If you don't mind using mutation for private state in a functional language, objects and closures are kinda the exact same thing. (define (make-queue)

If you don't mind using mutation for private state in a functional language, objects and closures are kinda the exact same thing. (define (make-queue) (define data empty) (lambda (cmd [arg #f]) (match cmd ['enqueue (set! data (append data (list arg)))] ['dequeue (define value (first data) (set! data (rest data)) value]))) Don't see the connection yet? Let me try again. (define (make-queue) (define data empty) (define (instance cmd [arg #f]) (match cmd ['enqueue (set! data (append data (list arg)))] ['dequeue (define value (first data) (set! data (rest data)) value])) instance)