Bitfield-style enum to strings?

[Nick Sabalausky via Digitalmars-d-learn]

Minor fix to work right for "none" fields. Already worked fine on 
combination fields liek "all".

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enum Foo
{
     none = 0,
     optionA = 1<<0,
     optionB = 1<<1,
     optionC = 1<<2,
     optionD = 1<<3,
     all = optionA | optionB | optionC | optionD,
}

import std.traits : isIntegral;
auto bitFieldValues(T)(T value) if(is(T==enum) && isIntegral!T)
{
     // There's gotta be a better way to convert EnumMembers!T
     // to a range, right? But std.range.only() didn't work,
     // due to a template instantiation error.
     T[] members;
     foreach(m; EnumMembers!(T))
         members ~= m;

     return members
         .filter!(member => member==0? value==0 : (value&member)==member)
         .map!(member => to!string(member));
}

void main()
{
     import std.range : join;
     import std.stdio : writeln;

     Foo fooVar = Foo.optionB | Foo.optionD;

     // Output:
     // optionB | optionD
     // none
     // optionA | optionB | optionC | optionD | all

     writeln(bitFieldValues(Foo.optionB | Foo.optionD).join(" | "));
     writeln(bitFieldValues(Foo.none).join(" | "));
     writeln(bitFieldValues(Foo.all).join(" | "));
}
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