(constantly x)
Returns a function that takes any number of arguments and returns x.
user=> (def boring (constantly 10))
#'user/boring
user=> (boring 1 2 3)
10
user=> (boring)
10
user=> (boring "Is anybody home?")
10
;; A really goofy way to find the size of a collection
user=> (reduce + (map (constantly 1) [:a :b :c]))
3
;; constantly returns a function which always returns the same value
(map (constantly 9) [1 2 3])
user=> (9 9 9)
(map (constantly (rand-int 100)) [:a :b :c])
user=> (43 43 43)
;; 'Removed' example that was more about transducers than `constantly`.
:O