On 9/20/13 8:52 AM, Simen Kjaeraas wrote:
>> I see no way to extract the scaffolding into a library.
>
> Like this?
>
>
> import std.stdio;
>
> mixin template maybeStatic(bool isStatic, alias funDef, args...) {
>      static if (isStatic) {
>          static mixin funDef!args;
>      } else {
>          mixin funDef!args;
>      }
> }
>
> struct A
> {
>      enum hasState = false;
>      private mixin template funDef()
>      {
>          void fun(int x) { writeln(x); }
>      }
>      mixin maybeStatic!(!hasState, funDef);
> }
>
> void main()
> {
>      A a;
>      a.fun(42);
> }
>

This is nice. Works with shared, too.

Andrei

On Friday, 20 September 2013 at 15:20:36 UTC, Andrei Alexandrescu wrote:
> On 9/19/13 1:02 PM, Andrej Mitrovic wrote:
>> On 9/19/13, Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org> wrote:
>>> I'm not sure I understand how that would work.
>>
>> -----
>> module test;
> [snip]
>
> Thanks, that's the simplest and most effective. I reduced it to:
>
> struct A
> {
>     enum hasState = false;
>     private mixin template funDef()
>     {
>         void fun(int x) { writeln(x); }
>     }
>     static if (hasState)
>         mixin funDef!();
>     else
>         static mixin funDef!();
> }
>
> void main()
> {
>     A a;
>     a.fun(42);
> }
>
> I see no way to extract the scaffolding into a library.
>
>
> Andrei

You'll be very disapointed when some of your overloads will disapear.

On Thursday, 19 September 2013 at 17:10:43 UTC, Andrei Alexandrescu wrote:
> Consider a struct that may or may not have state depending on a type parameter:

I would like to note that this problem is a specific case of the general problem of changing a function's signature based on a compile-time value. The same problem exists with other attributes, and varying the presence of a template or function parameter. One example was that I wanted to define an overload set of function templates, where in some overloads, some parameters were function parameters, and in other overloads, the same parameters were template parameters (there was a significant optimization opportunity when the parameters were known at compile-time).