[Haskell-beginners] finding the cause of an error (here head: empty list)
etouzery at gmail.com
Sun Mar 31 23:03:31 CEST 2013
I asked more or less the same question in august 2012.
as I have gained more experience with Haskell, the problem has become less
important and I think it will be the same with you. But there is a better
solution than Maybe and others, haskell can give you a stack trace if you
compile with profiling enabled:
I now make sure to compile all my libraries with profiling enabled, just in
case I may need it...
On Sun, Mar 31, 2013 at 5:42 PM, Nathan Hüsken <nathan.huesken at posteo.de>wrote:
> I have written a program which, when executed produces:
> Main: Prelude.head: empty list
> Now, I can go through my program and replace all "head" with
> (\a -> trace ("<line-nr>: length=" ++ (show (length a))) a)
> Actually, I already did that, and by this I found the error.
> But I wonder if there would have been an easier way?
> Has anyone any debug advice how I could find out which call to "head"
> causes this without so much typing work?
> Beginners mailing list
> Beginners at haskell.org
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Beginners