Idea for ECMAScript 7: Number.compare(a, b)
On Thu, Jun 5, 2014 at 7:15 PM, Axel Rauschmayer <axel at rauschma.de> wrote:
// Compact ECMAScript 6 solution
// Risk: number overflow
[1, 5, 3, 12, 2].sort((a,b) => a-b)
Is this really an issue for IEEE floating point?
On 6 Jun 2014, at 01:15, Axel Rauschmayer <axel at rauschma.de> wrote:
It’d be nice to have a built-in way for comparing numbers, e.g. when sorting arrays.
// Compact ECMAScript 6 solution // Risk: number overflow [1, 5, 3, 12, 2].sort((a,b) => a-b) // Proposed new function: [1, 5, 3, 12, 2].sort(Number.compare)
That sorts in ascending order. What if you need to sort in descending order? Would there need to be a built-in function for that too?
Something like:
Number.compare = (n1, n2) -> (n1 - n2) / Math.abs(n1 - n2) || 0;
My bad! Miss read it. ^That still sorts in ascending order only.
Le 6 juin 2014 à 01:18, C. Scott Ananian <ecmascript at cscott.net> a écrit :
On Thu, Jun 5, 2014 at 7:15 PM, Axel Rauschmayer <axel at rauschma.de> wrote:
// Compact ECMAScript 6 solution // Risk: number overflow [1, 5, 3, 12, 2].sort((a,b) => a-b)Is this really an issue for IEEE floating point? --scott
Right. More precisely, if a and b are both finite, but too far apart fora - bto be representable by a finite number, we get eithera - b == Infinity > 0, ora - b == -Infinitiy < 0, so thataandb` are still correctly ordered.
There is a potential issue if some of the numbers you want to sort are infinite,
because you get, in some occasions, a - b is NaN where you need a - b == 0.
In that case, the behaviour of the sort function is explicitly left undefined by the current ES specification.
This could be simply resolved spec-wise by requiring to interpret the result of the compare function as 0 whenever it produces NaN.
For that case, I've filed: ecmascript#2978
(Naturally, if some of the numbers are NaN, you are out of luck.)
It’d be nice to have a built-in way for comparing numbers, e.g. when sorting arrays.
// Compact ECMAScript 6 solution // Risk: number overflow [1, 5, 3, 12, 2].sort((a,b) => a-b) // Proposed new function: [1, 5, 3, 12, 2].sort(Number.compare)