random   scheme

(define (random . args)
  (cond ((< (length args) 1)
         (random-real))
        ((list? (car args))
         (list-ref (car args) (random (length (car args)))))
        ((pair? (car args))
         (apply weighted-selection args))
        (else (let ((lower (if (> (length args) 1) (real->integer (car args)) 0))
                    (upper (if (> (length args) 1) (cadr args) (car args))))
                (+ lower (random-int (- upper lower)))))))