We need to rethink remove in std.container

[Lutger Blijdestijn]

Jonathan M Davis wrote:

> Okay, removing elements from a container sucks right now. You can do stuff
> like removeAny (generally pretty useless IMHO) or removeFront just fine,
> but removing an arbitrary range from a container just plain sucks.
> 
> remove takes a range type which is the range type for the container that
> it's on. That makes sense. It's obviously not going to be able to a take
> an arbitrary range and remove that from itself. How would it know which
> elements in that range corresponded to which elements in itself -
> especially when it could be a range which skips elements or something
> similar? So, _that_ part makes sense.

I don't understand why not. Given, as you said, that a lot of functions  
return a new type it would make sense. My answer as to how would be 
something like:

while range not empty
    container.remove range.front
    range.popFront

Is there a problem with that? 
 
> But have you actually tried to get a range of the appropriate type to
> remove from a container? It seems like almost ever function in std.range
> and std.algorithm returns a new range type, making them completely useless
> for processing a range to be removed from a container.
> 
> I was looking to remove a single element for a RedBlackTree. The best
> function that I could think to get the proper range was findSplit. The
> middle portion of the return value would be the portion that I was looking
> for. I'd take that and pass it to RedBlackTree's remove. Wrong. It uses
> takeExactly in its implementation and the first two portions of the result
> of findSplit aren't the right range type.
> 
> So, what do I do? The _only_ thing that I can think of at the moment is to
> use find to locate the beginning of the range that I want, take the length
> of the range with walkLength and then use popBackN to pop of the elements
> I don't want. e.g.

The table in the docs mention stableRemoveAny(v) which says "Same as 
c.removeAny(v), but is guaranteed to not invalidate any iterators." 

Though c.removeAny(v) itself is not listed in the table nor implemented in 
RedBlackTree, isn't this the right function for the job? (I take it v stands 
for a value of the container, rather than a range). builtin aa's also 
implement this function.