Re: Q on NaN

[Luc Teirlinck]

Drew Adams wrote:
   
   That doesn't tell me how to test if `foobar' is a NaN. See my previous
   email: I knew I could test `(equal foo 0.0e+Nan)', but I thought I would
   need to test against all of the possible NaN values.

The GNU C library has an isnan macro.  From Lisp you could do:

(defun nanp (obj)
  "Return t if OBJ is a NaN; nil otherwise,"
  (and (numberp obj) (/= obj obj)))

Sincerely,

Luc.