From owner-sc22wg5@dkuug.dk Fri Aug 8 18:03:33 2003 Received: (from majordom@localhost) by dkuug.dk (8.12.8p1/8.9.2) id h78G3Xgr031232 for sc22wg5-domo; Fri, 8 Aug 2003 18:03:33 +0200 (CEST) (envelope-from owner-sc22wg5@dkuug.dk) X-Authentication-Warning: ptah.dkuug.dk: majordom set sender to owner-sc22wg5@dkuug.dk using -f Received: from inf.rl.ac.uk (nfs7.inf.rl.ac.uk [130.246.72.7]) by dkuug.dk (8.12.8p1/8.9.2) with ESMTP id h78G3SEc031227 for ; Fri, 8 Aug 2003 18:03:30 +0200 (CEST) (envelope-from j.k.reid@rl.ac.uk) Received: from numerical.cc.rl.ac.uk (numerical [130.246.8.23]) by inf.rl.ac.uk (8.11.6+Sun/8.8.8) with ESMTP id h78G3RD28874 for ; Fri, 8 Aug 2003 17:03:27 +0100 (BST) Received: from rl.ac.uk (jkr.cse.rl.ac.uk [130.246.9.202]) by numerical.cc.rl.ac.uk (8.8.8+Sun/8.8.8) with ESMTP id RAA06408 for ; Fri, 8 Aug 2003 17:12:24 +0100 (BST) Message-ID: <3F33CBF1.7020002@rl.ac.uk> Date: Fri, 08 Aug 2003 17:12:33 +0100 From: John Reid Reply-To: j.k.reid@rl.ac.uk Organization: Rutherford Appleton Laboratory User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 X-Accept-Language: en-us, en MIME-Version: 1.0 CC: sc22wg5@dkuug.dk Subject: Re: (SC22WG5.2925) clarification of technical intent in N1553 References: <200308072303.h77N34rh026353@dkuug.dk> <200308081249.h78CnM0a030247@dkuug.dk> <200308081330.h78DUv8x030439@dkuug.dk> <200308081507.h78F7FHt030927@dkuug.dk> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-sc22wg5@dkuug.dk Precedence: bulk Richard Maine wrote: > John Reid writes: > > Yes, I agree. The subgroup overlooked the fact that the edit addressed > > point 4. > > That was my guess, but I wasn't 100% sure. > > > I suggest the following edit: > > > > [230:32] After the "." Insert > > "If the NaN is a signaling NaN, the string 'NaN' shall be followed > > by characters enclosed in parentheses." > > > Hmm. That raises another point of non-symmetry - one which I had > failed to note before. Again, I'm not sure whether it is intentional > or not. My suspicion is that it is unintentional, but I find it at > least concievable that there is technical reason for it (perhaps > relating to processor support for signalling vs quite NaNs). > > My proposed edit talked about what happens for quiet NaNs, because that > is how input was specified. For input, we specify that if there are > no characters after the "NaN", we get a quiet NaN. I'm a bit > suspicious that someone thought this conversely requires that if there > are characters after the "NaN", we get a signaling NaN, but that > implication is incorrect. (As workers on a mathematically oriented > language, we ought to know that a statement does not imply its > converse). Absolutely! > Does anyone know whether we assumed the converse or whether we meant > exactly what we said? I'm guessing that we also intended the > converse, but I'm not 100% sure of that guess. No, I think we meant exactly what we said. There may be some useful information that can be provided for a quiet NaN. Why disallow providing it? > Anyway, if we really meant exactly what we said for input (specifying > that we get a quiet NaN when there are no optional characters, but > allowing the form with optional characters to give either a quiet > or signalling NaN), then the above edit for output isn't symmetric. Why not? I intended it to be. On input, a NaN with no parentheses is a quiet NaN. So we need to disallow a signaling NaN to be output this way. Cheers, John.