From: Malte Milatz Subject: Re: [Haskell-cafe] Norvig's Sudoku Solver in Haskell

Your program was wrapped by your mail client, so you may want to hpaste your program for easier digestion.

here it is : http://hpaste.org/2452

Your profiling output suggests that much time is consumed by the lookup function. Since you're using (fromJust . lookup) everywhere anyway, a data structure not envolving the Maybe type is probably a more succint choice. And why bother with characters and strings?

no rationale except that's what the original Python script did use

...

newV2 <- case length newCell of 0 -> Nothing 1 -> do let peersOfS = [ s' | s' <- lookup s peers ] res <- foldM eliminate newV (zip peersOfS (cycle newCell)) return res _ -> return newV

The use of “length” here is not an actual performance problem, but unnecessary. Simply write: case newCell of [] -> ... [_] -> ... _ -> ...

The same is valid for your other use of length.

Malte

I see, thanks ! E.D