4 files changed, 65 insertions, 1 deletions
diff --git a/coding-exercises/2/78.rkt b/coding-exercises/2/78.rkt
index 3a4b100..637ea10 100644
--- a/coding-exercises/2/78.rkt
+++ b/coding-exercises/2/78.rkt
@@ -1,8 +1,13 @@
 #lang racket
 (require "../../shared/data-directed-programming.rkt")
+(require "./78/complex-rectangular.rkt")
+(require "./78/complex-polar.rkt")
 ;; We are basically making a data directed framework for arithmethic operations in this module
 (define pkg (make-dispatch-table))
 (define put (putter pkg))
 (define get (getter pkg))
+(define print-tbl (printer pkg))
 (define apply-generic (make-apply put get))
 
+(install-rectangular-package put)
+(install-polar-package put)
diff --git a/coding-exercises/2/78/complex-polar.rkt b/coding-exercises/2/78/complex-polar.rkt
new file mode 100644
index 0000000..661627d
--- /dev/null
+++ b/coding-exercises/2/78/complex-polar.rkt
@@ -0,0 +1,24 @@
+#lang racket
+(provide install-polar-package)
+
+(define (install-polar-package)
+  (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 (+ (sqr x) (sqr y)))
+          (atan y x)))
+  ;; register in data-driven package)
+  (define (typtag x)
+    (attach-tag 'polar x))
+  (put 'real-part '(polar) real-part)
+  (put 'imag-part '(polar) imag-part)
+  (put 'magnitude '(polar) magnitude)
+  (put 'angle '(polar)))
diff --git a/coding-exercises/2/78/complex-rectangular.rkt b/coding-exercises/2/78/complex-rectangular.rkt
new file mode 100644
index 0000000..41e93b6
--- /dev/null
+++ b/coding-exercises/2/78/complex-rectangular.rkt
@@ -0,0 +1,29 @@
+#lang racket
+(provide install-rectangular-package)
+(require "../../../shared/data-directed-programming.rkt")
+
+
+(define (install-rectangular-package put)
+  (define (real-part z) (car z))
+  (define (imag-part z) (cdr z))
+  (define (make-from-real-imag x y) (cons x y))
+  (define (magnitude z) (sqrt (+ (sqr (real-part z))
+                                 (sqr (real-part z)))))
+  (define (angle z)
+    (atan (imag-part z)
+          (real-part z)))
+  (define (make-from-mag-ang r a)
+    (cons (* r (cos a))
+          (* r (sin a))))
+  ;; interface part
+  (define (typtag x)
+    (attach-tag 'rectangular x))
+
+  (put 'real-part '(rectangular) real-part)
+  (put 'imag-part '(rectangular) imag-part)
+  (put 'magnitude '(rectangular) magnitude)
+  (put 'angle '(rectangular) angle)
+  (put 'make-from-real-imag 'rectangular
+       (lambda (x y) (typtag (make-from-real-imag x y))))
+  (put 'make-from-mag-ang 'rectangular
+       (lambda (r a) (typtag (make-from-mag-ang r a)))))
diff --git a/shared/data-directed-programming.rkt b/shared/data-directed-programming.rkt
index c756537..6cecaf1 100644
--- a/shared/data-directed-programming.rkt
+++ b/shared/data-directed-programming.rkt
@@ -2,6 +2,7 @@
 (provide
   make-apply
   make-dispatch-table
+  printer
   getter
   putter
   attach-tag
@@ -36,6 +37,9 @@
 ;; ('op (list ('(types) item)))
 (define (make-dispatch-table)
   (define dispatch-table '())
+  (define (printer)
+    (newline)
+    (display dispatch-table))
   (define (get op types)
     (let ((op-datum (find-type op dispatch-table)))
       (if op-datum
@@ -67,12 +71,14 @@
                              (attach-tag op
                                 (list (attach-tag types item)))
                              dispatch-table))))
-  (list dispatch-table get put))
+  (list dispatch-table get put printer))
 
 (define (getter t)
   (cadr t))
 (define (putter t)
   (caddr t))
+(define (printer t)
+  (cadddr t))
 
 (define (make-apply put get)
   (lambda (op . args)