digitalmars.D - Implement a class with mixins
- Frank Benoit (22/22) May 06 2006 Does a protected inheritance make sense in a language without multiple
- Frank Benoit (2/9) May 06 2006
- Sean Kelly (7/15) May 07 2006 It would be great if there were an easy way to make this work. As it
- Don Clugston (5/22) May 08 2006 In every case I've seen or dreamt up so far, a template is either
- Sean Kelly (5/10) May 08 2006 Perhaps it should, though I'm hesitant to suggest a special declaration
- pragma (10/19) May 08 2006 Personally, I just use the 'M' suffix convention (in place of 'T') to av...
- Derek Parnell (8/16) May 08 2006 Communication. It would tell code readers/maintainers the intention of t...
- Don Clugston (23/35) May 09 2006 Me too, but I feel that mixins ought to be much more useful than they
Does a protected inheritance make sense in a language without multiple
inheritance? Inherit private is for a "implemented with" relation. And
this is perhaps better made with the mixin feature.
But to use mixins like base classes for implementation, mixins are
missing a Ctor ( and DTor ) integration. It should be possible for a
mixin to have a Ctor which is automatically called while the object is
contructed. Or it can be called manually ( with args ) from the class ctor.
.template Foo(){
. this( int a ){}
.}
.
.template Bar(){
. this(){}
.}
.
.class C{
. mixin Foo foo;
. public this(){
. foo.this( 2 ); // if missing => compile error
. // bar.this() is implicit called, manually call is possible
. }
.}
May 06 2006
Frank Benoit <keinfarbton nospam.xyz> I missed the Bar mixin in the previous posting..class C{ . mixin Foo foo;. mixin Bar bar;. public this(){ . foo.this( 2 ); // if missing => compile error . // bar.this() is implicit called, manually call is possible . } .}
May 06 2006
Frank Benoit wrote:Does a protected inheritance make sense in a language without multiple inheritance? Inherit private is for a "implemented with" relation. And this is perhaps better made with the mixin feature. But to use mixins like base classes for implementation, mixins are missing a Ctor ( and DTor ) integration. It should be possible for a mixin to have a Ctor which is automatically called while the object is contructed. Or it can be called manually ( with args ) from the class ctor.It would be great if there were an easy way to make this work. As it is, I have to know in advance something is intended to be a mixin and create separate methods for this. For a somewhat more complicated example, I use the technique here: http://www.home.f4.ca/sean/d/stream.d Sean
May 07 2006
Sean Kelly wrote:Frank Benoit wrote:In every case I've seen or dreamt up so far, a template is either intended to be a mixin, or not. Is that your experience too? I suspect that 'mixin' should be specified in the template declaration, rather than just the instantiation.Does a protected inheritance make sense in a language without multiple inheritance? Inherit private is for a "implemented with" relation. And this is perhaps better made with the mixin feature. But to use mixins like base classes for implementation, mixins are missing a Ctor ( and DTor ) integration. It should be possible for a mixin to have a Ctor which is automatically called while the object is contructed. Or it can be called manually ( with args ) from the class ctor.It would be great if there were an easy way to make this work. As it is, I have to know in advance something is intended to be a mixin and create separate methods for this. For a somewhat more complicated example, I use the technique here: http://www.home.f4.ca/sean/d/stream.d
May 08 2006
Don Clugston wrote:In every case I've seen or dreamt up so far, a template is either intended to be a mixin, or not. Is that your experience too?Yes.I suspect that 'mixin' should be specified in the template declaration, rather than just the instantiation.Perhaps it should, though I'm hesitant to suggest a special declaration syntax unless it offers something over the current approach. Sean
May 08 2006
In article <e3nr1u$1ekk$1 digitaldaemon.com>, Sean Kelly says...Don Clugston wrote:Personally, I just use the 'M' suffix convention (in place of 'T') to avoid confusing myself with what's a type template and what is a mixin. But I do agree with the point made, that it would be nice to restrict the usage of templates according to their intended purpose. Offhand, I can't think of a single type template that would be useful in the same context as your typical mixin (or vice-versa). However, I'm hesitant to agree that using 'mixin' in the declaration is the answer - do we still require the 'auto' modifier for auto class declarations? - EricAnderton at yahooIn every case I've seen or dreamt up so far, a template is either intended to be a mixin, or not. Is that your experience too?Yes.I suspect that 'mixin' should be specified in the template declaration, rather than just the instantiation.Perhaps it should, though I'm hesitant to suggest a special declaration syntax unless it offers something over the current approach.
May 08 2006
On Tue, 09 May 2006 02:19:07 +1000, Sean Kelly <sean f4.ca> wrote:Don Clugston wrote:Yes.In every case I've seen or dreamt up so far, a template is either intended to be a mixin, or not. Is that your experience too?Yes.Communication. It would tell code readers/maintainers the intention of the author. It reduces guess work on their part, and this leads to cheaper maintenance costs (less mistakes, less reading time, etc). -- Derek Parnell Melbourne, AustraliaI suspect that 'mixin' should be specified in the template declaration, rather than just the instantiation.Perhaps it should, though I'm hesitant to suggest a special declaration syntax unless it offers something over the current approach.
May 08 2006
Sean Kelly wrote:Don Clugston wrote:Me too, but I feel that mixins ought to be much more useful than they currently are. They don't feel very disciplined. I can see two kinds of mixins: (a) 'in' mixins, which are just like normal templates, except that they can use variables/functions/etc from the instantiation scope. Their name is the only thing that needs to appear in the instantiation scope. (b) 'out' mixins, which can dump arbitrary declarations into the instantation scope. The second type are far more scary, and so far I've found them less useful. You'd always want a 'mixin' keyword in front of any instantiation of them, because they could easily obfuscate code. But I wonder if we really need it for the 'in' mixins. I'm finding cases where I write: int bar; // mixin 'foo' creates a local function that requires a local integer called 'bar'. mixin foo!(int) baz; baz(45); when actually I'd like to write int bar; foo!(int)(45); I'm just bouncing around ideas, don't take it too seriously.In every case I've seen or dreamt up so far, a template is either intended to be a mixin, or not. Is that your experience too?Yes.I suspect that 'mixin' should be specified in the template declaration, rather than just the instantiation.Perhaps it should, though I'm hesitant to suggest a special declaration syntax unless it offers something over the current approach.
May 09 2006