• Justin Johansson <no spam.com> Sep 01 2010
• retard <re tard.com.invalid> Sep 01 2010
• Jacob Carlborg <doob me.com> Sep 01 2010
• Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> Sep 01 2010
• Jacob Carlborg <doob me.com> Sep 02 2010
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 01 2010
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 01 2010
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 01 2010
• retard <re tard.com.invalid> Sep 01 2010
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 02 2010
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 02 2010
• Philippe Sigaud <philippe.sigaud gmail.com> Sep 01 2010

Justin Johansson <no spam.com> writes:

Whilst one admirable aspiration of D is to make for better
meta-programming capability in a PL, IMHO one seemingly-lacking
aspiration of D is in the area of improving OO inheritance models
over and above that provisioned for in C++ and Java.

Maybe I'm ill-informed though I'd say that D, C++ and Java
more-or-less share the same OO inheritance model being that
of inheritance/derivation by extension as opposed to, say,
inheritance/derivation by restriction.  (Observation: Java
even uses the 'extends' keyword to introduce derived classes;
this hardly caters for inheritance by restriction).

May I suggest that a discussion ensure about a taxonomy of
OO inheritance models, including the notions of inheritance
by extension, restriction, code refactoring purposes etc.
so that D can evolve to a position to be able to claim a
higher moral plane over C++, Java, et al.

Cheers
Justin Johansson

retard <re tard.com.invalid> writes:

Wed, 01 Sep 2010 23:16:15 +0930, Justin Johansson wrote:

 Whilst one admirable aspiration of D is to make for better
 meta-programming capability in a PL, IMHO one seemingly-lacking
 aspiration of D is in the area of improving OO inheritance models over
 and above that provisioned for in C++ and Java.
 
 Maybe I'm ill-informed though I'd say that D, C++ and Java more-or-less
 share the same OO inheritance model being that of inheritance/derivation
 by extension as opposed to, say, inheritance/derivation by restriction. 
 (Observation: Java even uses the 'extends' keyword to introduce derived
 classes; this hardly caters for inheritance by restriction).
 
 May I suggest that a discussion ensure about a taxonomy of OO
 inheritance models, including the notions of inheritance by extension,
 restriction, code refactoring purposes etc. so that D can evolve to a
 position to be able to claim a higher moral plane over C++, Java, et al.


Have you taken a loot at Scala & traits already? It would be a great 
starting point.

Jacob Carlborg <doob me.com> writes:

On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard <re tard.com.invalid> wrote:


     Have you taken a loot at Scala & traits already? It would be a great
     starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


You can't use D template mixins to add methods that will overload 
existing methods.


-- 
/Jacob Carlborg

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 9/1/10 16:56 CDT, retard wrote:
 Wed, 01 Sep 2010 23:30:08 +0200, Jacob Carlborg wrote:

 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard<re tard.com.invalid>  wrote:


      Have you taken a loot at Scala&  traits already? It would be a
      great starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload
 existing methods.


 I'm afraid D's template mixins are like a poor man's copy/paste macro
 system. Scala's approach takes subtyping into account. D 2 took a step
 towards traits actually since it allows some implementations&  contracts
 in interfaces. However, Scala is more flexible. Scala's design had the
 focus on nice OOP properties the whole time, but D will probably only get
 features if implementing them efficiently is a low hanging fruit.


I agree. Traits are my favorite feature of Scala and probably the main 
modeling advantage that Scala has over D and other languages. A 
carefully designed feature for the win.

Scala-style mixins aren't very difficult to implement for D, but I'm not 
sure if something like this would happen soon.


