Re: about dynamic/1 and file format

On 06/01/2014, at 12:21, Jiun-Shiung Wu <[email protected]> wrote:

> 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.

You can use something like (not tested but the code is simple):

save_facts(File) :-
	open(File, write, Stream, [bom(true), encoding(utf8)]),
	write_facts(Stream),
	close(Stream).

write_facts(Stream) :-
	write_canonical(Stream, (:- dynamic(father/2))), write(Stream, '.\n'),
	father(A, B),
	write_canonical(Stream, father(A,B)), write(Stream, '.\n'),
	fail.
write_facts(_).

Cheers,

Paulo

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Paulo Moura
Logtalk developer

Email: <mailto:[email protected]>
Web:   <http://logtalk.org/>
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