lib/Language/Befunge/Wrapping/LaheySpace.pm

   1 #
   2 # This file is part of Language::Befunge.
   3 # Copyright (c) 2001-2008 Jerome Quelin, all rights reserved.
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the same terms as Perl itself.
   7 #
   8 #
   9
  10 package Language::Befunge::Wrapping::LaheySpace;
  11
  12 use strict;
  13 use warnings;
  14
  15 use base qw{ Language::Befunge::Wrapping };
  16
  17
  18 # -- PUBLIC METHODS
  19
  20 #
  21 # $wrapping->wrap( $storage, $ip );
  22 #
  23 # Wrap $ip in $storage according to this module wrapping algorithm. Note
  24 # that $ip is already out of bounds, ie, it has been moved once by LBI.
  25 # As a side effect, $ip will have its position changed.
  26 #
  27 # LBW::LaheySpace implements a wrapping as defined in befunge specs -
  28 # ie, when hitting a bound of the storage, the ip reverses and
  29 # backtraces until it bumps into another bound, and then it reverses one
  30 # last time to keep its velocity.
  31 #
  32 sub wrap {
  33     my ($self, $storage, $ip) = @_;
  34
  35     # fetch the current position/velocity of the ip.
  36     my $v = $ip->get_position;
  37     my $d = $ip->get_delta;
  38
  39     # fetch the storage min / max
  40     my $min = $storage->min;
  41     my $max = $storage->max;
  42
  43     # funge98 says we should walk our current trajectory in reverse,
  44     # until we hit the other side of the storage, and then continue
  45     # along the same path.
  46     do {
  47         $v -= $d;
  48     } while ( $v->bounds_check($min, $max) );
  49
  50     # now that we've hit the wall, walk back into the valid code range.
  51     $v += $d;
  52
  53     # store new position.
  54     $ip->set_position($v);
  55 }
  56
  57 1;
  58 __END__
  59
  60
  61 =head1 NAME
  62
  63 Language::Befunge::Wrapping::LaheySpace - a LaheySpace wrapping
  64
  65
  66 =head1 DESCRIPTION
  67
  68 C<LBW::LaheySpace> implements a wrapping as defined in befunge specs - ie,
  69 when hitting a bound of the storage, the ip reverses and backtraces
  70 until it bumps into another bound, and then it reverses one last time to
  71 keep its velocity.
  72
  73
  74
  75 =head1 CONSTRUCTOR
  76
  77 =head2 LBW::LaheySpace->new;
  78
  79 Creates a new LaheySpace wrapping.
  80
  81
  82 =head1 PUBLIC METHODS
  83
  84 =head2 $wrapping->wrap( $storage, $ip )
  85
  86 Wrap C<$ip> in C<$storage> according to this module wrapping algorithm.
  87 See L<DESCRIPTION> for an overview of the algorithm used.
  88
  89 Note that C<$ip> is already out of bounds, ie, it has been moved once by
  90 LBI.
  91
  92 As a side effect, $ip will have its position changed.
  93
  94
  95
  96 =head1 SEE ALSO
  97
  98 L<Language::Befunge>.
  99
 100
 101 =head1 AUTHOR
 102
 103 Jerome Quelin, C<< <jquelin@cpan.org> >>
 104
 105
 106 =head1 COPYRIGHT & LICENSE
 107
 108 Copyright (c) 2001-2008 Jerome Quelin, all rights reserved.
 109
 110 This program is free software; you can redistribute it and/or modify
 111 it under the same terms as Perl itself.
 112
 113
 114 =cut
 115