[Haskell-cafe] Applying a value to a function generically
arnaud.oqube at gmail.com
Wed Jul 14 07:25:41 EDT 2010
I would like to construct a collection of function-like objects on
which I could apply some value, in a typesafe and clean way.
Let's say I have something like this:
> data Fun = forall a b . F (a -> b)
> type Callables = Map String Fun
I would like to be able to write:
> invoke :: Callables -> a -> String -> b
> invoke m d k = case lookup k m of
> Just (F f) -> f d
> Nothing -> error $ "unable to find function for key " ++ k
which of course does not compile nor even make sense. I suspect I need
to have more information in Fun to be able to apply functions
correctly, but don't know where to look at.
I read recently an article about implicit configurations that used
some type wizardry to ensure correct and typesafe use of external data
and sounded pretty cool,
(http://www.cs.rutgers.edu/~ccshan/prepose/prepose.pdf) but I suspect
this is 1) too complex for me an 2) overkill for my problem.
Could someone point me in the right direction ?
Thanks in advance
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