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📝 unprefix’s purpose.

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Rob Rix 2019-08-06 11:59:20 -04:00
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semantic-core/src/Data/Scope.hs
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@ -111,6 +111,8 @@ instantiateEither f = unScope >=> incr (f . Left) (>>= f . Right)
-- | Unwrap a (possibly-empty) prefix of @a@s wrapping a @t@ using a helper function.
--
-- This allows us to peel a prefix of syntax, typically binders, off of a term, returning a stack of prefixing values (e.g. variables) and the outermost term rejected by the function.
unprefix :: (Int -> t -> Maybe (a, t)) -> t -> (Stack a, t)
unprefix from = unprefixEither (matchMaybe . from)