[Haskell-cafe] Re: Splitting data and function declarations over
apfelmus at quantentunnel.de
Thu Oct 1 04:17:50 EDT 2009
Peter Verswyvelen wrote:
> I guess this is related to the expression problem.
> Suppose I have a datatype
> *data Actor = Ball ... | Paddle ... | Wall ...*
> and a function
> *move (Ball ...) = *
> *move (Paddle ...) = *
> *move (Wall ...) = *
> in Haskell one must put *Actor* and *move* into a single file.
Just a nitpick: you don't have to put Actor and move into the same
module A where
data Actor = Ball | Paddle | Wall
module B where
import A (Actor)
move Ball = ...
move Paddle = ...
move Wall = ...
But that's probably not what you meant.
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