I wrote:

...

Perhaps you would gain something if you used Data.Map.! instead of your "lookup".

Manu wrote:

I'm not sure I understand, do you mean I should have use a strict Map constructor ? like : Map !key !value ?

No, there is an operator in Data.Map called "!".

how can it replace the lookup function ?

Use

import qualified Data.Map as M import Data.Map (!)

Then, instead of "lookup k m" use "m ! k".

...

Other than that, I'm not sure why your code runs slower than mine.

Malte Milatz wrote: MM> The use of "length" here is not an actual MM> performance problem... Maybe not there, but I think Malte's suggestion might actually improve performance if you do the same thing a few lines further down, where you wrote:

case length dPlaces of

By using Malte's idea there instead of length, you might allow some calculations inside dPlaces to be lazily skipped. Regards, Yitz