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digitalmars.D.learn - Method overloading without Type2Type

reply Benjamin Thaut <code benjamin-thaut.de> writes:
I'm just reading Andreis book "Modern C++ Design" and try to translate a 
few examples to D 2. My most recent test looks as follows:

import std.stdio;

struct Type2Type(T){
	typedef T OriginalType;
}

class foo(T,R...) : foo!(R) {
	public void print(){
		super.print();
		writefln(T.stringof);
	}
	
	alias foo!(R).echo echo;
	public void echo(Type2Type!(T)) {
		writefln(T.stringof);
	}
}

class foo(T){
	public void print(){
		writefln("end " ~ T.stringof);
	}
	
	public void echo(Type2Type!(T)) {
		writefln(T.stringof);
	}
}

void main(string[] args){
	auto test = new foo!(int,float,double,short,byte)();
	test.print();
	
	test.echo(Type2Type!(double)());
	test.echo(Type2Type!(short)());
}

I'm wondering if there is any way in D 2 to not use Type2Type so that 
the calls to echo would look like:
test.echo!(double)();
test.echo!(short)();

The solution does not have to use inheritance, any idea?
-- 
Kind Regards
Benjamin Thaut
Apr 25 2011
parent reply bearophile <bearophileHUGS lycos.com> writes:
Benjamin Thaut:


 import std.stdio;
 
 struct Type2Type(T){
 	typedef T OriginalType;
 }
 
 class foo(T,R...) : foo!(R) {
 	public void print(){
 		super.print();
 		writefln(T.stringof);
 	}
 	
 	alias foo!(R).echo echo;
 	public void echo(Type2Type!(T)) {
 		writefln(T.stringof);
 	}
 }
 
 class foo(T){
 	public void print(){
 		writefln("end " ~ T.stringof);
 	}
 	
 	public void echo(Type2Type!(T)) {
 		writefln(T.stringof);
 	}
 }
 
 void main(string[] args){
 	auto test = new foo!(int,float,double,short,byte)();
 	test.print();
 	
 	test.echo(Type2Type!(double)());
 	test.echo(Type2Type!(short)());
 }


Try to compile that code with "-w" (warnings).

Bye,
bearophile
Apr 26 2011
parent reply bearophile <bearophileHUGS lycos.com> writes:
 Try to compile that code with "-w" (warnings).


http://d.puremagic.com/issues/show_bug.cgi?id=3836

Bye,
bearophile
Apr 26 2011
parent reply Benjamin Thaut <code benjamin-thaut.de> writes:
Am 26.04.2011 13:43, schrieb bearophile:

 Try to compile that code with "-w" (warnings).


 http://d.puremagic.com/issues/show_bug.cgi?id=3836

 Bye,
 bearophile


Thanks, but that is not connected to my question at all,
I want to implement the echo method so that the type is passed as a 
template argument, and not as a function argument. While that is 
happening I still want to be able to overload the function.
Is this possible in D 2?

-- 
Kind Regards
Benjamin Thaut
Apr 26 2011
parent reply Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Tue, Apr 26, 2011 at 18:41, Benjamin Thaut <code benjamin-thaut.de> wrote:

 Thanks, but that is not connected to my question at all,
 I want to implement the echo method so that the type is passed as a template
 argument, and not as a function argument. While that is happening I still
 want to be able to overload the function.
 Is this possible in D 2?


I'm not sure I understand what you're trying to do (didn't read
"Modern C++ design"). Here is something that compiles:

import std.stdio;

class Foo(T,R...) : Foo!(R) {
       public void print(){
               writeln(T.stringof);
               super.print();
       }

       public void echo(U)(U u = U.init) {
               writeln(U.stringof);
       }
}

class Foo(T){
       public void print(){
               writeln("end: " ~ T.stringof);
       }

       public void echo(U)(U u = U.init) {
               writeln(U.stringof);
       }
}

void main(string[] args){
       auto test = new Foo!(int,float,double,short,byte)();
       test.print();

       test.echo!double;
       test.echo!short;
}


I don't know if classes are necessary for what you've in mind. I tend
to use structs:

import std.stdio;

struct Foo(T,R...) {
    void print(){
        static if (R.length)
        {
            Foo!(R) fr;
            fr.print;
        }
        writeln(T.stringof);
    }

    void echo(U)(U u = U.init) { writefln(U.stringof);}
}

void main(string[] args){
       Foo!(int,float,double,short,byte) test;
       test.print;

       test.echo!double;
       test.echo!short;
}
Apr 26 2011
parent reply Benjamin Thaut <code benjamin-thaut.de> writes:
Am 26.04.2011 21:55, schrieb Philippe Sigaud:

 On Tue, Apr 26, 2011 at 18:41, Benjamin Thaut<code benjamin-thaut.de>  wrote:

 Thanks, but that is not connected to my question at all,
 I want to implement the echo method so that the type is passed as a template
 argument, and not as a function argument. While that is happening I still
 want to be able to overload the function.
 Is this possible in D 2?


