Re: [Haskell-cafe] Monad transformer to consume a list

On Mon, 6 Apr 2009, Stephan Friedrichs wrote:

Hello,

is there a monad transformer to consume an input list? I've got external events "streaming into the monad" that are consumed on demand and I'm not sure if there's something better than a StateT.

I wondered that, too. I wondered whether there is something inverse to Writer, and Reader is appearently not the answer. Now I think, that State is indeed the way to go to consume a list. Even better is StateT List Maybe: next :: StateT [a] Maybe a next = StateT Data.List.HT.viewL -- see utility-ht package