(identity x)
Returns its argument.
user=> (identity 4)
4
user=> (filter identity [1 2 3 nil 4 false true 1234])
(1 2 3 4 true 1234)
user=> (map #(%1 %2) (cycle [inc identity]) [1 2 3 4 5 6 7 8 9 10])
(2 2 4 4 6 6 8 8 10 10)
user=> (partition-by identity (sort "abcdaabccc"))
((\\a \\a \\a) (\\b \\b) (\\c \\c \\c \\c) (\\d))
user=> (map first (partition-by identity [1 1 2 3 3 1 1 5 5]))
(1 2 3 1 5)
user=> (group-by identity "abracadabra")
{\\a [\\a \\a \\a \\a \\a], \\b [\\b \\b], \\r [\\r \\r], \\c [\\c], \\d [\\d]}
user=> (map #(identity %) [1 2 3 4]) ; ~ (map (fn [x] x) [1 2 3 4])
(1 2 3 4)