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digitalmars.D.learn - Internal delegate and Stack Overflow

reply tsalm <tsalm free.fr> writes:
Hello,

I would do something like this, but this return me an execution error :
object.Exception: Stack Overflow

// --------CODE--------
class A
{
  void delegate() dg;

  void doIt()
  {
   dg();
  }
}

class B
{
  A a;

  this()
  {
   a = new A;
   a.dg = { doSomething(); };
  }

  void doSomething() { }
}

void main()
{
  auto b = new B;
  b.a.doIt();
}
// ------END CODE------

Is this a bug or have I do something wrong ?
Thanks in advance for your help,
TSalm
Nov 28 2008
next sibling parent BCS <ao pathlink.com> writes:
Reply to TSalm,

 Hello,
 
 I would do something like this, but this return me an execution error
 : object.Exception: Stack Overflow
 
 // --------CODE--------
 class A
 {
 void delegate() dg;
 void doIt()
 {
 dg();
 }
 }
 class B
 {
 A a;
 this()
 {
 a = new A;
 a.dg = { doSomething(); };
 }
 void doSomething() { }
 }
 void main()
 {
 auto b = new B;
 b.a.doIt();
 }
 // ------END CODE------
 
 Is this a bug or have I do something wrong ?
 Thanks in advance for your help,
 TSalm

If this is d1.0 the error is that you are allowing an anon delegate to escape the enclosing function. a.dg = &this.doSomething; // this would be ok if that helps. if it is 2.0, I think this is correct.
Nov 28 2008
prev sibling parent reply tsalm <tsalm free.fr> writes:
Le Sat, 29 Nov 2008 01:08:28 +0100, BCS <ao pathlink.com> a écrit:

 Reply to TSalm,

 Hello,
  I would do something like this, but this return me an execution error
 : object.Exception: Stack Overflow
  // --------CODE--------
 class A
 {
 void delegate() dg;
 void doIt()
 {
 dg();
 }
 }
 class B
 {
 A a;
 this()
 {
 a = new A;
 a.dg = { doSomething(); };
 }
 void doSomething() { }
 }
 void main()
 {
 auto b = new B;
 b.a.doIt();
 }
 // ------END CODE------
  Is this a bug or have I do something wrong ?
 Thanks in advance for your help,
 TSalm

If this is d1.0 the error is that you are allowing an anon delegate to escape the enclosing function.

Yes, it's on D1.036.
 a.dg = &this.doSomething;  // this would be ok if that helps.


  if it is 2.0, I think this is correct.

Yes, you are right. But this is an example code. The "true" code uses delegates with argument which differs from called functions, so I can't point delegate directly to them. And this anonymous function's way is really fastest to code... I must waiting for a D2 stable version ;-) Thanks
Nov 28 2008
next sibling parent BCS <ao pathlink.com> writes:
Reply to TSalm,

 Yes, you are right.
 But this is an example code. The "true" code uses delegates with
 argument
 which differs from called functions, so I can't point delegate
 directly to
 them.
 And this anonymous function's way is really fastest to code... I must
 waiting for a D2 stable version ;-)
 Thanks
 

you can store off the values you need like this: struct C(R, A...) { A args; R function(A) dg; static R delegate() opCall(R function(A) dg, A a) { C!(R, A) ret; ret.dg=dg; foreach(int i,_;A) ret.args[i] = a[i]; return &ret.fn; } R fn() { return dg(args); } } // test it import std.stdio; int delegate() dg(int i) { return C!(int,int)(function int(int j){return j;}, i); // <--- used here } void main() { auto d = dg(5); writef("%s\n", d()); }
Nov 28 2008
prev sibling parent tsalm <tsalm free.fr> writes:
Le Sat, 29 Nov 2008 01:49:20 +0100, BCS <ao pathlink.com> a écrit:

 struct C(R, A...)
 {
   A args;
   R function(A) dg;
   static R delegate() opCall(R function(A) dg, A a)
   {
      C!(R, A) ret;
      ret.dg=dg;
      foreach(int i,_;A)
         ret.args[i] = a[i];
      return &ret.fn;
   }
   R fn() { return dg(args); }
 }
   // test it
  import std.stdio;
  int delegate() dg(int i)
 {
   return C!(int,int)(function int(int j){return j;}, i);   // <--- used  
 here
 }
  void main()
 {
   auto d = dg(5);
   writef("%s\n", d());
 }

Interesting code. Thanks!
Nov 29 2008