Changeset 25802 in project

Timestamp:

01/10/12 22:12:53 (9 years ago)

Author:

sjamaan

Message:

Fix logarithm so it works for complex numbers (reported by Alexander Shendi)

Location:

release/4/numbers/trunk

Files:

• numbers.scm (modified) (1 diff)
• tests/numbers-test.scm (modified) (1 diff)

release/4/numbers/trunk/numbers.scm

@@ -1360 +1360 @@
 
 (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)

release/4/numbers/trunk/tests/numbers-test.scm

@@ -419 +419 @@
  (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)