[Q] type promotion in * and +

        Hi again,

if I compile these two functions below:

(defun my+ (a b)
  (declare (:explain :boxing :calls :types))
  (declare (type fixnum a))
  (declare (type fixnum b))
  (+ a b))

(defun my* (a b)
  (declare (:explain :boxing :calls :types))
  (declare (type fixnum a))
  (declare (type fixnum b))
  (* a b))

... and read the log file, I see that (+ FIXNUM FIXNUM) is considered to be a
FIXNUM, but that is not the case for * which returns a bigger integer.

I fail to understand why the addition doesn't return something bigger than a
fixnum, just like the multiplication. Actually, calling:

(my+ most-positive-fixnum most-positive-fixnum)

returns -2.


Thanks !

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Didier Verna, [email protected], http://www.lrde.epita.fr/~didier

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