RE: general conversions of floats to intervals
Dear Baker, dear Friends,
Yes, I meant conversion of strings to intervals, because a floating
point 1.5 and 1.50 is the same, so this has to be done with strings.
If the user wants the exact value 1.5, then it can be represented as a
floating point number 1.5; if the user wants 1.50 meaning [1.45,1.55],
then this can be represented as a string '1.50'.
I did not intend to propose a completely new idea, just tried to propose
an additional argument in favor of things that have already been
discussed: that we can keep exact transformation for numbers and expand
an intervals when transforming strings into intervals, so that
intval(1.5) is [1.5,1.5] while intval('1.50') is [1.45,1.55] (to be more
precise, its binary-rational enclosure, with endpoints appropriately
rounded).
It may be that I am misreading the opinion of others.
I agree with you that if this is a completely new idea, let us put it on
hold, because we already have enough ideas for this standard.
However, if I did capture the intent of some of the proposers correctly,
folks, please let me know, we can then work on a proposal as Baker
suggested.
-----Original Message-----
From: stds-1788@xxxxxxxx [mailto:stds-1788@xxxxxxxx] On Behalf Of R.
Baker Kearfott
Sent: Tuesday, November 11, 2008 9:23 AM
To: owner-stds-1788@xxxxxxxxxxxxxxxxx
Cc: stds-1788
Subject: Re: general conversions of floats to intervals
Vladik,
Yes. In fact, Siegfried Rump captures this meaning in INTLAB's
"significance notation." ( Try "intvalinit('Display_')" and see how
subsequent dialog proceeds.)
However, how is that relevant to converting a float to an interval?
We are given a float, and are converting it to an interval, without
context. If we're thinking of it with uncertainty, already there
is additional information (e.g. given as two end points or as a midpoint
and radius).
Are you speaking of conversion of strings to intervals? I suppose
that's
something we can consider, but I would vote against it in a formal
vote, because, what if the user really wanted the exact number input?
If you want it, please continue to advocate it, and bring it up as
a motion or position paper when we have our formal procedures in place.
Baker