[Haskell-cafe] Re: Exception handling in numeric computations

[Henning Thielemann]

On Tue, 24 Mar 2009, Xiao-Yong Jin wrote:

> Thanks for all the replies.  Now I understand more about
> Exceptions and Errors.  I guess all I need is to compose a
> larger monad, after all.  I need to learn how to make
> two different stacks of monad transformers cooperate
> seamlessly, though.

Until now it seems you only need Applicative functor. They can be combined 
in a more general way:
   http://hackage.haskell.org/packages/archive/TypeCompose/0.6.4/doc/html/Control-Compose.html

See the instances:
   (Applicative g, Applicative f) => Applicative (g :. f)