# sets

## Functions for Set Manipulation

Sets are collections of elements with no duplicate elements. The representation of a set is not defined.

This module provides exactly the same interface as the module ordsets but with a defined representation. One difference is that while this module considers two elements as different if they do not match (=:=), ordsets considers two elements as different if and only if they do not compare equal (==).

### set(Element)

As returned by new/0.

### new() -> set()

Returns a new empty set.

### is_set(Set) -> boolean()

• Set = term()

Returns true if Set is a set of elements, otherwise false.

### size(Set) -> integer() >= 0

Returns the number of elements in Set.

### to_list(Set) -> List

• Set = set(Element)
• List = [Element]

Returns the elements of Set as a list. The order of the returned elements is undefined.

### from_list(List) -> Set

• List = [Element]
• Set = set(Element)

Returns a set of the elements in List.

### is_element(Element, Set) -> boolean()

• Set = set(Element)

Returns true if Element is an element of Set, otherwise false.

• Set1 = Set2 = set(Element)

Returns a new set formed from Set1 with Element inserted.

### del_element(Element, Set1) -> Set2

• Set1 = Set2 = set(Element)

Returns Set1, but with Element removed.

### union(Set1, Set2) -> Set3

• Set1 = Set2 = Set3 = set(Element)

Returns the merged (union) set of Set1 and Set2.

### union(SetList) -> Set

• SetList = [set(Element)]
• Set = set(Element)

Returns the merged (union) set of the list of sets.

### intersection(Set1, Set2) -> Set3

• Set1 = Set2 = Set3 = set(Element)

Returns the intersection of Set1 and Set2.

### intersection(SetList) -> Set

• SetList = [set(Element), ...]
• Set = set(Element)

Returns the intersection of the non-empty list of sets.

### is_disjoint(Set1, Set2) -> boolean()

• Set1 = Set2 = set(Element)

Returns true if Set1 and Set2 are disjoint (have no elements in common), and false otherwise.

### subtract(Set1, Set2) -> Set3

• Set1 = Set2 = Set3 = set(Element)

Returns only the elements of Set1 which are not also elements of Set2.

### is_subset(Set1, Set2) -> boolean()

• Set1 = Set2 = set(Element)

Returns true when every element of Set11 is also a member of Set2, otherwise false.

### fold(Function, Acc0, Set) -> Acc1

• Function = fun((Element, AccIn) -> AccOut)
• Set = set(Element)
• Acc0 = Acc1 = AccIn = AccOut = Acc

Fold Function over every element in Set returning the final value of the accumulator. The evaluation order is undefined.

### filter(Pred, Set1) -> Set2

• Pred = fun((Element) -> boolean())
• Set1 = Set2 = set(Element)

Filter elements in Set1 with boolean function Pred.