示例:

$ swipl sport_names.pl
Please enter a name (or type `quit`):
|: john
Sportsname John writen to database.
Please enter a name (or type `quit`):
|: James
Sportsname James writen to database.
Please enter a name (or type `quit`):
|: suzan
Sportsname Suzan writen to database.
Please enter a name (or type `quit`):
|: quit

?- sportsname(X).
X = 'John' ;
X = 'James' ;
X = 'Suzan'.

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