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📝 Find.

This commit is contained in:
Rob Rix 2019-10-08 15:40:34 -04:00
parent abb6eff40f
commit 83bead5840
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@ -24,6 +24,7 @@ pattern Prj sub <- (prj -> Just sub)
-- | Where does the element occur in the tree?
data Side = None | Here | L | R
-- | Find where in a tree an element occurs.
type family Find sub sup :: Side where
Find t t = 'Here
Find t (l :+: r) = Find' 'L t l <> Find' 'R t r