Questions about IEEE754 floating point in D

[Don]

Trip Volpe wrote:
> 1. Does D guarantee the closest approximation for decimal floating-point literals?

Not at present.

> 
> 2. Minimum exponent. In D, double.min_exp is equal to -1021. However, the Wikipedia article on IEEE754-2008 and appendix D in Sun's Numerical Computation Guide ("What Every Computer Scientist Should Know About Floating-Point Arithmetic", http://docs.sun.com/source/806-3568/ncg_goldberg.html) list Emin for the IEEE754 double format as -1022. Is this an error?
[snip]

There are no errors anywhere. However, double.min_exp is defined in the 
spec as "the minimum value such that 2^^min_exp-1 is representable as a 
normalized value".
This means that 2^^min_exp-1 == 2^^Emin. And indeed min_exp-1 == -1022 = 
Emin.
I have no idea why min_exp is defined in such a peculiar way. In 
particular, I don't know why it's different from the definition of 
min_10_exp. It seems bizarre and useless.
I've had a sudden thought though -- DMC/DMD used to have an out-by-1 bug 
in the %a format for denormals. Maybe this behaviour isn't intentional, 
but was rather a mistake, caused by that?

Note to Walter: I changed min --> min_normal in the ddoc for my 
'floatingpoint' article long ago, but it hasn't been copied into the 
download.