Games-Go-SimpleBoard/SimpleBoard.pm

package Games::Go::SimpleBoard;

=head1 NAME

Games::Go::SimpleBoard - represent a simple go board

=head1 SYNOPSIS

   use Games::Go::SimpleBoard;

=head1 DESCRIPTION

Please supply a description )

=head2 EXPORTED CONSTANTS

Marker types for each board position (ORed together):

   MARK_TRIANGLE # triangle mark
   MARK_SQUARE   # square mark
   MARK_CIRCLE   # circle mark
   MARK_CROSS    # cross mark
   MARK_SMALL_B  # small stone, used for scoring or marking
   MARK_SMALL_W  # small stone, used for scoring or marking
   MARK_B        # normal black stone
   MARK_W        # normal whit stone
   MARK_GRAYED   # in conjunction with MARK_[BW], grays the stone
   MARK_LABEL    # a text label
   MARK_HOSHI    # this is a hoshi point (not used much)
   MARK_MOVE     # this is a regular move
   MARK_KO       # this is a ko position
   MARK_REDRAW   # ignored, can be used for your own purposes

   COLOUR_WHITE  # guarenteed to be 0
   COLOUR_BLACK  # guarenteed to be 1

   MOVE_HANDICAP # used as "x-coordinate" for handicap moves
   MOVE_PASS     # can be used as "x-coordinate" for pass moves

=head2 METHODS

=over 4

=cut

no warnings;
use strict;

use Carp ();

use base Exporter::;

our $VERSION = '1.0';

our @EXPORT = qw(
   MARK_TRIANGLE MARK_SQUARE MARK_CIRCLE MARK_SMALL_B MARK_SMALL_W MARK_B
   MARK_W MARK_GRAYED MARK_MOVE MARK_LABEL MARK_HOSHI MARK_KO MARK_CROSS
   MARK_REDRAW
   COLOUR_BLACK COLOUR_WHITE
   MOVE_HANDICAP MOVE_PASS
);

# marker types for each board position (ORed together)

sub MARK_TRIANGLE (){ 0x0001 }
sub MARK_SQUARE   (){ 0x0002 }
sub MARK_CIRCLE   (){ 0x0004 }
sub MARK_SMALL_B  (){ 0x0008 } # small stone, used for scoring or marking
sub MARK_SMALL_W  (){ 0x0010 } # small stone, used for scoring or marking
sub MARK_B        (){ 0x0020 } # normal black stone
sub MARK_W        (){ 0x0040 } # normal whit stone
sub MARK_GRAYED   (){ 0x0080 } # in conjunction with MARK_[BW], grays the stone
sub MARK_LABEL    (){ 0x0100 }
sub MARK_HOSHI    (){ 0x0200 } # this is a hoshi point (not used much)
sub MARK_MOVE     (){ 0x0400 } # this is a regular move
sub MARK_KO       (){ 0x0800 } # this is a ko position
sub MARK_CROSS    (){ 0x1000 }
sub MARK_REDRAW   (){ 0x8000 }

sub COLOUR_WHITE  (){ 0 }
sub COLOUR_BLACK  (){ 1 }

sub MOVE_PASS     (){ undef }
sub MOVE_HANDICAP (){ -2 }

=item my $board = new $size

Creates a new empty board of the given size.

C<< $board->{size} >> stores the board size.

C<< $board->{max} >> stores the maximum board coordinate (size-1).

C<< $board->{captures}[COLOUR_xxx] >> stores the number of captured stones for
the given colour.

C<< $board->{board} >> stores a two-dimensional array with board contents.

