# Sokoban solution rotator in Perl

This is a project I always meant to do, but now that I've done it, I am wondering if/how I can do it better. I've made some fixes and done general testing on the parsing to make sure it works, but I sense there is more to do that could be very instructive to me in terms of organizing my code and thoughts.

This came about because I played several Sokoban games and wrote solutions only to notice that many levels were rotations of others, so I wanted to save time. (There are Sokoban solvers out there, but I wanted to provide explanations with the solutions.)

The code below takes a text file (it need only be one line - the comments provide one) and user-suggested rotations (argument 1 on the command line) and changes all directions(2U, 3L, 4D, 5R) to how the user wants the board rotated.

Some of it seems a bit brute force, though, especially the for loop and the regular expression (I've only recently moved beyond ending with just /g or /gi). In particular, I am wondering whether I should use an array instead, especially since I may want an option to convert the full words "up"/"right"/"left"/"down" to their rotational equivalents.

Any suggestions big or small are appreciated...whether it's technical or code organization.

This seems like the sort of exercise that might help me learn other languages I'm not familiar with, so I wanted to see how things went with a language I was okay at, first.

Thanks to all who are able to contribute, and I hope my example is somewhat interesting.

################################
#sokoban solution rotator
################################
#sok.txt has lines like so: Your way to the end: 2U 4R 3D 5L 2u 4r 3d 5l.
#the command line argument is any combination of l r h u d v (d and v are equivalent to u, vertical flips. L/R rotate left/right, h = horizontal flip)
#

use strict;
use warnings;

my $file = "sok.txt"; my$dir;
my $anyDif; # checks for differences once we've parsed rotations # this hash transforms a move to a different direction. By default each move points to itself. my %rotate = ( 'u' => 'u', 'r' => 'r', 'd' => 'd', 'l' => 'l'); if (!defined($ARGV[0]))
{
die ("You need a command line argument (no spaces) to use rotations: R, L, H and V/U/D rotate right, left, horizontally and vertically.");
}

my @adjust = split(//, lc($ARGV[0])); for$dir (@adjust)
{
if ($dir eq 'r') # rotate right { ($rotate{'r'}, $rotate{'d'},$rotate{'l'}, $rotate{'u'}) = ($rotate{'u'}, $rotate{'r'},$rotate{'d'}, $rotate{'l'}); next; }; if ($dir eq 'l') # rotate left
{
($rotate{'l'},$rotate{'u'}, $rotate{'r'},$rotate{'d'}) = ($rotate{'u'},$rotate{'r'}, $rotate{'d'},$rotate{'l'});
next;
};
if (($dir eq 'v') || ($dir eq 'u') || ($dir eq 'd')) # vertical flip { ($rotate{'d'}, $rotate{'r'},$rotate{'u'}, $rotate{'l'}) = ($rotate{'u'}, $rotate{'r'},$rotate{'d'}, $rotate{'l'}); next; }; if ($dir eq 'h') # horizontal flip
{
($rotate{'u'},$rotate{'l'}, $rotate{'d'},$rotate{'r'}) = ($rotate{'u'},$rotate{'r'}, $rotate{'d'},$rotate{'l'});
next;
};
die ("I didn't recognize $dir. RLHVUD (case insensitive) are the only directions I do."); } for$dir (sort keys %rotate)
{
#print "$dir becomes$rotate{$dir}\n";$anyDif += ($dir ne$rotate{$dir}); } #print "Rotation: URDL =>$rotate{'u'}$rotate{'r'}$rotate{'d'}$rotate{'l'}\n"; if (!$anyDif) { die("The rotations you requested don't change the puzzle's orientation."); }

open(A, "sok.txt") || die ("No sok.txt.");

