[Haskell-cafe] Newtype derivation understanding problem
mbrock at goula.sh
Thu Jul 31 11:00:26 UTC 2014
Konstantine Rybnikov <k-bx at k-bx.com> writes:
> Excuse me if the question is silly.
> Thought this MonadCatchIO will be removed in next version of snap,
> current version has it and I can't understand this derivation: 
> L.Lensed seems like just a newtype wrapper around a function , and
> there is no instance of MonadCatchIO for a function.
> How is it derived?
You probably just missed it, but there's a MonadCatchIO instance for
L.Lensed, and so the derived instance for Handler is trivial.
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