# 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 (`==`

).

#### DATA TYPES

set() as returned by new/0

#### Functions

### new() -> Set

`Set = set()`

Returns a new empty set.

### is_set(Set) -> bool()

`Set = term()`

Returns `true`

if `Set`

is a set of
elements, otherwise `false`

.

### size(Set) -> int()

`Set = term()`

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) -> bool()

`Element = term()`

`Set = set()`

Returns `true`

if `Element`

is an element of
`Set`

, otherwise `false`

.

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

`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.

### 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) -> bool()

`Set1 = Set2 = set()`

Returns `true`

when every element of `Set`

1 is
also a member of `Set2`

, otherwise `false`

.

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

`Function = fun (E, AccIn) -> AccOut`

`Acc0 = Acc1 = AccIn = AccOut = term()`

`Set = set()`

Fold `Function`

over every element in `Set`

returning the final value of the accumulator.

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

`Pred = fun (E) -> bool()`

`Set1 = Set2 = set()`

Filter elements in `Set1`

with boolean function
`Fun`

.