Re: about dynamic/1 and file format

Hi Hunter:

On the business of dynamic predicates, it is not entirely clear what you are trying to accomplish.

There are two syntaxes for "dynamic" predicates: 1) as a directive (usage in the body of a headless predicate), and 2) as an ordinary predicate used in the body of a named predicate. The first provides for compile-time declaration of dynamic predicates and in that case, the grammar allows you to specify one or more name/arity combinations separated by commas. There are no parentheses. The second syntax provides for run-time declaration of dynamic predicates. It is structured as an ordinary predicate and allows exactly one name/arity compound as an argument. I believe that the postcondition is the same regardless of the form used.

When writing a text file using Prolog streams, you can specify the encoding of the file using the type(text) and encoding/1 options of open/3. I believe that you can also use set_set_stream_property/2 as well. When writing files (using external editors and such) that you wish to eventually consult with SWIPL, you may supply an encoding/1 directive as the first line of the file.

Regards,
Jeff R.

 

 

 

-----Original Message-----
From: Jiun-Shiung Wu <[email protected]>
To: swi-prolog <[email protected]>
Sent: Mon, Jan 6, 2014 7:22 am
Subject: [SWIPL] about dynamic/1 and file format


Hi, SWI-Prolog users,

I have two questions concerning dynamic/1 and saved file format. I am
wondering if someone can help me.

I used dynamic to declare that a predicate is dynamic. For example, I put
:- dynamic(father/2) at the beginning of my file. I used listing(father/2)
to list all instances of father/2. I found that the parentheses in dynamic
is gone. That is, when I did listing(father/2), I got: dynamic father/2.
When I used with_input_to to save all instances of father/2, I got :-
dynamic father/2 at the beginning of the new file. The parentheses are
missing. Is there a way not to remove the parentheses in this case?

Secondly, how can I save a file using the UTF-8 with the header BOM? I have
a knowledge base containing facts written in traditional Chinese (UTF-8).
When I used with_input_to to save those facts into a new file, the BOM head
seems to be gone and my Prolog program cannot read it. Though it is easy to
restore the BOM head using Notepadd++, I am still wondering whether
SWI-Prolog can save a file using UTF-8 with the BOM head.

Thank you!

Hunter Wu
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