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On Thu, 2013-02-28 at 14:12 +0100, Vincent Lefevre wrote:
> On 2013-02-27 22:22:41 +0100, Christian Keil wrote:
> > Am Tue, 19 Feb 2013 12:37:40 -0800
> > schrieb Richard Fateman <fateman@xxxxxxxxxxxxxxxxx>:
> >
> > > On 2/19/2013 2:00 AM, Guillaume Melquiond wrote:
> > > .... snip, , expressions meaning what they say...
> > >
> > > I think that whatever advantage can be gained by allowing an
> > > implementation to process string expressions like "0.1 + pi" is more
> > [...]
> >
> > probably I'm missing something here. But where does the idea to allow
> > "0.1 + pi" as an input to text2interval come from?
>
> AFAIK, the idea of text2interval was not to write expressions
> like "0.1 + pi", but rather text strings like "[0.1,0.2]" (or
> just "0.1"?). IMHO, some common forms should be standardized.
....
> > There is also the mention of an language- or implementation-defined
> > enhanced syntax which may includes other symbols for real constants
> > like Pi in floating literals, but---besides this being language- or
> >
I agree that the original intention of text2interval was as Vincent
mentioned above. However, if a symbol such as pi is defined AND we allow
the string to define <mid+rad> not just [inf, sup] then the string "0.1
+pi" is probably a valid input where mid=0.1 and rad=pi.
A possible problem would be how is the symbol pi defined? If pi is
defined as an interval (for example [3.14,3.15]) then the string "0.1
+pi" is not simply interpreted.
Also, as Vincent mentioned the definition of a symbol is important. Do
we want to specify within 1788 a limited set of symbols or allow
languages to define new symbols? For example, we may allow
languages/libraries to define arbitrary symbols such as sqrt_of_thirteen
and accept text2interval("sqrt_of_thirteen") to give a tight
representation for irrational numbers (as tight and with as large
precision as the language/library wants).
I am not currently for or against any of these ideas, I am just
exploring and would like to hear your opinions.
--
Hossam A. H. Fahmy
Associate Professor
Electronics and Communications Engineering
Cairo University
Egypt
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