disabling unary "-" for unsigned types

[Walter Bright]

Lutger wrote:
> It's a valid viewpoint, but it is a 'should'. I believe many programmers 
> have only passing familiarity if at all with the semantics of unsigned types 
> and floating point operations. At least when coding, they don't have these 
> semantics in mind. Why do you think Java doesn't have unsigned types? 

Naive programmers have trouble with Java floating point as well:

     http://www.eecs.berkeley.edu/~wkahan/JAVAhurt.pdf

There's just no getting around it. Should Java just remove floating 
point types as well?

Heck, I knew a degree'd mechanical engineer who could not understand why 
his calculator kept giving him answers off by a factor of 2 (he refused 
to understand roundoff error, no matter how many times I tried to 
explain it to him - he believed that calculators had mathematically 
perfect arithmetic). We could ban calculators, but misuse of slide rules 
is far worse.


> However D does seem to target C#/Java and even python programmers. It is 
> often suggested D's 'system programming' features are not actually *needed* 
> and it offers enough high-level and safe features for programmers not 
> comfortable with C / C++ to program effectively. This reasoning does not 
> hold for unsigned integers and floating point vagaries. 

Pointers are far more troublesome than negating an unsigned.

In my experience with beginning programming courses, the very first 
thing they explained was 2's complement arithmetic. I do not think it 
unreasonable at all that someone using a powerful systems programming 
language ought to understand it.