[Haskell] Mixing monadic and non-monadic functions

[Wolfgang Lux]

Frederik Eaton wrote:

> I want the type system to be able to do "automatic lifting" of monads,
> i.e., since [] is a monad, I should be able to write the following:
>
>
>
> and have it interpreted as "do {a<-[1,2]; b<-[3,4]; return (a+b)}".

Are you sure that this is the interpretation you have in mind? The
expression do {a<-[1,2]; b<-[3,4]; return (a+b)} does *not* compute the
element-wise sum of the two lists, but returns the list [4,5,5,6]. To
me, this would be a very counter intuitive result for an expression
[1,2]+[3,4].

Wolfgang