From malcolm@nag.co.uk Wed May 7 13:32:19 1997 Received: from red.nag.co.uk ([192.156.217.2]) by dkuug.dk (8.6.12/8.6.12) with SMTP id NAA03695 for ; Wed, 7 May 1997 13:32:16 +0200 Received: from sedi8.nag.co.uk by red.nag.co.uk via SMTP (920330.SGI/920502.SGI) for SC22WG5@dkuug.dk id AA22674; Wed, 7 May 97 12:27:52 +0100 Received: by sedi8.nag.co.uk (920330.SGI/920502.SGI) for @red.nag.co.uk:SC22WG5@dkuug.dk id AA12428; Wed, 7 May 97 12:27:49 +0100 From: malcolm@nag.co.uk (Malcolm Cohen) Message-Id: <9705071127.AA12428@sedi8.nag.co.uk> Subject: Re: (SC22WG5.1374) Floating-point arithmetic To: SC22WG5@dkuug.dk Date: Wed, 7 May 1997 12:27:46 +0000 (BST) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Length: 1027 Robert Corbett said: > IEC 559 includes direct rounding modes specifically to > make the implementation of interval arithmetic easier. I do not doubt Robert's greater familiarity with the authors of IEEE 754, however: IEEE 754 has no rationale for directed roundings (section 4.2). OTOH, it does have rationale for rounding precision (section 4.3) [this is not to do with interval arithmetic though] Moreover, directed roundings are rather useful in REAL->INTEGER conversion, when "round-to-nearest" is often not what is required. (CEILING, FLOOR and INT provide the directed rounding versions of this operation). > Be careful what you ask for. If you don't want interval > arithmetic, you probably do not want most of what IEC 559 > requires either. I do not agree at all. Almost none of IEEE 754 has anything to do with interval arithmetic. Almost all of IEEE 754 has general applicability. Cheers, -- ...........................Malcolm Cohen, NAG Ltd., Oxford, U.K. (malcolm@nag.co.uk)