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66 lines
2.8 KiB
Haskell
66 lines
2.8 KiB
Haskell
{-# LANGUAGE TypeSynonymInstances, UndecidableInstances #-}
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{-# OPTIONS_GHC -fno-warn-orphans #-}
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module Diff where
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import qualified Control.Comonad.Trans.Cofree as CofreeF
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import Control.DeepSeq
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import qualified Control.Monad.Free as Free
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import qualified Control.Monad.Trans.Free as FreeF
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import Data.Bifunctor
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import Data.Functor.Both as Both
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import Data.Mergeable
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import Data.Record
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import Patch
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import Syntax
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import Term
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-- | An annotated series of patches of terms.
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type DiffF f annotation = FreeF.FreeF (TermF f (Both annotation)) (Patch (Term f annotation))
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type Diff f annotation = Free.Free (TermF f (Both annotation)) (Patch (Term f annotation))
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type SyntaxDiff fields = Diff Syntax (Record fields)
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diffSum :: (Foldable f, Functor f) => (Patch (Term f annotation) -> Int) -> Diff f annotation -> Int
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diffSum patchCost diff = sum $ fmap patchCost diff
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-- | The sum of the node count of the diff’s patches.
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diffCost :: (Foldable f, Functor f) => Diff f annotation -> Int
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diffCost = diffSum $ patchSum termSize
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-- | Merge a diff using a function to provide the Term (in Maybe, to simplify recovery of the before/after state) for every Patch.
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mergeMaybe :: Mergeable f => (Patch (Term f annotation) -> Maybe (Term f annotation)) -> (Both annotation -> annotation) -> Diff f annotation -> Maybe (Term f annotation)
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mergeMaybe transform extractAnnotation = Free.iter algebra . fmap transform
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where algebra (annotations CofreeF.:< syntax) = cofree . (extractAnnotation annotations CofreeF.:<) <$> sequenceAlt syntax
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-- | Recover the before state of a diff.
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beforeTerm :: Mergeable f => Diff f annotation -> Maybe (Term f annotation)
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beforeTerm = mergeMaybe before Both.fst
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-- | Recover the after state of a diff.
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afterTerm :: Mergeable f => Diff f annotation -> Maybe (Term f annotation)
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afterTerm = mergeMaybe after Both.snd
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-- | Map a function over the annotations in a diff, whether in diff or term nodes.
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--
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-- Typed using Free so as to accommodate Free structures derived from diffs that don’t fit into the Diff type synonym.
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mapAnnotations :: (Functor f, Functor g)
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=> (annotation -> annotation')
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-> Free.Free (TermF f (g annotation)) (Patch (Term f annotation))
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-> Free.Free (TermF f (g annotation')) (Patch (Term f annotation'))
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mapAnnotations f = Free.hoistFree (first (fmap f)) . fmap (fmap (fmap f))
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instance (NFData (f (Diff f a)), NFData (f (Term f a)), NFData a, Functor f) => NFData (Diff f a) where
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rnf fa = case runFree fa of
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FreeF.Free f -> rnf f `seq` ()
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FreeF.Pure a -> rnf a `seq` ()
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free :: FreeF.FreeF f a (Free.Free f a) -> Free.Free f a
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free (FreeF.Free f) = Free.Free f
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free (FreeF.Pure a) = Free.Pure a
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runFree :: Free.Free f a -> FreeF.FreeF f a (Free.Free f a)
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runFree (Free.Free f) = FreeF.Free f
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runFree (Free.Pure a) = FreeF.Pure a
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