Re: Motion P1788/M0029.01: Level-3-interface-only --- Final version to vote on
> Subject: Re: Motion P1788/M0029.01: Level-3-interface-only --- Final version to vote on
> From: John Pryce <j.d.pryce@xxxxxxxxxxxx>
> Date: Wed, 14 Dec 2011 15:46:37 +0000
> Cc: John Pryce <prycejd1@xxxxxxxxxxxxx>
> To: stds-1788 <stds-1788@xxxxxxxxxxxxxxxxx>
>
> Dan and P1788, especially compiler people:
>
> On 14 Dec 2011, at 01:24, Dan Zuras Intervals wrote:
> >> However they also support an interchange medium at the binary level. One
> >> can't specify this for a "general" T assuming only what's in the Explicit/
> >> Implicit motion 19, but for each 754-conforming type we can easily define
> >> its interchange format (should it be "interchange type"?) as follows:
> >
> > You are correct that it SHOULD be "interchange type" but please
> > continue to use the expression "interchange format".
> >
> > . . .
> >
> > Indeed, the word "format" was controversial as well. And the
> > . . .
> > We use it to refer to an abstraction separate from its bit pattern
> > for which we reserve the word "representation".
> >
> > I am not a fan of such tortured prose but it is something that
> > seems to come out naturally in the committee process.
>
> Dan, I would prefer to use "type". I want to reserve "interval format"
> for Level 3, and "interval type" for Level 2.
>
> My reason is as follows. An interval type T is, like a 754 format F,
> an "abstraction separate from its bit pattern" but T is at a higher
> level of abstraction than F. Namely, a T-datum is basically
> "a mathematical interval that knows what type it belongs to",
> see my draft Level 2 text (from clause 6) copied below. So a T-datum
> exists above any representation, while I think an F-datum is defined
> by its representation (the radix, exponent width, and significand width).
>
> I hope the extract below makes my point sufficiently clear. A type name
> is something like "binary64". I would suggest that whatever names are
> used for types in P1788 are not necessarily those used by a language
> or an implementation.
>
> Compiler people, do you wish to object to this usage?
>
> John Pryce
>
John,
If our compiler people do not object, I think this is an
excellent idea. The use of "type" as an abstraction &
"format" as the layout in memory is more in keeping with
the colloquial use of these words. Therefore, more clear
to our users.
The only caveat that remains is that you should note when
you define them that these words are being used differently
than they were in 754.
It is better to correct tortured prose than propagate it.
Fantastic,
Dan