Issue #501 - odd/even must receive an integer

Raise an error if a decimal number is passed to these primitives.

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 Bug Fixes
 
+- Raise an error if `odd?` or `even?` is passed a decimal number. Thanks to jpellegrini for the bug report.
 - Fix `read-line` to read entire lines that consist of more than 1022 bytes. Previously the function would only return partial data up to this limit. Thanks to Robby Zambito for the bug report.
 - `(include "body.scm")` inside a file `path/to/lib.sld` will look for `path/to/body.scm`, then fallback to the legacy behavior, and look for `$(pwd)/body.scm`.
 - Pass append and prepend directories when compiling dependent libraries of a program. This prevents issues where the directories are not made available to any `include` directives within such libraries.

scheme/base.sld

@@ -1409,8 +1409,14 @@
       (if (< b 0)
         (if (<= res 0) res (+ res b))
         (if (>= res 0) res (+ res b)))))
-  (define (odd? num)   (= (modulo num 2) 1))
-  (define (even? num)  (= (modulo num 2) 0))
+  (define (odd? num)
+    (if (integer? num)
+        (= (modulo num 2) 1)
+        (error "Not an integer" num)))
+  (define (even? num) 
+    (if (integer? num)
+        (= (modulo num 2) 0)
+        (error "Not an integer" num)))
   (define-c bignum?
     "(void *data, int argc, closure _, object k, object obj)"
     " return_closcall1(data, k, Cyc_is_bignum(obj)); ")