Re^3: implementing a scrabble-esque game on Termux III

[tybalt89]

  $board =~ /(?<!\w).{2,}(?!\w)(?{ push @pat, [ $-[0], $& ] })(*FAIL)/
+;

This is the heart of finding a place to move. For a word to be a legal move, it must match one of the patterns in @pat. The (?<!\w) prevents putting the new word next to a preceding word, and the (?!\w) prevent putting the new word abutting a following word. The(*FAIL) forces the regex engine to try every possible place to find a match.

Try

perl -le ' "abcd" =~ /.{2,}(?{print $&})(*FAIL)/ '

and notice it prints out every substring with two or more characters.

[Aldebaran]

leaving vertical space for respondents...

Read more... (9 kB)

Thanks for your comment,

[tybalt89]

Explanation of the masking in "matchrule"



sub matchrule {
  my ( $old, $highs, $word ) = @_;
  $old eq $word and return 0;
  my $newmask = ( $old ^ $word ) =~ tr/\0/\xff/cr;
  ( $newmask & $highs ) =~ tr/5// and return 0;
  my $tiles = "@tiles";
  $tiles =~ s/$_// or return 0 for ( $newmask & $word ) =~ /\w/g;
  return 1;
}

Let's follow a call to matchrule('hello', '14222', 'world')

First off, if old and word are the same, it's not a valid move.

Next, get the mask. ( note: strings have been printed by Data::Dumper::Useqq = 1 )

'hello' ^ 'world' => "\37\n\36\0\13"

However, I want to change all non nulls ("\0") to "\xff" so that characters can pass through these positions unchanged.

my $newmask = ('hello' ^ 'world') =~ tr/\0/\xff/cr => "\377\377\377\0\
+377"

Now we use this mask against the tile heights and look for any 5's, because the "\xff" in $newmask are at the positions where new tiles will be added.

("\377\377\377\0\377" & '14222') => "142\0002"

and since there is no 5, the new word is not invalid (yet).

"\377\377\377\0\377" & 'world' => "wor\0d"

This leaves only the new tiles that must be played, ignoring the "\0" because those positions use the old tile. So remove each new letter from a string of the tile rack, and if any are not there, the move is invalid.

Hope this helps.

[tybalt89]

    my $newmask = ( $old ^ $word ) =~ tr/\0/\xff/cr;
    $flip and ( $board, $heights ) = flip $board, $heights;
    substr $board, $pos, length $word, $word;

    #say "new mask is $newmask";
    substr $heights, $pos, length $highs,
      ( $highs & $newmask ) =~ tr/0-4/1-5/r | ( $highs & ~$newmask );
    $flip and ( $board, $heights ) = flip $board, $heights;
    my $tiles = join '', @tiles;
    say "word is $word";
    $tiles =~ s/$_// for split //, $word & $newmask;

let me try...

    my $newmask = ( $old ^ $word ) =~ tr/\0/\xff/cr;

$newmask is "\xff" where the old and new words differ, that is a new tile must be used. It is "\0" where no tile is to be placed (using existing board state).

    $flip and ( $board, $heights ) = flip $board, $heights;
    substr $board, $pos, length $word, $word;

    #say "new mask is $newmask"; # $newmask has unprintable characters
+, use something like Data::Dump that will show them.
    substr $heights, $pos, length $highs,
      ( $highs & $newmask ) =~ tr/0-4/1-5/r | ( $highs & ~$newmask );

hehehe! GOAL => increment the stack sizes for only the new tiles.

$highs & $newmask produces a string that only has non-null characters where new tiles are to be played. In other words, it isolates the stacks for the new tiles, everywhere else is "\0".
=~ tr/0-4/1-5/r increments the height for each place a new tile is played.
~$newmask inverts $newmask to be "\xff" only where old tiles remain visible.
$highs & ~$newmask produces a string with only the unchanged stack values (and "\0" where the new values are).
Finally, the | puts the old and new stack counts together so they can be replaced in the heights string.

    $flip and ( $board, $heights ) = flip $board, $heights;
    my $tiles = join '', @tiles;
    say "word is $word";
    $tiles =~ s/$_// for split //, $word & $newmask;

This removes the tiles that are used for this word from the string of all tiles, soon to be replaced in @tiles.

Hope this helps...

[Aldebaran]

Hope this helps...

It does. I was able to see these masks by unpacking them as hexidecimal. Here's a bit of output:

Read more... (10 kB)

Fishing for tips. Thanks for your comment,