• Max Samukha <samukha voliacable.com> Mar 31 2007
• "Jarrett Billingsley" <kb3ctd2 yahoo.com> Mar 31 2007
• Max Samukha <samukha voliacable.com> Mar 31 2007
• Deewiant <deewiant.doesnotlike.spam gmail.com> Mar 31 2007
• Chris Nicholson-Sauls <ibisbasenji gmail.com> Mar 30 2007
• Kirk McDonald <kirklin.mcdonald gmail.com> Mar 31 2007

Max Samukha <samukha voliacable.com> writes:

What is the meaning of the value returned by the address operator
applied to an instance member function as if that function were
static?

class Foo
{
	void bar()
	{
	}		
}

void main()
{
	writefln(&Foo.bar);		
}

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Max Samukha" <samukha voliacable.com> wrote in message 
news:11js039sich4vjo364at18so5m625bdvc8 4ax.com...
 What is the meaning of the value returned by the address operator
 applied to an instance member function as if that function were
 static?

 class Foo
 {
 void bar()
 {
 }
 }

 void main()
 {
 writefln(&Foo.bar);
 }


It's a function pointer to that method.  It's actually useful -- you can 
simulate pointer-to-members using this and delegates:

class A
{
    int mX;

    this(int x)
    {
        mX = x;
    }

    void foo(int y)
    {
        writefln(mX, ", ", y);
    }
}

void main()
{
    scope a = new A(5);
    a.foo(4);

    void delegate(int) dg;
    dg.funcptr = &A.foo; // <<- dah
    dg.ptr = cast(void*)a;
    dg(8);
}

Max Samukha <samukha voliacable.com> writes:

On Sat, 31 Mar 2007 11:43:47 -0400, "Jarrett Billingsley"
<kb3ctd2 yahoo.com> wrote:

"Max Samukha" <samukha voliacable.com> wrote in message 
news:11js039sich4vjo364at18so5m625bdvc8 4ax.com...
 What is the meaning of the value returned by the address operator
 applied to an instance member function as if that function were
 static?

 class Foo
 {
 void bar()
 {
 }
 }

 void main()
 {
 writefln(&Foo.bar);
 }


It's a function pointer to that method.  It's actually useful -- you can 
simulate pointer-to-members using this and delegates:

class A
{
    int mX;

    this(int x)
    {
        mX = x;
    }

    void foo(int y)
    {
        writefln(mX, ", ", y);
    }
}

void main()
{
    scope a = new A(5);
    a.foo(4);

    void delegate(int) dg;
    dg.funcptr = &A.foo; // <<- dah
    dg.ptr = cast(void*)a;
    dg(8);
}

Deewiant <deewiant.doesnotlike.spam gmail.com> writes:

Jarrett Billingsley wrote:
 It's a function pointer to that method.  It's actually useful -- you can
 simulate pointer-to-members using this and delegates:
 
 class A
 {
     int mX;
 
     this(int x)
     {
         mX = x;
     }
 
     void foo(int y)
     {
         writefln(mX, ", ", y);
     }
 }
 
 void main()
 {
     scope a = new A(5);
     a.foo(4);
 
     void delegate(int) dg;
     dg.funcptr = &A.foo; // <<- dah
     dg.ptr = cast(void*)a;


Are there other uses? Doesn't the above essentially boil down to just:

auto dg = &a.foo;

     dg(8);
 }
 


-- 
Remove ".doesnotlike.spam" from the mail address.

Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:

Deewiant wrote:
 Jarrett Billingsley wrote:
  > It's a function pointer to that method.  It's actually useful -- you can
 simulate pointer-to-members using this and delegates:

 class A
 {
     int mX;

     this(int x)
     {
         mX = x;
     }

     void foo(int y)
     {
         writefln(mX, ", ", y);
     }
 }

 void main()
 {
     scope a = new A(5);
     a.foo(4);

     void delegate(int) dg;
     dg.funcptr = &A.foo; // <<- dah
     dg.ptr = cast(void*)a;


 Are there other uses? Doesn't the above essentially boil down to just:
 
 auto dg = &a.foo;
 


It does, except that you could later set dg.ptr to a /different/ instance.  Its
utility is 
in late binding to instances selected by some arbitrary (and possibly external)
means. 
I'd like to see if it plays well with inheritance, though.

-- Chris Nicholson-Sauls

Kirk McDonald <kirklin.mcdonald gmail.com> writes:

Chris Nicholson-Sauls wrote:
 Deewiant wrote:
 
 Jarrett Billingsley wrote:
  > It's a function pointer to that method.  It's actually useful -- 
 you can

 simulate pointer-to-members using this and delegates:

 class A
 {
     int mX;

     this(int x)
     {
         mX = x;
     }

     void foo(int y)
     {
         writefln(mX, ", ", y);
     }
 }

 void main()
 {
     scope a = new A(5);
     a.foo(4);

     void delegate(int) dg;
     dg.funcptr = &A.foo; // <<- dah
     dg.ptr = cast(void*)a;



 Are there other uses? Doesn't the above essentially boil down to just:

 auto dg = &a.foo;


 It does, except that you could later set dg.ptr to a /different/ 
 instance.  Its utility is in late binding to instances selected by some 
 arbitrary (and possibly external) means. I'd like to see if it plays 
 well with inheritance, though.
 
 -- Chris Nicholson-Sauls


It doesn't, really.

class Base {
     void foo() { writefln("Base"); }
}

class Derived : Base {
     void foo() { writefln("Derived"); }
}

void main() {
     void delegate() dg;
     dg.funcptr = &Base.foo;
     dg.ptr = new Derived;
     dg(); // will print "Base"
}

However, this is precisely the behavior I would expect, and in fact Pyd 
relies on it.

-- 
Kirk McDonald
http://kirkmcdonald.blogspot.com
Pyd: Connecting D and Python
http://pyd.dsource.org