On Fri, 02 Jul 2004 16:12:07 +1200, Regan Heath wrote:

> struct A {
> 	int aaa;
> 	int bbb;
> }
> struct B {
> 	A a_instance;
> 	alias a_instance.aaa aaa;
> 	alias a_instance.bbb bbb;
> }
> 
> void main() {
> 	B b;
> 
> 	b.aaa = 5;
> 	b.bbb = 6;
> }

This works ...

#struct A {
#    int aaa;
#    int bbb;
#}
#struct B {
#    A a_instance;
#    alias A.aaa aaa;
#    alias A.bbb bbb;
#}
#
#void main() {
#    B b;
#
#    b.aaa = 5;
#    b.bbb = 6;
#}

But doesn't help if you have two or more instances of A inside B.

-- 
Derek
Melbourne, Australia
2/Jul/04 2:19:58 PM

On Fri, 2 Jul 2004 14:27:17 +1000, Derek Parnell <derek@psych.ward> wrote:

> On Fri, 02 Jul 2004 16:12:07 +1200, Regan Heath wrote:
>
>> struct A {
>> 	int aaa;
>> 	int bbb;
>> }
>> struct B {
>> 	A a_instance;
>> 	alias a_instance.aaa aaa;
>> 	alias a_instance.bbb bbb;	
>> }
>>
>> void main() {
>> 	B b;
>> 	
>> 	b.aaa = 5;
>> 	b.bbb = 6;
>> }
>
> This works ...
>
> #struct A {
> #    int aaa;
> #    int bbb;
> #}
> #struct B {
> #    A a_instance;
> #    alias A.aaa aaa;
> #    alias A.bbb bbb;
> #}
> #
> #void main() {
> #    B b;
> #
> #    b.aaa = 5;
> #    b.bbb = 6;
> #}
>
> But doesn't help if you have two or more instances of A inside B.

Thanks.. I still have not got the hang of aliases like this. :)

I am trying to emulate having a base struct (like a base class only no virtual functions etc), so there will not be more than one instance of A inside B.

This workaround isn't too bad so long as there aren't too many members in the 'base' struct.
You can go another level deep but it requires some copy/pasting...

struct A {
	int var1;
	int var2;
}
struct B {
	A a;
	alias A.var1 var1;
	alias A.var2 var2;	
	int var3;
	int var4;
}
struct C {
	B b;
	alias B.var1 var1;
	alias B.var2 var2;	
	alias B.var3 var3;
	alias B.var4 var4;	
}

void main() {
	C c;
	
	c.var1 = 5;
	c.var2 = 6;
	c.var3 = 7;
	c.var4 = 8;
}

Walter: it would be nice if the above could be achieved with

struct A {
	int var1;
	int var2;
}

struct B : A {
	int var3;
	int var4;
}

struct C : B {
}

Much simpler!

Regan.

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

"Regan Heath" <regan@netwin.co.nz> wrote in message news:opsahbksx25a2sq9@digitalmars.com...
> On Thu, 1 Jul 2004 14:12:37 +0200, Ivan Senji <ivan.senji@public.srce.hr> wrote:
>
> > "Walter" <newshound@digitalmars.com> wrote in message news:cc0hlu$9gv$2@digitaldaemon.com...
> >>
> >> You can do the following:
> >>
> >> struct A { ... }
> >>
> >> struct B
> >> {
> >>     A a;
> >>     ... more members ...
> >> }
> >>
> >
> > Or even (maybe) better:
> >
> > struct A() { }
> >
> > struct B
> > {
> >     mixin A!();
> >  //   ... more members ...
> > }
> >
>
> Nope: mixin A!() A is not a template
>

I am a real idiot for not trying to add member variables.

> Besides which you cannot use a mixin to add private members.

I tried this and it seems that i can

template A()
{
     int x,y;
}

struct B
{
    private mixin A!();
     float a,b;
}

And i get a nice message "struct B A!().x is private"
 B b;
 b.a=3;
 b.x=4;//<-error here
but ofcourse it has to be in another module to manifest
this behaviour!

