Re: textToIntevsal(s) and exceptions
On 2015-03-18 11:22:09 +0000, John Pryce wrote:
> A big change when moving text from the set-based flavor to the
> "all flavors" part is that one must answer what I think of as
> meta-questions: what does the standard require/permit a flavor
> to require/permit?
>
> Above, I agree with Vincent. Here's another:
> What shall be said about the syntax & semantics of decorated interval
> literals in *all* flavors?
>
> I think the standard should
> - *Require* the sx_sd form to be used by all flavors.
> That is, if sx and sd denote interval x and decoration d in the flavor
> then sx_sd shall denote x_d, provided this is a valid combination in
> the flavor.
I'm not opposed, but I'm not sure that this is really necessary
in practice. A "should" may be better since we are not sure about
the usefulness and the consequences.
> - *Permit* other forms, such as "nai".
Yes.
> Please comment on this, also on the promotion bare->decorated
> question and the reverse, demotion.
>
> I think the standard should forbid demotion, but this may be my prejudice.
I think that it should only be a recommendation on flavors.
BTW, in an implementation supporting only common intervals, demotion
doesn't seem to be a problem since there's no ambiguity.
> For promotion I'm undecided, and wait for advice from language experts.
> If it's part of the standard, does that make it different at implementation
> level, from making it a consequence of library design and language features,
> e.g., by using class inheritance?
Do you have an example?
> If 1788 *permits* promotion, I think it should *require* that a bare interval
> literal sx with value x be promoted to x_d with d=newDec(x) (at Level 1).
Yes, probably.
> BTW, do we say anywhere that any interval x in any flavor shall be
> decoratable? I.e., there is at least one d such that x_d is a
> permitted combination?
Isn't it a consequence of newDec(x)? I mean that if d = newDec(x),
then x_d must be a permitted combination.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)