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Define lenses for the starts/ends of Range.

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Rob Rix 2019-09-20 16:27:11 -04:00
parent a00a78e522
commit bb204715a1
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@ -1,8 +1,11 @@
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DeriveGeneric, RankNTypes #-}
module Source.Range
( Range(..)
, rangeLength
, subtractRange
-- * Lenses
, start_
, end_
) where
import Control.DeepSeq (NFData)
@ -37,6 +40,18 @@ subtractRange :: Range -> Range -> Range
subtractRange range1 range2 = Range (start range1) (end range1 - rangeLength (Range (start range2) (max (end range1) (end range2))))
start_, end_ :: Lens' Range Int
start_ = lens start (\r s -> r { start = s })
end_ = lens end (\r e -> r { end = e })
type Lens' s a = forall f . Functor f => (a -> f a) -> (s -> f s)
lens :: (s -> a) -> (s -> a -> s) -> Lens' s a
lens get put afa s = fmap (put s) (afa (get s))
{-# INLINE lens #-}
-- $setup
-- >>> import Test.QuickCheck
-- >>> instance Arbitrary Range where arbitrary = Range <$> arbitrary <*> arbitrary ; shrink (Range s e) = Range <$> shrink s <*> shrink e