Unfortunately Claude, ES Math.sign is not Signum; it has five outputs, not three, like Oliver was asking about. Observe:
> Math.sign(1 / 0) 1 > Math.sign(-1 / 0) -1 > Math.sign(-1 / 0 * 0) NaN > Math.sign(0 * -1) -0 > Math.sign(0 * 1) 0 Signum as specified in your link produces three outputs: 0, -1, and 1. On Wed, Oct 30, 2013 at 1:15 AM, Claude Pache <[email protected]>wrote: > > Le 30 oct. 2013 à 04:54, Oliver Hunt <[email protected]> a écrit : > > > As currently specified Math.sign has 5 different return values and, as > far as i can tell, does not solve the problem I thought it was trying to > address. That is the difficulty in distinguishing positive and negative > numbers without having to manually do the divide -> ±Infinity cruft. > > > > What is the rational for this behaviour? > > > > Current Math.sign is a new, and unexpectedly complex API that doesn’t > solve the common use case. > > > > —Oliver > > > > `Math.sign` is expected to represent the mathematical sign function, which > has a precise definition, see [1], [2]. Please note that `+0` and `-0` are > the same value as far as maths is concerned, and that value is neither > positive nor negative. (Or both nonnegative and nonpositive, if you prefer.) > > More generally, ES treats mathematically equal values as equal for any > well-defined mathematical operation: doing otherwise would be new and > unexpectedly complex (if you allow me to borrow your words). > > —Claude > > [1] http://mathworld.wolfram.com/Sign.html > [2] https://en.wikipedia.org/wiki/Signum_function > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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