=cut

sub new {
   my $class = shift;
   my $size = shift;

   bless {
      max       => $size - 1,
      size      => $size,
      board     => [map [(0) x $size], 1 .. $size],
      captures  => [0, 0], # captures
     #timer     => [],
     #score     => [],
      @_,
   }, $class
}

# inefficient and primitive, I hear you say?
# well... you are right :)
# use an extremely dumb floodfill algorithm to get rid of captured stones
sub capture {
   my ($self, $mark, $x, $y) = @_;

   my %seen;
   my @found;
   my @nodes = ([$x,$y]);
   my $board = $self->{board};

   my $max = $self->{max};

   while (@nodes) {
      my ($x, $y) = @{pop @nodes};
      unless ($seen{$x,$y}++) {
         if ($board->[$x][$y] & $mark) {
            push @found, [$x, $y];

            push @nodes, [$x-1, $y] unless $seen{$x-1, $y} || $x <= 0;
            push @nodes, [$x+1, $y] unless $seen{$x+1, $y} || $x >= $max;
            push @nodes, [$x, $y-1] unless $seen{$x, $y-1} || $y <= 0;
            push @nodes, [$x, $y+1] unless $seen{$x, $y+1} || $y >= $max;
         } elsif (!($board->[$x][$y] & (MARK_B | MARK_W))) {
            return;
         }
      }
   }

   @found
}

=item $hint = $board->update ([update-structures...])

Each update-structure itself is also an array-ref:

   [$x, $y, $clr, $set, $label, $hint] # update or move
   [MOVE_HANDICAP, $handicap]          # black move, setup handicap
   [MOVE_PASS]                         # pass
   []                                  # also pass (deprecated!)

It changes the board or executes a move, by first clearing the bits
specified in C<$clr>, then setting bits specified in C<$set>.

If C<$set> includes C<MARK_LABEL>, the label text must be given in
C<$label>.

If C<$set> contains C<MARK_MOVE> then surrounded stones will be removed
from the board and (simple) Kos are detected and marked with square
symbols and C<MARK_KO>, after removing other marking symbols. The
markings are also removed with the next next update structure that uses
C<MARK_MOVE>, so this flag is suited well for marking, well, moves. Note
that you can make invalid "moves" (such as suicide) and C<update> will
try to cope with it. You can use C<is_valid_move> to avoid making illegal
moves.

For handicap "moves", currently only board sizes 9, 13 and 19 are
supported and only handicap values from 2 to 9. The placement follows the
IGS rules, if you want other placements, you have to set it up yourself.

This function modifies the C<$hint> member of the specified structure
to speed up repeated board generation and updates with the same update
structures.

If the hint member is a reference the scalar pointed to by the reference
is updated instead.

If all this hint member thing is confusing, just ignore it and specify
it as C<undef> or leave it out of the array entirely. Do make sure that
you keep your update structures around as long as previous updates don't
change, however, as regenerating a full board position from hinted
update structures is I<much> faster then recreating it from fresh update
structures.

Example, make two silly moves:

  $board->update ([[0, 18, -1, MARK_B | MARK_MOVE],
                   [0, 17, -1, MARK_W | MARK_MOVE]]);

=cut

our %HANDICAP_COORD =  (
    9 => [2, 4,  6],
   13 => [3, 6,  9],
   19 => [3, 9, 15],
);
our %HANDICAP_XY = (
   2 => [qw(0,2 2,0                            )],
   3 => [qw(0,2 2,0 0,0                        )],
   4 => [qw(0,2 2,0 0,0 2,2                    )],
   5 => [qw(0,2 2,0 0,0 2,2                 1,1)],
   6 => [qw(0,2 2,0 0,0 2,2 0,1 2,1            )],
   7 => [qw(0,2 2,0 0,0 2,2 0,1 2,1         1,1)],
   8 => [qw(0,2 2,0 0,0 2,2 0,1 2,1 1,0 1,2    )],
   9 => [qw(0,2 2,0 0,0 2,2 0,1 2,1 1,0 1,2 1,1)],
);

our $mark_symbols = MARK_CIRCLE | MARK_SQUARE | MARK_TRIANGLE | MARK_CROSS | MARK_KO;

sub update {
   my ($self, $path) = @_;

   my $board = $self->{board};

   for (@$path) {
      my ($x, $y, $clr, $set, $label) = @$_;

      if (!defined $x) {
         $$_ &= ~$mark_symbols for @{ delete $self->{unmark} || [] };
         # pass

