Re: Motion to finalise interval literals
John, Richard, P1788
Am 09.06.2013 08:22, schrieb John Pryce:
Richard and P1788
On 9 Jun 2013, at 01:27, Richard Fateman wrote:
On 6/8/2013 6:32 AM, John Pryce wrote:
Jürgen and P1788
On 7 Jun 2013, at 19:02, Jürgen Wolff von Gudenberg wrote:
as already stated in one of my last emails, I think interval literals should not be required. They will involve languages and compilers, and ,hence, augment the workload in dissemination the of standard.
so change the "shall" into a "should"
With respect, I disagree entirely with this and wonder if the draft text doesn't make the purpose of interval literals (ILs) clear enough.
- For some time to come, interval computation will not be integrated
within a language; Sun Fortran & C++ are an exception.
Instead it will be provided by a bolt-on library. Interval literals
give a standard specification for reading (especially) and writing
intervals -- important both for interactive work and for reading/
writing text files.
I think that I differ in my view of what the standard is aiming for...
I find your arguments quite strong and am more inclined to make interval literals (ILs) optional. But do you and Jürgen intend
- text2interval "should" be provided, and if it is, it *shall* accept
the stated syntax & semantics?
or
- text2interval "shall" be provided, and *should* accept the stated
syntax & semantics? If it doesn't, I suppose it accepts the host
language's syntax & semantics of intervals.
or some other variant?
my imtention was not to extend the HL so
- text2interval "shall" be provided, and it *shall* accept
the stated syntax & semantics?
having read Richard Fateman's mail I suppose that available syntax in HL
should be used
However:
On 9 Jun 2013, at 01:27, Richard Fateman wrote:
Whichever, I continue to say that to conform, the implementation needs
either to implement text2interval() or to embed its syntax+semantics
of intervals within the language.
I'm not sure I understand this. If I can construct any interval whatsoever with
containment guaranteed (or tightness guaranteed) by constructing A, B and [A,B],
does that mean I have embedded enough to conform?
Probably, but I'll have to think more about it. I pass over it for now.
While I take issue with
0.1 and "0.1" having different meanings, a program to parse "0.1" as
1/10 is just a few lines in Lisp. I am not objecting to doing the computation,
just that it has, in Lisp, nothing to do with intervals.
Do you take issue with Sun Fortran? If I understand right, in
real x
interval xx
x = 0.1 !machine approximation
xx = [0.1] !enclosure of exact value
the two 0.1's have "different meanings" in your sense.
You don't like 0.1 changing its meaning when you put string quotes
round it, so what about when you put square brackets round?
I don't like either
[0.1,0.1] indicates that there are 2 numbers in the game. Yes I would
also write [0.5,0.5]
At present we should use xx = text2interval("0.1"."0.1") , or
textinterval"[0.1]". the former receives to literaly encoded fp-numbers
the latter gets an interval string
Jürgen
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