[Haskell-cafe] Re: Optimizing 'sequence'

Antoine Latter writes:

The function "runIdentity" is found in Control.Monad.Identity in the mtl package.

Thanks, I see it now! Laziness is not there! But still... Identity is a bit special monad. What other monads need full laziness in sequence? As far as I know IO is strict. What about lazy/strict state monad? Initially I spotted this possible optimization in context of monadic parser. I am not really sure if I need this property there or not. How do I prove this to myself? Thanks to others who responded. -- Gracjan