 I'm not sure I understand what you're trying to do (didn't read
 "Modern C++ design"). Here is something that compiles:

 import std.stdio;

 class Foo(T,R...) : Foo!(R) {
         public void print(){
                 writeln(T.stringof);
                 super.print();
         }

         public void echo(U)(U u = U.init) {
                 writeln(U.stringof);
         }
 }

 class Foo(T){
         public void print(){
                 writeln("end: " ~ T.stringof);
         }

         public void echo(U)(U u = U.init) {
                 writeln(U.stringof);
         }
 }

 void main(string[] args){
         auto test = new Foo!(int,float,double,short,byte)();
         test.print();

         test.echo!double;
         test.echo!short;
 }


The Problem with that version is, that the code that is generated looks like

void main(string[] args){
          auto test = new Foo!(int,float,double,short,byte)();
          test.print();
          test.echo!double(double.init);
         test.echo!short(short.init);
}

If the types that are used, are no simple data types, but rather large 
structs, they are copied on every function call. Thats exactly what I 
want to avoid. The Type2Type template has a size of 0, thats why I'm 
using that in the first place.

-- 
Kind Regards
Benjamin Thaut
Apr 26 2011
next sibling parent reply Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Tue, Apr 26, 2011 at 22:06, Benjamin Thaut <code benjamin-thaut.de> wrot=
e:

 The Problem with that version is, that the code that is generated looks l=


ike

 void main(string[] args){
 =C2=A0 =C2=A0 =C2=A0 =C2=A0 auto test =3D new Foo!(int,float,double,short=


,byte)();

 =C2=A0 =C2=A0 =C2=A0 =C2=A0 test.print();
 =C2=A0 =C2=A0 =C2=A0 =C2=A0 test.echo!double(double.init);
 =C2=A0 =C2=A0 =C2=A0 =C2=A0test.echo!short(short.init);
 }

 If the types that are used, are no simple data types, but rather large
 structs, they are copied on every function call. Thats exactly what I wan=


t

 to avoid. The Type2Type template has a size of 0, thats why I'm using tha=


t

 in the first place.


In that case, just use echo(U)() { ...}, like this:

import std.stdio;

class Foo(T,R...) : Foo!(R) {
       public void print(){
               writefln(T.stringof);
               super.print();
       }

       public void echo(U)() {
               writefln(U.stringof);
       }
}

class Foo(T){
       public void print(){
               writefln("end: " ~ T.stringof);
       }

       public void echo(U)() {
               writefln(U.stringof);
       }
}

void main(string[] args){
       auto test =3D new Foo!(int,float,double,short,byte)();
       test.print();

       test.echo!double;
       test.echo!short;
}

What's your global goal with this construction? What are you trying to achi=
eve?
Apr 26 2011
parent Benjamin Thaut <code benjamin-thaut.de> writes:
Am 26.04.2011 22:41, schrieb Philippe Sigaud:

 On Tue, Apr 26, 2011 at 22:06, Benjamin Thaut<code benjamin-thaut.de>  wrote:

 The Problem with that version is, that the code that is generated looks like

 void main(string[] args){
          auto test = new Foo!(int,float,double,short,byte)();
          test.print();
          test.echo!double(double.init);
         test.echo!short(short.init);
 }

 If the types that are used, are no simple data types, but rather large
 structs, they are copied on every function call. Thats exactly what I want
 to avoid. The Type2Type template has a size of 0, thats why I'm using that
 in the first place.


 In that case, just use echo(U)() { ...}, like this:

 import std.stdio;

 class Foo(T,R...) : Foo!(R) {
         public void print(){
                 writefln(T.stringof);
                 super.print();
         }

         public void echo(U)() {
                 writefln(U.stringof);
         }
 }

 class Foo(T){
         public void print(){
                 writefln("end: " ~ T.stringof);
         }

         public void echo(U)() {
                 writefln(U.stringof);
         }
 }

 void main(string[] args){
         auto test = new Foo!(int,float,double,short,byte)();
         test.print();

         test.echo!double;
         test.echo!short;
 }

 What's your global goal with this construction? What are you trying to achieve?


struct Foo {...}
struct Bar {...}

void* poolAllocate(size_t sz){...};

abstract class Allocator(T){
	//needs to be implemented by user to fill obj with data
	public abstract void init(ref T obj);

	public void make(Type2Type!(T)){
		void* ptr = poolAllocate(T.sizeof);
		T* obj = emplace!(T)(ptr[0..T.sizeof]);
		init(*obj);
	}

	abstract void produce();
}

abstract class Allocator(T,R...) : Allocator!(R) {
	//needs to be implemented by user to fill obj with data
	public abstract void init(ref T obj);

	alias Allocator!(R).make make;
	public void make(Type2Type!(T)){
		void* ptr = poolAllocate(T.sizeof);
		T* obj = emplace!(T)(ptr[0..T.sizeof]);
		init(*obj);
	}
}

class UserImpl : Allocator!(Foo,Bar){
	override void init(ref Foo obj){
		//fill Foo with data
	}

	override void init(ref Bar obj){
		//fill Bar with data
	}

	override void produce(){
		for(...){
			make(Type2Type!(Foo));
		}
		for(...){
			make(Type2Type!(Bar));
		}
	}
}

I do this to hide away allocation and pointer arithmetic from the user.

-- 
Kind Regards
Benjamin Thaut
Apr 26 2011
prev sibling parent bearophile <bearophileHUGS lycos.com> writes:
Benjamin Thaut:


 The Type2Type template has a size of 0, thats why I'm 
 using that in the first place.


Almost. Maybe to allow addressability with pointers the minimal struct size in
D is 1 byte (0-length fixed-sized arrays may require zero bytes on DMD and 1
bit on LDC):

struct Type2Type(T){
        typedef T OriginalType;
}
static assert ((Type2Type!int).sizeof == 1);
void main() {}

Bye,
bearophile
Apr 26 2011