Bug in ^^

[Brett]

On Tuesday, 17 September 2019 at 02:38:03 UTC, jmh530 wrote:
> On Tuesday, 17 September 2019 at 01:53:12 UTC, Brett wrote:
>> 10^^16 = 1874919424	???
>>
>> 10L^^16 is valid, but
>>
>> enum x = 10^^16 gives wrong value.
>>
>> I didn't catch this ;/
>
> 10 and 16 are ints. The largest int is 2147483647, which is 
> several orders of magnitude below 1e16. So you can think of it 
> as wrapping around multiple times and that is the remainder: 
> 1E16 - (10214748367 + 1) * 4656612 = 1874919424
>
> Probably more appropriate for the Learn forum.


Um, duh, but the problem why are they ints?

It is a compile time constant, it doesn't matter the size, there 
are no limitations in type size at compile time(in theory).

For it to wrap around silently is error prone and can introduce 
bugs in to programs.

The compiler should always use the largest value possible and if 
appropriate cast down, an enum is not appropriate to cast down to 
int.

The issue is not how 32-bit math works BUT that it is using 
32-bit math by default(and my app is 64-bit).

Even if I use ulong as the type it still computes it in 32-bit. 
It should not do that, that is the point. It's wrong and bad 
behavior.

Else, what is the difference of it first calculating in L and 
then casting down and wrapping silently? It's the same problem 
yet if I do that in a program it will complain about precision, 
yet it does not do that here.

Again, just so it is clear, it has nothing to do with 32-bit 
arithmetic but that 32-bit arithmetic is used as instead of 
64-bit. I could potentially go with it in a 32-bit program but 
not in 64-bit, but even then it would be difficult because it is 
a constant... it's shorthand for writing out the long version, it 
shouldn't silently wrap, If I write out the long version it craps 
out so why not the computation itself?


Of course I imagine you still don't get it or believe me so I can 
prove it:


enum x = 100000000000000000;
enum y = 10^^17;

void main()
{
    ulong a = x;
    ulong b = y;

}

What do you think a and b are, do you think they are the same or 
different?

Do you think they *should* be the same or different?