On Wed Aug 21 13:43:54 EDT 2013, ba...@bitblocks.com wrote: > On Aug 21, 2013, at 9:55 AM, erik quanstrom <quans...@quanstro.net> wrote: > > > On Wed Aug 21 12:09:26 EDT 2013, 9f...@hamnavoe.com wrote: > >>> at least in terms of passing floating point test suites > >>> (like python's) the NaN issue doesn't come up > >> > >> Actually it was a test suite that revealed the NaN errors. > >> I wouldn't think it's something anyone needs in normal > >> day-to-day computation, but sometimes boxes must be ticked. > > > > :-) it is hard to imagine how this is useful. it's not like > > ∑{i→∞}-0 is interesting. at least ∏{i→∞}-0 has an alternating > > sign. (so does it converge with no limit?) > > > > the difference i have seen is a situation like > > atan2(-0, x) ≡ -π > > atan2(+0, x) ≡ pi, ∀ x<0. > > > > any ideas on how this is useful? > > > See comments by Stephen Canon in > http://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-comparisons-returning-false-for-ieee754-nan-values
i think you selected a different antecedent for "this" than i did. by "this" i ment to refer to -0. - erik