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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 Fandi�o, <sfandino AT yahoo.com>
SF> COPYRIGHT AND LICENSE
SF> Copyright 2003 by Salvador Fandi�o
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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