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Define a smart constructor for let-binding diffs.

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Rob Rix 2017-09-10 19:56:06 +01:00
parent d68a8790ce
commit 289cb11912
1 changed files with 5 additions and 0 deletions
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src/Diff.hs
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@ -61,6 +61,11 @@ maxBoundMetavariable = cata $ \ diff -> case diff of
foldMaxMap :: (Foldable t, Ord b) => (a -> Maybe b) -> t a -> Maybe b
foldMaxMap f = foldr (max . f) Nothing
letDiff :: (Foldable syntax, Functor syntax) => Diff syntax ann -> (Metavar -> TermF syntax (Both ann) (Diff syntax ann)) -> Diff syntax ann
letDiff diff f = Diff (Copy [(n, diff)] body)
where body = f n
n = maybe (Metavar 0) succ (foldMaxMap maxBoundMetavariable (termSyntax body))
newtype Env a = Env { unEnv :: [(Metavar, a)] }
deriving (Eq, Foldable, Functor, Monoid, Ord, Show, Traversable)