[Haskell-beginners] Type for lists with one or more elements

[Frerich Raabe]

Hi,

is there an existing (or conventional) way to model lists of one or more 
items? I often deal with functions with don't make sense with empty 
lists, and the caller already verified that the lists are not empty. So 
to avoid getting warnings from ghc, I'd like to have a dedicated type 
for this case.

I could do something like

   data List a = Singleton a | Cons a (List a)

but before I go ahead I wonder: is there an existing Haskell package for 
this? Maybe even with prettier names than what I wrote above, and 
convenient functions for transforming from/to plain [] lists? It would 
probably be straightforward to write it myself, but because of that, I 
suspect that somebody else already did it. :-)

-- 
Frerich Raabe - raabe at froglogic.com
www.froglogic.com - Multi-Platform GUI Testing