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Add fromAlt #90

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Add fromAlt #90

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67e1522
add fromAlt
Jul 13, 2018
c8324b4
whitespace
Jul 13, 2018
c2c778c
caps
Jul 13, 2018
bf06fa4
change name and haddock, updated logic to prioritize error from This …
Jul 17, 2018
f301605
fix commend
Jul 17, 2018
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4 changes: 4 additions & 0 deletions Data/These.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ module Data.These (
, fromThese
, mergeThese
, mergeTheseWith
, fromAlt

-- * Traversals
, here, there
Expand Down Expand Up @@ -109,6 +110,9 @@ mergeThese = these id id
mergeTheseWith :: (a -> c) -> (b -> c) -> (c -> c -> c) -> These a b -> c
mergeTheseWith f g op t = mergeThese op $ mapThese f g t

-- | Construct These inside an Alternative.
fromAlt :: Alternative f => f a -> f b -> f (These a b)
fromAlt x y = These <$> x <*> y <|> That <$> y <|> This <$> x

-- | A @Traversal@ of the first half of a 'These', suitable for use with @Control.Lens@.
here :: (Applicative f) => (a -> f b) -> These a t -> f (These b t)
Expand Down