More on semantics of opPow: return type

[Andrei Alexandrescu]

Don wrote:
> Bill Baxter wrote:
>> On Tue, Dec 8, 2009 at 10:18 AM, Bill Baxter <wbaxter at gmail.com> wrote:
>>>> I agree. Then at least why not make the type of the exponent 
>>>> unsigned? That
>>>> gives the type system a fighting chance (via e.g. value range 
>>>> propagation).
>>>> Give Willy a chance!
>>> Honestly, I don't really understand this concern with range
>>> propagation.   Seems to me that allowing a negative exponent doesn't
>>> much expand the range, if a truncation rule is used.  The result is
>>> either undefined, 0 or 1.  The range is much greater with a
>>> non-negative exponent.  Could be undefined, zero, or most any negative
>>> or positive number.
>>
>> This was meant sincerely, by the way.  As in, I am ignorant about this
>> issue (the trouble with range propagation and negative exponents) and
>> would appreciate it if someone could explain it.
>>
>> --bb
> 
> I'm bitterly opposed to making int^^negative int return 0. Doing that is 
> making up a new operation. And it does really bad things. Why is 2^^-1 
> == 0, and not 1 ? If you're evaluating with the floating point unit, it 
> will be 1 when using "round up" mode.
> It's foul.

Awesome! Don please please require the exponent to be of unsigned type :o).

Andrei