Minor documentation updates

core/classes/tuple/tuple-docs.factor

@@ -202,6 +202,8 @@ ARTICLE: "tuple-introspection" "Tuple introspection"
 }
 "Tuple classes can also be defined at run time:"
 { $subsections define-tuple-class }
+"Tuples can be compared for slot equality even if the tuple class overrides " { $link equal? } ":"
+{ $subsections tuple= }
 { $see-also "slots" "mirrors" } ;
 
 ARTICLE: "tuple-examples" "Tuple examples"

core/kernel/kernel-docs.factor

@@ -672,6 +672,9 @@ HELP: object
 HELP: null
 { $class-description
     "The canonical empty class with no instances."
+}
+{ $notes
+    "Unlike " { $snippet "null" } " in Java or " { $snippet "NULL" } " in C++, this is not a value signifying empty, or nothing. Use " { $link f } " for this purpose."
 } ;
 
 HELP: most