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*To*: Charles Stevens <charles.stevens@xxxxxxxx>*Subject*: Re: Two technical questions on IEEE Std 754-2008*From*: Dan Zuras IEEE <forieee@xxxxxxxxxxxxxx>*Date*: Thu, 24 Feb 2011 11:12:24 -0800*Cc*: IEEE 754 <stds-754@xxxxxxxxxxxxxxxxx>, Dan Zuras IEEE <forieee@xxxxxxxxxxxxxx>*Comments*: In-reply-to Charles Stevens <charles.stevens@xxxxxxxx> message dated "Thu, 24 Feb 2011 10:40:24 -0700."*In-reply-to*: <col112-w38D158B18431141D3D155D83DA0@phx.gbl>*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*: <COL112-W320851D3DFAE4E27B00FF883D80@phx.gbl> <20110222211919.538921212581@zuras.org>,<COL112-W6154EC77D5442121966F9783D80@phx.gbl> <20110223074800.9B97B1212585@zuras.org>,<COL112-W5825C502072E032EFFE2A83DB0@phx.gbl> <20110223164745.157C812125A5@zuras.org>,<AANLkTinR42yT4GW-92Vu+TwetygSU+WrcMGRDnSScZR2@mail.gmail.com> <COL112-W55A960B5DBC3C28438A4DE83DA0@phx.gbl>,<AANLkTimnOZPW2Es7YxBRiP=TO+Mb2=0YvgL+GnijTWM=@mail.gmail.com> <col112-w38D158B18431141D3D155D83DA0@phx.gbl>*Reply-to*: Dan Zuras IEEE <forieee@xxxxxxxxxxxxxx>*Sender*: stds-754@xxxxxxxx

To: <khbkhb@xxxxxxxxx> CC: <forieee@xxxxxxxxxxxxxx>, IEEE 754 <stds-754@xxxxxxxxxxxxxxxxx> Subject: RE: Two technical questions on IEEE Std 754-2008 Date: Thu, 24 Feb 2011 10:40:24 -0700 . . . As a side note: it's been argued that IEEE arithmetic is the same regardle= ss of the encoding. Offhand=2C I don't see anything that requires that dec= imal-format operands to IEEE arithmetic operations be in the same encoding= =2C or that the result of the operation is in that same encoding. It seems = to me that the result of adding a decimal-encoded decimal128 item to a bina= ry-encoded decimal128 item will NOT be the same as it would if both were en= coded in decimal in the first place. The results are (almost?) always vali= d numeric values=3B they're just wrong if the presumption is that the opera= nds and the result are all in the same encoding. This is the same dilemma = COBOL faces if the presumption is that the data in IEEE decimal formats is = encoded in decimal=3B the difference is that COBOL explicitly states that o= nly decimal is permitted to begin with. -Chuck Stevens

Charles, As you seem determined to follow your current path I thought I had written my last word on this subject but I guess I have another one in me. This is a false analogy. It is equivalent to saying that adding a DPD encoded Decimal128 to an ASCII string would be dangerous. Of course it would. If it hurts, don't do that. Anytime you import data without knowing its format you make such errors. Almost always fatal. We spent at least 2 years putting decimal arithmetic into 754. About a year & a half shoehorning it in in the first place. And later, another 6 months or a year when the conflict between IBM & Intel came up. But we resolved all that. And we did it for you. The arithmetic *IS* identical in both DPD & BID. We made damn sure of that. That you don't seem to be interested in using both encodings wastes that latter time. That you don't seem to be willing to support decimal even to the point of changing the fundamentals of the arithmetic WRT NaNs & infinities wastes the rest. I was hoping to persuade you to make your variances much more slight (in the form of more Cobol-like exception defaults) but even that has gone nowhere. I'm sure you know far better than I what is best for your users. And what you can do in the time you have available to you. But it seems a shame. Yours, Dan

**Follow-Ups**:**RE: Two technical questions on IEEE Std 754-2008***From:*William M Klein

**RE: Two technical questions on IEEE Std 754-2008***From:*Charles Stevens

**RE: Two technical questions on IEEE Std 754-2008***From:*Mike Cowlishaw

**References**:**Two technical questions on IEEE Std 754-2008***From:*Charles Stevens

**Re: Two technical questions on IEEE Std 754-2008***From:*Dan Zuras IEEE

**RE: Two technical questions on IEEE Std 754-2008***From:*Charles Stevens

**RE: Two technical questions on IEEE Std 754-2008***From:*Charles Stevens

**Re: Two technical questions on IEEE Std 754-2008***From:*Dan Zuras IEEE

**Re: Two technical questions on IEEE Std 754-2008***From:*Keith Bierman

**RE: Two technical questions on IEEE Std 754-2008***From:*Charles Stevens

**Re: Two technical questions on IEEE Std 754-2008***From:*Keith Bierman

**RE: Two technical questions on IEEE Std 754-2008***From:*Charles Stevens

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