www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - template mixin in class is virtual function?

reply strtr <strtr spam.com> writes:
Will template-mixin-functions always be virtual in classes?

"Mixins can add virtual functions to a class"
http://www.digitalmars.com/d/1.0/template-mixin.html

related:
http://odefu.blogspot.com/2008/12/composite-oriented-programming.html
May 19 2010
parent reply strtr <strtr spam.com> writes:
Or more to the point:

Can (Class) template mixin functions be devirtualized by the compiler or do I
(as
optimization) need to manually copy paste the boiler plate code?
May 21 2010
parent reply div0 <div0 users.sourceforge.net> writes:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

strtr wrote:

 Or more to the point:
 
 Can (Class) template mixin functions be devirtualized by the compiler or do I
(as
 optimization) need to manually copy paste the boiler plate code?


You can just wrap the mixin in a final block:

import std.stdio;

template bar(T) {
	void test(T t) {
		writefln("t: %s", t);
	}
}

class foo {
	final {
		mixin bar!(int);
	}
}

int main(){
	scope f = new foo;
	f.test(3);
	return 0;
}

- --
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iD8DBQFL9uBpT9LetA9XoXwRAv83AKDNlqLgcI7C0g5x5t6CnUq82C5/xACghKUF
p9whtC6i/L7jrJyuLg+RZWo=
=BGBu
-----END PGP SIGNATURE-----
May 21 2010
parent reply strtr <strtr spam.com> writes:
== Quote from div0 (div0 users.sourceforge.net)'s article

 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1
 strtr wrote:

 Or more to the point:

 Can (Class) template mixin functions be devirtualized by the compiler or do I
(as
 optimization) need to manually copy paste the boiler plate code?


 You can just wrap the mixin in a final block:
 import std.stdio;
 template bar(T) {
 	void test(T t) {
 		writefln("t: %s", t);
 	}
 }
 class foo {
 	final {
 		mixin bar!(int);
 	}
 }
 int main(){
 	scope f = new foo;
 	f.test(3);
 	return 0;
 }


Is that different from making all functions within the template final?
May 21 2010
parent reply div0 <div0 users.sourceforge.net> writes:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

strtr wrote:

 == Quote from div0 (div0 users.sourceforge.net)'s article

 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1
 strtr wrote:

 Or more to the point:

 Can (Class) template mixin functions be devirtualized by the compiler or do I
(as
 optimization) need to manually copy paste the boiler plate code?


 You can just wrap the mixin in a final block:
 import std.stdio;
 template bar(T) {
 	void test(T t) {
 		writefln("t: %s", t);
 	}
 }
 class foo {
 	final {
 		mixin bar!(int);
 	}
 }
 int main(){
 	scope f = new foo;
 	f.test(3);
 	return 0;
 }


 
 Is that different from making all functions within the template final?
 


Well it delegates the choice of virtual versus non virtual to the class
using the mixin. No idea if that's a good idea or a bad one; I guess
you'd have to think very carefully about what your mixin is trying to
achieve.

I just tried marking a function in the template final
and that seems to work as well, so you could have a mix of virtual and
non virtual in a template, but that feels like a hackish design.

So you can it appears do this: (though that's dmd 2.028)

template bar(T) {
   final:
	void test(T t) {
		writefln("t: %s", t);
	}
	void test2() {
	}
}

class foo {
	mixin bar!(int);
}

int main(){
	foo f = new foo;
	f.test(3);
	f.test2();
	return 0;
}

- --
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iD8DBQFL9v4HT9LetA9XoXwRAgIvAKC8zwQP1EeaU/XkRijfm7m00nXqUQCdEdsN
CV/vi6l5JGnqH5M2WXU6gjU=
=0n7A
-----END PGP SIGNATURE-----
May 21 2010
parent strtr <strtr spam.com> writes:
== Quote from div0 (div0 users.sourceforge.net)'s article

 strtr wrote:

 Is that different from making all functions within the template final?


 Well it delegates the choice of virtual versus non virtual to the class
 using the mixin. No idea if that's a good idea or a bad one; I guess
 you'd have to think very carefully about what your mixin is trying to
 achieve.
 I just tried marking a function in the template final
 and that seems to work as well, so you could have a mix of virtual and
 non virtual in a template, but that feels like a hackish design.
 So you can it appears do this: (though that's dmd 2.028)
 template bar(T) {
    final:
 	void test(T t) {
 		writefln("t: %s", t);
 	}
 	void test2() {
 	}
 }
 class foo {
 	mixin bar!(int);
 }
 int main(){
 	foo f = new foo;
 	f.test(3);
 	f.test2();
 	return 0;
 }


I've been marking functions final on a per function basis within the templates
but
after reading the docs I was afraid the compiler might just ignore the attribute
and make all mixin-template-functions virtual.

"Mixins can add virtual functions to a class"
http://www.digitalmars.com/d/1.0/template-mixin.html

But that sentence was probably meant as an example not the exclusive
description :)

Anyway, Thanks!!
Shouldn't be thinking about optimization anyways ;)
May 21 2010