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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
parent reply 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
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
parent reply 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
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