is it possible to create a delegate that takes an optional number of parameters and/or return type?

T delegate(S...)(S) special_delegate;

I guess this is impossible?

On Sunday, 2 April 2017 at 19:24:14 UTC, Inquie wrote:
> is it possible to create a delegate that takes an optional number of parameters and/or return type?
>
> T delegate(S...)(S) special_delegate;
>
> I guess this is impossible?

alias Dg(Return, Params...) = Return delegate(Params);

Dg!(int,float, string) myDg;

On Sunday, 2 April 2017 at 20:02:56 UTC, Basile B. wrote:
> On Sunday, 2 April 2017 at 19:24:14 UTC, Inquie wrote:
>> is it possible to create a delegate that takes an optional number of parameters and/or return type?
>>
>> T delegate(S...)(S) special_delegate;
>>
>> I guess this is impossible?
>
> alias Dg(Return, Params...) = Return delegate(Params);
>
> Dg!(int,float, string) myDg;

What I mean is that I want to be able to overload delegates like one can do with normal members.

On Sunday, 2 April 2017 at 20:48:09 UTC, Inquie wrote:
> On Sunday, 2 April 2017 at 20:02:56 UTC, Basile B. wrote:
>> On Sunday, 2 April 2017 at 19:24:14 UTC, Inquie wrote:
>>> is it possible to create a delegate that takes an optional number of parameters and/or return type?
>>>
>>> T delegate(S...)(S) special_delegate;
>>>
>>> I guess this is impossible?
>>
>> alias Dg(Return, Params...) = Return delegate(Params);
>>
>> Dg!(int,float, string) myDg;
>
> What I mean is that I want to be able to overload delegates like one can do with normal members.

Show a usage, someone certainly propose a pattern that does the job.

On Sunday, 2 April 2017 at 21:47:55 UTC, Basile B. wrote:
> On Sunday, 2 April 2017 at 20:48:09 UTC, Inquie wrote:
>> On Sunday, 2 April 2017 at 20:02:56 UTC, Basile B. wrote:
>>> On Sunday, 2 April 2017 at 19:24:14 UTC, Inquie wrote:
>>>> is it possible to create a delegate that takes an optional number of parameters and/or return type?
>>>>
>>>> T delegate(S...)(S) special_delegate;
>>>>
>>>> I guess this is impossible?
>>>
>>> alias Dg(Return, Params...) = Return delegate(Params);
>>>
>>> Dg!(int,float, string) myDg;
>>
>> What I mean is that I want to be able to overload delegates like one can do with normal members.
>
> Show a usage, someone certainly propose a pattern that does the job.

int delegate() f;
void delegate(int) f;

These are effectively overload methods, but my guess is that D won't support it like overloads.
e.g.,

int f();
void f(int);

On 04/02/2017 03:24 PM, Inquie wrote:

>> Show a usage, someone certainly propose a pattern that does the job.
>
> int delegate() f;
> void delegate(int) f;

That won't work because both of those are variables and variables don't have overloading.

> These are effectively overload methods, but my guess is that D won't
> support it like overloads.
> e.g.,
>
> int f();
> void f(int);

Yep, both 'f' are functions there.

I'm having difficulty understanding your actual need as well. :/ A guess: It is possible to determine delegate parameter list at compile time like std.concurrency.receive does.

Ali

On Monday, 3 April 2017 at 03:08:22 UTC, Ali Çehreli wrote:
> On 04/02/2017 03:24 PM, Inquie wrote:
>
> >> Show a usage, someone certainly propose a pattern that does
> the job.
> >
> > int delegate() f;
> > void delegate(int) f;
>
> That won't work because both of those are variables and variables don't have overloading.
>
> > These are effectively overload methods, but my guess is that
> D won't
> > support it like overloads.
> > e.g.,
> >
> > int f();
> > void f(int);
>
> Yep, both 'f' are functions there.
>
> I'm having difficulty understanding your actual need as well. :/ A guess: It is possible to determine delegate parameter list at compile time like std.concurrency.receive does.
>
> Ali

Yes, but they are really not any different. They only look different. A field can be a function just like a method because they look exactly the same except on is in a vtable and the other is in the fields memory. But both point functions.

The only difference is that we can't write to the vtable to overwrite a value easily but we can to a delegate(no hackery).

So, it would be nice to be able to overload them. Effectively we can extend the vtable out in to the fields. (it would require a bit of work to make it work identical to a class, but it could, the outside world would know no difference).

If one wants: It essentially allows for methods to be modifiable at run time(something that classes can't do without unsafely hacking the vtable) and that is exactly why I have used it, but overloading causes a problem because only the name collides yet it works with the methods case but not the field delegates(a field delegate is essentially a method, is the point(for functional usage)).

On Monday, 3 April 2017 at 05:00:15 UTC, Inquie wrote:
> Yes, but they are really not any different. They only look different. A field can be a function just like a method because they look exactly the same except on is in a vtable and the other is in the fields memory. But both point functions.

It should be possible to create a wrapper struct around your 'overloads' with an opDispatch which selects the right delegate.