How do I nullify a delegate in an easy way?

I have an array of delegates and want to have
the possibility to remove some of them.

dg = null;
don't work:
cannot implicitly convert void* to void delegate(Foo)

I can take the address of a dummy static function,
but that seems silly. I guess it will work if I assign
an uninitialized delegate to it, but I really want to
use null.

Lars Ivar Igesund

Does a cast (from 0 or null) not work?

"Lars Ivar Igesund" <larsivi@stud.ntnu.no> wrote in message news:bkidhp$2lpr$1@digitaldaemon.com...
> How do I nullify a delegate in an easy way?
>
> I have an array of delegates and want to have
> the possibility to remove some of them.
>
> dg = null;
> don't work:
> cannot implicitly convert void* to void delegate(Foo)
>
> I can take the address of a dummy static function,
> but that seems silly. I guess it will work if I assign
> an uninitialized delegate to it, but I really want to
> use null.
>
> Lars Ivar Igesund
>
>

> How do I nullify a delegate in an easy way?

This should do it:

delete dg;

"Matthew Wilson" <matthew@stlsoft.org> wrote in message news:bkie1g$2me6$1@digitaldaemon.com...
> Does a cast (from 0 or null) not work?
>

Nope;

e2ir: cannot cast from int to void delegate(Foo)
e2ir: cannot cast from void* to void delegate(Foo)

I guess
delete dg;
might work, but it feels wrong as I don't
new
the delegate.

Another thing; how do I check if the delegate is null,
zero, empty or whatever?
Hmm, seems like !dg might work.

Lars Ivar Igesund

Julio César Carrascal Urquijo wrote:
>>How do I nullify a delegate in an easy way?
> 
> 
> This should do it:
> 
> delete dg;
> 
> 

I would check what you post! that will cause a seg fault, delete is for removing items from a hashtable/assoc array.

I tried ...
import c.stdio;
alias int delegate( int ) iid;
class foo {
	int bar(int a){ return a;}
}

int evoke( iid func ) {
	if ( func ) {
		return func( 3 );
	}
	return 0;
}

void nulldel( out iid ignore ) {
}

int main( char[][] args ) {
	iid fb;
	printf( "delegate = null (0)\n" );
	printf( "delegate != null (3)\n" );
	printf( "fb clr %d\n", evoke( fb ) );
	fb = &((new foo()).bar);
	printf( "fb set %d\n", evoke( fb ) );
	nulldel( fb );
	printf( "fb clr %d\n", evoke( fb ) );
	return evoke( fb );
}

---------------------
but has no effect!! (Walker, I assume this it a bug out should init to null/0)
-------------------
however ... this workaround works.
import c.stdio;
alias int delegate( int ) iid;
class foo {
	int bar(int a){ return a;}
}

int evoke( iid func ) {
	if ( func ) {
		return func( 3 );
	}
	return 0;
}

void nulldel( out iid ignore ) {
	iid fake;
	ignore = fake;
}

int main( char[][] args ) {
	iid fb;
	printf( "delegate = null (0)\n" );
	printf( "delegate != null (3)\n" );
	printf( "fb clr %d\n", evoke( fb ) );
	fb = &((new foo()).bar);
	printf( "fb set %d\n", evoke( fb ) );
	nulldel( fb );
	printf( "fb clr %d\n", evoke( fb ) );
	return evoke( fb );
}

I did tried that before posting using DMD 0.73 on windows. I wrote this small program:

void main()
{
 Test t = new Test();
 void delegate(char[]) printer = &t.print;

 printer("Hello, world!\n");
 printf("printer = %p\n", printer);

 delete printer;
 printf("printer = %p\n", printer);
}


class Test
{
 void print(char[] message)
 {
  printf(message);
 }
}

That works just fine and writes:

Hello, world!
printer = 00690FD0
printer = 00000000

With no segmentation fault.


> I would check what you post! that will cause a seg fault, delete is for removing items from a hashtable/assoc array.

Delete is also used to delete pointers/references wich is what I did (remove a pointer to a member function).

Julio César Carrascal Urquijo wrote:
> I did tried that before posting using DMD 0.73 on windows. I wrote this
> small program:
> 
> void main()
> {
>  Test t = new Test();
>  void delegate(char[]) printer = &t.print;
> 
>  printer("Hello, world!\n");
>  printf("printer = %p\n", printer);
> 
>  delete printer;
>  printf("printer = %p\n", printer);
> }
> 
> 
> class Test
> {
>  void print(char[] message)
>  {
>   printf(message);
>  }
> }
> 
> That works just fine and writes:
> 
> Hello, world!
> printer = 00690FD0
> printer = 00000000
> 
> With no segmentation fault.
> 
> 
> 
>>I would check what you post! that will cause a seg fault, delete is for
>>removing items from a hashtable/assoc array.
> 
> 
> Delete is also used to delete pointers/references wich is what I did (remove
> a pointer to a member function).
> 

but it does not do as you expect ....

import c.stdio;

class Test {
	int b;
	this() {b = 100;}
	int func(int a) {
	  printf( "test[%d]::func(%d)\n", b, a );
	  return a+b;
	}
}

alias int delegate(int) memfunc;

int main( char[][] args )
{
	int a;
	memfunc printer;
	
	if ( printer ) {
		printf("b4: printer is not null\n" );
	} else {
		printf("b4: printer is null\n" );
	}
	
	printer = &((new Test()).func);

	a = printer( 22 );
	if ( printer ) {
		printf("set: printer is not null\n" );
	} else {
		printf("set: printer is null\n" );
	}

	delete printer;
	
	if ( printer ) {
		printf("post delete: printer is not null\n" );
	} else {
		printf("post delete: printer is null\n" );
	}
	
	return 0;
}

outputs .... (linux dmd)
> b4: printer is null
> test[100]::func(22)
> set: printer is not null
> post delete: printer is not null

(I changed the delegate to int(int) 'cos the delete seggy'd when I first  tried it, can't get it do do that again, forgot what code I actually wrote).

"Lars Ivar Igesund" <larsivi@stud.ntnu.no> wrote in message news:bkidhp$2lpr$1@digitaldaemon.com...
> How do I nullify a delegate in an easy way?
>
> I have an array of delegates and want to have
> the possibility to remove some of them.
>
> dg = null;
> don't work:
> cannot implicitly convert void* to void delegate(Foo)

That should work. I'll fix it. -Walter

Lars Ivar Igesund:
> How do I nullify a delegate in an easy way?
>
> I have an array of delegates and want to have
> the possibility to remove some of them.
>
> dg = null;
> don't work:
> cannot implicitly convert void* to void delegate(Foo)

You can use "dg = dg.init" until Walter fix the bug.