clojure.core/set!

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Type: var Added: Clojure unknown Examples: 4 Runnable: 1

()

Assignment special form. When the first operand is a field member access form, the assignment is to the corresponding field. If it is an instance field, the instance expr will be evaluated, then the expr. In all cases the value of expr is returned. Note - you cannot assign to function params or local bindings. Only Java fields, Vars, Refs and Agents are mutable in Clojure. See http://clojure.org/special_forms for more information.

Examples

by ninjudd on 2011-06-03 . May have evaluation errors. ▶

(set! var-symbol expr)

by AtKaaZ on 2013-02-18 ▶

(set! *warn-on-reflection* true)

by nhlx2 on 2019-03-13 . May have evaluation errors. ▶

(let [object (java.awt.Point. 1 2)] (set! (. object -y) 8) (bean object) ) {:class java.awt.Point, :location #object[java.awt.Point 0x383fc59b "java.awt.Point[x=1,y=8]"], :x 1.0, :y 8.0}

by reborg on 2019-04-03 . May have evaluation errors. ▶

;; A mutable (and thread unsafe) Counter class. ;; set! is used to mutate the internal cnt attribute. (deftype Counter [^:unsynchronized-mutable cnt] clojure.lang.IFn (invoke [this] (set! cnt (inc cnt)))) (def counter (->Counter 0)) (counter) ;; 1 (counter) ;; 2

Note by gregg-williams

As of Clojure 1.2, the basic info for set! has moved to http://clojure.org/vars.

See also

• clojure.core/reset!
• clojure.core/binding (2)
• clojure.core/alter-var-root (2)
• clojure.core/atom (2)

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