Well, yes and no. I said

and then, either computing each of the valid moves for each space, or just verifying them on a per-move basis.

If all you're doing is having a chess game between two human players, it may be enough to validate each move on a per-move basis. If you're trying to create an AI, then I'd have some initialization function that runs at startup to build the complex per-space tables based on the simple formulas.

So, for instance, in your case, as you're using an AI, you could compute all of the valid rook moves with:

my %moves;
foreach my $i ( -7..-1, 1..7 ) {
  push @{$moves{'rook'}}, [$i,0], [0,$i];
}

my %valid_moves;
$valid_moves{'rook'} = [];
foreach my $i ( 0 .. 7 ) {
  $valid_moves{'rook'}->[$i] = [];
  foreach my $j ( 0 .. 7 ) {
    $valid_moves{'rook'}->[$i]->[$j] = [];
    foreach my $move ( @{$moves{'rook'}} ) {
      my $x = $i - ($move->[0]);
      next if ( $x < 0 or $x > 7 );
      my $y = $j - ($move->[1]);
      next if ( $y < 0 or $y > 7 );
      push @{$valid_moves{'rook'}->[$i]->[$j]}, [$x,$y];
    }
  }
}

[download]

You can shorten it, of course (rely on autovivication, etc ...) I just did that for the sake of what I find to be easy to come back to at some future point. And to save some time, a queen's valid moves are the union of a bishop and a rook's valid moves.

Oh -- and I have no idea how you'd handle castling after building this table (whereas, by validating each move individually, it's an easy case to test for).

In reply to Re^3: Representing Complex but Static Data in Perl by jhourcle
in thread Representing Complex but Static Data in Perl by cyocum

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