--- symmetry.pl	2007/08/26 02:53:41	1
+++ symmetry.pl	2007/08/26 09:20:07	2
@@ -6,8 +6,6 @@
 
 use strict;
 
-use Data::Dump qw/dump/;
-
 my $board = << '_BOARD_';
 +-+-+-+-+-+-+-+-+
 | |   |o| |     |
@@ -51,9 +49,7 @@
 my $step = 0;	# right
 
 # offset 0, top-left corner
-my $pos = 0;
-$pos = 2;
-$pos = 6;
+my $pos = shift @ARGV || 0;
 
 my @trace = ('x') x ( $#board + 1 );
 sub trace {
@@ -82,10 +78,12 @@
 my $ok_path = qr/[\|\-]/;
 
 sub can_turn {
-	my $step = shift;
-	die "no step?" unless defined $step;
+	my $try_step = shift;
+	die "no step?" unless defined $try_step;
+
+	$try_step %= 4;
 
-	my $turn_pos = $pos + $move_by[ $step % 4 ];
+	my $turn_pos = $pos + $move_by[$try_step];
 
 	my $old = $trace[ $turn_pos ];
 	$trace[ $turn_pos ] = '?';
@@ -93,10 +91,11 @@
 	$trace[ $turn_pos ] = $old;
 
 	if ( $board[ $turn_pos ] =~ $ok_path ) {
-		warn "OK can_turn $step_name[$step] turn_pos = $turn_pos b($board[$turn_pos]) t($trace[$turn_pos])";
+		warn "OK can_turn $try_step $step_name[$try_step] turn_pos = $turn_pos b($board[$turn_pos]) t($trace[$turn_pos])";
+		$step = $try_step;
 		return 1;
 	} else {
-		warn "NOPE can_turn $step_name[$step] turn_pos = $turn_pos b($board[$turn_pos]) t($trace[$turn_pos])";
+		warn "NOPE can_turn $try_step $step_name[$try_step] turn_pos = $turn_pos b($board[$turn_pos]) t($trace[$turn_pos])";
 		return 0;
 	}
 }
@@ -112,17 +111,10 @@
 	} elsif ( $board[ $next_pos ] =~ $ok_path ) {
 		warn "OK next_pos = $next_pos b($board[$next_pos]) t($trace[$next_pos])\n";
 		move;
-		follow( $step+1 ) if can_turn( $step+1 );
+		can_turn( $step + 1 );
 	} else {
 		warn "find line continuation from $step $step_name[$step]...\n";
-		foreach my $o ( -1, 1 ) {
-			if ( can_turn( $step + $o ) ) {
-				$step = $step+$o;
-				warn "new direction: $step $step_name[$step]\n";
-				follow( $step );
-				last;
-			}
-		}
+		can_turn( $step - 1 ) || can_turn( $step + 1 ) || die "can't find new direction";
 	}
 	warn draw( @trace );