Rename Number.prototype.clz to Math.clz

Brendan Eich brendan at mozilla.com
Sat Jan 18 10:16:55 PST 2014


Nick Krempel wrote:
> Whether log(0) is -Infinity or NaN should depend in some sense on what 
> side you approach 0 from (I arbitrarily claim to be approaching it 
> from the left in my formula, to give a NaN result there too).
>
> I feel Math.log(-0) should be NaN in js for that reason, but it is 
> defined to be -Infinity in the standard. Maybe there are industry 
> standards pertaining to floating point transcendental functions that 
> mandate this? Similarly, Math.sqrt(-0) is -0 rather than NaN. Perhaps 
> using the more correct NaN values in these cases have caused more 
> problems than they have solved in practice?

These cases (log(-0), sqrt(-0)) conform to IEEE 754. See

http://grouper.ieee.org/groups/754/

http://stackoverflow.com/questions/19232157/square-root-of-negative-zero

http://msdn.microsoft.com/en-us/library/windows/desktop/cc308050%28v=vs.85%29.aspx

and many others.

The "Signed Zero" section of

http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

is worth reading.

Further reading from Prof. Wm. Kahan:

http://www.cs.berkeley.edu/~wkahan/
http://www.cs.berkeley.edu/~wkahan/ieee754status/

/be


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