P1788, and Chair
On 2013 Nov 19, at 14:08, John Pryce wrote:
Attached is the version of Clause 6 "Expressions" that I would like voted on.
Sorry, we need to hold up for a day or so.
Vincent (2013 November 20 00:36) indicates he has been busy but wants to comment further on §6.1 when he has had some sleep!
Also, I had been concentrating on the change to §6.1 and forgot a needed change to 6.4, pointed out by Dmitry Nazhedin. The correspondence between bare and decorated interval operations applies
*except when NaI is involved*.
I changed the last paragraph of 6.4; it now reads
"The standard requires that at Level 2, for all interval types, all operations and all inputs other than NaI, the interval part of a decorated interval operation equal the corresponding bare interval operation. This ensures that converting bare interval program code to use decorated intervals leaves the data flow entirely unchanged (provided no conditionals depend on decoration values, and NaI does not occur)—hence the computed expression and the interval part of its result are unchanged. If this were not so, there might in principle be an arbitrarily large discrepancy between the bare and the decorated versions of a computation that contains conditionals."
Like Dmitry, I don't see a good alternative to this exception to the bare-versus-decorated operation correspondence. If you see any other exception to it, please point out ASAP.
John Pryce