my attempt to do the exercises in sicp.

Tuesday, August 12, 2008

sicp exercise 2.83

;; Exercise 2.83.  Suppose you are designing a generic arithmetic system for dealing with the tower of types shown in figure 2.25: integer, rational, real, complex. For each type (except complex), design a procedure that raises objects of that type one level in the tower. Show how to install a generic raise operation that will work for each type (except complex).

(define (install-rational-number-package)
  (define (raise rat-num)
    (make-complex-from-real-imag rat-num 0))
  (put 'raise '(rational) raise)

(define (install-scheme-number-package)
  (define (raise number)
    (make-rat number 1))
  (put 'raise '(scheme-number) raise)

(define (raise num)
  (apply-generic 'raise num))

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