I would like to use enums with elements that are either a struct type
or a class type.  However, using struct type seems inefficient because
structs are pass by value.  Apparently you can't pass an enum as a reference,
so eliminating the pass by value for enums does not seem possible. I have read
on this forum that someday enums may be able to be made with class elements.
Can enums be made of classes yet, or is there a way to make the enum based
on structs more efficient?

Thanks,
Eric

On Tuesday, 18 March 2014 at 20:40:36 UTC, Eric wrote:
> However, using struct type seems inefficient because structs are pass by value.

That's not necessarily a problem, especially if the struct is small, passing by value is faster than by reference.

What is your code trying to do?

> Can enums be made of classes yet, or is there a way to make the enum based on structs more efficient?

enums can't be classes, but you could make a static class constructed at compile time and pass that reference around.

On Tuesday, 18 March 2014 at 20:56:45 UTC, Adam D. Ruppe wrote:
> On Tuesday, 18 March 2014 at 20:40:36 UTC, Eric wrote:
>> However, using struct type seems inefficient because structs are pass by value.
>
> That's not necessarily a problem, especially if the struct is small, passing by value is faster than by reference.
>
> What is your code trying to do?
>
>> Can enums be made of classes yet, or is there a way to make the enum based on structs more efficient?
>
> enums can't be classes, but you could make a static class constructed at compile time and pass that reference around.

Hmmm... What do you think the crossover point is for performance
of value vs reference? ie, how large can a struct be before
passing it around gets slower than passing around a reference?
(I would guess 8 bytes, but that's just a guess).

I am trying to emulate the java enum type. Enums are great for data
safety in API design.  The more immutable data they contain the
better in my opinion - hence my concern about performance.

-Eric

On 03/18/2014 01:40 PM, Eric wrote:

> Apparently you can't pass an enum as a reference,

It is possible as seen in the following code.

> I have read on this forum that someday enums may be able to be
> made with class elements.

Someday is today! :)

class C
{
    int i;

    this(int i)
    {
        this.i = i;
    }
}

enum E : C
{
    one = new C(1),
    two = new C(2)
}

void foo(ref E e)
{
    e = E.two;
}

void main()
{
    auto e = E.one;
    foo(e);
    assert(e == E.two);
}

Ali