refactor to use arithmetic package for working with polys

1 files changed, 33 insertions, 0 deletions

diff --git a/coding-exercises/2/83/install-integer.rkt b/coding-exercises/2/83/install-integer.rkt
new file mode 100644
index 0000000..2fabf3a
--- /dev/null
+++ b/coding-exercises/2/83/install-integer.rkt
@@ -0,0 +1,33 @@
+#lang racket
+(provide install-integer)
+(require "../../../shared/data-directed-programming.rkt")
+
+(define (install-integer put get)
+  ;; local methods
+  (define (tagme datum)
+    (attach-tag 'integer datum))
+  (define (make i)
+    (inexact->exact (round i)))
+  (define (raiseme i)
+    (if (equal? (type-tag i) 'integer)
+      ((get 'make 'rational) i 1)
+      (error "cannot raise non integer in integer package")))
+  ;; constructor
+  (put 'make 'integer (lambda (x) (tagme (make x))))
+  ;; methods
+  (put 'add '(integer integer) (lambda (x y) (tagme (make (+ x y)))))
+  (put 'sub '(integer integer) (lambda (x y) (tagme (make (- x y)))))
+  (put 'mul '(integer integer) (lambda (x y) (tagme (make (* x y)))))
+  (put 'div '(integer integer) (lambda (x y) (tagme (make (/ x y)))))
+  (put 'raise '(integer) raiseme)
+  ;; sqrt and trig methods for complex nums
+  (put 'sqr '(integer) sqr)
+  (put 'sqrt '(integer) sqrt)
+  (put 'atan '(integer) atan)
+  (put 'cos  '(integer) cos)
+  (put 'sin '(integer) sin)
+  ;; predicates
+  (put 'equ? '(integer integer) (lambda (x y) (= x y)))
+  (put '=zero? '(integer) (lambda (x) (= 0 x)))
+  'done)
+