(j3.2006) (SC22WG5.5785) [ukfortran] edits to clarify SQRTtreatment of negative zero, for comments

[Cohen Malcolm]

>The real part of log of zero is well defined - it is minus infinity.

No, the log of real zero is not defined in maths, though it is in a 
recommended (not mandatory) function in 60559.

60559 does not however define the log of complex zero.  According to its 
usual rules, one might expect (-INF,NaN).

>Hence exp( log(x) ) is also well defined - it is zero.

Actually that would be (NaN,NaN).

>3 out of 3 compilers agree with me

And a fourth produces

(-Infinity,NaN)
(NaN,NaN)

Anyway, compilers do not implement maths, nor are they are reliable guide to 
the finer points of 60559.

Also, non-60559 machines exist and are still used, and their compilers 
cannot agree with you.

>Perhaps [we should add more features]

Perhaps not at this time.

Cheers,
-- 
........................Malcolm Cohen, Nihon NAG, Tokyo.