Talk:Prefix code

Is UTF8 a prefix code in use today? If so, I think it should be included. 71.158.69.195 22:27, 20 March 2007 (UTC)[reply]

Comma-Free Codes

Comma-Free codes are not the same thing as prefix codes. Any set with 11 (or any code word comprised of only one bit for that matter) cannot be a comma-free code. This is shown in "Comma-Free Codes" by Golomb, Gordon and Welch in the Canadian Journal of Mathematics vol. 10, no. 2, pp. 202-209 (1958).

What definition of "comma" does Golomb use in that paper? --68.0.124.33 (talk) 14:21, 14 April 2008 (UTC)[reply]

Do I get it right that comma-free code is the same as self-synchronizing code? Jaan Vajakas (talk) 16:42, 23 October 2010 (UTC)[reply]

I don't think so, at least according to the definitions given here. The code with the single codeword 0101 is comma-free (the sequence 01010101 formed by two consecutive codewords does not have a codeword starting from its second symbol) but not self-synchronizing (it does have a codeword starting from its third symbol). —David Eppstein (talk) 18:45, 23 October 2010 (UTC)[reply]

The article says that code is comma-free if "the substring starting at the second symbol and ending at the second-last symbol does not contain any codewords". In your example, the aforementioned substring is 101010 and it does contain the codeword 0101 as a substring (but, indeed, not as a prefix). So if you are right then it should be specified in the article that "contains" means "contains as a prefix", to make the definition unambiguous. However, I don't quite see why such a definition would be useful, so I still rather believe that "contains" means "contains as a substring" (and hence comma-free = self-synchronizing). Jaan Vajakas (talk) 20:42, 23 October 2010 (UTC)[reply]

Probably you're right. —David Eppstein (talk) 22:31, 23 October 2010 (UTC)[reply]

I edited the pages Self-synchronizing code and Prefix code to reflect that self-synchronizing code = comma-free code, and redirected Comma-free code to Self-synchronizing code. Jaan Vajakas (talk) 19:28, 4 December 2010 (UTC)[reply]