How to define variadic delegate with a ref/out argument?

[pham]

On Friday, 17 November 2017 at 06:21:50 UTC, Jerry A. wrote:
> On Friday, 17 November 2017 at 05:08:23 UTC, pham wrote:
>> struct DelegateList(Args...)
>> {
>> public:
>>     alias DelegateHandler = void delegate(Args args) nothrow;
>>
>>     DelegateHandler[] items;
>>
>>     void opCall(Args args) nothrow
>>     {
>>         foreach (i; items)
>>             i(args);
>>     }
>> }
>>
>> DelegateList!(string, int) list; // Compile OK so far
>> DelegateList!(string, int*) list2; // Compile OK so far
>> DelegateList!(string, ref int) list3; // Compile error -> How 
>> to make it work?
>>
>> Thanks
>> Pham
>
> The only way I know of is using  a template which behaves like 
> a reference.
> Which can be done with nullableRef I suppose. Haven't actually 
> tried it.
>
> import std.typecons : NullableRef, nullableRef;
>
> DelegateList!(NullableRef!int)(nullableRef(some_int));

nullableRef is same as passing pointer. Using "ref" is stronger 
guarantee that the var is never be passed as null.

variadic parameter passed by "ref" should be supported

Thanks.
Pham