Re: inout, delegates, and visitor functions.

[Sebastien Alaiwan via Digitalmars-d-learn]

Hi ponce,
Thanks for your suggestion.
I think I may have found the beginning of a solution:
class E
{
  import std.traits;

  void apply(this F, U)(void delegate(U e) f)
    if(is(Unqual!U == E))
  {
    f(this);
  }

  int val;
}

int main()
{
  void setToZero(E e)
  {
    e.val = 0;
  }

  void printValue(const E e)
  {
    import std.stdio;
    writefln("Value: %s", e.val);
  }

  E obj;

  obj.apply(&setToZero);
  obj.apply(&printValue);

  const(E) objConst;
  //objConst.apply(&setToZero);
  objConst.apply(&printValue);

  return 0;
}


Basically, I avoid the 'const'/'inout' attribute of the 'apply' 
function by using a 'this F' template argument.
Then, I need a second template argument 'U', otherwise, I can't 
call 'printValue' on a non-const E instance.