fixup

1 files changed, 73 insertions, 0 deletions

diff --git a/coding-exercises/2/78/install-complex-package.rkt b/coding-exercises/2/78/install-complex-package.rkt
new file mode 100644
index 0000000..a656495
--- /dev/null
+++ b/coding-exercises/2/78/install-complex-package.rkt
@@ -0,0 +1,73 @@
+#lang racket
+(provide install-complex-package)
+(require "../../../shared/data-directed-programming.rkt")
+(require "./complex-rectangular.rkt")
+(require "./complex-polar.rkt")
+
+
+(define (install-complex-package apply-generic get put)
+  ;; install and import methods
+  (install-rectangular-package put)
+  (install-polar-package put)
+  (define (make-from-real-imag x y)
+    ((get 'make-from-real-imag 'rectangular) x y))
+  (define (make-from-mag-ang r a)
+    ((get 'make-from-mag-ang 'polar) r a))
+
+  (define (real-part z)
+    (apply-generic 'real-part z))
+  (define (imag-part z)
+    (apply-generic 'imag-part z))
+  (define (magnitude z)
+    (apply-generic 'magnitude z))
+  (define (angle z)
+    (apply-generic 'angle z))
+
+  ;; internal
+  (define (add-complex z1 z2)
+    (make-from-real-imag (+ (real-part z1) (real-part z2))
+                         (+ (imag-part z1) (imag-part z2))))
+  (define (sub-complex z1 z2)
+    (make-from-real-imag (- (real-part z1) (real-part z2))
+                         (- (imag-part z1) (imag-part z2))))
+  (define (mul-complex z1 z2)
+    (make-from-mag-ang (* (magnitude z1) (magnitude z2))
+                       (+ (angle z1) (angle z2))))
+  (define (div-complex z1 z2)
+    (make-from-mag-ang (/ (magnitude z1) (magnitude z2))
+                       (- (angle z1) (angle z2))))
+
+  ;; predicates (...) -> bool
+  (define (equ? z1 z2)
+    (and (equal? (real-part z1) (real-part z2))
+         (equal? (imag-part z1) (imag-part z2))))
+  (define (=zero? z)
+    (and (= (real-part z)) (= (imag-part z))))
+
+  ;; interface
+  (define (typetag z) (attach-tag 'complex z))
+  (put 'real-part '(complex) real-part)
+  (put 'imag-part '(complex) imag-part)
+  (put 'magnitude '(complex) magnitude)
+  (put 'angle '(complex) angle)
+
+  (put 'add '(complex complex)
+       (lambda (z1 z2) (typetag (add-complex z1 z2))))
+  (put 'sub '(complex complex)
+       (lambda (z1 z2) (typetag (sub-complex z1 z2))))
+  (put 'mul '(complex complex)
+       (lambda (z1 z2) (typetag (mul-complex z1 z2))))
+  (put 'div '(complex complex)
+       (lambda (z1 z2) (typetag (div-complex z1 z2))))
+
+  (put 'equ? '(complex complex)
+       (lambda (z1 z2) (equ? z1 z2)))
+  (put '=zero? '(complex)
+       (lambda (z1) (=zero? z1)))
+
+  (put 'make-from-real-imag 'complex
+       (lambda (x y) (typetag (make-from-real-imag x y))))
+  (put 'make-from-mag-ang 'complex
+       (lambda (r a) (typetag (make-from-mag-ang r a))))
+  'done)
+