      } elsif ($x == MOVE_HANDICAP) {
         $$_ &= ~$mark_symbols for @{ delete $self->{unmark} || [] };

         # $y = #handicap stones
         my $c = $HANDICAP_COORD{$self->{size}}
            or Carp::croak "$self->{size}: illegal board size for handicap";
         my $h = $HANDICAP_XY{$y}
            or Carp::croak "$y: illegal number of handicap stones";

         for (@$h) {
            my ($x, $y) = map $c->[$_], split /,/;
            $board->[$x][$y] = MARK_B | MARK_MOVE;
         }

      } else {
         my $space = \$board->[$x][$y];

         $$space = $$space & ~$clr | $set;

         $self->{label}[$x][$y] = $label if $set & MARK_LABEL;

         if ($set & MARK_MOVE) {
            $$_ &= ~$mark_symbols for @{ $self->{unmark} || [] };
            @{ $self->{unmark} } = $space;

            unless (${ $_->[5] ||= \my $hint }) {
               my ($own, $opp) =
                  $set & MARK_B
                     ? (MARK_B, MARK_W)
                     : (MARK_W, MARK_B);

               my (@capture, $suicide);

               push @capture, $self->capture ($opp, $x-1, $y) if $x > 0            && $board->[$x-1][$y] & $opp;
               push @capture, $self->capture ($opp, $x+1, $y) if $x < $self->{max} && $board->[$x+1][$y] & $opp;
               push @capture, $self->capture ($opp, $x, $y-1) if $y > 0            && $board->[$x][$y-1] & $opp;
               push @capture, $self->capture ($opp, $x, $y+1) if $y < $self->{max} && $board->[$x][$y+1] & $opp;

               # keep only unique coordinates
               @capture = do { my %seen; grep !$seen{"$_->[0],$_->[1]"}++, @capture };

               # remove captured stones
               $self->{captures}[$own == MARK_B ? COLOUR_BLACK : COLOUR_WHITE] += @capture;
               $self->{board}[$_->[0]][$_->[1]] = 0
                  for @capture;

               $suicide += $self->capture ($own, $x, $y);

               ${ $_->[5] } ||= !(@capture || $suicide);

               if (!$suicide && @capture == 1) {
                  # possible ko. now check liberties on placed stone

                  my $libs;

                  $libs++ if $x > 0            && !($board->[$x-1][$y] & $opp);
                  $libs++ if $x < $self->{max} && !($board->[$x+1][$y] & $opp);
                  $libs++ if $y > 0            && !($board->[$x][$y-1] & $opp);
                  $libs++ if $y < $self->{max} && !($board->[$x][$y+1] & $opp);
                  
                  if ($libs == 1) {
                     $$space = $$space & ~$mark_symbols | MARK_KO;

                     ($x, $y) = @{$capture[0]};
                     $board->[$x][$y] |= MARK_KO;

                     push @{ $self->{unmark} }, \$board->[$x][$y];
                  }
               }
            }
         }
      }
   }
}

=item $board->is_valid_move ($colour, $x, $y[, $may_suicide])

Returns true if the move of the given colour on the given coordinates is
valid or not. Kos are taken into account as long as they are marked with
C<MARK_KO>. Suicides are invalid unless C<$may_suicide> is true (e.g. for
new zealand rules)

=cut

sub is_valid_move {
   my ($self, $colour, $x, $y, $may_suicide) = @_;

   my $board = $self->{board};

   return if $board->[$x][$y] & (MARK_B | MARK_W | MARK_KO);

   if ($may_suicide) {
      return 1;
   } else {
      my ($own, $opp) = $colour == COLOUR_BLACK
                           ? (MARK_B, MARK_W)
                           : (MARK_W, MARK_B);

