Re: [P-1788]: Anything else to be said about interval overlapping?
Am 19.11.2010 15:47, schrieb Dan Zuras Intervals:
Folks,
In 754, the 28 comparisons that an implementation is
required to support were listed& organized W.R.T. how
they affected 4 state bits {<, =,>, ||}. As a result,
most implementations ACTUALLY created those 4 state bits
to represent the results of a comparison.
This inadvertent writing style had the effect of creating
global state, side effects,& interlock requirements that
were, frankly, not appreciated at the time. We live with
that mistake to this day.
It would have been better if we had said, "This is the
list of comparisons you are required to support"& put
all the rest in an informative annex.
Motion 21.2 is much the same.
indeed it says : The list of comparisons we have decided to be normative
in motion 13.4 are those 7 comparisons
(equal, subset, lessThanOrEqual, precedesOrTouches, interior, less,
precedes)
Those are good candidates to define all other recommended comparisons.
The overlapping relation producing a 4-byte status information may be
additionally implemented. And if you want, you may take it (overlapping
rel) to implement all the others.
It would be a shame if future generations of computers
ended up creating& maintaining 13 new bits of state to
only 4 bits are maintained
support comparisons. Not fatal, really. But it might
inhibit innovation in ways we do not yet understand.
I think it will stimulate innovation
I would organize our description of comparisons in much
the same way as we should have done in 754: The list in
the normative text& the states in an informative annex.
If you read the many shoulds in the motion we are close to this
But with no more clear alternative, I admit this opinion
lacks credibility.
as already said, the alternative is motion 13.4
Yours,
Juergen
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