# 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()

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

• `Set = set()`

Returns the number of elements in `Set`.

### to_list(Set) -> List

• `Set = set()`
• `List = [term()]`

Returns the elements of `Set` as a list.

### from_list(List) -> Set

• `List = [term()]`
• `Set = set()`

Returns an set of the elements in `List`.

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

• `Element = term()`
• `Set = set()`

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

• `Element = term()`
• `Set1 = Set2 = set()`

Returns a new set formed from `Set1` with `Element` inserted.

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

• `Element = term()`
• `Set1 = Set2 = set()`

Returns `Set1`, but with `Element` removed.

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

• `Set1 = Set2 = Set3 = set()`

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

### union(SetList) -> Set

• `SetList = [set()]`
• `Set = set()`

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

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

• `Set1 = Set2 = Set3 = set()`

Returns the intersection of `Set1` and `Set2`.

### intersection(SetList) -> Set

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

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

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

• `Set1 = Set2 = set()`

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

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

• `Set1 = Set2 = Set3 = set()`

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

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

• `Set1 = Set2 = set()`

Returns `true` when every element of `Set1`1 is also a member of `Set2`, otherwise `false`.

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

• `Function = fun((E :: term(), AccIn) -> AccOut)`
• `Set = set()`
• `Acc0 = Acc1 = AccIn = AccOut = T`

Fold `Function` over every element in `Set` returning the final value of the accumulator.

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

• `Pred = fun((E :: term()) -> boolean())`
• `Set1 = Set2 = set()`

Filter elements in `Set1` with boolean function `Pred`.