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	close FILE;

}

sub addFacts {

	my $name = $_[0];
	my @facts = @{$_[1]};
	my $append = $_[2];
	my $filename = $_[3];
	
	open FILE, $append, $filename;

	foreach my $f (@facts) {
		print FILE "$name($f).\n";
	}
	close FILE;
}


1;
__END__

# 

=head1 NAME

AI::Logic::AnswerSet - Perl extension for embedding ASP (Answer Set Programming) programs in Perl.


=head1 SYNOPSIS

  use AI::Logic::AnswerSet;
  
  # invoke DLV( AnwerSetProgramming-based system) and save the stdoutput
  my @stdoutput = AI::Logic::AnswerSet::singleExec("3-colorability.txt");

  # parse the output
  my @res = AI::Logic::AnswerSet::getAS(@stdoutput);

  # map the results
  my @mappedAS = AI::Logic::AnswerSet::mapAS(\@res);

  # get a predicate from the results
  my @col = AI::Logic::AnswerSet::getPred(\@mappedAS,1,"col");

  # get a term of a predicate
  my @term = AI::Logic::AnswerSet::getProjection(\@mappedAS,1,"col",2);


=head1 DESCRIPTION

This extension allows to interact with DLV, an Artificial Intelligence system
for Answer Set Programming (ASP).
Please note that the DLV system must appear in the same folder of the perl program
and it must be renamed as "dlv";
DLV can be freely obtained at www.dlvsystem.com.
For further info about DLV and Answer Set Programming please start from www.dlvsystem.com.

The module was originally published as "ASPerl", but suffered from
some problems with the namespace, now changed. The module has been
also significantly rearranged according to the advices coming from the
community. Thank you all!
If you are using this module, please let us know: we are always
interested in end-users desires, and we wish to improve our library:
comments are truly welcome!

=head2 Methods

=head3 executeFromFileAndSave

This method allows to execute DLV with and input file and save the output in another file.

	AI::Logic::AnswerSet::executeFromFileAndSave("outprog.txt","dlvprog.txt","");

In this case the file "outprog.txt" consists of the result of the DLV invocation 
with the file "dlvprog.txt".
No code is specified in the third value of the method. It can be used to add code 
to an existing file or to a new one.

	AI::Logic::AnswerSet::executeFromFileAndSave("outprog.txt","dlvprog.txt",
	"b(X):-a(X). a(1).");
  
=head3 executeAndSave

To call DLV without an input file, directly writing the ASP code from the terminal, 
use this method, passing only the name of the output file.

	AI::Logic::AnswerSet::executeAndSave("outprog.txt");

Press Ctrl+D to stop using the DLV terminal and execute the program.

=head3 singleExec

Use this method to execute DLV whit several input files, including also
DLV options like "-nofacts".
The output will be stored inside an array.

	my @out = AI::Logic::AnswerSet::singleExec("3col.txt","nodes.txt","edges.txt","-nofacts");

Another way to use this method:

	my @out = AI::Logic::AnswerSet::singleExec();

In this way it will work like C<executeAndSave()> without saving the output to a file.

=head3 iterativeExec

This method allows to call multiples DLV executions for several instances of the same problem.
Suppose you have a program that calculates the 3-colorability of a graph; in this case
one might have more than a graph, and each graph instance can be stored in a different file.
A Perl programmer might want to work with the results of all the graphs she has in her files,
so this function will be useful for this purpose.
Use it like in the following:

	my @outputs = AI::Logic::AnswerSet::iterativeExec("3col.txt","nodes.txt","./instances");

In this case the nodes of each graph are the same, but not the edges.
Notice that in order to correctly use this method, the user must specify the path 
to the instances (the edges, in this case).