NAME

Language::Prolog::SWI - Perl extension for SWI-Prolog (OO Interface)

SYNOPSIS

use Language::Prolog::SWI::base;

# create an engine (actually for initialisation)
my $e = new Language::Prolog::SWI::PlEngine();
# add some knowledge
Language::Prolog::SWI::PlCall ("assert(islocatedin(bonduni,robina))");
Language::Prolog::SWI::PlCall ("assert(islocatedin(robina,goldcoast))");
Language::Prolog::SWI::PlCall ("assert(islocatedin(goldcoast,qld))");
Language::Prolog::SWI::PlCall ("assert((islocatedin2(X,Z):-islocatedin(X,Z)))");
Language::Prolog::SWI::PlCall ("assert((islocatedin2(X,Z):-islocatedin(X,Y),islocatedin2(Y,Z)))");
# bind one term, but not the other one
my $t1 = new Language::Prolog::SWI::PlTerm ("bonduni");
my $t2 = new Language::Prolog::SWI::PlTerm ();
# create a Term vector
my $av = new Language::Prolog::SWI::PlTermv ($t1, $t2);
my $q  = new Language::Prolog::SWI::PlQuery ("islocatedin2", $av);
$q->DISOWN(); # read CAVEATS below

# iterate over all solutions
while ($q->next_solution) {
  warn "match ".$t1->toString." ".$t2->toString;
}

DESCRIPTION

This package is a wrapper for the SWI-Prolog CPP API described at

http://www.swi-prolog.org/packages/pl2cpp.html

and implements the classes there with the following exceptions:

• the operator PlAtom::const char *(void) has been renamed to toString

• the operators PlAtom::== have been renamed to eq

• the operator PlTerm::const char *(void) has been renamed to toString

• operators PlTerm::(long|int|double) have been omitted

CAVEATS

As usual with C-based Perl packages there are some issues concerning the memory allocation. There a good description of the problem at

http://www.swig.org/Doc1.3/Perl5.html#n41

For the user of this packages this means that for some constructors the user has to call the DISOWN method to let the wrapper class know that it should NOT try to DESTROY the object itself. When this really happens can only be determined by looking at the implementation, sorry.

If you are haunted by segfaults then obviously there is a allocation bug.

INSTALLATION

See the README file.

AUTHOR

Robert Barta, rho@bond.edu.au

SEE ALSO

perl.