Andrei

Jacob Carlborg <doob me.com> writes:

On 2010-09-01 23:39, Andrej Mitrovic wrote:
 You mean like this?:
 module add_virtual_functions;

 import std.stdio : writeln;

 void main()
 {
      test();
 }

 mixin template Foo()
 {
      void func()
      {
          writeln("Foo.func()");
      }
 }

 class Bar
 {
      void func()
      {
          writeln("Bar.func()");
      }
 }

 class Code : Bar
 {
      mixin Foo;
 }

 void test()
 {
      Bar b = new Bar();
      b.func();   // calls Bar.func()

      Code c = new Code();
      c.func();   // calls Code.func()
 }


No, that is overriding. Overloading is having several methods with the 
same name taking different number of parameters or parameters of 
different types.

module test;

mixin template Foo ()
{
	void bar (int i) {};
}

class Bar
{
	void bar () {};
	mixin Foo;
}

void main ()
{
	auto bar = new Bar;
	bar.bar(4); // line 17
	bar.bar();
}

The above code results in these errors:

test.d(17): Error: function test.Bar.bar () is not callable using 
argument types (int)
test.d(17): Error: expected 0 arguments, not 1 for non-variadic function 
type void()


 On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg<doob me.com>  wrote:
 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard<re tard.com.invalid>  wrote:


     Have you taken a loot at Scala&  traits already? It would be a great
     starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload existing
 methods.


 --
 /Jacob Carlborg





-- 
/Jacob Carlborg

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

You mean like this?:
module add_virtual_functions;

import std.stdio : writeln;

void main()
{
    test();
}

mixin template Foo()
{
    void func()
    {
        writeln("Foo.func()");
    }
}

class Bar
{
    void func()
    {
        writeln("Bar.func()");
    }
}

class Code : Bar
{
    mixin Foo;
}

void test()
{
    Bar b =3D new Bar();
    b.func();   // calls Bar.func()

    Code c =3D new Code();
    c.func();   // calls Code.func()
}


On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg <doob me.com> wrote:
 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard <re tard.com.invalid> wrote:


 =A0 =A0Have you taken a loot at Scala & traits already? It would be a gr=




 =A0 =A0starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload existin=


 methods.


 --
 /Jacob Carlborg

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Disregard the module name declaration. The original example had the
template mixin create a virtual method, and then you can override it
in the inheriting class.

On Wed, Sep 1, 2010 at 11:39 PM, Andrej Mitrovic
<andrej.mitrovich gmail.com> wrote:
 You mean like this?:
 module add_virtual_functions;

 import std.stdio : writeln;

 void main()
 {
 =A0 =A0test();
 }

 mixin template Foo()
 {
 =A0 =A0void func()
 =A0 =A0{
 =A0 =A0 =A0 =A0writeln("Foo.func()");
 =A0 =A0}
 }

 class Bar
 {
 =A0 =A0void func()
 =A0 =A0{
 =A0 =A0 =A0 =A0writeln("Bar.func()");
 =A0 =A0}
 }

 class Code : Bar
 {
 =A0 =A0mixin Foo;
 }

 void test()
 {
 =A0 =A0Bar b =3D new Bar();
 =A0 =A0b.func(); =A0 // calls Bar.func()

 =A0 =A0Code c =3D new Code();
 =A0 =A0c.func(); =A0 // calls Code.func()
 }


 On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg <doob me.com> wrote:
 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard <re tard.com.invalid> wrote:


 =A0 =A0Have you taken a loot at Scala & traits already? It would be a g=






 =A0 =A0starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload existi=




 methods.


 --
 /Jacob Carlborg

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Ah nevermind. I didn't realize you've said "overload".

On Wed, Sep 1, 2010 at 11:39 PM, Andrej Mitrovic
<andrej.mitrovich gmail.com> wrote:
 You mean like this?:
 module add_virtual_functions;

 import std.stdio : writeln;

 void main()
 {
 =A0 =A0test();
 }

 mixin template Foo()
 {
 =A0 =A0void func()
 =A0 =A0{
 =A0 =A0 =A0 =A0writeln("Foo.func()");
 =A0 =A0}
 }

 class Bar
 {
 =A0 =A0void func()
 =A0 =A0{
 =A0 =A0 =A0 =A0writeln("Bar.func()");
 =A0 =A0}
 }

 class Code : Bar
 {
 =A0 =A0mixin Foo;
 }

 void test()
 {
 =A0 =A0Bar b =3D new Bar();
 =A0 =A0b.func(); =A0 // calls Bar.func()

 =A0 =A0Code c =3D new Code();
 =A0 =A0c.func(); =A0 // calls Code.func()
 }


 On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg <doob me.com> wrote:
 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard <re tard.com.invalid> wrote:


 =A0 =A0Have you taken a loot at Scala & traits already? It would be a g=






 =A0 =A0starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload existi=




 methods.


