Re: an enum inside another enum

[Simen Kjaeraas]

On Thu, 26 Jul 2012 13:40:06 +0200, maarten van damme  
<maartenvd1...@gmail.com> wrote:

enum first : string{
 a="a",
 b="b"
}
enum second : string{
 a=first.a,
 b=first.b,
 c="c"
}

Is there a way to make this cleaner?

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
        ~ "}");
}

enum bar
{
        a = 1,
        b = 7,
        c = 19
}

import std.typetuple;

void main() {
//-----------------------
    alias ExtendEnum!(bar, q{ // Usage example here.
        d = 25
    }) bar2;
//-----------------------
    foreach (i, e; __traits(allMembers, bar2)) {
        static assert( e == TypeTuple!("a", "b", "c", "d")[i] );
    }
    assert( bar2.a == bar.a );
    assert( bar2.b == bar.b );
    assert( bar2.c == bar.c );
    assert( bar2.d == 25 );
    static assert(!is(typeof( ExtendEnum!(int, "a"))));
    static assert(!is(typeof( ExtendEnum!(bar, "25"))));
}

--
Simen