Prolog中事实的持久性 [英] Persistence of facts in Prolog

问题描述

我是 Prolog 的新手，我正在使用 SWI-Prolog v6.6 将断言存储在 *.pl 文件中.

I'm kinda new in Prolog and I'm using SWI-Prolog v6.6 to storage asserts in a *.pl file.

:- dynamic fact/2.

assert(fact(fact1,fact2)).

使用上面的代码，我可以进行断言并且工作正常，但问题是当我关闭 SWI-Prolog 并再次打开 *.pl 文件时，我所做的断言是走了……

With the code above I can make asserts and it works fine, but the problem is when I close SWI-Prolog and I open the *.pl file again, the asserts I've made are gone...

有没有办法做出断言，即使我退出 Prolog 进程，这些断言也会被存储?

Is there a way to make asserts and those get stored even if I exit the Prolog process?

抱歉我的英语不好，谢谢！(:

Sorry about my bad english and Thanks! (:

推荐答案

保存状态有一定的限制，另见 最近的讨论 在 SWI-Prolog 邮件列表中.

Saving state has certain limitations, also see the recent discussion on the SWI-Prolog mailing list.

我认为在 SWI-Prolog 上持久存储事实的最简单方法是使用 persistency 库.为此，我将按以下方式重写您的代码:

I think the easiest way to persistently store facts on SWI-Prolog is to use the persistency library. For that I would rewrite your code in the following way:

:- use_module(library(persistency)).

:- persistent fact(fact1:any, fact2:any).

:- initialization(init).

init:-
  absolute_file_name('fact.db', File, [access(write)]),
  db_attach(File, []).

您现在可以使用 assert_fact/2、retract_fact/2 和 retractall_fact/2 添加/删除事实.

You can now add/remove facts using assert_fact/2, retract_fact/2, and retractall_fact/2.

退出 Prolog 后，断言的事实会自动保存到 fact.db.

Upon exiting Prolog the asserted facts are automatically saved to fact.db.

示例用法:

$ swipl my_facts.pl
?- assert_fact(some(fact), some(other,fact)).
true.
?- halt.
$ swipl my_facts.pl
?- fact(X, Y).
X = some(fact),
Y = some(other, fact).

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