clojure.core/boolean

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

([x])

Coerce to boolean

Examples

by nipra on 2010-07-13 . May have evaluation errors. ▶

;; Everything except `false' and `nil' is true in boolean context. (into {} (map #(vector % (boolean %)) [true false nil [] {} '() #{} ""])) {true true, false false, nil false, [] true, {} true, #{} true, "" true} (clojure.pprint/pp) {true true, false false, nil false, [] true, {} true, #{} true, "" true} nil ;; Unrelated to `boolean`, but notice that the `'()` entry is missing. This ;; due to Clojure treating `[]` and `'()` as equal. When combined into the map ;; the `'() => true` key-value pair is overwritten by the `[] => true` key-value ;; pair. See https://github.com/zk/clojuredocs/issues/114#issuecomment-132153637

by nickzam on 2015-02-27 ▶

;; Beware that boolean returns true for numbers 0 and 1 (boolean 0) true (boolean 1) true

by Jarzka on 2016-09-30 ▶

;; Simply defined: Everything except false and nil is logically true in Clojure.

by dottedmag on 2017-05-31 ▶

;; Corrected definition: ;; returns `false' for `false', `nil' and `(Boolean. false)`. ;; returns `true' for everything else.

See also

• clojure.core/boolean?
• clojure.core/parse-boolean

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