Re: [Haskell-cafe] ANNOUNCE: htzaar-0.0.1

On Thu, Oct 8, 2009 at 12:56 AM, Tom Hawkins wrote:

Known bugs: Occasionally HTZAAR throws a Prelude.head: empty list. I'm still trying to track this down.

I used the following function to track down a similar problem: myhead :: String -> [a] -> a myhead msg [] = error msg myhead _ (x:_) = x Then you can replace your calls to head with myhead "bla". This way it is faster to pin-point which head is applied to an empty list.