add polynomial number system(WIP).

Author: ramsayleung

chapter2/poly.rkt

@@ -0,0 +1,43 @@
+#lang racket
+(require "generic_operation.scm")
+
+(define (variable? x) (symbol? x))
+
+(define (same-variable? v1 v2)
+  (and (variable? v1) (variable? v2) (eq? v1 v2)))
+
+(define (install-polynomial-package)
+  ;; internal procedures
+
+  ;; representation of poly
+  (define (make-poly variable term-list)
+    (cons variable term-list))
+
+  (define (variable p) (car p))
+
+  (define (term-list p) (cdr p))
+
+  (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 to the rest of the system.
+  (define (tag p) (attach-tag 'polynomial p))
+
+  (put 'add '(polynomial polynomial) (lambda (p1 p2) (tag (add-poly p1 p2))))
+
+  (put 'mul '(polynomial polynomial) (lambda (p1 p2) (tag (mul-poly p1 p2))))
+
+  (put 'make 'polynomial (lambda (var terms) (tag (make-poly var terms))))
+
+  'done)