(define make-multiplier
(lambda (scaling-factor)
(lambda (x) (* x scaling-factor))))
(define double (make-multiplier 2))
(define triple (make-multiplier 3))
(define quadruple (make-multiplier 4))
(double 7) ⇒ 14
(triple 12) ⇒ 36
(quadruple 10) ⇒ 40
make-multiplier acts like a procedure factory.
Exercise 5.7: very similar (use expt)