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Define lenses for the starts/ends of Range.
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@ -1,8 +1,11 @@
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{-# LANGUAGE DeriveGeneric #-}
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{-# LANGUAGE DeriveGeneric, RankNTypes #-}
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module Source.Range
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( Range(..)
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, rangeLength
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, subtractRange
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-- * Lenses
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, start_
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, end_
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) where
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import Control.DeepSeq (NFData)
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@ -37,6 +40,18 @@ subtractRange :: Range -> Range -> Range
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subtractRange range1 range2 = Range (start range1) (end range1 - rangeLength (Range (start range2) (max (end range1) (end range2))))
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start_, end_ :: Lens' Range Int
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start_ = lens start (\r s -> r { start = s })
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end_ = lens end (\r e -> r { end = e })
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type Lens' s a = forall f . Functor f => (a -> f a) -> (s -> f s)
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lens :: (s -> a) -> (s -> a -> s) -> Lens' s a
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lens get put afa s = fmap (put s) (afa (get s))
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{-# INLINE lens #-}
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-- $setup
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-- >>> import Test.QuickCheck
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-- >>> instance Arbitrary Range where arbitrary = Range <$> arbitrary <*> arbitrary ; shrink (Range s e) = Range <$> shrink s <*> shrink e
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