On Tue, Jan 10, 2012 at 03:36:04AM +0100, Alexander Shendi wrote:
> Dear Chicken users,
>
> I have encounterd what seems to be a bug in the numbers egg. The problem
> occurs when I evaluate "(log 297.0+0.1i)".
Please try the attached patch (or numbers trunk, as of r25802).
#;1> (use numbers)
#;2> (log 297.0+0.1i)
5.69373219548625+0.000336700323976755i
Cheers,
Peter
--
http://sjamaan.ath.cx
--
"The process of preparing programs for a digital computer
is especially attractive, not only because it can be economically
and scientifically rewarding, but also because it can be an aesthetic
experience much like composing poetry or music."
-- Donald Knuth
Index: numbers.scm
===================================================================
--- numbers.scm (revision 25798)
+++ numbers.scm (working copy)
@@ -1359,15 +1359,17 @@
(define exp %exp)
(define (%log x)
- (cond
- ((%> x 0.0 'log) ; avoid calling inexact->exact on X here (to avoid
overflow?)
- (##core#inline_allocate ("C_a_i_log" 4) (%exact->inexact x)))
- ((%= x 0.0)
- (if (%exact? x)
- (log0 'log x)
- (##core#inline_allocate ("C_a_i_log" 4) (%exact->inexact x))))
- (else ; negative
- (%+ (%log (%magnitude x)) (* (make-complex 0 1) (%angle x))))))
+ (let ((type (%check-number x)))
+ (cond
+ ;; avoid calling inexact->exact on X here (to avoid overflow?)
+ ((or (eq? type COMP) (%< x 0.0 'log)) ; General case
+ (%+ (%log (%magnitude x)) (* (make-complex 0 1) (%angle x))))
+ ((eq? x 0) ; Exact zero? That's undefined
+ (log0 'log x))
+ ((eq? type NONE)
+ (bad-number 'exp x))
+ (else ; Simple real number case
+ (##core#inline_allocate ("C_a_i_log" 4) (%exact->inexact x))))))
(define log %log)
Index: tests/numbers-test.scm
===================================================================
--- tests/numbers-test.scm (revision 25798)
+++ tests/numbers-test.scm (working copy)
@@ -418,6 +418,13 @@
(test "log of exp = 1" 1.0 (log (exp 1)))
(test "log of -1" (string->number "0.0+3.141592653589793i") (log -1))
+ (test "log with complex number"
+ (string->number "0.0+1.5707963267948966i")
+ (log (string->number "+i")))
+
+ (test "exp(log(x)) = x"
+ (string->number "2.0-3.0i") (exp (log (string->number "2.0-3.0i"))))
+
(letrec ((fac (lambda (n)
(if (zero? n)
1
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