GDC release 0.23

[Walter Bright]

Don Clugston wrote:
> There's just no way D real can be equal to C long double in general, 
> when the C long double is playing silly games. The only reason gcc can 
> even do that, is that the C spec for floating point is ridiculously 
> vague, and consequently no-one actually uses long double. To mimic it is 
> to immediately break D's support for IEEE.
> 
> Seriously, the viability of D as a numeric computing platform is at 
> stake here.

I don't really understand the issues with the PPC 'double double', but:

1) real.sizeof is 10 on Win32, and 12 on Linux. This caused some (now 
fixed) compiler bugs, but shouldn't have affected any user code.

2) D floating point arithmetic is supposed to be IEEE 754. Some wacky 
real type for the PPC is going to cause grief and break code in 
irritating and unforeseeable ways.

3) The D implementation is allowed to evaluate floating point ops in 
higher precision than that specified by the type. FP algorithms should 
be coded to not break if more accurate answers are delivered.

4) I suggest supporting the wacky PPC double double with:
a) a special type, like __doubledouble, that is NOT real, ireal, or creal.
b) real should map to C's double, but still be a distinct type to the 
compiler
c) if doing __doubledouble is a pain as an inbuilt type, perhaps do it 
as a struct and a library type?