add perl example code

perl-example/xor.pl

@@ -0,0 +1,71 @@
+#!/usr/bin/perl -w
+
+use strict;
+use neat;
+
+my $neat = new neat( "start.xor.pl" );
+
+my $FINISHED = 0;
+
+$SIG{INT} = sub { $FINISHED = 1 };
+
+my $inputs = [
+	{ 'bias' => 1, 'one' => 0, 'two' => 0, 'output' => 0, 'expected' => 0 },
+	{ 'bias' => 1, 'one' => 1, 'two' => 0, 'output' => 0, 'expected' => 1 },
+	{ 'bias' => 1, 'one' => 0, 'two' => 1, 'output' => 0, 'expected' => 1 },
+	{ 'bias' => 1, 'one' => 1, 'two' => 1, 'output' => 0, 'expected' => 0 },
+	];
+
+sub EvaluateXOR
+{
+	my $net = shift;
+
+	# why retest someone who hasn't changed?
+	return $net->{'fitness'}
+		if ( $net->{'elite'} );
+
+	my $total = 0;
+	my $values;
+	my $average;
+	my $i;
+	my $difference;
+	$total = 0;
+	for ( $i = 0 ; $i < 4 ; $i++ )
+	{
+		$values = Copy( $inputs->[$i] );
+		$neat->Activate( $net, $values );
+#		printf( " %d%d=%lf", $values->{'one'}, $values->{'two'},
+#				$values->{'output'} );
+		$difference = abs( $values->{'output'} - $values->{'expected'} );
+		$total += $difference;
+	}
+#	printf( "  %lf\n", 1 - $average );
+	my $fitness = 1 - ( $total / 4 );
+	$FINISHED = 1 if ( $total < 0.04 ); # close enough!
+	return $fitness;
+}
+
+$neat->EvaluationFunction( \&EvaluateXOR );
+
+# initial generation
+$neat->EvaluateAll();
+
+my $count = 0;
+while ( ! $FINISHED )
+{
+	$neat->Epoch();
+	printf( "%s\n", $neat->Stats() );
+	$neat->EvaluateAll();
+	#$FINISHED = 1 if ( ++$count == 100 );
+}
+
+$neat->Champions();
+$neat->Save( "xor.final.pl" );
+
+my $champion = $neat->ChampionNetwork();
+my $code = $neat->ActivationFunction_C_PartialEval( $champion, 
+		{ bias => 1 } );
+open INDENT, "|indent -st > activate.xor.c";
+print INDENT $code;
+close INDENT;
+#system "cat activate.xor.c";