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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