# ordsets

### MODULE

ordsets

### MODULE SUMMARY

Functions for Manipulating Sets as Ordered Lists

### DESCRIPTION

Sets are collections of elements with no duplicate elements. An `ordset` is a representation of a set, where an ordered list is used to store the elements of the set. An ordered list is more efficient than an unordered list.

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

### DATA TYPES

    ordered_set()
      as returned by new/0

### EXPORTS

`new() -> Ordset`

Types:

`Ordset = ordered_set()`

Returns a new empty ordered set.

`is_set(Ordset) -> bool()`

Types:

`Ordset = term()`

Returns `true` if `Ordset` is an ordered set of elements, otherwise `false`.

`size(Ordset) -> int()`

Types:

`Ordset = term()`

Returns the number of elements in `Ordset`.

`to_list(Ordset) -> List`

Types:

`Ordset = ordered_set()`
`List = [term()]`

Returns the elements of `Ordset` as a list.

`from_list(List) -> Ordset`

Types:

`List = [term()]`
`Ordset = ordered_set()`

Returns an ordered set of the elements in `List`.

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

Types:

`Element = term()`
`Ordset = ordered_set()`

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

`add_element(Element, Ordset1) -> Ordset2`

Types:

`Element = term()`
`Ordset1 = Ordset2 = ordered_set()`

Returns a new ordered set formed from `Ordset1` with `Element` inserted.

`del_element(Element, Ordset1) -> Ordset2`

Types:

`Element = term()`
`Ordset1 = Ordset2 = ordered_set()`

Returns `Ordset1`, but with `Element` removed.

`union(Ordset1, Ordset2) -> Ordset3`

Types:

`Ordset1 = Ordset2 = Ordset3 = ordered_set()`

Returns the merged (union) set of `Ordset1` and `Ordset2`.

`union(OrdsetList) -> Ordset`

Types:

`OrdsetList = [ordered_set()]`
`Ordset = ordered_set()`

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

`intersection(Ordset1, Ordset2) -> Ordset3`

Types:

`Ordset1 = Ordset2 = Ordset3 = ordered_set()`

Returns the intersection of `Ordset1` and `Ordset2`.

`intersection(OrdsetList) -> Ordset`

Types:

`OrdsetList = [ordered_set()]`
`Ordset = ordered_set()`

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

`subtract(Ordset1, Ordset2) -> Ordset3`

Types:

`Ordset1 = Ordset2 = Ordset3 = ordered_set()`

Returns only the elements of `Ordset1` which are not also elements of `Ordset2`.

`is_subset(Ordset1, Ordset2) -> bool()`

Types:

`Ordset1 = Ordset2 = ordered_set()`

Returns `true` when every element of `Ordset`1 is also a member of `Ordset2`, otherwise `false`.

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

Types:

`Function = fun (E, AccIn) -> AccOut`
`Acc0 = Acc1 = AccIn = AccOut = term()`
`Ordset = ordered_set()`

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

`filter(Pred, Ordset1) -> Set2`

Types:

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

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

### See Also

gb_sets(3), sets(3)

### AUTHORS

Robert Virding - support@erlang.ericsson.se

stdlib 1.14.5
Copyright © 1991-2007 Ericsson AB