Template mixin enum stringof

Lemonfiend via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Wed Dec 10 06:32:12 PST 2014


On Wednesday, 10 December 2014 at 14:25:30 UTC, ketmar via 
Digitalmars-d-learn wrote:
> On Wed, 10 Dec 2014 13:58:20 +0000
> Lemonfiend via Digitalmars-d-learn 
> <digitalmars-d-learn at puremagic.com>
> wrote:
>
>> On Wednesday, 10 December 2014 at 12:57:16 UTC, ketmar via 
>> Digitalmars-d-learn wrote:
>> > On Wed, 10 Dec 2014 12:35:44 +0000
>> > Lemonfiend via Digitalmars-d-learn 
>> > <digitalmars-d-learn at puremagic.com>
>> > wrote:
>> >
>> >> On Wednesday, 10 December 2014 at 12:08:34 UTC, ketmar via 
>> >> Digitalmars-d-learn wrote:
>> >> > On Wed, 10 Dec 2014 11:52:11 +0000
>> >> > Lemonfiend via Digitalmars-d-learn 
>> >> > <digitalmars-d-learn at puremagic.com>
>> >> > wrote:
>> >> >
>> >> >> Consider the following:
>> >> >> 
>> >> >> ---
>> >> >> enum Foo { BAR, }
>> >> >> 
>> >> >> mixin template S(string s_)
>> >> >> {
>> >> >> 	enum s = s_;
>> >> >> }
>> >> >> 
>> >> >> void main()
>> >> >> {
>> >> >> 	mixin S!(Foo.BAR.stringof); // Error: identifier 
>> >> >> 'stringof' of 'Foo.BAR.stringof' is not defined
>> >> >> 
>> >> >> 	enum e = Foo.BAR.stringof;
>> >> >> 	mixin S!(e); // works fine
>> >> >> }
>> >> >> ---
>> >> >> 
>> >> >> Why doesn't the first work? And is there an alternative 
>> >> >> to the second version?
>> >> >
>> >> >   mixin S!((Foo.BAR).stringof);
>> >> >
>> >> > sorry, don't remember the parsing rule for this.
>> >> 
>> >> Wow, I didn't even consider that.. Thanks!
>> > also, you can use this:
>> >
>> >   import std.conv : to;
>> >   ...
>> >   mixin S!(to!string(Foo.BAR));
>> >
>> > people tend to forget that many `to!` variants are usable in 
>> > CTFE.
>> 
>> Seems like I'd want to move the converting-to-string 
>> functionality to within the template mixin then, something 
>> like:
>> 
>> ---
>> mixin template S(T, T t) if (is(T == enum))
>> {
>> 	//import std.traits;
>> 	//enum s = fullyQualifiedName!(t); // unfortunately this 
>> results in "t"
>> 
>> 	import std.conv: to;
>> 	enum s = to!string(t); // this works
>> }
>> 
>> mixin S!(Foo, Foo.BAR);
>> ---
>> 
>> But passing an enum as parameter seems to be somewhat 
>> annoying. If I leave off the first Foo, then it complains 
>> about no-matching template for int parameter.
>> !(Foo, Foo.BAR) seems kinda redundant..
> something like this?
>
>   mixin template S(alias fld) if (is(typeof(fld) == enum))
>   {
>     import std.conv : to;
>     enum s = to!string(fld); // "BAR"
>     // or this:
>     //import std.traits : fullyQualifiedName;
>     //enum s = to!string(fullyQualifiedName!(fld)); // 
> "test.Foo.BAR"
>   }
>
>   enum Foo { BAR, }
>
>   void main()
>   {
>     mixin S!(Foo.BAR);
>   }

Perfect, thanks.


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