disabling unary "-" for unsigned types

[Ellery Newcomer]

On 02/16/2010 09:36 AM, Daniel Keep wrote:
>
>
> Ellery Newcomer wrote:
>> On 02/15/2010 09:15 PM, Steven Schveighoffer wrote:
>>>
>>> For example, there is no possible way a person unfamiliar with computers
>>> (and most programmers who have not run into this) would believe that
>>>
>>> b = 5;
>>> a = -b;
>>>
>>
>> Tell any math major that fixnum arithmetic is really just arithmetic
>> modulo 2^32 and they would believe you, even if they had never heard of
>> computers
>>
>
> It's fun to note that one of the fixes the author proposes in the
> article was actually shown to itself be wrong... nearly two years later.
>
> Clearly, knowing that computers use two's complement fixed-width integer
> arithmetic is insufficient to write correct code.  To believe otherwise
> is to believe that humans are infallible.

In the same vein, having opposable thumbs is insufficient to peel 
bananas. To believe otherwise is a failure in logic.

But I don't recall saying anywhere that writing correct code is possible.

I will say that if I wanted my code to be reasonably correct, I probably 
wouldn't use fixnum arithmetic.

OT: I kinda wish BigInt could be dropped in as a replacement for int 
with less hassle.

OT: has anyone written a wrapper for int/long/etc that throws exceptions 
on overflow/underflow? Maybe such a thing should exist in the standard 
library?