From: Charles D Hixson <charleshixsn@...>
Date: 2002-03-10T07:17:06+09:00
Subject: 2-dimensional regular expression patterns(?)

I am contemplating a kind of two dimensional regular expression 
based on strings.

These patterns would operate on strings that were defined as an mXn 
array of characters, though the actual implementation is planned to 
be a single string.  Resizing the mXn would be an expensive 
operation, but the built-in operations on strings make it appear to 
be the best choice.  (Actually, even were I doing this in C, I 
would choose to map the a[m][n] logical array into an a[m*n] array 
for implementation, but with the built-in pattern operations the 
choice seems open and shut.)

A sample pattern might look like this:
            22.2.22
               \\^//.
         5<dlldd>5l
            .<dal>3d
	 .led.
              //ed.
            3..V..\
              ...3...3
Here the desired interpretations are:
a == anchor, this is where the interpretation begins
d == darker than the anchor (could be g for greater than the anchor)
l == lighter than the anchor (could be for less than the anchor)
e == equal to the anchor
^ == carry the pattern up
V == carry the pattern down
> == carry the pattern to the right
< == carry the pattern to the left
/ == carry the pattern at a diagonal away from the anchor at 45 or  
               225 degrees
\ == carry the pattern at a diagonal away from the anchor at 135 or 
               315 degrees
. == don't care
# == the number of times to carry the pattern in this direction
+ == carry the pattern once or twice
? == carry the pattern zero or one time
* == carry the pattern an optional distance

Places where I would consider using this are in an algorithm for 
recognizing icons in images (colors would need to be reduced to fit 
into string values [16 bits?]) and to describe the possible 
movements of pieces in a board game, e.g., chess.

Does anyone know of anything like this?

-- 
 Charles Hixson
 
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