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diff --git a/coding-exercises/2/83/polynomials.rkt b/coding-exercises/2/83/polynomials.rkt
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+++ b/coding-exercises/2/83/polynomials.rkt
@@ -0,0 +1,369 @@
+#lang racket
+(provide install-polynomial)
+(require "../../../shared/data-directed-programming.rkt")
+
+(define (install-term-package get put apply-fn)
+  (define (tagme term)
+    (attach-tag 'term term))
+  (put 'make-from-order-coeff 'term (lambda (order coeff) (tagme (list order coeff))))
+  (put 'order '(term) (lambda (term) (car term)))
+  (put 'coeff '(term) (lambda (term) (cadr term))))
+
+(define (install-sparse-termlist-package get put apply-fn)
+  ;; methods imported from term package
+  (define (order term)
+    ((get 'order '(term)) term))
+  (define (coeff term)
+    ((get 'coeff '(term)) term))
+  (define (make-term order coeff)
+    ((get 'make-from-order-coeff 'term) order coeff))
+
+  (define (=zero? a)
+    (apply-fn '=zero? a))
+  (define (equ? a b)
+    (apply-fn 'equ? a b))
+  (define (add a b)
+    (apply-fn 'add a b))
+  (define (sub a b)
+    (apply-fn 'sub a b))
+  (define (mul a b)
+    (apply-fn 'mul a b))
+  (define (div a b)
+    (apply-fn 'div a b))
+  (define (cos a)
+    (apply-fn 'cos a))
+  (define (sin a)
+    (apply-fn 'sin a))
+  (define (sqr a)
+    (apply-fn 'sqr a))
+  (define (sqrt a)
+    (apply-fn 'sqrt a))
+  (define (atan a b)
+    (apply-fn 'atan a b))
+
+  ;; selectors
+  ;; export first term as typed term
+  (define (first-term term-list)
+    (let ((term (car term-list)))
+      (make-term (car term)
+                 (cdr term))))
+  (define (rest-terms term-list) (cdr term-list))
+
+  ;; ops
+  ;; map neg over internal storage type (order coeff)
+  (define (neg termlist)
+    (map (lambda (term)
+           (cons
+             (car term)
+             (apply-fn 'neg (cdr term))))
+         termlist))
+
+  ;; convert term contents to our format
+  (define (term-contents->order-coeff-pair term)
+    (cons (order term)
+          (coeff term)))
+  (define (adjoin-term term term-list)
+    (if (=zero? (coeff term))
+      term-list
+      (cons (term-contents->order-coeff-pair term)
+            term-list)))
+
+  ;; preds
+  (define (the-empty-termlist) '())
+  (define (empty-termlist? term-list) (null? term-list))
+
+  ;; constructors
+  ;; store as ((order coeff)), list of untyped (order coeff) pairs
+  (define (term->order-coeff-pair term)
+    (cons (apply-fn 'order term)
+          (apply-fn 'coeff term)))
+  (define (make-from-terms terms)
+    (map term->order-coeff-pair terms))
+
+
+  ;; interface methods
+  (define (tagme datum)
+    (attach-tag 'sparse-termlist datum))
+  ;; constructors
+  (put 'make-from-terms 'sparse-termlist (lambda (t) (tagme (make-from-terms t))))
+  ;; ops
+  (put 'neg '(sparse-termlist) (lambda (termlist) (tagme (neg termlist))))
+  (put 'adjoin-term '(term sparse-termlist) (lambda (term termlist) (tagme (adjoin-term term termlist))))
+  (put 'rest-terms '(sparse-termlist) (lambda (termlist) (tagme (rest-terms termlist))))
+  ;; term selector
+  (put 'first-term '(sparse-termlist) first-term)
+  ;; pred
+  (put 'empty-termlist? '(sparse-termlist) empty-termlist?)
+  (put 'the-empty-termlist 'sparse-termlist (lambda () (tagme (the-empty-termlist)))))
+
+(define (install-dense-termlist-package get put apply-fn)
+  ;; methods imported from term package
+  (define (order term)
+    ((get 'order '(term)) term))
+  (define (coeff term)
+    ((get 'coeff '(term)) term))
+  (define (make-term order coeff)
+    ((get 'make-from-order-coeff 'term) order coeff))
+
+  (define (=zero? a)
+    (apply-fn '=zero? a))
+  (define (equ? a b)
+    (apply-fn 'equ? a b))
+  (define (add a b)
+    (apply-fn 'add a b))
+  (define (sub a b)
+    (apply-fn 'sub a b))
+  (define (mul a b)
+    (apply-fn 'mul a b))
+  (define (div a b)
+    (apply-fn 'div a b))
+  (define (cos a)
+    (apply-fn 'cos a))
+  (define (sin a)
+    (apply-fn 'sin a))
+  (define (sqr a)
+    (apply-fn 'sqr a))
+  (define (sqrt a)
+    (apply-fn 'sqrt a))
+  (define (atan a b)
+    (apply-fn 'atan a b))
+
+  ;; selectors
+  ;; export first term as typed term
+  (define (first-term term-list)
+    (let ((term (car term-list)))
+      (make-term (- (length term-list) 1)
+                 term)))
+  (define (rest-terms term-list) (cdr term-list))
+
+  ;; ops
+  ;; map neg over internal storage type (coeff ...)