      # try the move
      local $board->[$x][$y] = $board->[$x][$y] | $own;

      return 1 if $x > 0            && $board->[$x-1][$y] & $opp && $self->capture ($opp, $x-1, $y, 1);
      return 1 if $x < $self->{max} && $board->[$x+1][$y] & $opp && $self->capture ($opp, $x+1, $y, 1);
      return 1 if $y > 0            && $board->[$x][$y-1] & $opp && $self->capture ($opp, $x, $y-1, 1);
      return 1 if $y < $self->{max} && $board->[$x][$y+1] & $opp && $self->capture ($opp, $x, $y+1, 1);

      return !$self->capture ($own, $x, $y, 1);
   }
}

1;

=back

=head2 AUTHOR

Marc Lehmann <schmorp@schmorp.de>

=head2 SEE ALSO

L<Gtk2::GoBoard>.

=cut

Revision:	1.10
Committed:	Wed Jun 25 20:49:38 2008 UTC (15 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.9:	+4 -2 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package Games::Go::SimpleBoard;
2
3			=head1 NAME
4
5			Games::Go::SimpleBoard - represent a simple go board
6
7			=head1 SYNOPSIS
8
9			use Games::Go::SimpleBoard;
10
11			=head1 DESCRIPTION
12
13			Please supply a description )
14
15			=head2 EXPORTED CONSTANTS
16
17			Marker types for each board position (ORed together):
18
19			MARK_TRIANGLE # triangle mark
20			MARK_SQUARE # square mark
21			MARK_CIRCLE # circle mark
22	root	1.6	MARK_CROSS # cross mark
23	root	1.1	MARK_SMALL_B # small stone, used for scoring or marking
24			MARK_SMALL_W # small stone, used for scoring or marking
25			MARK_B # normal black stone
26			MARK_W # normal whit stone
27			MARK_GRAYED # in conjunction with MARK_[BW], grays the stone
28			MARK_LABEL # a text label
29			MARK_HOSHI # this is a hoshi point (not used much)
30			MARK_MOVE # this is a regular move
31			MARK_KO # this is a ko position
32			MARK_REDRAW # ignored, can be used for your own purposes
33
34	root	1.9	COLOUR_WHITE # guarenteed to be 0
35			COLOUR_BLACK # guarenteed to be 1
36	root	1.1
37	root	1.3	MOVE_HANDICAP # used as "x-coordinate" for handicap moves
38	root	1.9	MOVE_PASS # can be used as "x-coordinate" for pass moves
39	root	1.3
40	root	1.1	=head2 METHODS
41
42			=over 4
43
44			=cut
45
46	root	1.3	no warnings;
47			use strict;
48
49			use Carp ();
50
51			use base Exporter::;
52	root	1.1
53			our $VERSION = '1.0';
54
55	root	1.3	our @EXPORT = qw(
56	root	1.1	MARK_TRIANGLE MARK_SQUARE MARK_CIRCLE MARK_SMALL_B MARK_SMALL_W MARK_B
57	root	1.7	MARK_W MARK_GRAYED MARK_MOVE MARK_LABEL MARK_HOSHI MARK_KO MARK_CROSS
58	root	1.1	MARK_REDRAW
59			COLOUR_BLACK COLOUR_WHITE
60	root	1.3	MOVE_HANDICAP MOVE_PASS
61	root	1.1	);
62
63			# marker types for each board position (ORed together)
64
65			sub MARK_TRIANGLE (){ 0x0001 }
66			sub MARK_SQUARE (){ 0x0002 }
67			sub MARK_CIRCLE (){ 0x0004 }
68			sub MARK_SMALL_B (){ 0x0008 } # small stone, used for scoring or marking
69			sub MARK_SMALL_W (){ 0x0010 } # small stone, used for scoring or marking
70			sub MARK_B (){ 0x0020 } # normal black stone
71			sub MARK_W (){ 0x0040 } # normal whit stone
72			sub MARK_GRAYED (){ 0x0080 } # in conjunction with MARK_[BW], grays the stone
73			sub MARK_LABEL (){ 0x0100 }
