finished chapter 2 finally

1 files changed, 13 insertions, 6 deletions

diff --git a/coding-exercises/2/83/install-real.rkt b/coding-exercises/2/83/install-real.rkt
index 2141059..2089437 100644
--- a/coding-exercises/2/83/install-real.rkt
+++ b/coding-exercises/2/83/install-real.rkt
@@ -19,12 +19,18 @@
   ;; methods
 
   (define (gcd-real a b)
-    (if (and (integer? a)
-             (integer? b))
-      (if (= b 0)
-        a
-        (gcd-real b (remainder a b)))
-      a))
+    (cond ((and (integer? a)
+                (integer? b))
+           (if (= b 0)
+             a
+             (gcd-real b (remainder a b))))
+          ((= b 1) a)
+          (else (error "gcd for reals not implemented"))))
+
+  (define (reduce-integers n d)
+    (let ((g (gcd-real n d)))
+      (list (/ n g)
+            (/ d g))))
 
   (put 'add '(real real) (lambda (x y) (tagme (make (+ x y)))))
   (put 'neg '(real) (lambda (x) (tagme (make (- x)))))
@@ -36,6 +42,7 @@
                           ((get 'make 'rational) n 1.0)))
   (put 'greatest-common-divisor '(real real) (lambda (a b) (tagme (gcd-real a b))))
   ;; expt for integerizing factor
+  (put 'reduce '(real real) (lambda (n d) (reduce-integers n d)))
   (put 'expt '(real real) expt)
   ;; sqrt and trig methods for complex nums
   (put 'sqr '(real) sqr)