Re: Motion 52 -- Time to revive the "Expression" subgroup?
On 2013-11-05 07:10:33 -0800, Richard Fateman wrote:
> On 11/4/2013 5:44 PM, Jean-Pierre Merlet wrote:
> > I think that by default the compiler should take the expression
> > "as it" and provides simplification only on demand.
The compiler should follow the semantics of the language.
Allowed optimizations with depend on that.
> I think we cannot depend on a language implementation ignoring
> optimization settings etc. Thus some systems will 'optimize'
> x-x to 0. So we cannot advocate writing x-x, at least if the answer
> matters!
Systems don't blindly "optimize" x-x to 0 (unless x is necessarily
a number). An interval isn't a number. 0 isn't an interval.
Optimizing x-x to 0 when x is an interval is an error.
Note: If in some language, x represents a number but the evaluation
is done with interval arithmetic, then compiler could be allowed to
optimize x-x to 0, but that's out of the scope of P1788, because the
optimization (or simplification) is done before interval arithmetic
comes into play.
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Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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