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You're viewing version 1.2.0 of trampoline. The latest stable version of Clojure Core is 1.3.0.

1.2.0

1.2.0
1.3.0

trampoline

trampoline can be used to convert algorithms requiring mutual
recursion without stack consumption. Calls f with supplied args, if
any. If f returns a fn, calls that fn with no arguments, and
continues to repeat, until the return value is not a fn, then
returns that non-fn value. Note that if you want to return a fn as a
final value, you must wrap it in some data structure and unpack it
after trampoline returns.

1 Example top

link | changes
```
user> (defn foo [x]
        (if (< x 0)
          (println "done")
          #(foo (do (println :x x) (dec x)))))
#'user/foo

;; trampoline will keep calling the function for as long as "foo" returns a function.
user> (trampoline foo 10)
:x 10
:x 9
:x 8
:x 7
:x 6
:x 5
:x 4
:x 3
:x 2
:x 1
:x 0
done
nil
```
user> (defn foo [x] (if (< x 0) (println "done") #(foo (do (println :x x) (dec x))))) #'user/foo ;; trampoline will keep calling the function for as long as "foo" returns a function. user> (trampoline foo 10) :x 10 :x 9 :x 8 :x 7 :x 6 :x 5 :x 4 :x 3 :x 2 :x 1 :x 0 done nil

Source clojure/core.clj:5040 top

(defn trampoline
  "trampoline can be used to convert algorithms requiring mutual
  recursion without stack consumption. Calls f with supplied args, if
  any. If f returns a fn, calls that fn with no arguments, and
  continues to repeat, until the return value is not a fn, then
  returns that non-fn value. Note that if you want to return a fn as a
  final value, you must wrap it in some data structure and unpack it
  after trampoline returns."
  {:added "1.0"}
  ([f]
     (let [ret (f)]
       (if (fn? ret)
         (recur ret)
         ret)))
  ([f & args]
     (trampoline #(apply f args))))

Vars in clojure.core/trampoline: apply defn fn? let

Used in 0 other vars

Comments top

1 comment(s) for trampoline.

gstamp

link

A tutorial on how to use trampoline is available here:

http://pramode.net/clojure/2010/05/08/clojure-trampoline/

and here:

http://jakemccrary.com/blog/2010/12/06/trampolining-through-mutual-recursion.html

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