1 files changed, 42 insertions, 0 deletions
diff --git a/coding-exercises/2/87.rkt b/coding-exercises/2/87.rkt
index cda82ce..6c2a3f6 100644
--- a/coding-exercises/2/87.rkt
+++ b/coding-exercises/2/87.rkt
@@ -1,2 +1,44 @@
 #lang racket
+(require "./83/install.rkt")
+;; arithmetic package
+(define get-put-apply (install-arithmetic-package))
+(define get (car get-put-apply))
+(define put (cadr get-put-apply))
+(define apply-fn (caddr get-put-apply))
+
+(define (install-polynomial-package put)
+  ;; internal procedures
+  (define (tagme p)
+    (attach-tag 'polynomial p))
+  ;;repr
+  (define (make-poly variable term-list)
+    (cons variable term-list))
+  (define (variable p) (car p))
+  (define (term-list p) (cdr p))
+  ;; preds
+  (define (variable? x) (symbol? x))
+  (define (same-variable? x y) (and (variable? x) (variable? y) (eq? x y)))
+  ;; term list
+  (define (adjoin-term term-list term)
+    '())
+  (define (coeff term)
+    '())
+  ;; ops
+  (define (add-poly p1 p2)
+    (if (same-variable? (variable p1) (variable p2))
+      (make-poly (variable p1)
+                 (add-terms (term-list p1)
+                            (term-list p2)))
+      (error "Polys not in same var -- ADD-POLY" (list p1 p2))))
+  (define (mul-poly p1 p2)
+    (if (same-variable? (variable p1)
+                        (variable p2))
+      (make-poly (variable p1)
+                 (mul-terms (term-list p1)
+                            (term-list p2)))
+      (error "Polys not in same var -- MUL-POLY" (list p1 p2)))))
+  ;; interface)
+
+
+