Re: using module as fact store

I think you should continue studying available meta programming facilities:
for instance, look for
predicate_property<http://www.swi-prolog.org/pldoc/doc_for?object=predicate_property/2>,
specifically, see *imported_from* property

HTH Carlo



2014/1/15 Lumj <[email protected]>

> I tried this:
>  1 ?- current_predicate(w:P).
> false.
>  2 ?- w:current_predicate(N,H).
> false.
>
>   //so far it is good
>
>  3 ?- w:current_predicate(N,H),clause(H,B).
> N = current_predicate,
> H = current_predicate(_G1868, _G1877:_G1878),
> B = ((var(_G1877);var(_G1878)), !, generate_current_predicate(_G1868,
> _G1877, _G1878)) ;
> N = current_predicate,
> H = current_predicate(_G1868, _G1869),
> B = ('$c_current_predicate'(_G1868, _G1869), '$defined_predicate'(_G1869),
> !) ;
> ...
>  ...
>
>  //And after this, we get:
> 4 ?- current_predicate(w:P).
> P = current_predicate/2 ;
> false.
>
>  The current_predicate predicate is again enumerated out.
>
>
>  ------------------ Original ------------------
>   From:  "Lumj";<[email protected]>;
>  Date:  Wed, Jan 15, 2014 01:43 AM
>  To:  "Paulo Moura"<[email protected]>;
>  Cc:  "SWI-Prolog"<[email protected]>;
>  Subject:  Re: [SWIPL] using module as fact store
>
>
>
> Wow, the difference on current_predicate call you show me is hopeful, I
> didn't notice this. Cannot wait to try next morning. :)
>
>
>
>  ------------------ Original ------------------
>   From:  "Paulo Moura";<[email protected]>;
>  Date:  Wed, Jan 15, 2014 00:57 AM
>  To:  "SWI-Prolog"<[email protected]>;
>
>  Subject:  Re: [SWIPL] using module as fact store
>
>
>
>
> On 14/01/2014, at 16:40, Lumj <[email protected]> wrote:
>
> > Hi, I've come to a situation where the data my application is processing
> is in unit of database. For example, I want to transform a world into
> another, where both worlds are described in the form of a database.
>
> How much typically changes in those transformations?
>
> > Naturally the first approach I thought about is simply using dynamic
> modules to represent databases, but soon I find:
> > Enumerating facts is troublesome(especially in my application the fact
> types supported may not be statically determined)--I have to use stuff like
> current_predicate and clause, and the fatal thing is that,
> current_predicate may enumerate predicates not defined by my
> application(system predicates that may be autoloaded), thus makes this
> approach less attractive.
>
> That depends on how you call current_predicate/1. A simple example
> illustrating the differences:
>
> ?- assertz(m:foo(1)).
> true.
>
> ?- assertz(m:foo(2)).
> true.
>
> ?- assertz(m:foo(3)).
> true.
>
> ?- current_predicate(m:P).
> P = foo/1 ;
> false.
>
> ?- m:current_predicate(P).
> P = foo/1 ;
> P = portray/1 ;
> P = file_search_path/2 ;
> P = term_expansion/4 ;
> P = ansi_format/3 ;
> P = prolog_file_type/2 ;
> P = (multifile)/1
> ...
>
> > Is the module system in SWI prolog suitable for this situation?
>
> You could also use Logtalk objects but modules should be slightly more
> efficient.
>
> > PS: The way I'm taking now(mainly to temporarily work around this) is
> refactoring w:f(x) into w:fact(f(x)), and then do w:fact(F) to get all
> facts. This is quite clean and straight to my expection but it introduces a
> meta layer.
>
> And that meta-layer also hurst indexing and thus performance. Better
> avoided if possible.
>
> Cheers,
>
> Paulo
>
> -----------------------------------------------------------------
> Paulo Moura
> Logtalk developer
>
> Email: <mailto:[email protected]>
> Web:   <http://logtalk.org/>
> -----------------------------------------------------------------
>
>
>
>
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