Re: Delegate returning itself

[Jonathan Marler via Digitalmars-d-learn]

On Monday, 8 December 2014 at 14:08:33 UTC, Jonathan Marler wrote:
On Saturday, 6 December 2014 at 15:46:16 UTC, Adam D. Ruppe 
wrote:
The problem is the recursive *alias* rather than the delegate. 
Just don't use the alias name inside itself so like

alias MyDelegate = void delegate() delegate();

will work. The first void delegate() is the return value of 
the MyDelegate type.

Yes I tried that as well.  It still doesn't solve the issue.  
The delegate being returned doesn't return a delegate, it 
returns the "void" type.  You would need to write delegate() 
delegate() delegate() delegate() ...FOREVER.  I can't figure 
out a way to write this in the language even though the machine 
code it generates should be quite trivial.

I did some digging and realized that C/C++ have the same problem. 
 I found a nice post on it with 2 potential solutions 
(http://c-faq.com/decl/recurfuncp.html).  I liked the second 
solution so I wrote up an example in D.  If anyone has any other 
ideas or can think of a way to improve my example feel free to 
post and let me know, thanks.import std.stdio;

struct StateFunc
{
  StateFunc function() func;
}
StateFunc state1()
{
  writeln("state1");
  return StateFunc(&state2);
}
StateFunc state2()
{
  writeln("state2");
  return StateFunc(&state3);
}
StateFunc state3()
{
  writeln("state3");
  return StateFunc(null);
}
void main(string[] args)
{
  StateFunc state = StateFunc(&state1);

  while(state.func != null) {
    state = state.func();
  }
}