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Applicative instance for Only #270

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robinp opened this issue Dec 5, 2018 · 2 comments
Open

Applicative instance for Only #270

robinp opened this issue Dec 5, 2018 · 2 comments

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@robinp
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robinp commented Dec 5, 2018

This would be useful to do fmap join . sequenceA . listToMaybe on a query which normally returns [Only (Maybe a)]. With the magic sequence this becomes Only (Maybe a).
@robinp
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robinp commented Dec 5, 2018

Or, to golf more, join . fromOnly . sequenceA . listToMaybe to get Maybe a.

@phadej
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phadej commented Jan 30, 2019

Only is defined in http://hackage.haskell.org/package/Only package

@robinp robinp mentioned this issue Jan 30, 2019
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@phadej @robinp