+  (define (neg termlist)
+    (map (lambda (term)
+           (apply-fn 'neg term))
+         termlist))
+
+  ;; convert term contents to our format
+  (define (term-contents->dense-format term)
+    (coeff term))
+  (define (adjoin-term term term-list)
+    (cond ((=zero? (coeff term)) term-list)
+          ((= (order term)
+              (length term-list))
+           (cons (term-contents->dense-format term) term-list))
+          (else (adjoin-term term (cons 0 term-list)))))
+
+  ;; preds
+  (define (the-empty-termlist) '())
+  (define (empty-termlist? term-list) (null? term-list))
+
+  ;; constructors
+  ;; store as ((order coeff)), list of untyped (order coeff) pairs
+  (define (make-from-terms terms)
+    (if (and (pair? terms)
+             (not (equal? 'term (type-tag (car terms)))))
+      (error "Make-from-terms encountered non-term --" terms)
+      (cond ((null? terms) (the-empty-termlist))
+            (else (adjoin-term (contents (car terms))
+                               (make-from-terms (cdr terms)))))))
+
+
+  ;; interface methods
+  (define (tagme datum)
+    (attach-tag 'dense-termlist datum))
+  ;; constructors
+  (put 'make-from-terms 'dense-termlist (lambda (t) (tagme (make-from-terms t))))
+  ;; ops
+  (put 'neg '(dense-termlist) (lambda (termlist) (tagme (neg termlist))))
+  (put 'adjoin-term '(term dense-termlist) (lambda (term termlist) (tagme (adjoin-term term termlist))))
+  (put 'rest-terms '(dense-termlist) (lambda (termlist) (tagme (rest-terms termlist))))
+  ;; term selector
+  (put 'first-term '(dense-termlist) first-term)
+  ;; pred
+  (put 'empty-termlist? '(dense-termlist) empty-termlist?)
+  (put 'the-empty-termlist 'dense-termlist (lambda () (tagme (the-empty-termlist)))))
+
+(define (install-polynomial get put apply-fn)
+  ;; import methods
+
+  (define (=zero? a)
+    (apply-fn '=zero? a))
+  (define (equ? a b)
+    (apply-fn 'equ? a b))
+  (define (add a b)
+    (apply-fn 'add a b))
+  (define (sub a b)
+    (apply-fn 'sub a b))
+  (define (mul a b)
+    (apply-fn 'mul a b))
+  (define (div a b)
+    (apply-fn 'div a b))
+  (define (cos a)
+    (apply-fn 'cos a))
+  (define (sin a)
+    (apply-fn 'sin a))
+  (define (sqr a)
+    (apply-fn 'sqr a))
+  (define (sqrt a)
+    (apply-fn 'sqrt a))
+  (define (atan a b)
+    (apply-fn 'atan a b))
+
+  ;; internal procedures
+  (define (tagme p)
+    (attach-tag 'polynomial p))
+  (define (variable? x) (symbol? x))
+  (define (same-variable? x y) (and (variable? x) (variable? y) (eq? x y)))
+
+  ;; terms
+  (install-term-package get put apply-fn)
+  (define (make-term order coeff)
+    ((get 'make-from-order-coeff 'term) order coeff))
+  (define (order term)
+    (apply-fn 'order term))
+  (define (coeff term)
+    (apply-fn 'coeff term))
+
+  ;; termlists
+  (install-sparse-termlist-package get put apply-fn)
+  (install-dense-termlist-package get put apply-fn)
+  (define (make-term-list terms)
+    ((get 'make-from-terms 'sparse-termlist) terms))
+  (define (empty-termlist? termlist)
+    (apply-fn 'empty-termlist? termlist))
+  (define (the-empty-termlist termlist)
+    ((get 'the-empty-termlist (type-tag termlist))))
+  (define (first-term termlist)
+    (apply-fn 'first-term termlist))
+  (define (adjoin-term term termlist)
+    (apply-fn 'adjoin-term term termlist))
+  (define (rest-terms termlist)
+    (apply-fn 'rest-terms termlist))
+
+  ;; polys
+  (define (ensure-termlist termlist)
+    (if (or
+          (equal? 'sparse-termlist (type-tag termlist))
+          (equal? 'dense-termlist (type-tag termlist)))
+      termlist
+      (error "Unsupported type-tag for termlist --" termlist)))
+  (define (make-poly variable term-list)
+    (cons variable (ensure-termlist term-list)))
+  (define (variable p) (car p))
+  (define (term-list p) (cdr p))
+
+  ;; ops
+  (define (add-terms L1 L2)
+    (cond ((empty-termlist? L1) L2)
+          ((empty-termlist? L2) L1)
