J3/06-125

To: J3
From: Michael Ingrassia
Subject: Value of decimal exponent for a real zero value
Date: 2006 January 30


NUMBER: F03/0079
TITLE: Value of decimal exponent for a real zero value
KEYWORDS: Data edit descriptors, Numeric editing, decimal exponent, zero value
DEFECT TYPE: CLARIFICATION/ERRATUM
STATUS: J3 consideration in progress

QUESTION:

     In formatted output, what is the value of the
     decimal exponent produced for a real zero value
     under the D, E, EN, ES, and G edit descriptors?

SUGGESTED ANSWER:
     In such a case, the decimal exponent should have
     the value zero whether or not a nonzero scale factor
     is in effect.   Edits are supplied to make this clear.

DISCUSSION:

The Fortran 2003 standard does not specify what the value
of the decimal exponent of a real zero value should be
under formatted output.  Every implementation of which Sun
is aware uses the value zero for the decimal exponent
unless a nonzero scale factor is in effect.  As a member
of the committee has pointed out, different
implementations format real zeros differently under
nonzero scale factors.

The C and C++ standards both explicitly state that the
value of the decimal exponent produced for the real value
zero under a format that includes an exponent is zero.
The Fortran standard should also.

EDITS:

[227:16+] Add:
        (7) On output of a real zero value, the digits in the
                exponent field shall all be zero, whether or not
                a nonzero scale factor is in effect.


SUBMITTED BY: Michael Ingrassia
HISTORY: J3/06-125 submitted to J3 meeting 175