[Haskell-cafe] The container problem
andrewcoppin at btinternet.com
Sat Sep 27 13:23:47 EDT 2008
Albert Y. C. Lai wrote:
> Andrew Coppin wrote:
>> If I understand this correctly, to solve this problem you need either
>> Functional Dependencies or Associated Types. Is that correct?
> A motivating example in papers on FD is exactly typeclasses for
> containers. Okasaki puts this into practice in the Edison library.
> Despite its comprehensiveness, elegance, and the Okasaki name brand,
> it did not become mainstream. I don't know why.
Can anybody actually demonstrate concretely how FDs and/or ATs would
solve this problem? (I.e., enable you to write a class that any
container can be a member of, despite constraints on the element types.)
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