Use implicit tag for scheme-number or integer

2_78.rkt

@@ -139,13 +139,20 @@
           (newline)
           result))))
 
+;; scheme-number is for reals only
+(define (scheme-number? x)
+  (and (real? x)
+       (not (integer? x))))
 
 (define (attach-tag type-tag contents)
-  (cond ((number? contents) contents)
+  (cond ((or (scheme-number? contents)
+             (integer? contents))
+         contents)
         (else (cons type-tag contents))))
 
 (define (type-tag datum)
-  (cond ((number? datum) 'scheme-number)
+  (cond ((scheme-number? datum) 'scheme-number)
+        ((integer? datum) 'integer)
         ((pair? datum) (car datum))
         (else (error "Bad tagged datum -- TYPE-TAG" datum))))
 
@@ -154,7 +161,9 @@
         ((pair? datum) (cdr datum))
         (else (error "Bad tagged datum -- CONTENTS" datum))))
 
-(define type-tagged? pair?)
+(define type-tagged?
+  (lambda (x)
+    (or (number? x) (pair? x))))
 
 ;; Scheme numbers