d編譯時計數

​​原文​​

enum counter(size_t x = [__traits(allMembers, mixin(__MODULE__))].length)=x;
char[] member(ulong x)
{
    char[] buf = "void[0] _X0000000000000000;".dup;
    enum mapping = "0123456789abcdef";
    foreach_reverse(i; buf.length-17 .. buf.length-1)
    {
        buf[i] = mapping[x & 0xf];
        x >>= 4;
    }
    return buf;
}
mixin template increment()
{
    mixin(member(counter!()));
}

pragma(msg, counter!());
mixin increment;
pragma(msg, counter!());
mixin increment;
pragma(msg, counter!());      

enum gensym = q{"_gensym" ~ __traits(identifier, {})["__lambda".length .. $]};
//通過λ來求計數.

// 同一行,也工作.
pragma(msg, mixin(gensym)); pragma(msg, mixin(gensym));