+(defvar +whitespace-chars+
+ '(#\space #\tab #\newline #\return
+ ;; Tested: sbcl, allegrocl, and clisp use #\no-break_space
+ ;; lispworks uses #\no-break-space
+ #+lispworks #\no-break-space
+ #-lispworks #\no-break_space
+ )
+ "List of whitespace characters for this lisp implementation.")
+