Eq1, Ord1, Show1: move from eq1, compare1, showsPrec1 to liftEq, liftCompare, liftShowsPrec

Ryan Scott ryan.gl.scott at gmail.com
Mon Jan 11 19:04:05 UTC 2016

> Btw. I already defined my own Apply type (I called it Wrap) because I found it useful. Would you mind to export it from 'transformers'?

You're talking about this transformers issue [1], correct? If so, I
doubt that's ever going to happen. The changes to Eq1/Ord1/Read1/Show1
rendered Apply obsolete, since it's no longer necessary to use Apply
to define Eq1 instances for nested applications of a type parameter of
kind * -> *. Not only that, but there are a couple of datatypes in
transformers that already resolve their Eq instances in an identical
way to how Apply would (for instance, IdentityT, which is isomorphic
to Apply [2]).

Ryan S.
[1] http://hub.darcs.net/ross/transformers/issue/8
[2] http://hackage.haskell.org/package/transformers-

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