Clay language

[Andrei Alexandrescu]

On 12/30/10 9:22 AM, Michel Fortin wrote:
> On 2010-12-30 10:00:05 -0500, "Steven Schveighoffer"
> <schveiguy at yahoo.com> said:
>
>> The thing I find ironic is that with the original operator overloading
>> scheme, the issue was that for types that define multiple operator
>> overloads in a similar fashion, forcing you to repeat boilerplate
>> code. The solution to it was a mixin similar to what you are
>> suggesting. Except now, even mundane and common operator overloads
>> require verbose template definitions (possibly with mixins), and it's
>> the uncommon case that benefits. So really, we haven't made any
>> progress (mixins are still required, except now they will be more
>> common). I think this is one area where D has gotten decidedly worse.
>> I mean, just look at the difference above between defining the opcat
>> operator in D1 and your mixin solution!
>
> I'm with you, I preferred the old design.

This is water under the bridge now, but I am definitely interested. What 
are the reasons for which you find the old design better?

>> As a compromise, can we work on a way to forward covariance, or to
>> have the compiler reevaluate the template in more derived types?
>
> I stubbled upon this yesterday:
>
> Template This Parameters
>
> TemplateThisParameters are used in member function templates to pick up
> the type of the this reference.
> import std.stdio;
>
> struct S
> {
> const void foo(this T)(int i)
> {
> writeln(typeid(T));
> }
> }
>
> <http://www.digitalmars.com/d/2.0/template.html>
>
> Looks like you could return the type of this this way...

typeof(this) works too.


Andrei