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I wondered, why not take an n-tuple of arguments s.t.

multApply' :: (a1->a2->...->an->o) -> (a1,(a2,(...(an,o)...))) -> o

I'm not sure what you're trying to do here. Why is there an o in the argument? Also, do you really mean the number of arguments expected to match the number of arguments given?

You are right. It should rather be multApply' :: (a1->a2->...->an->o) -> (a1,(a2,(...(an-1,an)...))) -> o as e.g. in: multApply' take (2,['a','b','c'])

Also you might want to check out Olegon polyvariadic functions: http://okmij.org/ftp/Haskell/vararg-fn.lhs

Thanks, I will have a look at this. Martin