Done set union for ordered list representation

2.3/2.62.scm

@@ -0,0 +1,49 @@
+(load "displaylib.scm")
+(title "Exercise 2.62")
+(print "
+        Give a Θ(n) implementation of union-set for sets represented as ordered lists. 
+       ")
+
+; -- given lib --
+(define (element-of-set? x set)
+  (cond ((null? set) false)
+        ((= x (car set)) true)
+        ((< x (car set)) false)
+        (else (element-of-set? x (cdr set)))))
+
+(define (intersection-set set1 set2)
+  (if (or (null? set1) (null? set2))
+    '()    
+    (let ((x1 (car set1)) (x2 (car set2)))
+      (cond ((= x1 x2)
+             (cons x1
+                   (intersection-set (cdr set1)
+                                     (cdr set2))))
+            ((< x1 x2)
+             (intersection-set (cdr set1) set2))
+            ((< x2 x1)
+             (intersection-set set1 (cdr set2)))))))
+
+(define (adjoin-set x set) 
+  (cond ((null? set) (list x))
+        ((> x (car set)) 
+         (cons (car set) (adjoin-set x (cdr set))))
+        ((= x (car set)) set)
+        ((< x (car set)) (cons x set))))
+; -- START --
+
+(define (union-set e f)
+  (cond ((null? e) f)
+        ((null? f) e)
+        (else
+          (let ((x1 (car e)) (x2 (car f)))
+            (cond ((= x1 x2) (cons x1 (union-set (cdr e) (cdr f))))
+                  ((< x1 x2) (cons x1 (union-set (cdr e) f)))
+                  ((> x1 x2) (cons x2 (union-set e (cdr f)))))))))
+
+(define set1 '(10 20 30))
+(define set2 '(20 40 50))
+(display "set1 = '")(display set1)(newline)
+(display "set2 = '")(display set2)(newline)
+(display "(union-set set1 set2)")(newline)
+(display (union-set set1 set2))(newline)