Improve chicken pffi-pointer-null?

retropikzel/r7rs-pffi.sld

@@ -4,8 +4,8 @@
     (chicken
       (import (scheme base)
               (scheme write)
-              (scheme file)
               (scheme char)
+              (scheme file)
               (scheme process-context)
               (chicken foreign)
               (chicken locative)

retropikzel/r7rs-pffi/chicken.scm

@@ -200,9 +200,11 @@
 
 (define pffi-pointer-null?
   (lambda (pointer)
-    (if (not (pointer? pointer))
+    (if (and (not (pointer? pointer))
+             pointer)
       #f
-      (= (pointer->address pointer) 0))))
+      (or (not pointer) ; #f counts as null pointer on Chicken
+          (= (pointer->address pointer) 0)))))
 
 (define pffi-pointer-set!
   (lambda (pointer type offset value)

retropikzel/r7rs-pffi/stklos.scm

@@ -118,6 +118,7 @@
   (lambda (pointer type offset)
     (error "Not implemented")))
 
-(define pffi-pointer-deref
+(define pffi-pointer-address
   (lambda (pointer)
     (error "Not implemented")))
+