Rename Number.prototype.clz to Math.clz

Mark S. Miller erights at google.com
Thu Jan 16 10:07:40 PST 2014


On Thu, Jan 16, 2014 at 8:40 AM, Jason Orendorff
<jason.orendorff at gmail.com>wrote:

> At the risk of putting too many nails in the board...
>
> The rationale seems to propose that (0).clz() === 32, but the
> hypothetical uint64(0).clz() would return 64. That seems like a bad
> idea though. It's weird for two zero values to get such different
> behavior from the same method. It's weird for floating-point numbers
> to have a clz() method in the first place.
>
> Since these are two different mathematical functions, they should have
> different names: Math.clz32(zero) would be 32 no matter what type of
> zero you pass it; the hypothetical Math.clz64(zero) would of course be
> 64. That way users can focus on the mathematical function being
> computed, rather than runtime types.
>
> Or maybe: flip the function around so that it returns the number of
> bits in the binary expansion of the value: Math.bitlen(15) === 4. This
> is just (32 - CLZ), so it effectively computes the same thing as clz.
> The advantage is that it extends naturally to integers of any size.
>

+1. I like this flipping idea by far the best. It can be explained in terms
of the number being denoted, without referring to the internal limitations
of any particular representation. With this change, I agree it should be a
static on Math.

With this flipped idea, let's think through what the proper .bitlen answers
are for fractions, negative numbers, NaN, +/- Infinity, and -0.0.


>
> -j
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-- 
    Cheers,
    --MarkM
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