[Haskell-cafe] Re: Is this haskelly enough?

[Daniel McAllansmith]

On Wednesday 18 July 2007 21:16, Johan Tibell wrote:
> It would be nice if it was possible to capture this kind of behavior in a
> high order function just like map though. I guess the problem is that the
> function to map will take different number of arguments depending on the
> use case.
>
> lookAtTwo a b = ...
>
> lookAtThree a b c = ...
>
> map' :: (a -> ... -> b) -> [a] -> [b]
>
> The parameter take a variable number of parameters.
>
> Note: I don't know if there is a sensible way to write map' at all. Perhaps
> explicit recursion is better in this case.

Oleg (unsurprisingly) has some type-class hackery for polyvariadic/keyword 
functions.  Probably do what you need, possibly be overkill for what you 
want... here it is anyway.

http://okmij.org/ftp/Haskell/keyword-arguments.lhs