[Haskell-cafe] Debugging methods for haskell

Anton van Straaten anton at appsolutions.com
Wed Jul 15 19:59:36 EDT 2009


Fernan Bolando wrote:
> Program error: Prelude.!!: index too large
> 
> This is not very informative. It did not give me a hint which function
> was causing this. 

In addition to the debugging methods that have been mentioned, the 
"Safe" library provides a way to write the code more robustly and/or 
informatively:

   http://hackage.haskell.org/package/safe
   http://community.haskell.org/~ndm/safe/

Among other things, it provides replacements for the (!!) operator which 
would have likely have helped in this case.

Anton



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