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53 lines
2.6 KiB
Haskell
53 lines
2.6 KiB
Haskell
{-# LANGUAGE TypeSynonymInstances, ScopedTypeVariables #-}
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module Diff where
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import Prologue
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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 (TermF f (Both annotation)) (Patch (Term f annotation))
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type Diff f annotation = Free (TermF f (Both annotation)) (Patch (Term f annotation))
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type SyntaxDiff leaf fields = Diff (Syntax leaf) (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 :: forall f annotation. 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 = iter algebra . fmap transform
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where algebra :: TermF f (Both annotation) (Maybe (Term f annotation)) -> Maybe (Term f annotation)
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algebra (annotations :< syntax) = cofree . (extractAnnotation annotations :<) <$> 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 (TermF f (g annotation)) (Patch (Term f annotation))
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-> Free (TermF f (g annotation')) (Patch (Term f annotation'))
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mapAnnotations f = iter (\ (h :< functor) -> wrap (fmap f h :< functor)) . fmap (pure . fmap (fmap f))
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-- | Map a function over the annotations of a single diff node, if it is in Free.
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modifyAnnotations :: (Functor f, Functor g) => (annotation -> annotation) -> Free (TermF f (g annotation)) a -> Free (TermF f (g annotation)) a
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modifyAnnotations f r = case runFree r of
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Free (ga :< functor) -> wrap (fmap f ga :< functor)
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_ -> r
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