Wrong result with enum

[Salih Dincer]

On Thursday, 11 November 2021 at 14:52:45 UTC, Stanislav Blinov 
wrote:
> On Thursday, 11 November 2021 at 09:11:37 UTC, Salih Dincer 
> wrote:
>
>>> Unless explicitly set, default type is int. 10000100000 is 
>>> greater than int.max.
>> 100001
>> ```d
>>   enum w = 100_000;
>>   size_t b = w * w;
>>   // size_t b = 100000 * 100000; // ???
>>   assert(b == 10_000_000_000); // Assert Failure
>> ```
>> The w!(int) is not greater than the b!(size_t)...
>
> That code is
> ```
> size_t b = int(w) * int(w);
> ```
>
> That is, `multiply two ints and assign result to a size_t`. 
> Multiplication of two ints is still an int though, and you 
> can't fit ten billion in an int, so that's overflow. It doesn't 
> matter that you declare `b` as `size_t` here. Overflow happens 
> before that assignment.

Thank you all :)

DMD still has to type inference...

I think the safest and most practical method is to explicitly use 
double types:

```d
import std.stdio;

enum factors { n =  1e+9, n1 }

auto gauss (double a = factors.n,
             double b = factors.n1)
{ return cast(size_t)(a * b)/2; }

void main()
{
   gauss.writeln;

   ulong.max.writeln;
}
```