74			sub MARK_HOSHI (){ 0x0200 } # this is a hoshi point (not used much)
75			sub MARK_MOVE (){ 0x0400 } # this is a regular move
76			sub MARK_KO (){ 0x0800 } # this is a ko position
77	root	1.8	sub MARK_CROSS (){ 0x1000 }
78	root	1.1	sub MARK_REDRAW (){ 0x8000 }
79
80	root	1.9	sub COLOUR_WHITE (){ 0 }
81			sub COLOUR_BLACK (){ 1 }
82	root	1.1
83	root	1.3	sub MOVE_PASS (){ undef }
84			sub MOVE_HANDICAP (){ -2 }
85
86	root	1.1	=item my $board = new $size
87
88			Creates a new empty board of the given size.
89
90	root	1.3	C<< $board->{size} >> stores the board size.
91
92	root	1.1	C<< $board->{max} >> stores the maximum board coordinate (size-1).
93
94	root	1.9	C<< $board->{captures}[COLOUR_xxx] >> stores the number of captured stones for
95	root	1.1	the given colour.
96
97			C<< $board->{board} >> stores a two-dimensional array with board contents.
98
99			=cut
100
101			sub new {
102			my $class = shift;
103			my $size = shift;
104	root	1.9
105	root	1.1	bless {
106	root	1.9	max => $size - 1,
107			size => $size,
108			board => [map [(0) x $size], 1 .. $size],
109			captures => [0, 0], # captures
110			#timer => [],
111			#score => [],
112			@_,
113			}, $class
114	root	1.1	}
115
116			# inefficient and primitive, I hear you say?
117			# well... you are right :)
118			# use an extremely dumb floodfill algorithm to get rid of captured stones
119			sub capture {
120			my ($self, $mark, $x, $y) = @_;
121
122			my %seen;
123			my @found;
124			my @nodes = ([$x,$y]);
125			my $board = $self->{board};
126
127			my $max = $self->{max};
128
129			while (@nodes) {
130			my ($x, $y) = @{pop @nodes};
131			unless ($seen{$x,$y}++) {
132			if ($board->[$x][$y] & $mark) {
133			push @found, [$x, $y];
134
135			push @nodes, [$x-1, $y] unless $seen{$x-1, $y} \|\| $x <= 0;
136			push @nodes, [$x+1, $y] unless $seen{$x+1, $y} \|\| $x >= $max;
137			push @nodes, [$x, $y-1] unless $seen{$x, $y-1} \|\| $y <= 0;
138			push @nodes, [$x, $y+1] unless $seen{$x, $y+1} \|\| $y >= $max;
139			} elsif (!($board->[$x][$y] & (MARK_B \| MARK_W))) {
140			return;
141			}
142			}
143			}
144
145			@found
146			}
147
148	root	1.2	=item $hint = $board->update ([update-structures...])
149	root	1.1
150	root	1.2	Each update-structure itself is also an array-ref:
151	root	1.1
152			[$x, $y, $clr, $set, $label, $hint] # update or move
153	root	1.4	[MOVE_HANDICAP, $handicap] # black move, setup handicap
154	root	1.3	[MOVE_PASS] # pass
155	root	1.4	[] # also pass (deprecated!)
156	root	1.1
157	root	1.2	It changes the board or executes a move, by first clearing the bits
158	root	1.1	specified in C<$clr>, then setting bits specified in C<$set>.
159
160			If C<$set> includes C<MARK_LABEL>, the label text must be given in
161			C<$label>.
162
163	root	1.9	If C<$set> contains C<MARK_MOVE> then surrounded stones will be removed
164			from the board and (simple) Kos are detected and marked with square
165			symbols and C<MARK_KO>, after removing other marking symbols. The
166			markings are also removed with the next next update structure that uses
167			C<MARK_MOVE>, so this flag is suited well for marking, well, moves. Note
