From: Henry Zongaro <zongaro@ca.ibm.com>

Date: Tue, 14 Sep 2004 10:49:44 -0400

To: Ashok Malhotra <ashok.malhotra@oracle.com>

Cc: public-qt-comments@w3.org

Message-ID: <OFD59D3CB6.CCD6A2D0-ON85256F0F.00502E26-85256F0F.005174D2@ca.ibm.com>

Date: Tue, 14 Sep 2004 10:49:44 -0400

To: Ashok Malhotra <ashok.malhotra@oracle.com>

Cc: public-qt-comments@w3.org

Message-ID: <OFD59D3CB6.CCD6A2D0-ON85256F0F.00502E26-85256F0F.005174D2@ca.ibm.com>

Hi, Ashok. On July 27, I wrote: > According to section 6.2 of the 2004-07-23 Working Draft of F&O, "For > op:numeric-add, op:numeric-subtract and op:numeric-multiply if either > operand is INF or -INF the result is NaN." > > I believe that statement is not consistent with IEEE-754. Multiplying > a zero value by an Infinity, adding Infinities that have opposite signs, > or subtracting Infinities that have the same sign should result in NaN. In > addition, adding, subtracting or multiplying an Infinity and a NaN should > result in a NaN. Other combinations involving an operand with infinite > magnitude will result in an infinity with the appropriate sign. And Ashok responded: > I believe you are referring to adding, subtracting and multiplying a finite > number by +/- INF. In this case, it seems reasonable that the > result should be > +/- INF. Also, INF + INF = INF and -INF - (-INF) = -INF. > > While these seem reasonable, I come to that conclusion by inference from what > IEEE-754 does say and not from any direct statement therein. If you were > quoting directly from 754 please provide a reference. I could not find one. > > I suggest we remove statement you objected to and add notes to op: > numeric-add/subtract/multiply, covering these cases, similar to the > note we added for > op:numeric-divide. I'm sorry for the long delay in following up. I sent my comment just before taking time off, and forgot to follow up until yesterday's editors' call. Section 6.1 of IEEE-754 "Infinity Arithmetic" states that "Arithmetic on [infinity] is always exact and therefore shall signal no exceptions, except for the invalid operations specified for [infinity] in 7.1." Section 7.1 lists the invalid operations on infinity as follows: (2) Addition or subtraction - magnitude subtraction of infinites such as (+infinity) + (-infinity) (3) Multiplication - 0*infinity (4) Division - 0/0 or infinity/infinity (5) Remainder - x REM y, where y is zero or x is infinite I agree that any information should be placed in notes - we just have ensure it doesn't contradict IEEE-754. Thanks, Henry ------------------------------------------------------------------ Henry Zongaro Xalan development IBM SWS Toronto Lab T/L 969-6044; Phone +1 905 413-6044 mailto:zongaro@ca.ibm.comReceived on Tuesday, 14 September 2004 14:50:19 UTC

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