[Cfp-interest] aA formatting with small precision modifier

[Rajan Bhakta]

At least one IBM implementation gets INF for the case below. For the 
precision modifier of zero case, we treat that as a missing modifier.

Regards,

Rajan Bhakta
z/OS XL C/C++ Compiler Technical Architect
ISO C Standards Representative for Canada
C Compiler Development
Contact: rbhakta at ca.ibm.com, Rajan Bhakta/Toronto/IBM
Telephone: (905) 413-3995



From:
Jim Thomas <jaswthomas at sbcglobal.net>
To:
CFP <cfp-interest at ucbtest.org>
Date:
08/21/2012 03:02 PM
Subject:
[Cfp-interest] aA formatting with small precision modifier
Sent by:
cfp-interest-bounces at oakapple.net





What is the result of:
 printf("%.1Ha\n", DEC32_MAX);
Is it INFINITY or 1e97?  I believe it is INFINITY. 
As if round source value.

Yes, (0, 9999999, 90) -> inf

What if rounding down? what does "rounds the input, in the type, according 
to the current rounding direction for decimal floating-point operations, 
to the number of digits specified by the precision modifier" really mean?

(0, 1234567, 0) -> (0, 1000000, 0) or (0, 1, 6)? Check implementations. 
Former has same quantum exponent as input.

For the max case the latter isn't an option because it's at the limit of 
the exponent range:
 (0, 9999999, 90) -> (0, 9000000, 90) -> 9.000000e96
Designed to reflect the quantum exponent?

In the Aug teleconference we agreed to check the 754-2008 standard for 
guidance on this issue and if none is given to use the first (quantum 
preserving) approach, where the intermediate rounding in the example above 
gives

(0, 1234567, 0) -> (0, 1000000, 0)

I didn't find any help in 754-2008 on this issue. Did anyone else?

-Jim
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