Hi all,
I seem to recall Rich saying "I like the destructuring part of pattern
matching." In my efforts to appreciate that statement, I am playing
around with porting simple Haskell examples to Clojure, trying to use
destructuring (and multimethods) where the Haskell does pattern matches.
For example:
-- Haskell
qsort [] = []
qsort (x:xs) = qsort smaller ++ [x] ++ qsort bigger
where smaller = filter (<x) xs
bigger = filter (>=x) xs
; Clojure, destructuring pivot and vals
(defn quicksort-1 [[pivot & vals]]
(if pivot
(let [smaller (partial filter #(< % pivot))
bigger (partial filter #(>= % pivot))]
(lazy-cat (quicksort-1 (smaller vals)) [pivot] (quicksort-1
(bigger vals))))
nil))
; Clojure again, using multimethod to separate base and recur
(defmulti quicksort-2 first)
(defmethod quicksort-2 nil [_] nil)
(defmethod quicksort-2 :default [[pivot & vals]]
(let [smaller (partial filter #(< % pivot))
bigger (partial filter #(>= % pivot))]
(lazy-cat (quicksort-2 (smaller vals)) [pivot] (quicksort-2
(bigger vals)))))
I am confident that the Clojure could be prettier, but not sure how.
Suggestions?
Cheers,
Stuart
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