bug#29387: Guile-2.2.2 complex numbers edge case

[Jan Wedekind]

Thanks Daniel,
I see. So I need to use "=" for numerical comparisons. "equal?" is only true if the types are the same, too:

(equal? 1.0 1)
; #f
(= 1.0 1)
; #t

Sorry for filing a bug report. Feel free to close the bug.

Regards
Jan

On November 22, 2017 3:53:00 PM GMT, Daniel Llorens <address@hidden> wrote:

From: Jan Wedekind <address@hidden>

Subject: bug#29387: Guile-2.2.2 complex numbers edge case

Date: 21 Nov 2017 23:09:57 GMT+1

To: address@hidden

Reply-To: Jan Wedekind <address@hidden>

Hi,
I think I encountered a bug in the numerical stack.
i times i should equal -1:

   (equal? -1 (* 0+i 0+i))
   ; #f

i times i plus one is zero (which is correct):
   (zero? (+ (* 0+i 0+i) 1))
   ; #t

Regards
Jan

In Guile 0+i and (* 0+i 0+i) are inexact numbers, but -1 is exact. That's why equal? fails.

You can check that either of

(equal? -1.+0. (* 0+i 0+i))

or

 (= -1 (* 0+i 0+i))

return true, as expected.

I don't know if the fact that Guile doesn't have exact complex numbers could be considered a bug. AFAIR none of the standards require them to be implemented. On the other hand I just checked and both Racket and Chez seem to have them, so...

regards

Daniel