`clojure.core/destructure`¶

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

([bindings])

Examples¶

by reborg on 2014-04-01

by phreed on 2018-02-26 . May have evaluation errors.

;; Based on the previous example...

;; Suppose you want to do some work at the repl.
;; It would be nice if the def and let had similar syntax but they do not.

(defn def+ [bindings] 
  (let [bings (partition 2 (destructure bindings))
        obj (first bings)
        redef (rest bings)]

(intern *ns* (first obj) (eval (second obj)))  
    (map #(intern *ns* (first %) (eval (last %))) redef)))

(def+ '[[u s v] [1 5 9]])

;; def+ is better implemented as a macro.
;; It does have the drawback of introducing some intermediate gen variables.
;; But, it prints the names of all variables.

(defmacro def+
  "binding => binding-form
  internalizes binding-forms as if by def."
  {:added "1.9", :special-form true, :forms '[(def+ [bindings*])]}
  [& bindings]
  (let [bings (partition 2 (destructure bindings))]
    (sequence cat 
      ['(do) 
       (map (fn [[var value]] `(def ~var ~value)) bings)
       [(mapv (fn [[var _]] (str var)) bings)]])))

(def+ [u s v] [1 5 9] 
      foo "bar" 
      [a b] ["abc" "bcd"])
;=> #'user/b

a
;=> "abc"

;; The justification for such a macro is manifest when
;; debugging at the repl.
;; Suppose the following is in a function and 
(let [[a b] ["a" "b"]] 
  (str a b)   ; is this correct?
  (conj a b)  ; how about this?
  (cat a b))  ; or this?

;; Now in this case the problem is clear but in general it may not be.
;; So you get set up to track down this problem. 
(def+ [a b] ["a" "b"])

;; Without def+ you would have to do something like the following...
(def ab ["a" "b"])
(def a (nth ab 0))
(def b (nth ab 1))
;; ...to get set up in the repl.

Note by Ragsboss¶

I found https://clojure.org/guides/destructuring extremely useful

Note by cljlc¶

"[The destructure function] implements the destructuring logic and [...] is designed to be invoked in a macro". For more info about desctructure see https://clojure.org/guides/destructuring#_macros.

Content from the matching ClojureDocs page, with authors credited on each contribution.

clojure.core/destructure¶

Examples¶

Note by Ragsboss¶

Note by cljlc¶

`clojure.core/destructure`¶