>
> Regan
>
> --
> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

On Fri, 2 Jul 2004 09:06:25 +0200, Ivan Senji <ivan.senji@public.srce.hr> wrote:

> "Regan Heath" <regan@netwin.co.nz> wrote in message
> news:opsahbksx25a2sq9@digitalmars.com...
>> On Thu, 1 Jul 2004 14:12:37 +0200, Ivan Senji <ivan.senji@public.srce.hr>
>> wrote:
>>
>> > "Walter" <newshound@digitalmars.com> wrote in message
>> > news:cc0hlu$9gv$2@digitaldaemon.com...
>> >>
>> >> You can do the following:
>> >>
>> >> struct A { ... }
>> >>
>> >> struct B
>> >> {
>> >>     A a;
>> >>     ... more members ...
>> >> }
>> >>
>> >
>> > Or even (maybe) better:
>> >
>> > struct A() { }
>> >
>> > struct B
>> > {
>> >     mixin A!();
>> >  //   ... more members ...
>> > }
>> >
>>
>> Nope: mixin A!() A is not a template
>>
>
> I am a real idiot for not trying to add member variables.
>
>> Besides which you cannot use a mixin to add private members.
>
> I tried this and it seems that i can
>
> template A()
> {
>      int x,y;
> }
>
> struct B
> {
>     private mixin A!();
>      float a,b;
> }
>
> And i get a nice message "struct B A!().x is private"
>  B b;
>  b.a=3;
>  b.x=4;//<-error here
> but ofcourse it has to be in another module to manifest
> this behaviour!

Yes you can do that, what I actually mean't to say was, you cannot go...

template A()
{
public:
	void foo() {
		bar();
	}
private:
	int a;
}

struct B
{
	mixin A;
	void bar() {
		a = 5;
	}
}

'int a' is private to mixin A and not accessable at all to B. But, now that I think about it, were I allowed to go...

struct A {
public:
	void foo() {
		bar();
	}
private:
	int a;
}

struct B : A {
	mixin A;
	void bar() {
		a = 5;
	}
}

it wouldn't work either as (I assume) A's privates would not be accessable to B (using standard C++ class inheritance etc).

So my workaround to make the private section protected is probably the correct way to do it anyway.

I'll go put my head in a paper bag now :)
(not plastic - cos that's dangerous)

Regan.

>>
>> Regan
>>
>> --
>> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
>
>



-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

"Regan Heath" <regan@netwin.co.nz> wrote in message news:opsaigb8o15a2sq9@digitalmars.com...
> On Fri, 2 Jul 2004 09:06:25 +0200, Ivan Senji <ivan.senji@public.srce.hr> wrote:
>
> > "Regan Heath" <regan@netwin.co.nz> wrote in message news:opsahbksx25a2sq9@digitalmars.com...
> .......
> Yes you can do that, what I actually mean't to say was, you cannot go...

I finally understand what is troubling you. I read yout previous posts about
this
but didn't have any time to try it out.

> template A()
> {
> public:
> void foo() {
> bar();
> }
> private:
> int a;
> }
>
> struct B
> {
> mixin A;
> void bar() {
> a = 5;
> }
> }
>
> 'int a' is private to mixin A and not accessable at all to B. But, now that I think about it, were I allowed to go...
>
> struct A {
> public:
> void foo() {
> bar();
> }
> private:
> int a;
> }
>
> struct B : A {
> mixin A;
> void bar() {
> a = 5;
> }
> }
>
> it wouldn't work either as (I assume) A's privates would not be accessable
> to B (using standard C++ class inheritance etc).

Yes i also think you are right, mixin has its own scope and decides what to give access to.

> So my workaround to make the private section protected is probably the correct way to do it anyway.

Conclusion: your workaround isn't a workaround at all, but the way it should work.


>
> I'll go put my head in a paper bag now :)
> (not plastic - cos that's dangerous)

:)

>
> Regan.
>
> >>
> >> Regan
> >>
> >> --
> >> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
> >
> >
>
>
>
> --
> Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/