# sets

### MODULE

sets

### MODULE SUMMARY

Functions for Set Manipulation

### DESCRIPTION

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

### EXPORTS

`new() -> Set`

Types:

`Set = set()`

Returns a new empty set.

`is_set(Set) -> bool()`

Types:

`Set = term()`

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

`size(Set) -> int()`

Types:

`Set = term()`

Returns the number of elements in `Set`.

`to_list(Set) -> List`

Types:

`Set = set()`
`List = [term()]`

Returns the elements of `Set` as a list.

`from_list(List) -> Set`

Types:

`List = [term()]`
`Set = set()`

Returns an set of the elements in `List`.

`is_element(Element, Set) -> bool()`

Types:

`Element = term()`
`Set = set()`

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

`add_element(Element, Set1) -> Set2`

Types:

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

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

`del_element(Element, Set1) -> Set2`

Types:

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

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

`union(Set1, Set2) -> Set3`

Types:

`Set1 = Set2 = Set3 = set()`

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

`union(SetList) -> Set`

Types:

`SetList = [set()]`
`Set = set()`

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

`intersection(Set1, Set2) -> Set3`

Types:

`Set1 = Set2 = Set3 = set()`

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

`intersection(SetList) -> Set`

Types:

`SetList = [set()]`
`Set = set()`

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

`subtract(Set1, Set2) -> Set3`

Types:

`Set1 = Set2 = Set3 = set()`

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

`is_subset(Set1, Set2) -> bool()`

Types:

`Set1 = Set2 = set()`

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

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

Types:

`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`

Types:

`Pred = fun (E) -> bool()`
`Set1 = Set2 = set()`

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

### See Also

ordsets(3), gb_sets(3)

### AUTHORS

Robert Virding - support@erlang.ericsson.se

stdlib 1.14.5
Copyright © 1991-2007 Ericsson AB