Add meaningful instances to ZipList

Roman Cheplyaka roma at
Mon Dec 19 23:14:26 CET 2011

* wren ng thornton <wren at> [2011-12-19 16:45:50-0500]
> While we're on the topic, is there any reason why ZipList is a data
> type instead of a newtype? Is the extra bottom actually necessary for
> the Applicative semantics? If not, then I'd suggest changing it to a
> newtype in order to remove the extra indirection.

It is actually a newtype, and has been at least since base- (the
oldest 'base' available on hackage).

Roman I. Cheplyaka ::

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