• Jack Applegame (29/29) Nov 11 2012 I'm trying creating template for intrusive double-linked list:
• Jacob Carlborg (5/21) Nov 11 2012 This won't work. The "node" template doesn't evaluate to a type and you
• Jack Applegame (16/18) Nov 11 2012 But this is works! Why?
• David Nadlinger (7/9) Nov 11 2012 You _can_ actually use an identifier for mixin templates, it is

"Jack Applegame" <japplegame gmail.com> writes:

I'm trying creating template for intrusive double-linked list:

mixin template node() {
   static if(is(this == struct))
     alias typeof(this)* E;
   else
     alias typeof(this) E;
   E prev, next;
}

struct list(alias N) {
   N.E head;
   N.E tail;
}

class A {
   mixin node;
}

list!A l;

All works great.
If it's need to store one object in two different lists I plan 
something like this:

class A {
   mixin node L1;
   mixin node L2;
}

list!(A.L1) l1;
list!(A.L2) l2;

But compiler doesn't compile that whith error:
"this is not in a class or struct scope|"
in line with
"alias typeof(this) E;"

Jacob Carlborg <doob me.com> writes:

On 2012-11-11 10:04, Jack Applegame wrote:
 I'm trying creating template for intrusive double-linked list:

 mixin template node() {
    static if(is(this == struct))
      alias typeof(this)* E;
    else
      alias typeof(this) E;
    E prev, next;
 }
 class A {
    mixin node L1;
    mixin node L2;
 }

This won't work. The "node" template doesn't evaluate to a type and you 
wouldn't use it as a mixin if it did.

 But compiler doesn't compile that whith error:
 "this is not in a class or struct scope|"
 in line with
 "alias typeof(this) E;"



-- 
/Jacob Carlborg

"Jack Applegame" <japplegame gmail.com> writes:

On Sunday, 11 November 2012 at 10:36:42 UTC, Jacob Carlborg wrote:
 This won't work. The "node" template doesn't evaluate to a type 
 and you wouldn't use it as a mixin if it did.

But this is works! Why?

mixin template node() {
   alias int E;
   E prev, next;
}

struct list(alias N) {
   N.E head;
   N.E tail;
}

class A {
   mixin node L1;
   mixin node L2;
}

list!(A.L1) l1;
list!(A.L2) l2;

"David Nadlinger" <see klickverbot.at> writes:

On Sunday, 11 November 2012 at 10:36:42 UTC, Jacob Carlborg wrote:
 This won't work. The "node" template doesn't evaluate to a type 
 and you wouldn't use it as a mixin if it did.

You _can_ actually use an identifier for mixin templates, it is 
used to disambiguate in case of name collisions.

As far as the original question goes, I don't see a reason why 
this shouldn't work; you might want to add a bug report at 
http://d.puremagic.com/issues.

David