can-derive

Derive live can.List and can.Maps from source lists.

This supports O(log n) maintaintence of mapped and filtered can.Lists. Basically this means if you setup a derived list like completed in the following example:

var sourceList = new can.List([{name: "dishes", complete: true}, 
                               {name: "lawn", complete: false}, 
                              ...])

var completed = sourceList.filter(function(todo){
  return todo.attr("complete");
});

Any changes to sourceList will automatically update the derived completed list in O(log n) time.
This avoids the standard O(n) times done everywhere else.

It does this by:

• keeping completed in a RBTree.
• listening to when any items are added or removed from the source list.
• listening to when the predicate function value changes for any item.

The general algorithim was worked out in this thread.