disabling unary "-" for unsigned types

[Walter Bright]

bearophile wrote:
> Some of the ways C uses fixnums, its undefined situations, are bad
> today. The Ada language is not handy to use, but it shows that if you
> want to create reliable software able to fly planes, you want a
> language with a more tidy arithmetic than C.

1. Ada seems to be a language people use only when they're forced to. D 
doesn't have the US government forcing its use.

2. Neither Ada nor its design decisions seem to have caught on with 
other languages, despite being around for 30 years.

3. Plenty of military and civil avionics use C++ anyway, despite 
attempts by the US government to force Ada.


This is an old, old *old* issue. All the various solutions tried over 
the decades have failed to catch on. This leads me to believe that 
either these obvious solutions do not work, or they cause more problems 
than they fix.

Heaven knows we are trying out a lot of new design ideas in D, but I'm 
not eager to embrace ideas that have failed over and over for 30 years.