Clojure tips: patterns matching

This is how it can be done in clojure:

user=> (defmulti fib (fn [x] x) :default :default)
#'user/fib
user=> (defmethod fib 0 [x] 0)
#<MultiFn clojure.lang.MultiFn@de1b8a>
user=> (defmethod fib 1 [x] 1)
#<MultiFn clojure.lang.MultiFn@de1b8a>
user=> (defmethod fib :default [n] (+ (fib (- n 2)) (fib (- n 1))))
#<MultiFn clojure.lang.MultiFn@de1b8a>
user=> (fib 32)
2178309
user=> (time (fib 32))
"Elapsed time: 3406.246008 msecs"
2178309
user=>

Factorial pattern matching:

(defmulti fac (fn [x] x) :default :default)
(defmethod fac 1 [x] 1)
(defmethod fac :default [n] (* n (fac (- n 1))))

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