On Fri, Jul 12, 2013 at 3:54 PM, Jeff Walden <jwalden...@mit.edu> wrote: > On 07/12/2013 10:27 AM, Tab Atkins Jr. wrote: >> And, because of what we discussed in the recent thread... >> >> Number.isInteger(Math.pow(2,53)-1) == true >> Number.isInteger(Math.pow(2,53)) == false > > I need to comment in the other thread again and push back against what people > have said there, but that thread's issues aside entirely, this is very very > wrong. 2**53 is an integer. That there are multiple mathematical integer > values that, when converted to IEEE-754 format, are equal to 2**53 is > irrelevant. An integer value, that operations claim is not an integer, is > very very wat.
2^53 + 2 is also an integer, but it's clearly outside the range of *exactly-representable integers*, where each integer has one and only one representation. You can't tell if the number you got is actually 2^53+2 or not - it might have been input as 2^53+3, or 2^53+.1, or any number of other starting inputs. If you agree with that reasoning that 2^53+2 should return false from isInteger(), then you must agree that 2^53 should also return false. If you don't agree with that reasoning, then I suppose you'd argue that *all* numbers > 2^53 should return true, since they're all forced into being represented as integers? If neither of these describe your position, could you explain your position in more detail? ~TJ _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
