TC39 Implementers
2025-05-29
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04:49
<rkirsling>
just noticed a fascinating thing about https://tc39.es/ecma262/#sec-math.log10e
04:52
<rkirsling>

the spec notes that

The value of Math.LOG10E is approximately the reciprocal of the value of Math.LN10.

but

04:53
<rkirsling>
whereas 1/Math.log(2) === Math.log2(Math.E) and therefore Math.LOG2E can be defined either way,
04:54
<rkirsling>
1/Math.log(10) !== Math.log10(Math.E) and therefore Math.LOG10E needs to be defined as the latter
04:55
<rkirsling>

i.e.

λ eshost -se "[Math.LOG10E, Math.log10(Math.E), 1/Math.log(10)]"
#### engine262, JavaScriptCore, SpiderMonkey, V8
0.4342944819032518,0.4342944819032518,0.43429448190325176
04:57
<rkirsling>
I guess this might not be that interesting from V8's perspective, where log2(kE) and log10(kE) are being used, but
04:58
<rkirsling>
for 15 years, JSC has had these defined as 1.0 / log(2.0) and 0.4342944819032518, and I was like, huh that's weird