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*To*: "'Hossam A. H. Fahmy'" <hfahmy@xxxxxxxxxxxxxxxxxxxxxxx>, "'stds-754'" <stds-754@xxxxxxxxxxxxxxxxx>*Subject*: RE: division(x,infinity)=0*From*: "Mike Cowlishaw" <mfc@xxxxxxxxxxxxxxx>*Date*: Sat, 26 Feb 2011 12:57:27 -0000*In-reply-to*: <AANLkTi=SoSp2YBRVj8VqKs8mBUKHuROOzWeK3F6KzjVq@mail.gmail.com>*List-help*: <http://listserv.ieee.org/cgi-bin/wa?LIST=STDS-754>, <mailto:LISTSERV@LISTSERV.IEEE.ORG?body=INFO%20STDS-754>*List-owner*: <mailto:STDS-754-request@LISTSERV.IEEE.ORG>*List-subscribe*: <mailto:STDS-754-subscribe-request@LISTSERV.IEEE.ORG>*List-unsubscribe*: <mailto:STDS-754-unsubscribe-request@LISTSERV.IEEE.ORG>*References*: <AANLkTi=SoSp2YBRVj8VqKs8mBUKHuROOzWeK3F6KzjVq@mail.gmail.com>*Sender*: stds-754@xxxxxxxx*Thread-index*: AcvVmj8RTk9vMf9PSBKShUr2rbjyAwAGkVZQ

The last sentences of 5.2 read:

In the descriptions that follow, Q(

x) is the exponentqof the representation of a finite floating-point numberx.Ifxis infinite, Q(x) is +∞.

which answers your question?

Mike

From:stds-754@xxxxxxxx [mailto:stds-754@xxxxxxxx]On Behalf OfHossam A. H. FahmySent:26 February 2011 09:43To:stds-754Subject:division(x,infinity)=0Dear 754 people,

Just wanted to check with you all:

For decimal FP, the division of a finite x by infinity should be zero but what is the resulting exponent?

In clause 6.1 on page 34 (infinity arithmetic) nothing is specified regarding that.

In clause 5.2 on page 18, it is clear that when the result is exact (which is the case here as confirmed in clause 6.1) then we should have the preferred exponent of the operation.

In clause 5.4.1. on page 21, the division(x, y) has a preferred exponent Q(x) -Q(y). That leads one to ask what is the "exponent" of infinity?

In clause 3.5.2 on page 11, point b) explains that remaining bits in G and T are ignored for infinities but it does not explicitly say that the exponent is treated as if it were zero as the previous point of the same clause states clearly for NaNs.

So, is the correct approach to treat the exponent of infinity as zero similar to NaNs? Shall we explicitly mention that in the following revision of the standard?

Thanks

--

Hossam A. H. Fahmy

**References**:**division(x,infinity)=0***From:*Hossam A. H. Fahmy

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