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[Bug math/15901] New: Bessel functions y0, y1, yn are incorrect on non-positive values


http://sourceware.org/bugzilla/show_bug.cgi?id=15901

            Bug ID: 15901
           Summary: Bessel functions y0, y1, yn are incorrect on
                    non-positive values
           Product: glibc
           Version: 2.17
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: vincent-srcware at vinc17 dot net

yn(n,Â0.0) on odd negative integer n gives -Inf, while the limit is +Inf. This
incorrect result probably comes from a defect in POSIX[*] and should be
changed.

[*] http://austingroupbugs.net/view.php?id=714

yn(n,x) on negative values x gives -Inf instead of NaN. Though the value -Inf
is currently allowed by POSIX, NaN is a much better result (and the only
expected one according to general rules on undefined math functions), just like
log(negative) or sqrt(negative) is NaN.

I've posted a message about such values in the Austin Group list:

  http://permalink.gmane.org/gmane.comp.standards.posix.austin.general/7982

and replies would appear here:

  http://comments.gmane.org/gmane.comp.standards.posix.austin.general/7982

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