testing various reals

[berni44]

How do you test the different real implementations, when you've 
got to go into the internals of them?

I ask, because for the replacement of snprintf in std.format I 
sooner or later need to add support for reals. While it should 
not be too much a problem to look up the supported types and 
their layout in memory in std.math, I still have no means to test 
them (only intel's 80bit version and real=double). How did you do 
that in the past? Is there any simulation or something, that can 
be used for this? And does anyone know which formats are 
supported by the 10 auto-tester-machines?