168			that you can make invalid "moves" (such as suicide) and C<update> will
169			try to cope with it. You can use C<is_valid_move> to avoid making illegal
170			moves.
171	root	1.3
172			For handicap "moves", currently only board sizes 9, 13 and 19 are
173			supported and only handicap values from 2 to 9. The placement follows the
174			IGS rules, if you want other placements, you have to set it up yourself.
175
176	root	1.4	This function modifies the C<$hint> member of the specified structure
177			to speed up repeated board generation and updates with the same update
178			structures.
179	root	1.1
180			If the hint member is a reference the scalar pointed to by the reference
181			is updated instead.
182
183	root	1.4	If all this hint member thing is confusing, just ignore it and specify
184			it as C<undef> or leave it out of the array entirely. Do make sure that
185			you keep your update structures around as long as previous updates don't
186			change, however, as regenerating a full board position from hinted
187			update structures is I<much> faster then recreating it from fresh update
188			structures.
189	root	1.2
190	root	1.1	Example, make two silly moves:
191
192	root	1.4	$board->update ([[0, 18, -1, MARK_B \| MARK_MOVE],
193			[0, 17, -1, MARK_W \| MARK_MOVE]]);
194	root	1.1
195			=cut
196
197	root	1.3	our %HANDICAP_COORD = (
198			9 => [2, 4, 6],
199			13 => [3, 6, 9],
200			19 => [3, 9, 15],
201			);
202			our %HANDICAP_XY = (
203			2 => [qw(0,2 2,0 )],
204	root	1.5	3 => [qw(0,2 2,0 0,0 )],
205			4 => [qw(0,2 2,0 0,0 2,2 )],
206			5 => [qw(0,2 2,0 0,0 2,2 1,1)],
207			6 => [qw(0,2 2,0 0,0 2,2 0,1 2,1 )],
208			7 => [qw(0,2 2,0 0,0 2,2 0,1 2,1 1,1)],
209			8 => [qw(0,2 2,0 0,0 2,2 0,1 2,1 1,0 1,2 )],
210			9 => [qw(0,2 2,0 0,0 2,2 0,1 2,1 1,0 1,2 1,1)],
211	root	1.3	);
212
213	root	1.9	our $mark_symbols = MARK_CIRCLE \| MARK_SQUARE \| MARK_TRIANGLE \| MARK_CROSS \| MARK_KO;
214
215	root	1.1	sub update {
216			my ($self, $path) = @_;
217
218			my $board = $self->{board};
219
220			for (@$path) {
221			my ($x, $y, $clr, $set, $label) = @$_;
222
223	root	1.3	if (!defined $x) {
224	root	1.10	$$_ &= ~$mark_symbols for @{ delete $self->{unmark} \|\| [] };
225	root	1.3	# pass
226
227			} elsif ($x == MOVE_HANDICAP) {
228	root	1.10	$$_ &= ~$mark_symbols for @{ delete $self->{unmark} \|\| [] };
229
230	root	1.3	# $y = #handicap stones
231			my $c = $HANDICAP_COORD{$self->{size}}
232			or Carp::croak "$self->{size}: illegal board size for handicap";
233			my $h = $HANDICAP_XY{$y}
234			or Carp::croak "$y: illegal number of handicap stones";
235
236			for (@$h) {
237			my ($x, $y) = map $c->[$_], split /,/;
238			$board->[$x][$y] = MARK_B \| MARK_MOVE;
239			}
240
241			} else {
242	root	1.9	my $space = \$board->[$x][$y];
243
244			$$space = $$space & ~$clr \| $set;
245	root	1.1
246			$self->{label}[$x][$y] = $label if $set & MARK_LABEL;
247
248			if ($set & MARK_MOVE) {
249	root	1.10	$$_ &= ~$mark_symbols for @{ $self->{unmark} \|\| [] };
250	root	1.9	@{ $self->{unmark} } = $space;
251	root	1.1
252			unless (${ $_->[5] \|\|= \my $hint }) {