 --
 /Jacob Carlborg

retard <re tard.com.invalid> writes:

Wed, 01 Sep 2010 23:30:08 +0200, Jacob Carlborg wrote:

 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard <re tard.com.invalid> wrote:


     Have you taken a loot at Scala & traits already? It would be a
     great starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too.
 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload
 existing methods.


I'm afraid D's template mixins are like a poor man's copy/paste macro 
system. Scala's approach takes subtyping into account. D 2 took a step 
towards traits actually since it allows some implementations & contracts 
in interfaces. However, Scala is more flexible. Scala's design had the 
focus on nice OOP properties the whole time, but D will probably only get 
features if implementing them efficiently is a low hanging fruit.

One interesting feature in Scala are the types of objects in this case:

class A {}
trait T {}

class B extends A with T {}

val foo = (new B) : (A with T)

--

I suppose D doesn't allow this:

class A {}
interface T {}

class B : A, T {}

(A & T) foo = new B


In Scala the inheritance graph looks like:

 Any
  |
AnyRef
  |
Object
  |
  A      ____ T
  |     /
A with T
  |
  B

In D it's just:

 Object
   |
   A  ____T
   | /
   B

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Yeah, my mistake. I missread your post. :)

But, you can use mixin expressions to add overloaded methods. E.g.:

import std.stdio;

class Bar
{
    void func()
    {
        writeln("Bar.func()");
    }

    mixin("void func(string x) { writeln(x); }");
}

void main()
{
    Bar bar =3D new Bar;
    bar.func();
    bar.func("test");
}

So I'm wondering if there could be an easy way to use mixin
expressions with mixin templates..

On Thu, Sep 2, 2010 at 10:17 AM, Jacob Carlborg <doob me.com> wrote:
 On 2010-09-01 23:39, Andrej Mitrovic wrote:
 You mean like this?:
 module add_virtual_functions;

 import std.stdio : writeln;

 void main()
 {
 =A0 =A0 test();
 }

 mixin template Foo()
 {
 =A0 =A0 void func()
 =A0 =A0 {
 =A0 =A0 =A0 =A0 writeln("Foo.func()");
 =A0 =A0 }
 }

 class Bar
 {
 =A0 =A0 void func()
 =A0 =A0 {
 =A0 =A0 =A0 =A0 writeln("Bar.func()");
 =A0 =A0 }
 }

 class Code : Bar
 {
 =A0 =A0 mixin Foo;
 }

 void test()
 {
 =A0 =A0 Bar b =3D new Bar();
 =A0 =A0 b.func(); =A0 // calls Bar.func()

 =A0 =A0 Code c =3D new Code();
 =A0 =A0 c.func(); =A0 // calls Code.func()
 }


 No, that is overriding. Overloading is having several methods with the sa=


 name taking different number of parameters or parameters of different typ=


 module test;

 mixin template Foo ()
 {
 =A0 =A0 =A0 =A0void bar (int i) {};
 }

 class Bar
 {
 =A0 =A0 =A0 =A0void bar () {};
 =A0 =A0 =A0 =A0mixin Foo;
 }

 void main ()
 {
 =A0 =A0 =A0 =A0auto bar =3D new Bar;
 =A0 =A0 =A0 =A0bar.bar(4); // line 17
 =A0 =A0 =A0 =A0bar.bar();
 }

 The above code results in these errors:

 test.d(17): Error: function test.Bar.bar () is not callable using argumen=


 types (int)
 test.d(17): Error: expected 0 arguments, not 1 for non-variadic function
 type void()


 On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg<doob me.com> =A0wrote:
 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard<re tard.com.invalid> =A0wrote:


 =A0 =A0Have you taken a loot at Scala& =A0traits already? It would be =








 =A0 =A0starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too=








 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload
 existing
 methods.


