http://t3x.org/s9fes/adjoin.scm.html (light|dark)
Location: lib, 4 Lines
; Scheme 9 from Empty Space, Function Library ; By Nils M Holm, 2010 ; Placed in the Public Domain ; ; (adjoin object list) ==> list ; ; Add an element to a set. ; ; Example: (adjoin 'x '(a b c)) ==> (x a b c) ; (adjoin 'c '(a b c)) ==> (a b c) (define (adjoin x a) (if (member x a) a (cons x a)))