John,
I neglected to add at the end of the first paragraph that
More accuracy can be specified with trailing zero digits. That
is,
".123000E-10", is interpreted as the infinitely precise interval
"[122999, 124001]/10000000000000".
-------- Original Message --------
Thanks for your kind words, John.
What I wanted to do is to eliminate the default practice that now
exists, in which users are misled by interpreting their string inputs as
infinitely precise. To do this, I let the appearance of a decimal point
in a numerical string be the trigger for precision to be determined by
the last decimal digit in the string. The lack of a decimal point
requires the ability to scale integers so that 123E-10 is interpreted as
the infinitely precise rational number "123/10000000000". The converse,
".123E-10", is interpreted as the infinitely precise interval
"[122,124]/10000000000".
Conversion from these strings to internal floating-point intervals is
done with absolutely rigorous directed rounding, but only when
required. The same is true for conversion from internal floating-point
intervals to strings for output. Rigorous I/O was one of the most
difficult parts of an interval compiler to implement. I had done one
before Sun's in CDC's Compass assembly language in the '70s on the
University of Minnesota's MNF Fortran compiler.
<http://www.comp.tc-ieee.org/archive/FORTRAN.html>
You, or somebody else will have to read the Sun Interval User Reference
to compare it to the Vienna proposal.
Regards,
Bill
On 6/1/13 9:34 AM, John Pryce wrote:
> <I first sent this to George by mistake, and to the group>
> Bill
>
> On 31 May 2013, at 03:14, Corliss, George wrote:
> On May 30, 2013 6:29:08 PM CDT, Bill Walster wrote:
>> I am unable (perhaps it is me) to determine if the scheme implemented in Sun's implementation of string to interval and interval to string conversion will be standard conforming or not. The Sun Fortran 95 implementation explicitly deals with strings as infinitely precise decimal numbers versus strings in which interval width is determined by the last decimal digit in a string.
>>
>> If the Sun Fortran implementation is standard conforming, or if the draft can be updated to allow the sun string conversion implementation to be standard conforming, I will change my vote to Yes.
> I have much respect for the Sun Fortran implementation and we could probably learn from it about this issue. Could you just remind us of the details of its scheme that you mention above? And also how much it overlaps with the scheme in the Vienna proposal, which has a similar feature of "infinitely precise decimal numbers versus ... interval width determined by the last decimal digit"?
>
> John Pryce