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September 13, 2020 Get enum value name as string at compile time? | ||||
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Consider the enum: enum Foo { a, b } Foo.a.stringof => "a" enum x = Foo.a; x.stringof => "cast(Foo)0" Is there another way I can take an enum value that's known at compile time (but not the actual identifier), and get the name of it? I know I can use a switch, or to!string. But I was hoping this was easy for the compiler to figure out some way without involving CTFE. -Steve |
September 14, 2020 Re: Get enum value name as string at compile time? | ||||
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Posted in reply to Steven Schveighoffer | On Monday, 14 September 2020 at 03:48:51 UTC, Steven Schveighoffer wrote:
> Consider the enum:
>
> enum Foo { a, b }
>
> Foo.a.stringof => "a"
> enum x = Foo.a;
> x.stringof => "cast(Foo)0"
>
> Is there another way I can take an enum value that's known at compile time (but not the actual identifier), and get the name of it? I know I can use a switch, or to!string. But I was hoping this was easy for the compiler to figure out some way without involving CTFE.
It is a bit weird that x.stringof doesn't simply return the name like Foo.a.stringof does. Anyways, this works:
template enumName(alias a) {
import std.meta : staticIndexOf, staticMap;
alias T = typeof(a);
enum getValue(string name) = __traits(getMember, T, name);
alias enumValues = staticMap!(getValue, __traits(allMembers, T));
enum enumName = __traits(allMembers, T)[staticIndexOf!(a, enumValues)];
}
enum Foo { a = 2, b = 19 }
enum x = Foo.a;
pragma(msg, enumName!x); // "a"
--
Simen
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September 14, 2020 Re: Get enum value name as string at compile time? | ||||
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Posted in reply to Simen Kjærås | On 9/14/20 2:25 AM, Simen Kjærås wrote:
> On Monday, 14 September 2020 at 03:48:51 UTC, Steven Schveighoffer wrote:
>> Consider the enum:
>>
>> enum Foo { a, b }
>>
>> Foo.a.stringof => "a"
>> enum x = Foo.a;
>> x.stringof => "cast(Foo)0"
>>
>> Is there another way I can take an enum value that's known at compile time (but not the actual identifier), and get the name of it? I know I can use a switch, or to!string. But I was hoping this was easy for the compiler to figure out some way without involving CTFE.
>
> It is a bit weird that x.stringof doesn't simply return the name like Foo.a.stringof does. Anyways, this works:
>
> template enumName(alias a) {
> import std.meta : staticIndexOf, staticMap;
>
> alias T = typeof(a);
> enum getValue(string name) = __traits(getMember, T, name);
> alias enumValues = staticMap!(getValue, __traits(allMembers, T));
>
> enum enumName = __traits(allMembers, T)[staticIndexOf!(a, enumValues)];
> }
>
> enum Foo { a = 2, b = 19 }
>
> enum x = Foo.a;
> pragma(msg, enumName!x); // "a"
>
Thanks.
I never considered doing something like that. Not sure I like that better than the CTFE version. I just punted and used to!string in my code anyway.
A CTFE linear search in a compile-time array probably wouldn't be too bad, especially when the list of elements is not long.
Again, we could use that ... DIP to make things a lot less complex.
-Steve
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