On Jul 12, 2013, at 4:18 PM, Jeff Walden wrote:
> On 07/12/2013 04:03 PM, Allen Wirfs-Brock wrote:
>> are you suggesting that if we want such an function, it should be named
>> something else, such as isExactInteger, isPreciseInteger,
>> isUnambiguousInteger, etc?
>
> Possibly, but I don't think so. Whether a value is exact or precise is a
> function not of the value itself, but of how it was computed. Math.pow(2,
> 53) computed that way is an exact value. Math.pow(2, 53) - 1 + 2 is (in
> IEEE-754 terms) the same value. But it is not exact, because it derived from
> an inexact computation. It all depends how you got the value you're passing
> in.
>
> "isUnambiguousInteger" is in a different league from exact/precise. Assuming
> a definition like so, it might be reasonable:
>
> function isUnambiguousInteger(n)
> {
> if ((n % 1) !== 0)
> return false;
> return Math.abs(n) < Math.pow(2, 53);
> }
>
> I'm not sure whether it would be useful enough to carry weight, tho, given it
> has fairly esoteric use cases. And anyone asking these sorts of questions
> really needs to know the IEEE-754 design well enough to understand how/why
> things go wrong, well enough that they could code it themselves. The
> existence of such a method doesn't make it any more likely that they will
> understand these details.
So the other thread was a discussion concerning the appropriate value of
Number.MAX_INTEGER. Do you think it should be 2^53-1, or 2^53, or the same
thing as Math..MAX_VALUE.
Allen
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