• Carlos Santander B. (36/36) Aug 23 2003 This code:
• Helmut Leitner (12/30) Aug 24 2003 I think allowing this would at least also require a way to block methods...
• Mike Wynn (38/65) Aug 24 2003 I believe that walter has added `alias A.a a;` to solve this,

"Carlos Santander B." <carlos8294 msn.com> writes:

This code:

class A { void a(float b) { printf("%f\n",b); } }
class B:A { void a(int b) { printf("%d\n",b); } }
void main() {
    B b=new B;
    b.a(3);
    b.a(4.5);
}

Outputs
3
4

To print correctly 4.5 I need to do b.A.a(4.5), which I personally find
unatractive. So why, just like C++, doesn't D support polymorphism into
derived classes?

Hey, but at least C++ lets us bring the methods from the base class, while D
doesn't.

-------------------------
Carlos Santander
This code:

class A { void a(float b) { printf("%f\n",b); } }
class B:A { void a(int b) { printf("%d\n",b); } }
void main() {
    B b=new B;
    b.a(3);
    b.a(4.5);
}

Outputs
3
4

To print correctly 4.5 I need to do b.A.a(4.5), which I personally find
unatractive. So why, just like C++, doesn't D support polymorphism into
derived classes?

Hey, but at least C++ lets us bring the methods from the base class, while D
doesn't.

-------------------------
Carlos Santander

Helmut Leitner <helmut.leitner chello.at> writes:

"Carlos Santander B." wrote:
 
 This code:
 
 class A { void a(float b) { printf("%f\n",b); } }
 class B:A { void a(int b) { printf("%d\n",b); } }
 void main() {
     B b=new B;
     b.a(3);
     b.a(4.5);
 }
 
 Outputs
 3
 4
 
 To print correctly 4.5 I need to do b.A.a(4.5), which I personally find
 unatractive. So why, just like C++, doesn't D support polymorphism into
 derived classes?

I think allowing this would at least also require a way to block methods 
from parent classes. 

On the other hand I think you could write

 class B:A { 
   void a(int b) { printf("%d\n",b); } 
   void a(float b) { super.a(b); } 
 }

easily. 

--
Helmut Leitner    leitner hls.via.at   
Graz, Austria   www.hls-software.com

"Mike Wynn" <mike.wynn l8night.co.uk> writes:

"Helmut Leitner" <helmut.leitner chello.at> wrote in message
news:3F486C58.C9FC7929 chello.at...
 "Carlos Santander B." wrote:
 This code:

 class A { void a(float b) { printf("%f\n",b); } }
 class B:A { void a(int b) { printf("%d\n",b); } }
 void main() {
     B b=new B;
     b.a(3);
     b.a(4.5);
 }

 Outputs
 3
 4

 To print correctly 4.5 I need to do b.A.a(4.5), which I personally find
 unatractive. So why, just like C++, doesn't D support polymorphism into
 derived classes?

 I think allowing this would at least also require a way to block methods
 from parent classes.

 On the other hand I think you could write

  class B:A {
    void a(int b) { printf("%d\n",b); }
    void a(float b) { super.a(b); }
  }

 easily.

I believe that walter has added `alias A.a a;` to solve this,
I still think that all non overrided methods from the super class should be
added into the sub class's search list.
void a( float b ) { super.a(b); } why ?? that rewrites a vtbl entry that's
already there and does the right thing.
can someone give a good example of why an overloaded methods show hide the
not overrriden superclasses methods. (passing the object as a sub class
would calls the right code!)

as in  (it should be noted that I changed 4.5 to 4.5f (4.5 is a double) so
has no direct match
import c.stdio;

class A {
    void a(float b) { printf("A::a(f)%f\n",b); }
    void a(int b) { printf("A::a(i) %d\n",b); }
}
class B:A {
    void a(int b) { printf("B::a(i) %d\n",b); }
}
void func(A a ) {
    a.a(3);
    a.a(4.5f);
}
void main() {
    B b=new B;
    printf("B ---");
    b.a(3);
    b.a(4.5f);
    printf("cast(A)B ---");
    func( b );
}
----------- 
B ---B::a(i) 3
B::a(i) 4
cast(A)B ---B::a(i) 3
A::a(f)4.500000

as you would expect.