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Hi Salvador,

Looks very interesting, but if it is an interface to
a specific prolog, shouldn't it all be in a namespace
reflecting that?

Like Language::Prolog::SWI, rather than just Language::Prolog?

lee

On Wednesday, January 22, 2003 at 4:09:06 PM, you wrote:

SF>  NAME
SF>      Language::Prolog::Yaswi - Yet another interface to
SF>  SWI-Prolog

SF>  SYNOPSIS
SF>        use Language::Prolog::Yaswi ':query';
SF>        use Language::Prolog::Types::overload;
SF>        use Language::Prolog::Sugar functors => { equal =>
SF>  '='
SF>                                                  is    =>
SF>  'is' },
SF>                                    chains => { orn => ';',
SF>                                                andn => ',',
SF>                                                add => '+' },
SF>                                    vars => [qw (X Y Z)];

SF>        swi_set_query( equal(X, Y),
SF>                       orn( equal(X, 27),
SF>                            equal(Y, 'hello')));

SF>        while (swi_next) {
SF>            printf "Query=".swi_query()."\n";
SF>            printf "  X=%_, Y=%_\n\n", swi_var(X),
SF>  swi_var(Y);
SF>        }

SF>        print join("\n",
SF>                   xsb_findall(andn(equal(X, 2),
SF>                                    orn(equal(Y, 1),
SF>                                        equal(Y, 3.1416))
SF>                                    is(Z, plus(X,Y,Y))),
SF>                               [X, Y, Z]);

SF>  ABSTRACT
SF>      Language::Prolog::Yaswi implements a bidirectional
SF>  interface to the
SF>      SWI-Prolog system (<http://www.swi-prolog.org/>).

SF>  DESCRIPTION
SF>      This package provides a bidirectional interface to
SF>  SWI-Prolog. That
SF>      means that Prolog code can be called from Perl that can
SF>  call Perl code
SF>      again and so on:

SF>        Perl -> Prolog -> Perl -> Prolog -> ...

SF>      (unfortunately, by now, the cicle has to be started
SF>  from Perl, although
SF>      it is very easy to circunvent this limitation with the
SF>  help of a dummy
SF>      Perl script that just calls Prolog the first time).

SF>      The interface is based on the set of classes defined in
SF>      Language::Prolog::Types. Package
SF>  Language::Prolog::Sugar can also be
SF>      used to improve the look and readability of scripts
SF>  mixing Perl and
SF>      Prolog code.

SF>      The interface to call Prolog from Perl is very simple,
SF>  at least if you
SF>      are used to Prolog non deterministic.

SF>    SUBROUTINES
SF>      Grouped by export tag:

SF>      ":query"

SF>          "swi_set_query($query1, $query2, $query3, ...)"
SF>              Compose a query with all its parameters and
SF>  sets it. Return the
SF>              set of free variables found in the query.

SF>          "swi_set_query_module($query, $module,
SF>  $ctx_module)"
SF>              Allows to set a query in a different module
SF>  than the default.

SF>          "swi_result()"
SF>              Return the values binded to the variables in
SF>  the query.

SF>          "swi_next()"
SF>              Iterates over the query solutions.

SF>              If a new solution is available returns true, if
SF>  not, closes the
SF>              query and returns false.

SF>              It should be called after "swi_set_query(...)"
SF>  to obtain the
SF>              first solution.

SF>          "swi_var($var)"
SF>              Returns the value binded to $var in the current
SF>  query/solution
SF>              combination.

SF>          "swi_query"
SF>              Returns the current query with the variables
SF>  binded to its
SF>              values in the current solution (or unbinded if
SF>  swi_next has not
SF>              been called yet).

SF>          "swi_cut"
SF>              Closes the current query even if not all of its
SF>  solutions have
SF>              been retrieved. Similar to prolog "!".

SF>          "swi_find_all($query, @pattern)"
SF>              iterates over $query and returns and array with
SF>  @pattern binded
SF>              to every solution. i.e:

SF>                swi_find_all(member(X, [1, 3, 7, 21]), X)

SF>              returns the array "(1, 3, 7, 21)" and

SF>                swi_find_all(member(X, [1, 3, 7, 21]), [X])

SF>              returns the array "([1], [3], [7], [21])".

