clojure.core/when

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Type: macro Added: Clojure 1.0 Examples: 4 Runnable: 3

([test & body])

Evaluates test. If logical true, evaluates body in an implicit do.

Examples

by dpritchett on 2010-07-14 ▶

(when (= 1 1) true) true (when (not= 1 1) true) nil

by OnesimusUnbound on 2011-07-27 . May have evaluation errors. ▶

(def has-value (when true (println "Hello World") "Returned Value")) Hello World #'user/has-value has-value "Returned Value"

by jafingerhut on 2012-04-13 ▶

;; See examples for "if" explaining Clojure's idea of logical true ;; and logical false.

by nickzam on 2015-01-21 ▶

;; When is a macro of (if .. do ..) (macroexpand '(when 1 2 3 4)) (if 1 (do 2 3 4)) ;; if 1 is true, do will evaluate 2 3 4, but return values of 2 and 3 would be ;; ignored. Value of 4 (last value) would always be returned. ;; See https://clojuredocs.org/clojure.core/do for details (if 1 (do 2 3 4)) 4

See also

• clojure.core/when-not (5)
• clojure.core/when-let (6)
• clojure.core/if (2)
• clojure.core/boolean (3)
• clojure.core/when-some (3)

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