On Monday, 8 December 2014 at 14:38:37 UTC, Marc Schütz wrote:
On Monday, 8 December 2014 at 14:31:53 UTC, Jonathan Marler
wrote:
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();
}
}
Nice! Using alias this, you can call the struct directly:
struct StateFunc
{
StateFunc function() func;
alias func this;
}
state = state();
Now there still needs to be a way to just `return &state2;`
instead of `return StateFunc(&state2);`...
Nice addition! I can't think of a way to solve the implicit
conversion from function pointer to struct, but not a big deal.
I'm mostly glad I found a way to do this with no overhead and no
awkward casting. Adding the implicit conversion would be icing
on the cake.
