Re: A Level 2 query

["G. William (Bill) Walster" <bill@xxxxxxxxxxx>]

Suppose you have the function

SUB(X)
INTERVAL X
SUB = X-X
RETURN

and in the calling program

INTERVAL X
X = [-1,1]
Y = X-X
Z = SUB(X)
PRINT, X, Y, Z
END

Do you expect to get [0,0] for Z and [-2,2] for Y?  Isn't that what your 
"without dependency slop" remark implies?

If so, then the standard should make it very clear that interval 
arguments of functions are to be evaluated differently from regular 
interval variables.

Cheers,

Bill

On 6/20/13 7:27 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>