[Cfp-interest 1396] Re: Math functions & range errors

[David Hough CFP]

I think the discussion of tgamma makes the point that range errors are about 
the result, not the argument.    For monotonic functions, that can be mapped
back into statements about the argument.    What about functions of two
arguments?

For consistency, one might want to say something  like a range
error occurs 
when the magnitude of the correct result lies outside the range of normalized
numbers.    Or maybe "sufficiently outside" instead of "outside" to allow
for results that happen to round back in to the normalized range.

But then what about subnormal numbers?    In 754, exact subnormal results
are exceptional - but you only notice if alternate exception handling is
enabled.     Does C consistently classify exact subnormal results as range
errors or not?