Public Comment Number PC-UK0159

ISO/IEC CD 9899 (SC22N2620) Public Comment

=========================================== 

Date: 1998-02-25
Author: N.M Maclaren
Author Affiliation: Self
Postal Address:
    University of Cambridge,
    Computer Laboratory,
    New Museums Site,
    Pembroke Street,
    Cambridge CB3 3QG,
    United Kingdom
E-mail Address: <nmm1@cam.ac.uk>
Telephone Number: +44 1223 334761
Fax Number:       +44 1223 334679
Number of individual comments: 1


Comment 1. 

Category: Normative change to existing feature retaining the original intent

Committee Draft subsection: F.9.1.4

Title: atan2(+-0,+-0) and IEEE


Detailed description:

Defining atan2(+-0,+-0) to return a finite value and not raise the invalid
exception is mathematically incorrect, incompatible with robust code and
the wording of LIA-1, and actually prevents an implementation from
conforming to both C9X and the proposed LIA-2 simultaneously.  I suggest
changing these cases to do the correct thing:

    atan2(+-0,+-0) returns a NaN and raises the invalid exception.