Article View: comp.std.c
Article #1352Re: Questions about NCEG
From: Doug Gwyn
Date: Thu, 31 May 1990 15:23
Date: Thu, 31 May 1990 15:23
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1976 bytes
In article <1990May30.203146.11442@twinsun.com> eggert@twinsun.com (Paul Eggert) writes: > The C standard supports use of IEEE floating-point. However, it > doesn't require that access be granted to all features of it, just the > consistent subset chosen for the C implementation. >The question is whether an implementation can conform to both ANSI C and IEEE >754. For example, IEEE 754 requires that -0.0 and 0.0 be distinguishable. Yes, but C doesn't. C can be implemented on top of IEEE 754 conforming hardware. As someone else pointed out, the IEEE 754 "user" can be taken as the C implementation. There is no requirement that the "user" actually exploit all the features that IEEE 754 requires be made available to the "user". Now, some programmers (for example those involved with NCEG) may well want to provide some means by which a C programmer who is using a C implementation on top of an IEEE 754 platform would be able to get his hands on some of the weird IEEE 754 features other than the default subset that the implementation uses. Although I wouldn't recommend this myself, I understand that some people feel they "need" this. Such additional access can be provided as extensions in a conforming C implementation. Any time a programmer uses such extensions his program is no longer strictly conforming, so they can alter the behavior of the implementation in ways that would not be suitable for support of strictly conforming programs. I see no problem here.
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arc1-ca.pugleaf.net!utzoo!attcan!uunet!zephyr.ens.tek.com!uw-beaver!milton!dali!uakari.primate.wisc.edu!aplcen!haven!adm!smoke!gwynReferences:
<1990May29.193451.6533@twinsun.com> <13016@smoke.BRL.MIL> <1990May30.203146.11442@twinsun.com>Show Full Headers
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!zephyr.ens.tek.com!uw-beaver!milton!dali!uakari.primate.wisc.edu!aplcen!haven!adm!smoke!gwyn From: gwyn@smoke.BRL.MIL (Doug Gwyn) Newsgroups: comp.std.c Subject: Re: Questions about NCEG Message-ID: <13027@smoke.BRL.MIL> Date: 31 May 90 15:23:26 GMT References: <1990May29.193451.6533@twinsun.com> <13016@smoke.BRL.MIL> <1990May30.203146.11442@twinsun.com> Organization: U.S. Army Ballistic Research Laboratory, APG, MD. Lines: 24