apfelmus wrote:
Note that due to parametricity, any function of this type is necessarily
either id or _|_. In other words, there are only two functions of type
∀a∀b. (a->b) -> (a->b)
You managed to type ∀ but you couldn't find ⊥ ?
OOC, can anybody tell me what ∀ actually means anyway?
That's because the functions has to work for all types a and b in the
same way, i.e. it may not even inspect how the given types a or b look
like. You need type classes to get a reasonable type for the function
you want
memoize :: Memoizable a => (a->b) -> (a->b)
Ah... most optimal!
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