Source code in the racket programming language

-> (remove-duplicates '(2 1 3 2.0 a 4 5 b 4 3 a 7 1 3 x 2))
'(2 1 3 2.0 a 4 5 b 7 x)

(define (unique/hash lst)
  (hash-keys (for/hash ([x (in-list lst)]) (values x #t))))

(define unique/set (compose1 set->list list->set))

(define (unique seq #:same-test [same? equal?])
  (for/fold ([res '()])
            ([x seq] #:unless (memf (curry same? x) res))
    (cons x res)))