Re: [ANN] Language::Prolog::Yaswi and DBD::Yaswi

[Salvador Fandiņo]

Hi,
Ovid wrote:
--- Salvador Fandiņo <[EMAIL PROTECTED]> wrote:
I have uploaded to CPAN version 0.07 of Language::Prolog::Yaswi, 
 an interface to SWI-Prolog.

I have also released DBD::Yaswi, an experimental DBI interface to 
SWI-Prolog. I am not completely sure if this module is a real 
improvement over the raw Language::Prolog::Yaswi... well, 
comments are welcome!!!

Hi Salvador,
It's great to see stuff happening with this again!
When I first tried to isntall DBD::Yaswi, I got:  
...
DBD::Yaswi has to be registered on the DBI module, Tim Bunce (the 
DBI author) have accepted to do it, but has not released a new 
DBI yet.

You can modify your local DBI.pm:
Look for the registry hash $dbd_prefix_registry definition and 
add an entry for DBD::Yaswi at the end as...

   yaswi_   => { class => 'DBD::Yaswi',          },
then it should work.

Also, from the docs, it's not clear how to build a database or issue
queries against it.  So let's say I want to find all X and Y that
satisfy append/3, would I do something like this?


  my $dbh = DBI->connect('dbi:Yaswi:user');
  my $sth = $dbh->prepare(<<'END_PROLOG');
    find [X,Y] where Z=[a,b,c,d], \
    append([],X,X). \
    append([W|X],Y,[W|Z]) :- append(X,Y,Z).
  END_PROLOG
From your docs and the tests, that doesn't seem right.
Can I load a pre-existing prolog program, call assert, retract, etc?

You can freely mix calls to Language::Prolog::Yaswi and 
DBD::Query, the only requirement is to not let queries open from 
one module when calling the other (calling finish() on open 
DBD::Yaswi queries or swi_cut on the Language::Prolog::Yaswi side).

There are new functions to consult files swi_consult() function 
to consult files, i.e:

  swi_consult qw(foo, bar)
  swi_use_modules qw(foo, bar)
and the swi_inline function to consult inline modules.
  swi_inline <<PROLOG;
  append([], X, X).
  append([W|X],Y,[W|Z]) :- append(X,Y,Z).
  PROLOG
DBD::Yaswi can be extended via the multifile predicate 
dbd:dbd_map_query/3.

I have included support for two simple operations, "find" and 
"insert", just for experimentation, but others can be easyly 
added, for example "consult":

  $db=DBI->connect('dbi:Yaswi:user')
  # and then, always after the connect call to ensure that
  # DBD::Yaswi has been loaded (or alternatively, loading
  # DBD::Yaswi explicitly):
  swi_inline << PROLOG;
  dbd:dbd_map_query(consult(X), consult(X), []).
  PROLOG
  $db->do('consult(foo)')
or even
  $sth_consult=$db->prepare('consult(?)')
  for (qw(foo bar doo) ) {
      $sth_consult->execute($_)
  }
I know module documentation is poor, but I have not really made 
my mind yet about the right query language for DBD::Yaswi... and 
anyway, the code is available and it is also a good example of 
how to use Language::Prolog::Yaswi ;-)

Cheers,
  - Salvador