问Lua中的LZW压缩

EN

 pattern = get input character
 while ( not end-of-file ) {
     K = get input character
     if ( <<pattern, K>> is NOT in 
             the string table ){
         output the code for pattern
         add <<pattern, K>> to the string table
         pattern = K
     }
     else { pattern = <<pattern, K>> }
 }
 output the code for pattern
 output EOF_CODE

 function compress(uncompressed)

 local dict_size = 256
 local dictionary = {}

 w = ""
 result = {}
 for c in uncompressed do
  -- while c is in the function compress
     local wc = w + c
     if dictionary[wc] == true then
         w = wc
     else
         dictionary[w] = ""
         -- Add wc to the dictionary.
         dictionary[wc] = dict_size
         dict_size = dict_size + 1
         w = c
    end
 -- Output the code for w.
 if w then
   dictionary[w] = ""
 end
 end
 return dictionary
 end

 compressed = compress('TOBEORNOTTOBEORTOBEORNOT')
 print (compressed)