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Re: Motion P1788/M0044:Constructors -- Voting Period begins

Richard et al,

I'm not sure I understand your objection.  My perception is that
persons doing interval notation associate the text string 0.1
with the exact real number 1/10, and that any text2interval
conversion into a binary floating point system would have
to convert it into some non-zero-width interval with lower bound
and upper bound representable in the system and containing
the exact number 0.1.  To do so would require a facility
for rounding the text value 0.1 down into the binary format
and also rounding it up.  I know of packages that do this
(some of which are buggy), but I don't think it is readily
accessible by default in common programming languages.

How should we spell this out or clarify this?

Baker

On Sat, 11 May 2013 08:15:39 -0700
 Richard Fateman <fateman@xxxxxxxxxxxxxxxxx> wrote:

The motion seems to be no more than changing the cross reference to
the new location.
I vote  YES.

However, I would prefer that 1788 remove entirely text2interval...
given that such issues
as decimal-to-binary conversion, parsing and evaluation of exact
arithmetic quotients,
values for pi (etc),  are either routine parts of programming
languages, or in their libraries.

And to cap it off, this complicated and unnecessary part is (at
least in the current motion) OPTIONAL.

My view is that the host programming language must be adequate to
create any literal number
which is the inf or sup value stored in a bare interval, and to
create from any bare interval
the two numbers which are its inf and sup values  (including
infinity, NaN).  If this is the
case, there is no need for text2interval.    If this is NOT the
case, the language is essentially
unsuitable for interval arithmetic.  (A clever enough person could
still build interval
arithmetic out of character strings or some other hacks, but I would
call this evidence of
unsuitability...)

Furthermore, text2interval violates what would seem to be a
fundamental rule of "good hygiene".
That is it admits of notation like 0.1 which is close, but not the
same, in meaning as 0.1 in the programming
language.

Richard Fateman