DList and SList missing length property?

[Steven Schveighoffer]

On Tue, 28 May 2013 17:11:06 -0400, monarch_dodra <monarchdodra at gmail.com>  
wrote:

> A proper implementation should be able to track length anyway: provide  
> 0(1) splice, and an "amortized" 0(1) length.
>
> I've always wondered why the standard didn't decide to do *that*? I  
> think *we* should provide that...

I'm not sure how that works, can you explain/have a link?

-Steve