SF>              More elaborate constructions can be used:

SF>                %mothers=swi_find_all(mother(X,Y), X, Y)

SF>              There is also an example of its usage in the
SF>  SYNOPSIS.

SF>          "swi_find_one($query, @pattern"
SF>              as "swi_find_all" but only for the first
SF>  solution.

SF>          "swi_call"
SF>              runs the query once and return true if a
SF>  solution was found or
SF>              false otherwise.

SF>      ":interactive"

SF>          "swi_toplevel"
SF>              mostly for debugging pourposes, runs SWI-Prolog
SF>  shell.

SF>      ":assert"

SF>          "swi_assert($head => @body)"
SF>          "swi_assertz($head => @body)"
SF>              add new definitions at the botton of the
SF>  database

SF>          "swi_asserta($head => @body)"
SF>              adds new definitions at the top of the database

SF>          "swi_facts(@facts)"
SF>              commodity subroutine to add several facts
SF>  (facts, doesn't have
SF>              body) to the database in one call.

SF>              i.e.:

SF>                use Language::Prolog::Sugar functors=>[qw(man
SF>  woman)];

SF>                swi_facts( man('teodoro'),
SF>                           man('socrates'),
SF>                           woman('teresa'),
SF>                           woman('mary') );

SF>      ":context"

SF>          $swi_module
SF>          $swi_ctx_module
SF>              allows to change the module and the context
SF>  module for the
SF>              upcoming queries.

SF>              use ALWAYS the "local" operator when changing
SF>  its value!!!

SF>              i.e.:

SF>                 local $swi_module='mymodule'
SF>                 swi_set_query($query_from_mymodule);

SF>          $swi_converter
SF>              allows to change the way data is converter from
SF>  Perl to Prolog.

SF>              You should not use it for any other thing that
SF>  to configure perl
SF>              classes as opaque, i.e.:


$swi_converter-> >pass_as_opaque(qw(LWP::UserAgent

SF>  HTTP::Request

SF>  HTTP::Result))

SF>    CALLBACKS
SF>      Yaswi adds to SWI-Prolog three new predicates to call
SF>  perl back.

SF>      All the calls are make in array contest and the Result
SF>  value is always a
SF>      list. There is not way to make a call in scalar context
SF>  yet.

SF>      "perl5_eval(+Code, -Result)"
SF>          makes perl evaluate the string "Code" (really a
SF>  Prolog atom) and
SF>          returns the results.

SF>      "perl5_call(+Sub, +Args, -Result)"
SF>          calls a perl sub.

SF>      "perl5_method(+Object, +Method, +Args, -Result)"
SF>          calls the method "Method" from the perl object
SF>  "Object".

SF>          To get objects passed to prolog as opaques instead
SF>  of marshaled to
SF>          prolog types, its class (or one of its parent
SF>  classes) has to be
SF>          previously register as opaque with the
SF>  $swi_converter object. i.e.:


SF>  perl5_eval('$swi_converter->pass_as_opaque("HTTP::Request")',_),
SF>            perl5_eval('use HTTP::Request',_),
SF>            perl5_method('HTTP::Request', new, [],
SF>  [Request]),
SF>            perl5_method(Request, as_string, [], [Text]);

SF>          Registering class "UNIVERSAL" makes all objects to
SF>  be passed to
SF>          prolog as opaques.

SF>    EXPORT
SF>      This module doesn't export anything by default.
SF>  Subroutines should be
SF>      explicitely imported.

SF>  SEE ALSO
SF>      SWI-Prolog documentation <http://www.swi-prolog.org/>,
SF>      Languages::Prolog::Types, Language::Prolog::Sugar

SF>  AUTHOR
SF>      Salvador Fandiño, <sfandino AT yahoo.com>

SF>  COPYRIGHT AND LICENSE
SF>      Copyright 2003 by Salvador Fandiño

SF>      This library is free software; you can redistribute it
SF>  and/or modify it
SF>      under the same terms as Perl itself.

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