[Haskell-cafe] Re: Debugging methods for haskell

Fernan Bolando writes:

On Thu, Jul 16, 2009 at 4:10 PM, Jon Fairbairn wrote:

...

I wonder if your code has to use !! at all? I took a look at a random module from the above link, and (without making much attempt at understanding it), I'd guess that using accumArray and friends would be more appropriate. Mostly you don't want to be doing indexing on lists.

Most of the !! are used to access a list of parameters similar to accessing structures in C.

Ah. I wondered why so many of them were x!!0. list!!constant is almost always something that could be done better.

I am not particularly sure how to apply accumArray for something like that?

You [probably] don't. My apologies for not looking more carefully (I really did just glance at it), but the remark about not using !! still stands. I've been trying to look at your source again, but the link doesn't respond to requests at the moment, so I can't be much help. Haskell has much richer mechanisms for doing structure-like things than C. Tuples and data types being the most obvious. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk