Units of Measurement Library: units-d

[Simen Kjaeraas via Digitalmars-d-announce]

On Friday, 1 April 2016 at 21:46:35 UTC, ag0aep6g wrote:
> On 01.04.2016 22:59, Simen Kjaeraas wrote:
>> The usual way to fix it would be to include __FILE__ and 
>> __LINE__ in the
>> template arguments:
>
> Right, no mixin this way. I wouldn't call this "truly nice", 
> though.
>
> It depends on code formatting to work. Put everything on one 
> line and it breaks. Significant whitespace is a pain when 
> generating code. Though this is not nearly as bad as 
> significant indentation, of course.
>
> __FILE__ also kind of breaks separate compilation. All object 
> files have to be compiled from the same directory. Otherwise 
> __FILE__ will be different.
>
> __LINE__ has a similar (maybe even more obscure) issue. Add or 
> remove a newline before compiling dependent modules and things 
> break. Usually, one recompiles all dependents when a dependency 
> changes, but a significant newline, really?

I kinda agree. And looking at https://dlang.org/spec/traits.html, 
I see there's __MODULE__, which would probably be a better choice 
than __FILE__.

As for __LINE__, what we'd want is basically something like 
__CONTEXT__, which doesn't exist, but might be the .mangleof of 
the surrounding scope:

struct S(string ctx = __CONTEXT__) {
     pragma(msg, ctx);
}

S!() a; // "3foo"

void bar() {
     S!() b; // "_D3foo3barFZv"
}

struct S2 {
     S!() c; // "S3foo2S2"
     void baz() {
         S!() d; // "_D3foo2S23bazMFZv"
     }
}

That'd remove the problem of significant whitespace. In fact, 
it'd also eliminate the need for __MODULE__ in this case.

Still though, that's not enough if we want this to work:

void foo() {
     alias a = Foo!(); alias b = Foo!();
     assert(!isSame!(a, b));
}

We could also add __COLUMN__, which would be the horizontal index 
of the instantiation's beginning:

     foo(3, Bar!3.baz);
//         ^Here. Position 11.

Next problem:

void main() {
     pragma(msg, __LINE__);
     mixin("pragma(msg, __LINE__);\npragma(msg, __LINE__);");
     pragma(msg, __LINE__);
}

That prints '4' twice - once for the actual line 4, the other for 
the second line of the mixin. However, __FILE__ is different, so 
I guess __CONTEXT__ could also be.

--
   Simen