while (my $line = <A>) { print "Orig:$line";
print "NEW:: ";
$line =~ s/\b([0-9\*]*)([URDL])\b/$1 . newdir($2)/gei; # I included * with numbers because it means "push to the end" chomp($line);
print "$line\n"; #this is to avoid orig/new appearing on the same line at the end of a file. } close(A); ##################################subroutine sub newdir { if ($_[0] eq lc($_[0])) { return$rotate{$_[0]}; } return uc($rotate{lc($_[0])}); }  • Looks interesting! I have not played the game, could you try explain what the codes in sok.txt represent? You say it represents how the user wants the board rotated, but why would he write 5L 3d for example? Why not just 1L 1D? If he flips the board 3 times down, wouldn't that be the same as 1 time down? since flipping 2 times down would return the board to the original configuration – Håkon Hægland Apr 27 '17 at 19:20 • @HåkonHægland with the rotations, yeah, I took care of some unlikely test cases. I suppose I could put in a check for too many letters in the command. As for the codes, they are just shorthand, e.g. move your player 3 squares left, then 2 up, 4 down, 1 right, then so forth. I suppose I could've used up/down/left/right as well. I don't know how much Sokoban you've played, but in youtube.com/watch?v=i_WmVBwEE4U the first part is 1U 3L 3U 1L 1U 2L 1D 2L 3D and now *R would send the box right because I'm too lazy to count. The 1's are optional of course. – aschultz Apr 27 '17 at 21:41 • Ok I think I understand, but there is still something in your code I don't get. Line 37: why does the moveU becomes R when rotating with L? If I rotate the board 90 degrees counter clockwise (i.e rotate left), the move U should become L, and not R? What am I missing here? – Håkon Hægland Apr 27 '17 at 22:02 ## 1 Answer Please check for additional comments in the code, use strict; use warnings; # no need to die() when open() use autodie; # this hash transforms a move to a different direction. By default each move points to itself. my %rotate = ( 'u' => 'u', 'r' => 'r', 'd' => 'd', 'l' => 'l' ); if (!defined($ARGV[0]))
{
die ("You need a command line argument (no spaces) to use rotations: R, L, H and V/U/D rotate right, left, horizontally and vertically.");
}

my @adjust = split(//, lc($ARGV[0])); #/(fix stackexchange code coloring) for my$dir (@adjust) {
my @keys;

# rotate right
if ($dir eq 'r') { @keys = qw(r d l u); } # rotate left elsif ($dir eq 'l') { @keys = qw(l u r d); }
# vertical flip
elsif ($dir eq 'v' or$dir eq 'u' or $dir eq 'd') { @keys = qw(d r u l); } # horizontal flip elsif ($dir eq 'h')  { @keys = qw(u l d r); }
else {
die ("I didn't recognize $dir. RLHVUD (case insensitive) are the only directions I do."); } # check "hash slice" @rotate{@keys} = @rotate{qw(u r d l)}; } my$anyDif; # checks for differences once we've parsed rotations
for my $dir (keys %rotate) { #print "$dir becomes $rotate{$dir}\n";
$anyDif += ($dir ne $rotate{$dir});
}

#print "Rotation: URDL => $rotate{'u'}$rotate{'r'}$rotate{'d'}$rotate{'l'}\n";

if (!$anyDif) { die("The rotations you requested don't change the puzzle's orientation."); } # check "three argument open" open(my$A, "<", "sok.txt");

while (my $line = <$A>) {
print "Orig: $line"; print "NEW:: ";$line =~ s/\b([0-9\*]*)([URDL])\b/$1 . newdir($2)/gei; # I included * with numbers because it means "push to the end"
chomp($line); print "$line\n"; #this is to avoid orig/new appearing on the same line at the end of a file.
}
close($A); ##################################subroutine sub newdir { my ($v) = @_;
my $lc = lc($v);

# check "ternary operator"
return ($v eq$lc) ? $rotate{$v} : uc($rotate{$lc});
}

• There is a lot of stuff in your code I'd seen but remember thinking, well, the shorthand is for advanced PERL programmers...and I never got around to really using it. I really appreciate this, because so much here is not just being economical for code golf sake. I usually wait a day or so before giving a best answer, but if there's a better one I'll really be thrilled. Thanks! – aschultz Apr 27 '17 at 21:36