Dear developers and community,
I want to draw you attention to the topic which was already discussed here:
http://forum.dlang.org/thread/9to6n8$12d6$1@digitaldaemon.com
and here:
http://forum.dlang.org/thread/bl1n0e$1km5$1@digitaldaemon.com

My question is: was something similar already done? are there some plans to do that?

On Wednesday, 16 May 2012 at 04:22:18 UTC, Comrad wrote:
> Dear developers and community,
> I want to draw you attention to the topic which was already discussed here:
> http://forum.dlang.org/thread/9to6n8$12d6$1@digitaldaemon.com
> and here:
> http://forum.dlang.org/thread/bl1n0e$1km5$1@digitaldaemon.com
>
> My question is: was something similar already done? are there some plans to do that?

Dunno... but the way I'd use them would be more like:

enum AccessMask
{
	GENERIC_READ = 0x80000000,
	GENERIC_WRITE = 0x40000000,
	GENERIC_EXECUTE = 0x20000000,
	GENERIC_ALL = 0x10000000,
	//....
}

enum FileAccessMask : AccessMask
{
	FILE_READ_DATA = 0x0001,
	//...
}

On Wed, 16 May 2012 06:22:15 +0200, Comrad <comrad.karlovich@googlemail.com> wrote:

> Dear developers and community,
> I want to draw you attention to the topic which was already discussed here:
> http://forum.dlang.org/thread/9to6n8$12d6$1@digitaldaemon.com
> and here:
> http://forum.dlang.org/thread/bl1n0e$1km5$1@digitaldaemon.com
>
> My question is: was something similar already done? are there some plans to do that?

I have implemented this functionality in user code, with some caveats:

module enumMagic;

string EnumDefAsString(T)()
	if (is(T == enum))
{
	string result = "";
	foreach (e; __traits(allMembers, T)) {
		result ~= e ~ " = T." ~ e ~ ",";
	}
	return result;
}

template ExtendEnum(T, string s)
	if (is(T == enum) &&
		is(typeof({mixin("enum a{"~s~"}");})))
{
	mixin(
		"enum ExtendEnum {"
		~ EnumDefAsString!T()
		~ s
		~ "}");
}

unittest {
    enum Foo {
        a,
        b,
        c
    }
    alias ExtendEnum!( Foo, q{
        d,
        e
    }) Bar;

    Bar b;
    b = Bar.a; // Look ma, I stole this from Foo!
    b = Bar.d;
    assert( Bar.a == Foo.a ); // Can compare the two.
    //b = Foo.a; // But cannot assign from one to the other.
}

void main( ) {
}

A library implementation with the missing features is possible, but would use a
struct instead of an enum, an be a rather larger piece of code than this.

On Wednesday, 16 May 2012 at 05:49:01 UTC, Mehrdad wrote:
> On Wednesday, 16 May 2012 at 04:22:18 UTC, Comrad wrote:
>> Dear developers and community,
>> I want to draw you attention to the topic which was already discussed here:
>> http://forum.dlang.org/thread/9to6n8$12d6$1@digitaldaemon.com
>> and here:
>> http://forum.dlang.org/thread/bl1n0e$1km5$1@digitaldaemon.com
>>
>> My question is: was something similar already done? are there some plans to do that?
>
> Dunno... but the way I'd use them would be more like:
>
> enum AccessMask
> {
> 	GENERIC_READ = 0x80000000,
> 	GENERIC_WRITE = 0x40000000,
> 	GENERIC_EXECUTE = 0x20000000,
> 	GENERIC_ALL = 0x10000000,
> 	//....
> }
>
> enum FileAccessMask : AccessMask
> {
> 	FILE_READ_DATA = 0x0001,
> 	//...
> }

The inheritances notation implies that it's a subset and can be assigned to an instances of the base. This would not be true with enums.

FileAccessMask foo = FileAccessMask.FILE_READ_DATA;
AccessMask bar = foo; // Error

On Wednesday, 16 May 2012 at 05:54:45 UTC, Simen Kjaeraas wrote:
> On Wed, 16 May 2012 06:22:15 +0200, Comrad <comrad.karlovich@googlemail.com> wrote:
>
>> Dear developers and community,
>> I want to draw you attention to the topic which was already discussed here:
>> http://forum.dlang.org/thread/9to6n8$12d6$1@digitaldaemon.com
>> and here:
>> http://forum.dlang.org/thread/bl1n0e$1km5$1@digitaldaemon.com
>>
>> My question is: was something similar already done? are there some plans to do that?
>
> I have implemented this functionality in user code, with some caveats:
>
> module enumMagic;
>
> string EnumDefAsString(T)()
> 	if (is(T == enum))
> {
> 	string result = "";
> 	foreach (e; __traits(allMembers, T)) {
> 		result ~= e ~ " = T." ~ e ~ ",";
> 	}
> 	return result;
> }
>
> template ExtendEnum(T, string s)
> 	if (is(T == enum) &&
> 		is(typeof({mixin("enum a{"~s~"}");})))
> {
> 	mixin(
> 		"enum ExtendEnum {"
> 		~ EnumDefAsString!T()
> 		~ s
> 		~ "}");
> }
>
> unittest {
>     enum Foo {
>         a,
>         b,
>         c
>     }
>     alias ExtendEnum!( Foo, q{
>         d,
>         e
>     }) Bar;
>
>     Bar b;
>     b = Bar.a; // Look ma, I stole this from Foo!
>     b = Bar.d;
>     assert( Bar.a == Foo.a ); // Can compare the two.
>     //b = Foo.a; // But cannot assign from one to the other.
> }
>
> void main( ) {
> }
>
> A library implementation with the missing features is possible, but would use a
> struct instead of an enum, an be a rather larger piece of code than this.

This is not really useful, because one can't pass Foo into a function if it's declared to take Bar...

On Wednesday, 16 May 2012 at 06:24:54 UTC, Robert DaSilva wrote:
> The inheritances notation implies that it's a subset and can be assigned to an instances of the base. This would not be true with enums.
> FileAccessMask foo = FileAccessMask.FILE_READ_DATA;
> AccessMask bar = foo; // Error

Actually, that^ *should* work in my case; that was my point...

On Thursday, 17 May 2012 at 18:27:07 UTC, Mehrdad wrote:
> On Wednesday, 16 May 2012 at 06:24:54 UTC, Robert DaSilva wrote:
>> The inheritances notation implies that it's a subset and can be assigned to an instances of the base. This would not be true with enums.
>> FileAccessMask foo = FileAccessMask.FILE_READ_DATA;
>> AccessMask bar = foo; // Error
>
> Actually, that^ *should* work in my case; that was my point...

Wait, no, scratch that, I misread it; you're right.
It shouldn't work without a cast, but it should work with a cast.