253			my ($own, $opp) =
254			$set & MARK_B
255			? (MARK_B, MARK_W)
256			: (MARK_W, MARK_B);
257
258			my (@capture, $suicide);
259
260			push @capture, $self->capture ($opp, $x-1, $y) if $x > 0 && $board->[$x-1][$y] & $opp;
261			push @capture, $self->capture ($opp, $x+1, $y) if $x < $self->{max} && $board->[$x+1][$y] & $opp;
262			push @capture, $self->capture ($opp, $x, $y-1) if $y > 0 && $board->[$x][$y-1] & $opp;
263			push @capture, $self->capture ($opp, $x, $y+1) if $y < $self->{max} && $board->[$x][$y+1] & $opp;
264
265			# keep only unique coordinates
266			@capture = do { my %seen; grep !$seen{"$_->[0],$_->[1]"}++, @capture };
267
268			# remove captured stones
269	root	1.9	$self->{captures}[$own == MARK_B ? COLOUR_BLACK : COLOUR_WHITE] += @capture;
270			$self->{board}[$_->[0]][$_->[1]] = 0
271	root	1.1	for @capture;
272
273			$suicide += $self->capture ($own, $x, $y);
274
275			${ $_->[5] } \|\|= !(@capture \|\| $suicide);
276
277			if (!$suicide && @capture == 1) {
278			# possible ko. now check liberties on placed stone
279
280			my $libs;
281
282			$libs++ if $x > 0 && !($board->[$x-1][$y] & $opp);
283			$libs++ if $x < $self->{max} && !($board->[$x+1][$y] & $opp);
284			$libs++ if $y > 0 && !($board->[$x][$y-1] & $opp);
285			$libs++ if $y < $self->{max} && !($board->[$x][$y+1] & $opp);
286
287			if ($libs == 1) {
288	root	1.9	$$space = $$space & ~$mark_symbols \| MARK_KO;
289
290	root	1.1	($x, $y) = @{$capture[0]};
291	root	1.9	$board->[$x][$y] \|= MARK_KO;
292
293			push @{ $self->{unmark} }, \$board->[$x][$y];
294	root	1.1	}
295			}
296			}
297			}
298			}
299			}
300			}
301
302			=item $board->is_valid_move ($colour, $x, $y[, $may_suicide])
303
304			Returns true if the move of the given colour on the given coordinates is
305	root	1.4	valid or not. Kos are taken into account as long as they are marked with
306			C<MARK_KO>. Suicides are invalid unless C<$may_suicide> is true (e.g. for
307			new zealand rules)
308	root	1.1
309			=cut
310
311			sub is_valid_move {
312			my ($self, $colour, $x, $y, $may_suicide) = @_;
313
314			my $board = $self->{board};
315
316			return if $board->[$x][$y] & (MARK_B \| MARK_W \| MARK_KO);
317
318			if ($may_suicide) {
319			return 1;
320			} else {
321			my ($own, $opp) = $colour == COLOUR_BLACK
322			? (MARK_B, MARK_W)
323			: (MARK_W, MARK_B);
324
325			# try the move
326			local $board->[$x][$y] = $board->[$x][$y] \| $own;
327
328			return 1 if $x > 0 && $board->[$x-1][$y] & $opp && $self->capture ($opp, $x-1, $y, 1);
329			return 1 if $x < $self->{max} && $board->[$x+1][$y] & $opp && $self->capture ($opp, $x+1, $y, 1);
330			return 1 if $y > 0 && $board->[$x][$y-1] & $opp && $self->capture ($opp, $x, $y-1, 1);
331			return 1 if $y < $self->{max} && $board->[$x][$y+1] & $opp && $self->capture ($opp, $x, $y+1, 1);
332
333			return !$self->capture ($own, $x, $y, 1);
334			}
335			}
336
337			1;
338
339			=back
340
341			=head2 AUTHOR
342
343			Marc Lehmann <schmorp@schmorp.de>
344
345			=head2 SEE ALSO
346
347	root	1.3	L<Gtk2::GoBoard>.
348	root	1.1
349			=cut
350