[Haskell-cafe] Re: Optimizing 'sequence'

[Gracjan Polak]

Antoine Latter <aslatter <at> gmail.com> 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