On 05/10/2013 02:32 PM, deadalnix wrote:
http://www.deadalnix.me/2013/05/10/type-safe-tagged-union-in-d-programming-language/
A trick that I used to use more and more, so I ended up creating a
generic solution and wrote an article about it.
I'd have implemented your TaggedUnion struct as follows. (I believe this
is equivalent to your implementation.)
struct TaggedUnion(T...){
private{
union{ T members; }
int tag;
static int indexOf(S)(){
foreach(i,t;T) static if(is(S==t)) return i;
return -1;
}
}
this(T)(T t) if(~indexOf!T){
members[indexOf!T]=t;
tag=indexOf!T;
}
auto ref apply(alias fun)(){
switch(tag){
foreach(i,_;T) case i: return fun(members[i]);
default: assert(0);
}
}
}
But note that this is as unsafe as the original implementation. You will
at least have to provide a postblit constructor and a destructor in
order to keep the promise of safety.
