Takes a fn f and returns a fn that takes the same arguments as f,
has the same effects, if any, and returns the opposite truth value.
;; a simple not-empty? predicate
user=> (def not-empty? (complement empty?))
#'user/not-empty?
user=> (not-empty? [])
false
user=> (not-empty? [1 2])
true
;; a slightly more complex example
;; this function takes two arguments, and sometimes returns nil
user=> (defn contains-char? [the-string, the-char]
(some #(= the-char %) the-string))
#'user/contains-char?
user=> (contains-char? "abc" \b)
true
user=> (contains-char? "abc" \j)
nil
;; define the complement, to check if a char is absent
user=> (def does-not-contain-char? (complement contains-char?))
#'user/does-not-contain-char?
;; our complement does exactly what we expect
user=> (does-not-contain-char? "abc" \b)
false
user=> (does-not-contain-char? "abc" \j)
true
Source
clojure/core.clj:1332
top
(defn complement
"Takes a fn f and returns a fn that takes the same arguments as f,
has the same effects, if any, and returns the opposite truth value."
{:added "1.0"
:static true}
[f]
(fn
([] (not (f)))
([x] (not (f x)))
([x y] (not (f x y)))
([x y & zs] (not (apply f x y zs)))))
Comments top
No comments for complement. Log in to add a comment.