polar¶

(define (install-polar-package)
    ;; internal procedures
    (define (magnitude z) (car z))
    (define (angle z) (cdr z))
    (define (make-from-mag-ang r a) (cons r a))
    (define (real-part z) (* (magnitude z) (cos (angle z))))
    (define (imag-part z) (* (magnitude z) (sin (angle z))))
    (define (make-from-real-imag x y)
        (cons (sqrt (+ (square x) (square y)))
              (atan y x)))
    ;; interface to the rest of the system
    (define (tag x) (attach-tag 'polar x))
    (put 'real-part '(polar) real-part)
    (put 'imag-part '(polar) imag-part)
    (put 'magnitude '(polar) magnitude)
    (put 'angle '(polar) angle)
    (put 'make-from-real-imag 'polar
         (lambda (x y) (tag (make-from-real-imag x y))))
    (put 'make-from-mag-ang 'polar
         (lambda (r a) (tag (make-from-mag-ang r a))))
    'done)