Implicit conversions through purity

[Steve Teale]

On Tuesday, 15 April 2014 at 18:02:00 UTC, bearophile wrote:
> Steve Teale:
>
>> Since this is D-Learn, I can be indignant, and say that D 
>> needs to get its act together, and have a clean definition of 
>> 'pure'. What you describe is not only undocumented, but also 
>> far too complicated - pure weak nothrow dontpiss kissmyass 
>> @never, and so on if the direction continues.
>
> There is a nice article on D purity that I suggest you to read. 
> Unfortunately I don't remember the link.
>
> To design a system language as complex as C++/D you need lot of 
> mathematics and theory. Andrei is good in computer science 
> theory and in complex programming too, but Walter is less 
> mathematically-minded and this could be visible in the design 
> of some parts of D. Anyway, everyone is doing their best, 
> Walter is very good and he has all my respect. And in a 
> real-world system language a clean definition of pure (like the 
> original pure implementation of D) is not very useful. The 
> current definition of pure of D is good enough and it's a part 
> very near to be completely implemented (unlike many other parts 
> of D like synchronized, scope, SIMD, vector operations, 
> operator overloading, dynamic libraries, GC, and more). So 
> please don't be too much indignant, we don't have the research 
> laboratories of Microsoft :-)
>
>
>> Nontheless, thank you for your assiduous efforets to make D 
>> internally consistent.
>
> In the end I am not doing much. At best I can only hope to spot 
> some sharp corners of the language, and ask for them to be 
> smoothed. But it's very hard to make progress. And lately 
> Andrei (perhaps rightfully) has raised the bar regarding the 
> acceptable breaking changes. And people like Kenji have a mind 
> better than mine (able to think about tens of corner cases, 
> able to keep in mind many complex interactions, etc) even when 
> they are sleeping :-)
>
> Bye,
> bearophile

Like I said, I allowed myself the luxury of being indignant 
because we were hidden away on D Learn. I have total respect for 
Walter. For one thing he is a self-taught programmer like me, 
though much more advanced, and I've known him on and off since 
the Zortech days in 1988. I don't much about Andrei and Kenji, 
except that they are out of my league.

I guess that rather than complain that the compiler does not 
appear to conform to the definition, I should help by trying to 
improve the documentation.

Anyway my view on the original subject is that the implicit 
conversion should be allowed for the out case, but not the ref.

Steve