+          (else
+            (let ((t1 (first-term L1))
+                  (t2 (first-term L2)))
+              (cond ((> (order t1)
+                        (order t2))
+                     (adjoin-term
+                       t1 (add-terms (rest-terms L1) L2)))
+                    ((> (order t2)
+                        (order t1))
+                     (adjoin-term
+                       t2 (add-terms L1 (rest-terms L2))))
+                    (else
+                      (adjoin-term
+                        (make-term
+                          (order t1)
+                          (add (coeff t1) (coeff t2)))
+                        (add-terms (rest-terms L1)
+                                   (rest-terms L2)))))))))
+  (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 (neg-poly p)
+    (make-poly (variable p)
+               (apply-fn 'neg (term-list p))))
+
+  (define (sub-terms L1 L2)
+    (add-terms L1
+               (apply-fn 'neg L2)))
+
+  (define (sub-poly p1 p2)
+    (if (same-variable? (variable p1)
+                        (variable p2))
+      (make-poly
+        (variable p1)
+        (sub-terms (term-list p1)
+                   (term-list p2)))
+      (error "Polys not in same var -- MUL-POLY" (list p1 p2))))
+
+
+  (define (mul-term-by-all-terms t1 L)
+    (if (empty-termlist? L)
+      (the-empty-termlist L)
+      (let ((t2 (first-term L)))
+        (adjoin-term (make-term
+                       (add (order t1) (order t2))
+                       (mul (coeff t1) (coeff t2)))
+                     (mul-term-by-all-terms t1 (rest-terms L))))))
+  (define (mul-terms L1 L2)
+    (if (empty-termlist? L1)
+      (the-empty-termlist L1)
+      (add-terms (mul-term-by-all-terms (first-term L1) L2)
+                 (mul-terms (rest-terms L1) L2))))
+  (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))))
+
+  (define (div-terms L1 L2)
+    (if (empty-termlist? L1)
+      (list (the-empty-termlist L1) (the-empty-termlist L1))
+      (let ((t1 (first-term L1))
+            (t2 (first-term L2)))
+        (if (> (order t2) (order t1))
+          (list (the-empty-termlist L1) L1)
+          (let ((new-c (div (coeff t1) (coeff t2)))
+                (new-o (sub (order t1) (order t2))))
+            (let ((rest-of-result (div-terms
+                                    (sub-terms L1
+                                               (mul-terms
+                                                 (make-term-list (list (make-term new-o new-c)))
+                                                 L2))
+                                    L2)))
+              (list
+                (adjoin-term
+                  (make-term new-o new-c)
+                  (car rest-of-result))
+                (cadr rest-of-result))))))))
+
+  (define (div-poly p1 p2)
+    (if (same-variable? (variable p1)
+                        (variable p2))
+      (cons
+        (variable p1)
+        (div-terms (term-list p1)
+                   (term-list p2)))
+      (error "Polys not in same var -- DIV-POLY" (list p1 p2))))
+
+  (define (polynomial-=zero? poly)
+    (define (rec term-list)
+      (cond ((empty-termlist? term-list) true)
+            ((not (apply-fn '=zero? (coeff (first-term term-list)))) false)
+            (else (rec (rest-terms term-list)))))
+    (rec (term-list poly)))
+  (put '=zero? '(polynomial) polynomial-=zero?)
+  ;;interface
+  (put 'add '(polynomial polynomial) (lambda (p1 p2) (tagme (add-poly p1 p2))))
+  (put 'neg '(polynomial) (lambda (p) (tagme (neg-poly p))))
+  (put 'sub '(polynomial polynomial) (lambda (p1 p2)
+                                       (tagme (sub-poly p1 p2))))
+  (put 'mul '(polynomial polynomial) (lambda (p1 p2) (tagme (mul-poly p1 p2))))
+  (put 'div '(polynomial polynomial) (lambda (p1 p2) (tagme (div-poly p1 p2))))
+  (put 'make 'polynomial
+       (lambda (var terms) (tagme (make-poly var terms))))
+  'done)