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Define a Diffable' instance for NonEmpty fields in syntax.

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Rob Rix 2017-08-14 16:42:13 -04:00
parent 07fda850f9
commit 2d6f130d32
1 changed files with 7 additions and 0 deletions
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7
src/Algorithm.hs
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@ -7,6 +7,7 @@ import Control.Monad.Free.Freer
import Data.Function (on)
import Data.Functor.Both
import Data.Functor.Classes
import Data.List.NonEmpty (NonEmpty(..))
import Data.Maybe
import Data.Proxy
import Data.These
@ -146,3 +147,9 @@ instance Diffable' U1 where
-- | Diff two lists of parameters.
instance Diffable' (Rec1 []) where
algorithmFor' a b = fmap Rec1 <$> Just ((byRWS `on` unRec1) a b)
-- | Diff two non-empty lists of parameters.
instance Diffable' (Rec1 NonEmpty) where
algorithmFor' (Rec1 (a:|as)) (Rec1 (b:|bs)) = Just $ do
d:ds <- byRWS (a:as) (b:bs)
pure (Rec1 (d :| ds))