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NAME
gb_sets - General Balanced Trees
DESCRIPTION
An implementation of ordered sets using Prof. Arne Andersson's General Balanced Trees. This can be much
more efficient than using ordered lists, for larger sets, but depends on the application.
This module considers two elements as different if and only if they do not compare equal (==).
COMPLEXITY NOTE
The complexity on set operations is bounded by either O(|S|) or O(|T| * log(|S|)), where S is the largest
given set, depending on which is fastest for any particular function call. For operating on sets of
almost equal size, this implementation is about 3 times slower than using ordered-list sets directly. For
sets of very different sizes, however, this solution can be arbitrarily much faster; in practical cases,
often between 10 and 100 times. This implementation is particularly suited for accumulating elements a
few at a time, building up a large set (more than 100-200 elements), and repeatedly testing for
membership in the current set.
As with normal tree structures, lookup (membership testing), insertion and deletion have logarithmic
complexity.
COMPATIBILITY
All of the following functions in this module also exist and do the same thing in the sets and ordsets
modules. That is, by only changing the module name for each call, you can try out different set
representations.
* add_element/2
* del_element/2
* filter/2
* fold/3
* from_list/1
* intersection/1
* intersection/2
* is_element/2
* is_set/1
* is_subset/2
* new/0
* size/1
* subtract/2
* to_list/1
* union/1
* union/2
DATA TYPES
set(Element)
A GB set.
set() = set(term())
iter(Element)
A GB set iterator.
iter() = iter(term())
EXPORTS
add(Element, Set1) -> Set2
add_element(Element, Set1) -> Set2
Types:
Set1 = Set2 = set(Element)
Returns a new set formed from Set1 with Element inserted. If Element is already an element in
Set1, nothing is changed.
balance(Set1) -> Set2
Types:
Set1 = Set2 = set(Element)
Rebalances the tree representation of Set1. Note that this is rarely necessary, but may be
motivated when a large number of elements have been deleted from the tree without further
insertions. Rebalancing could then be forced in order to minimise lookup times, since deletion
only does not rebalance the tree.
delete(Element, Set1) -> Set2
Types:
Set1 = Set2 = set(Element)
Returns a new set formed from Set1 with Element removed. Assumes that Element is present in Set1.
delete_any(Element, Set1) -> Set2
del_element(Element, Set1) -> Set2
Types:
Set1 = Set2 = set(Element)
Returns a new set formed from Set1 with Element removed. If Element is not an element in Set1,
nothing is changed.
difference(Set1, Set2) -> Set3
subtract(Set1, Set2) -> Set3
Types:
Set1 = Set2 = Set3 = set(Element)
Returns only the elements of Set1 which are not also elements of Set2.
empty() -> Set
new() -> Set
Types:
Set = set()
Returns a new empty set.
filter(Pred, Set1) -> Set2
Types:
Pred = fun((Element) -> boolean())
Set1 = Set2 = set(Element)
Filters elements in Set1 using predicate function Pred.
fold(Function, Acc0, Set) -> Acc1
Types:
Function = fun((Element, AccIn) -> AccOut)
Acc0 = Acc1 = AccIn = AccOut = Acc
Set = set(Element)
Folds Function over every element in Set returning the final value of the accumulator.
from_list(List) -> Set
Types:
List = [Element]
Set = set(Element)
Returns a set of the elements in List, where List may be unordered and contain duplicates.
from_ordset(List) -> Set
Types:
List = [Element]
Set = set(Element)
Turns an ordered-set list List into a set. The list must not contain duplicates.
insert(Element, Set1) -> Set2
Types:
Set1 = Set2 = set(Element)
Returns a new set formed from Set1 with Element inserted. Assumes that Element is not present in
Set1.
intersection(Set1, Set2) -> Set3
Types:
Set1 = Set2 = Set3 = set(Element)
Returns the intersection of Set1 and Set2.
intersection(SetList) -> Set
Types:
SetList = [set(Element), ...]
Set = set(Element)
Returns the intersection of the non-empty list of sets.
is_disjoint(Set1, Set2) -> boolean()
Types:
Set1 = Set2 = set(Element)
Returns true if Set1 and Set2 are disjoint (have no elements in common), and false otherwise.
is_empty(Set) -> boolean()
Types:
Set = set()
Returns true if Set is an empty set, and false otherwise.
is_member(Element, Set) -> boolean()
is_element(Element, Set) -> boolean()
Types:
Set = set(Element)
Returns true if Element is an element of Set, otherwise false.
is_set(Term) -> boolean()
Types:
Term = term()
Returns true if Term appears to be a set, otherwise false.
is_subset(Set1, Set2) -> boolean()
Types:
Set1 = Set2 = set(Element)
Returns true when every element of Set1 is also a member of Set2, otherwise false.
iterator(Set) -> Iter
Types:
Set = set(Element)
Iter = iter(Element)
Returns an iterator that can be used for traversing the entries of Set; see next/1. The
implementation of this is very efficient; traversing the whole set using next/1 is only slightly
slower than getting the list of all elements using to_list/1 and traversing that. The main
advantage of the iterator approach is that it does not require the complete list of all elements
to be built in memory at one time.
iterator_from(Element, Set) -> Iter
Types:
Set = set(Element)
Iter = iter(Element)
Returns an iterator that can be used for traversing the entries of Set; see next/1. The difference
as compared to the iterator returned by iterator/1 is that the first element greater than or equal
to Element is returned.
largest(Set) -> Element
Types:
Set = set(Element)
Returns the largest element in Set. Assumes that Set is nonempty.
next(Iter1) -> {Element, Iter2} | none
Types:
Iter1 = Iter2 = iter(Element)
Returns {Element, Iter2} where Element is the smallest element referred to by the iterator Iter1,
and Iter2 is the new iterator to be used for traversing the remaining elements, or the atom none
if no elements remain.
singleton(Element) -> set(Element)
Returns a set containing only the element Element.
size(Set) -> integer() >= 0
Types:
Set = set()
Returns the number of elements in Set.
smallest(Set) -> Element
Types:
Set = set(Element)
Returns the smallest element in Set. Assumes that Set is nonempty.
take_largest(Set1) -> {Element, Set2}
Types:
Set1 = Set2 = set(Element)
Returns {Element, Set2}, where Element is the largest element in Set1, and Set2 is this set with
Element deleted. Assumes that Set1 is nonempty.
take_smallest(Set1) -> {Element, Set2}
Types:
Set1 = Set2 = set(Element)
Returns {Element, Set2}, where Element is the smallest element in Set1, and Set2 is this set with
Element deleted. Assumes that Set1 is nonempty.
to_list(Set) -> List
Types:
Set = set(Element)
List = [Element]
Returns the elements of Set as a list.
union(Set1, Set2) -> Set3
Types:
Set1 = Set2 = Set3 = set(Element)
Returns the merged (union) set of Set1 and Set2.
union(SetList) -> Set
Types:
SetList = [set(Element), ...]
Set = set(Element)
Returns the merged (union) set of the list of sets.
SEE ALSO
gb_trees(3erl), ordsets(3erl), sets(3erl)
Ericsson AB stdlib 2.8 gb_sets(3erl)