[Ocaml-lib-devel] Enum, doubly linked lists, and thoughts

[Brian H. <bh...@sp...>]

I'm playing (while waiting for compiles) at writting a circular, mutable,
doubly linked list data structure.  The advantage of this is that inserts
anywhere into the list are O(1), if you have a pointer into the list.

Enum is almost a perfect vehicle for this- internal to the enum I'm 
keeping a reference to the current element.  If I could just 'reach into' 
the enum and snag this reference, all would be good with the world.  But I 
can't figure out how to do that (this may be because it's friday afternoon 
of a long, stressfull week and my brain is mush).

So this leaves me with three options, that I wanted to throw out to the 
listmind at large for input:

1) I can extend Enum to do what I want/need.  Nicolas is probably against 
this.  And here I think I actually agree with him- we don't want to extend 
Enum in ways that make it hard/inefficient/impossible to apply to native 
linked lists.

2) I can implement a whole new interface, call it Pointer for lack of a 
better name, and implement *that*.  One member of this interface being 
Pointer.enum_of, an O(1) creation of an enumeration given a pointer.

3) I can just add the pointer library, without any generalization (but
still with the enum_of function), to the Dllist library.

Thoughts?

Brian