* Re: Non-static constant propagation in
1990-01-05 1:37 Non-static constant propagation in optimizing Ada compilers Joe Orost
@ 1990-01-05 21:44 ` stt
1990-01-08 21:54 ` stt
1990-01-10 21:24 ` stt
2 siblings, 0 replies; 6+ messages in thread
From: stt @ 1990-01-05 21:44 UTC (permalink / raw)
An Ada expression is always allowed to evaluate to a result more
accurate than that required by the type.
This can be due either to compile-time infinite
precision calculation, or by simply using greater
precision at run-time.
The only absolute requirement for accuracy has to do
with operations where both operands are model numbers.
See ARM 4.5.7.
S. Tucker Taft
Intermetrics, Inc.
Cambridge, MA 02138
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Non-static constant propagation in
1990-01-05 1:37 Non-static constant propagation in optimizing Ada compilers Joe Orost
1990-01-05 21:44 ` Non-static constant propagation in stt
@ 1990-01-08 21:54 ` stt
1990-01-09 13:10 ` Robert Firth
1990-01-10 21:24 ` stt
2 siblings, 1 reply; 6+ messages in thread
From: stt @ 1990-01-08 21:54 UTC (permalink / raw)
With regard to accuracy of compile-time calculations...
In ARM 4.10:4, it states:
. . . Furthermore, if a universal expression is a static expression,
then the evaluation must be exact.
Let's hope they don't try to define "SQRT" on universal reals ! ;-*
S. Tucker Taft
Intermetrics, Inc.
Cambridge, MA 02138
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Non-static constant propagation in
1990-01-08 21:54 ` stt
@ 1990-01-09 13:10 ` Robert Firth
0 siblings, 0 replies; 6+ messages in thread
From: Robert Firth @ 1990-01-09 13:10 UTC (permalink / raw)
In article <20600032@inmet> stt@inmet.inmet.com writes:
>In ARM 4.10:4, it states:
> . . . Furthermore, if a universal expression is a static expression,
>then the evaluation must be exact.
>
>Let's hope they don't try to define "SQRT" on universal reals ! ;-*
The sentence quoted was perpetrated by one of the Neoplatonists on
the language design team. The point of the joke, of course, is that
in Ada all 'universal' expressions yield only rational results, and
so may indeed be computed exactly.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Non-static constant propagation in
@ 1990-01-10 4:00 Michael Hunter
0 siblings, 0 replies; 6+ messages in thread
From: Michael Hunter @ 1990-01-10 4:00 UTC (permalink / raw)
firth@sei.cmu.edu (Robert Firth) writes:
>In article <20600032@inmet> stt@inmet.inmet.com writes:
>
>>In ARM 4.10:4, it states:
>> . . . Furthermore, if a universal expression is a static expression,
>>then the evaluation must be exact.
>>
>>Let's hope they don't try to define "SQRT" on universal reals ! ;-*
>
>The sentence quoted was perpetrated by one of the Neoplatonists on
>the language design team. The point of the joke, of course, is that
>in Ada all 'universal' expressions yield only rational results, and
>so may indeed be computed exactly.
I'm missing something here....no matter how hard to try to compute the square
root of 2....you ain't gonna get it exactly...I don't care if you are doing
your arithmatic with rational immediate results!! The sqare root of 2 doesn't
exist in the rationals!!!! (go check with your college abstract algebra book
or if you want overkill check out galois theory!) Now you can computer the
root of 2 to maximum percision of the hardware percisely...that is a different
matter...!
Michael
Mike Hunter - Box's and CPU's from HELL: iapx80[012]86, PR1ME 50 Series, 1750a
UUCP: {ames!elroy, <routing site>}!gryphon!pnet02!bagpiper
INET: bagpiper@pnet02.gryphon.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Non-static constant propagation in
1990-01-05 1:37 Non-static constant propagation in optimizing Ada compilers Joe Orost
1990-01-05 21:44 ` Non-static constant propagation in stt
1990-01-08 21:54 ` stt
@ 1990-01-10 21:24 ` stt
2 siblings, 0 replies; 6+ messages in thread
From: stt @ 1990-01-10 21:24 UTC (permalink / raw)
As Robert Firth said, the point of my joke about SQRT on universals
was exactly that the result is not always a rational number.
The definition of Ada does not currently include any operations on universal
reals which produce irrational results. If we were to add SQRT,
then the cited wording would have to change. I have no expectation
that SQRT will be added to the set of operations defined on
universal reals, by the way...
S. Tucker Taft
Intermetrics, Inc.
Cambridge, MA 02138
P.S. I wouldn't rule out some clever implementation which could
represent all algebraic numbers "exactly", but it would clearly
have to be more complicated than simply a pair of universal
integers as is used for rationals
(probably a tree structure of some sort, requiring symbolic
evaluation, etc).
-T
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Non-static constant propagation in
@ 1990-01-12 5:20 Michael Hunter
0 siblings, 0 replies; 6+ messages in thread
From: Michael Hunter @ 1990-01-12 5:20 UTC (permalink / raw)
stt@inmet.inmet.com writes:
>
>As Robert Firth said, the point of my joke about SQRT on universals
>was exactly that the result is not always a rational number.
Someone on the net said that I insulted you with my comment that the square
root of two is not rational. I apologize if I did.
Michael
Mike Hunter - Box's and CPU's from HELL: iapx80[012]86, PR1ME 50 Series, 1750a
UUCP: {ames!elroy, <routing site>}!gryphon!pnet02!bagpiper
INET: bagpiper@pnet02.gryphon.com
^ permalink raw reply [flat|nested] 6+ messages in thread
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