Version 1.1 of ais/ai-00315.txt

!topic        IEEE 754 numerics model
!reference  RM95-G.2
!from         Juergen F H Winkler  2002.09.26
!keywords  numerics, IEEE 754,  rounding

!discussion
IEEE 754 is supported by most microprocessors in use today.
It has more useful features than are required by the strict mode of RM95.
Examples of such features are:
-  different rounding modes
-  infinities and NaNs
-  tight accuracy requirement for sqrt
   (Intel processors e.g. implement additional functions)

[Win 2002] contains an example, where the different rounding modes are
crucial (sect. 7.1).

[DK 98] contains several examples which show that the support of Java
for IEEE 754 is not sufficient.

Ada would be the first language to let the user use the IEEE 754
features of the processor. Up to now they can only be used in assembler.
It would therefore be useful if Ada contained a numerics model
with all the properties of IEEE 754.

DK 98
Kahan, W; Darcy, Joseph D.: How Java's Floating-Point Hurts Everyone Everywhere.  http://www.cs.berkeley.edu/~wkahan/JAVAhurt.pdf, June 18, 1998. (visited:  2000.Nov.04 )

Win 2002
Winkler, Jrgen F. H.: A safe variant of the unsafe integer arithmetic of Java.
Software - Practice and Experience 32, 7(2002) 669..701.  DOI: 10.1002/spe.454

****************************************************************

From: Robert Dewar
Sent: Thursday, September 26, 2002  11:47 AM

Please do NOT send HTML to public lists, this is totally uselress and
bad netiquette. If you are using some microsoft mailer that does this
by default, please turn off the option. Many people throw away messages
with HTML junk in them so probably your message got ignored by some people.

Regarding IEEE fpt, a lot of work has been done in this area. You should
familiarize yourself with the work of the NRG in this area, and you should
probably also read Brian Siritisky's thesis. This same advice applies to
anyone else who wants to discuss this issue technically.

****************************************************************

From: Randy Brukardt
Sent: Thursday, September 26, 2002  12:34 AM

Besides echoing Robert's comment that sending HTML to mailing lists is
frowned upon, I'd like to point that this list is for PROPOSALS and
discussion about proposals for changes and corrections to the Ada
Programming Language. There is no proposal in your message, simply a
statement that it would be nice if Ada supported something. You need to
include a proposal of how this support could be accomplished in Ada, and
(preferably) an example of some problem that can be solved with that
proposal that cannot be solved with existing Ada.

I've privately forwarded a rules summary to Juergen separately.

****************************************************************

From: Robert Dewar
Sent: Thursday, September 26, 2002  1:25 PM

Ed points out that I made a horrible mistake in my last message, for
which I apologize, must be losing my mind today (Ed = Ed Schonberg):

I said

<<Regarding IEEE fpt, a lot of work has been done in this area. You should
familiarize yourself with the work of the NRG in this area, and you should
probably also read Brian Siritisky's thesis. This same advice applies to
anyone else who wants to discuss this issue technically.
>>

I meant not Brian Siritsky, but rather Sam Figueroa. This is a PhD thesis
from the department of CS at New York University, 1999, Robert Dewar, advisor.
I will try to track down a better reference.

****************************************************************

From: Robert Dewar
Sent: Thursday, September 26, 2002  1:29 PM

Note that Sam's thesis contains a completely worked out proposal in this
area (IEEE754 support in Ada).

****************************************************************

From: John Halleck
Sent: Thursday, September 26, 2002  2:35 PM

  http://www.cs.nyu.edu/csweb/Research/Theses/figueroa_sam.pdf
  for the pdf version.  Back up one for other options.

****************************************************************