[Haskell-cafe] Toy compression algorithms

[Andrew Coppin]

ajb at spamcop.net wrote:
> G'day all.
>
> Andrew Coppin wrote:
>
>   
>>> Actually, LZW works surprisingly well for such a trivial little
>>> algorithm... When you compare it to the complexity of an arithmetic
>>> coder driven by a high-order adaptive PPM model (theoretically the best
>>> general-purpose algorithm that exists), it's amazing that anything so
>>> simple as LZW should work at all!
>>>       
>
> Not really.  LZW is basically PPM with a static (and flat!) frequency
> prediction model.  The contexts are build in a very similar way.
>   

Yes - but making it use a non-flat model opens a whole Pandora's Box of 
fiddly programming. ;-)

(It's not "hard" as such - just frustratingly fiddly to get correct...)