[Haskell-cafe] ANNOUNCE: htzaar-0.0.1

Roel van Dijk vandijk.roel at gmail.com
Fri Oct 9 07:50:42 EDT 2009

On Thu, Oct 8, 2009 at 12:56 AM, Tom Hawkins <tomahawkins at gmail.com> 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.

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