Looking for a Simple Doubly Linked List Implementation

[snow jhon]

On Saturday, 21 September 2019 at 18:52:23 UTC, Dennis wrote:
> On Saturday, 21 September 2019 at 08:34:09 UTC, Ron Tarrant 
> wrote:
>> Thanks, Dennis. Not performant... It doesn't work? I was 
>> hoping for a complete, working example, but maybe this'll help.
>
> Bad word choice (it appears it's debatable whether 'performant' 
> even is a word), I meant it was a simple implementation not 
> optimized for speed / memory efficiency.
> Making it 'complete' is a bit hard since I can think of tens of 
> methods and operator overloads you could use, but if I include 
> them all it's no longer minimal and it just becomes 
> std.container.dlist.
>
>> Does a doubly-linked list always have to be done with structs? 
>> Can it be classes instead?
>
> My example originally included classes actually. It was mostly 
> the same, except that Node!T* was just Node!T. The only problem 
> was with const:
>
> ```
> size_t length() const {
>     size_t result = 0;
>     for(auto a = head; a !is null; a = a.next) result++;
>     return result;
> }
>
> ```
>
> Since I marked the method as const, `auto a = head` got the 
> type const(Node!T) and `a = a.next` no longer compiled. With 
> structs you can declare a const(Node!T)* (mutable pointer to 
> const node), but I don't know if I can declare a mutable 
> reference to a const class, so I switched to structs.

Below is a simple doubly linked list with Garbage Collected 
memory.
It's not performant or complete by any means, just a minimal 
example in D like you wanted.
You probably also want methods for removing nodes or inserting in 
the middle (else why don't you use an array?), I think you can 
think of an implementation for those yourself (or look them up, 
there should be plenty examples online).