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digitalmars.D.learn - Overloaded function disappears on polymorphism

reply "tcak" <tcak gmail.com> writes:
main.d
===================================================
class Car{
	public void makeBeep( char c ){}
	public void makeBeep( string s ){}
}

class Tesla: Car{
	override public void makeBeep( char c ){
		writeln("C = ", c);
	}
}

void main(){
	auto t = new Tesla();

	t.makeBeep("Model S");
}
===================================================

Error: function main.Tesla.makeBeep (char c) is not callable 
using argument types (string)

For Tesla, I expected that makeBeep( string s ) would still be 
defined. Because I have overridden on makeBeep( char c ). Isn't 
that correct?
Jan 24 2015
next sibling parent ketmar <ketmar ketmar.no-ip.org> writes:
On Sat, 24 Jan 2015 18:55:58 +0000, tcak wrote:


 main.d =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D

 class Car{
 	public void makeBeep( char c ){}
 	public void makeBeep( string s ){}
 }
=20
 class Tesla: Car{
 	override public void makeBeep( char c ){
 		writeln("C =3D ", c);
 	}
 }
=20
 void main(){
 	auto t =3D new Tesla();
=20
 	t.makeBeep("Model S");
 }
 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D

=20
 Error: function main.Tesla.makeBeep (char c) is not callable using
 argument types (string)
=20
 For Tesla, I expected that makeBeep( string s ) would still be defined.
 Because I have overridden on makeBeep( char c ). Isn't that correct?


nope. overriding overloaded function cancels all overloads. it's by spec.=
Jan 24 2015
prev sibling next sibling parent "Tobias Pankrath" <tobias pankrath.net> writes:
 For Tesla, I expected that makeBeep( string s ) would still be 
 defined. Because I have overridden on makeBeep( char c ). Isn't 
 that correct?


alias makeBeep = Car.makeBeep; pulls the base classes overloads 
into your subclass.
Jan 24 2015
prev sibling parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 01/24/2015 10:55 AM, tcak wrote:


 main.d
 ===================================================
 class Car{
      public void makeBeep( char c ){}
      public void makeBeep( string s ){}
 }

 class Tesla: Car{
      override public void makeBeep( char c ){
          writeln("C = ", c);
      }
 }

 void main(){
      auto t = new Tesla();

      t.makeBeep("Model S");
 }
 ===================================================

 Error: function main.Tesla.makeBeep (char c) is not callable using
 argument types (string)

 For Tesla, I expected that makeBeep( string s ) would still be defined.
 Because I have overridden on makeBeep( char c ). Isn't that correct?


This is called "name hiding" and works the same at least in C++. The 
purpose is to avoiding function hijacking. Imagine the following 
scenario where a 'short' argument is dispatched to a function taking 'int':

class Base
{
     void foo(int)
     {}
}

class Derived : Base
{
     override void foo(int)
     {}
}

void main()
{
     // Compiles: 'short' is converted to 'int':
     (new Derived).foo(short.init);
}

Without name hiding, the following addition to Base (which, presumably 
the author of Derived has no control over) would cause the call to 
bypass Derived.foo(short) and go to Base.foo(short):

class Base
{
     void foo(int)
     {}

     void foo(short)    // <-- New function
     {}
}

class Derived : Base
{
     override void foo(int)
     {}
}

void main()
{
     /* Compilation ERROR:
      *
      * Deprecation: class deneme.Derived use of deneme.Base.foo(short
      * _param_0) hidden by Derived is deprecated; use 'alias foo = 
Base.foo;'
      * to introduce base class overload set
      */
     (new Derived).foo(short.init);
}

Ali
Jan 24 2015