ApplyFilter applies a filter to our UIDList.

IndexOf performs a binary search on the uids slice and returns the index at which it finds the uid, else returns -1.

IntersectSorted intersect a list of UIDLists.

MergeSorted merges sorted lists.

NewListIterator returns a read iterator for the list passed to it.

Slice returns a new task.List with the elements between start index and end index of the list passed to it.

ToUintsListForTest converts to list of uints for testing purpose only.

AsList implements sort.Interface by for block lists.

ListIterator is used to read through the task.List.

WriteIterator is used to append UIDs to a task.List.