O(log n). Combines insert operation with old value retrieval.
The expression (
insertLookupWithKey f k x map) is a
pair where the first element is equal to (
lookup k
map) and the second element equal to (
insertWithKey f
k x map).
let f key new_value old_value = (show key) ++ ":" ++ new_value ++ "|" ++ old_value
insertLookupWithKey f 5 "xxx" (fromList ((5,"a") :| [(3,"b")])) == (Just "a", fromList ((3, "b") :| [(5, "5:xxx|a")]))
insertLookupWithKey f 7 "xxx" (fromList ((5,"a") :| [(3,"b")])) == (Nothing, fromList ((3, "b") :| [(5, "a"), (7, "xxx")]))
This is how to define
insertLookup using
insertLookupWithKey:
let insertLookup kx x t = insertLookupWithKey (\_ a _ -> a) kx x t
insertLookup 5 "x" (fromList ((5,"a") :| [(3,"b")])) == (Just "a", fromList ((3, "b") :| [(5, "x")]))
insertLookup 7 "x" (fromList ((5,"a") :| [(3,"b")])) == (Nothing, fromList ((3, "b") :| [(5, "a"), (7, "x")]))