food for thought - swift 5 released - bottom types, string interpolation, and stuff.

[Andrei Alexandrescu]

On 4/13/19 3:04 AM, Julian wrote:
> On Saturday, 13 April 2019 at 04:40:08 UTC, Walter Bright wrote:
>> On 4/12/2019 9:15 PM, Nick Sabalausky (Abscissa) wrote:
>>> If for you, they're the same level of abstraction, that's great. For 
>>> most, it isn't.
>>
>> If you want to write a library of such, and contribute it to Dub, feel 
>> free. If you find an audience for it, great.
> 
> Done: https://code.dlang.org/packages/isodd

That we got to this kind of time investment is worrisome. There's so 
many places where work needs to go, and this is at the very best of 
negligible impact.

Ironically isOdd and isEven were not approved for Swift - see 
Implementation Notes. Instead, the only nontrivial function isMultiple 
was approved:

bool isMultiple(T)(T isThisMultiple, T of)
if (isIntegral!T)
{
     if (isThisMultiple == 0) return true;
     if (of == 0) return false;
     static if (T.min < 0)
         if (isThisMultiple == T.min && of == -1) return true;
     return isThisMultiple % of == 0;
}

Such a function has some subtleties and corner cases that even seasoned 
programmers can get wrong. It can't be reasonably written as inlined 
code. I find its presence in a language's standard library reasonable.

If isMultiple were proposed for Phobos, the argument should be centered 
on frequency of use. It does happen that such queries appear with a 
constant on the right (e.g. a power of two) but general queries for 
arbitrary integers are rare.