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Add an applyToBoth function.

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This commit is contained in:
Rob Rix 2016-05-27 10:22:24 -04:00
parent 55d952c4c1
commit 41d532dd2d
1 changed files with 4 additions and 0 deletions
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4
src/Alignment.hs
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@ -211,6 +211,10 @@ applyThese :: Join These (a -> b) -> Join These a -> Maybe (Join These b)
applyThese (Join fg) (Join ab) = fmap Join . uncurry maybeThese $ uncurry (***) (bimap (<*>) (<*>) (unpack fg)) (unpack ab)
where unpack = fromThese Nothing Nothing . bimap Just Just
-- | Like `<*>`, but it takes a `Both` on the right to ensure that it can always return a value.
applyToBoth :: Join These (a -> b) -> Both a -> Join These b
applyToBoth (Join fg) (Join (a, b)) = Join $ these (This . ($ a)) (That . ($ b)) (\ f g -> These (f a) (g b)) fg
-- Map over the bifunctor inside a Join, producing another Join.
modifyJoin :: (p a a -> q b b) -> Join p a -> Join q b
modifyJoin f = Join . f . runJoin