Re: Re-revised interval flavors motion (36.03 !!)
On 2012-07-30 19:10:13 +0100, John Pryce wrote:
> My conclusion is that to make flavors work, 1788 should specify a common
> set of intervals, and a common set of opinsts, and require all flavors to
> agree on these. But not make requirements beyond this.
I disagree (this is not what was decided at the end of the discussion).
The problem with this choice is the following: the standard needs to
specify requirements and recommendations for arbitrary functions (as
interval extensions of math functions) provided by an implementation
as part of the library (a bit like what IEEE 754-2008 does in its
section 9.1, about conforming language- and implementation-defined
functions).
For instance, a requirement would be the containment property. There
would also be requirements and recommendations concerning the accuracy.
And requirements about flavors are needed too. Thus instead of listing
a set of opinsts that would be specific for each function, the standard
needs to give a rule from which one would deduce the set of opinsts.
The rule you gave at the end of the discussion was: "the operation is
defined and continuous at each point of its input box". And the rule
should be simple enough so that the standard makes easy to implement
new functions from a minimal library.
Also, this was not discussed, but I think that an operation that is
not an interval extension of some math function shall not depend on
the flavor (at least if the result is in the common set). I wonder
what the intersection of [0,1] and [2,3] should be in the modal
flavor...
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Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)