 --
 /Jacob Carlborg





 --
 /Jacob Carlborg

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

Yeah, my mistake. I missread your post. :)

But, you can use mixin expressions to add overloaded methods. E.g.:

import std.stdio;

class Bar
{
    void func()
    {
        writeln("Bar.func()");
    }

    mixin("void func(string x) { writeln(x); }");
}

void main()
{
    Bar bar =3D new Bar;
    bar.func();
    bar.func("test");
}

So I'm wondering if there could be an easy way to use mixin
expressions with mixin templates..

On Thu, Sep 2, 2010 at 10:17 AM, Jacob Carlborg <doob me.com> wrote:
 On 2010-09-01 23:39, Andrej Mitrovic wrote:
 You mean like this?:
 module add_virtual_functions;

 import std.stdio : writeln;

 void main()
 {
 =A0 =A0 test();
 }

 mixin template Foo()
 {
 =A0 =A0 void func()
 =A0 =A0 {
 =A0 =A0 =A0 =A0 writeln("Foo.func()");
 =A0 =A0 }
 }

 class Bar
 {
 =A0 =A0 void func()
 =A0 =A0 {
 =A0 =A0 =A0 =A0 writeln("Bar.func()");
 =A0 =A0 }
 }

 class Code : Bar
 {
 =A0 =A0 mixin Foo;
 }

 void test()
 {
 =A0 =A0 Bar b =3D new Bar();
 =A0 =A0 b.func(); =A0 // calls Bar.func()

 =A0 =A0 Code c =3D new Code();
 =A0 =A0 c.func(); =A0 // calls Code.func()
 }


 No, that is overriding. Overloading is having several methods with the sa=


 name taking different number of parameters or parameters of different typ=


 module test;

 mixin template Foo ()
 {
 =A0 =A0 =A0 =A0void bar (int i) {};
 }

 class Bar
 {
 =A0 =A0 =A0 =A0void bar () {};
 =A0 =A0 =A0 =A0mixin Foo;
 }

 void main ()
 {
 =A0 =A0 =A0 =A0auto bar =3D new Bar;
 =A0 =A0 =A0 =A0bar.bar(4); // line 17
 =A0 =A0 =A0 =A0bar.bar();
 }

 The above code results in these errors:

 test.d(17): Error: function test.Bar.bar () is not callable using argumen=


 types (int)
 test.d(17): Error: expected 0 arguments, not 1 for non-variadic function
 type void()


 On Wed, Sep 1, 2010 at 11:30 PM, Jacob Carlborg<doob me.com> =A0wrote:
 On 2010-09-01 22:44, Philippe Sigaud wrote:
 On Wed, Sep 1, 2010 at 18:13, retard<re tard.com.invalid> =A0wrote:


 =A0 =A0Have you taken a loot at Scala& =A0traits already? It would be =








 =A0 =A0starting point.


 Scala's traits are great! Implicits in Scala are quite interesting too=








 Also, Haskell typeclasses

 I wonder if D can have part of Scala traits functionality with mixins?


 You can't use D template mixins to add methods that will overload
 existing
 methods.


 --
 /Jacob Carlborg





 --
 /Jacob Carlborg

Philippe Sigaud <philippe.sigaud gmail.com> writes:

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Content-Type: text/plain; charset=ISO-8859-1

On Wed, Sep 1, 2010 at 18:13, retard <re tard.com.invalid> wrote:

 Have you taken a loot at Scala & traits already? It would be a great
 starting point.


Scala's traits are great! Implicits in Scala are quite interesting too.
Also, Haskell typeclasses

I wonder if D can have part of Scala traits functionality with mixins?

--0015175cd9fc970b0e048f38c46d
Content-Type: text/html; charset=ISO-8859-1

<div class="gmail_quote">On Wed, Sep 1, 2010 at 18:13, retard <span
dir="ltr">&lt;re tard.com.invalid&gt;</span> wrote:<br><blockquote
class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid
rgb(204, 204, 204); padding-left: 1ex;">
<div><div></div><div class="h5"><br>
</div></div>Have you taken a loot at Scala &amp; traits already? It would be a
great<br>
starting point.<br>
</blockquote></div><br>Scala&#39;s traits are great! Implicits in Scala are
quite interesting too. Also, Haskell typeclasses<br><br>I wonder if D can have
part of Scala traits functionality with mixins?<br><br><br><br>

--0015175cd9fc970b0e048f38c46d--