Re: A Level 2 query
Richard,
May I chime in here? I would view such a polynomial
as a "function evaluation." If the polynomial were
one of the functions listed as required or recommended
by P-1788, and if we required the lower bound on its
value to be the closest number less than or equal to
the lower bound on the actual range, and the upper bound
on its value to be the closest number greater than or
equal to the upper bound on its range, then the implementation
of P would be standard-conforming (provided that is what you
mean by "no slop").
If P were not explicitly listed in the standard, and the value
it returned would contain the actual range, that certainly
would not be prohibited by the standard. (However, I would think
it would not be controversial that, if the evaluation of P were
part of a package claimed to be standard-conforming, the value of P
shall contain the actual range. I'll need to check our present
draft document carefully to see whether or not that is clear.)
That's just my personal take on it.
Best regards,
Baker
On 06/20/2013 09:27 AM, Richard Fateman wrote:
I am unclear as to whether you are excluding from consideration as
standard-conforming the following compiler
"optimization":
let y := ...some explicit polynomial P in the interval variable x.
The compiler recognizes P as a polynomial, computes (at compile time)
locations and values at
its relative maxima and minima, and at run-time uses this information to
compute inf(y) and sup(y) on the interval x entirely without
dependency slop.
And perhaps with great speed compared to evaluating P.
RJF
On 6/20/2013 6:05 AM, John Pryce wrote:
Ian, Jürgen, P1788
What I get from these replies is that the T -> T operation *should* be
mandatory. Ian's comments are important but they apply to expressions.
Those are a language issue and we IMO
(a) *should not* make requirements about expression-evaluation (beyond
containment);
(b) *should* make recommendations on the lines Ian proposes.
Actually, thinking about it, I'm less sure about (a).
<snip>
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Ralph Baker Kearfott, rbk@xxxxxxxxxxxxx (337) 482-5346 (fax)
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