On Thu, 27 May 2010 09:27:39 -0400, Steven Schveighoffer
<schvei...@yahoo.com> wrote:
On Thu, 27 May 2010 09:23:03 -0400, Steven Schveighoffer
<schvei...@yahoo.com> wrote:
On Thu, 27 May 2010 00:36:24 -0400, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
I just implemented a singly-linked list type to illustrate the
container abstraction.
http://erdani.com/d/phobos/std_container.html
http://erdani.com/d/phobos/container.d
One interesting aspect is that SList must cooperate with Take. More
details are to be found in code, but essentially SList ranges are all
sentinel-terminated, which makes them "right-bound". If you want to
only remove a few elements from the middle of a list, you need to
construct a range that spans a limited portion of the list. I encoded
that by using the Take abstraction in std.range.
Please let me know of how you find it. There are a few refinements and
ancillary functions to define, but those are pretty clear given the
rest.
Well, one thing I don't like about it is that you cannot do O(1)
insertion or removal. insertBefore requires O(n) complexity and
insertAfter requires O(m) complexity. Removal will require O(n)
complexity, even though it doesn't exist right now.
Fast removal and insertion are key to having a linked list. I'd
suggest modifying the range so it uses a Node ** instead, which points
to the _next element of the previous node of the one currently being
iterated, or _root if it's the first node in the list.
In fact, I'd say that it would be critical to split the insert and
remove functions to slow (O(n) or greater) versions and fast( O(lg(n) or
less)) functions. Some algorithms may depend on fast insertion and
removal, such as mergesort on a linked list.
Actualy mergesort could not be implemented without some sort of way to
restructure the list without allocating new nodes, requiring knowledge of
the link structure. I'm not sure it could be generic... I'll think about
this a bit.
-Steve
