`clojure.core/unreduced`¶

Type: function Added: Clojure 1.7 Examples: 2 Runnable: 1

([x])

If x is reduced?, returns (deref x), else returns x

Examples¶

by svenschoenung on 2016-02-28 . May have evaluation errors.

by tomdl89 on 2023-04-23

;; Transducers have a "completing arity" which is called at the end of the
;; reduction to finalize the output. This is done outside of the normal
;; reduction loop, so there is nothing to unwrap a reduced return value, should
;; the reducing function be called from the completing arity and happen to wrap
;; the return in a Reduced:

(defn conj-till-odd
  ([coll] coll)
  ([coll x] (cond-> (conj coll x) (odd? x) reduced)))

(defn inc-nums+7 [rf]
  (fn new-rf
    ([result] (rf result 7)) ; A bit contrived, but makes the point
    ([result x] (rf result (inc x)))))

(transduce inc-nums+7 conj-till-odd [] [1 3 5 7 9])
;; => #<Reduced@5c1e145d: [2 4 6 8 10 7]>

;; So we can wrap the return of the completing arity in `unreduced` to make sure
;; we don't return a Reduced. After all, it's the end of the reduction anyway:

(defn inc-nums+7 [rf]
  (fn new-rf
    ([result] (unreduced (rf result 7)))
    ([result x] (rf result (inc x)))))

(transduce inc-nums+7 conj-till-odd [] [1 3 5 7 9])
;; => [2 4 6 8 10 7]

clojure.core/unreduced¶

Examples¶

See also¶

`clojure.core/unreduced`¶