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📝 unprefix’s parameters.

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Rob Rix 2019-08-06 12:01:30 -04:00
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semantic-core/src/Data/Scope.hs
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@ -113,7 +113,10 @@ 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
:: (Int -> t -> Maybe (a, t)) -- ^ A function taking the 0-based index into the prefix & the current term, and optionally returning a pair of the prefixing value and the inner subterm.
-> t -- ^ The initial term.
-> (Stack a, t) -- ^ A stack of prefixing values & the final subterm.
unprefix from = unprefixEither (matchMaybe . from)
unprefixEither :: (Int -> t -> Either (a, t) b) -> t -> (Stack a, b)