MapSet

Functions that work on sets.

MapSet is the “go to” set data structure in Elixir. A set can be constructed using MapSet.new/0:

iex> MapSet.new
#MapSet<[]>

A set can contain any kind of elements, and elements in a set don’t have to be of the same type. By definition, sets can’t contain duplicate elements: when inserting an element in a set where it’s already present, the insertion is simply a no-op.

iex> map_set = MapSet.new
iex> MapSet.put(map_set, "foo")
#MapSet<["foo"]>
iex> map_set |> MapSet.put("foo") |> MapSet.put("foo")
#MapSet<["foo"]>

A MapSet is represented internally using the %MapSet{} struct. This struct can be used whenever there’s a need to pattern match on something being a MapSet:

iex> match?(%MapSet{}, MapSet.new())
true

Note that, however, the struct fields are private and must not be accessed directly; use the functions in this module to perform operations on sets.

MapSets can also be constructed starting from other collection-type data structures: for example, see MapSet.new/1 or Enum.into/2.

Summary

Functions

delete(map_set, value): Deletes value from map_set
difference(map_set1, map_set2): Returns a set that is map_set1 without the members of map_set2
disjoint?(map_set1, map_set2): Checks if map_set1 and map_set2 have no members in common
equal?(map_set1, map_set2): Checks if two sets are equal
intersection(map_set, map_set): Returns a set containing only members that map_set1 and map_set2 have in common
member?(map_set, value): Checks if map_set contains value
new(): Returns a new set
new(enumerable): Creates a set from an enumerable
new(enumerable, transform): Creates a set from an enumerable via the transformation function
put(map_set, value): Inserts value into map_set if map_set doesn’t already contain it
size(map_set): Returns the number of elements in map_set
subset?(map_set1, map_set2): Checks if map_set1’s members are all contained in map_set2
to_list(map_set): Converts map_set to a list
union(map_set1, map_set2): Returns a set containing all members of map_set1 and map_set2

Types

t()

t() :: t(term())

t(value) (opaque)

t(value)

value()

value() :: term()

Functions

delete(map_set, value)

delete(t(val1), val2) :: t(val1) when val1: value(), val2: value()

Deletes value from map_set.

Returns a new set which is a copy of map_set but without value.

Examples

iex> map_set = MapSet.new([1, 2, 3])
iex> MapSet.delete(map_set, 4)
#MapSet<[1, 2, 3]>
iex> MapSet.delete(map_set, 2)
#MapSet<[1, 3]>

difference(map_set1, map_set2)

difference(t(val1), t(val2)) :: t(val1)
when val1: value(), val2: value()

Returns a set that is map_set1 without the members of map_set2.

Examples

iex> MapSet.difference(MapSet.new([1, 2]), MapSet.new([2, 3, 4]))
#MapSet<[1]>

disjoint?(map_set1, map_set2)

disjoint?(t(), t()) :: boolean()

Checks if map_set1 and map_set2 have no members in common.

Examples

iex> MapSet.disjoint?(MapSet.new([1, 2]), MapSet.new([3, 4]))
true
iex> MapSet.disjoint?(MapSet.new([1, 2]), MapSet.new([2, 3]))
false

equal?(map_set1, map_set2)

equal?(t(), t()) :: boolean()

Checks if two sets are equal.

The comparison between elements must be done using ===.

Examples

iex> MapSet.equal?(MapSet.new([1, 2]), MapSet.new([2, 1, 1]))
true
iex> MapSet.equal?(MapSet.new([1, 2]), MapSet.new([3, 4]))
false

intersection(map_set, map_set)

intersection(t(val), t(val)) :: t(val) when val: value()

Returns a set containing only members that map_set1 and map_set2 have in common.

Examples

iex> MapSet.intersection(MapSet.new([1, 2]), MapSet.new([2, 3, 4]))
#MapSet<[2]>

iex> MapSet.intersection(MapSet.new([1, 2]), MapSet.new([3, 4]))
#MapSet<[]>

member?(map_set, value)

member?(t(), value()) :: boolean()

Checks if map_set contains value.

Examples

iex> MapSet.member?(MapSet.new([1, 2, 3]), 2)
true
iex> MapSet.member?(MapSet.new([1, 2, 3]), 4)
false

new()

new() :: t()

Returns a new set.

Examples

iex> MapSet.new
#MapSet<[]>

new(enumerable)

new(Enum.t()) :: t()

Creates a set from an enumerable.

Examples

iex> MapSet.new([:b, :a, 3])
#MapSet<[3, :a, :b]>
iex> MapSet.new([3, 3, 3, 2, 2, 1])
#MapSet<[1, 2, 3]>

new(enumerable, transform)

new(Enum.t(), (term() -> val)) :: t(val) when val: value()

Creates a set from an enumerable via the transformation function.

Examples

iex> MapSet.new([1, 2, 1], fn x -> 2 * x end)
#MapSet<[2, 4]>

put(map_set, value)

put(t(val), new_val) :: t(val | new_val)
when val: value(), new_val: value()

Inserts value into map_set if map_set doesn’t already contain it.

Examples

iex> MapSet.put(MapSet.new([1, 2, 3]), 3)
#MapSet<[1, 2, 3]>
iex> MapSet.put(MapSet.new([1, 2, 3]), 4)
#MapSet<[1, 2, 3, 4]>

size(map_set)

size(t()) :: non_neg_integer()

Returns the number of elements in map_set.

Examples

iex> MapSet.size(MapSet.new([1, 2, 3]))
3

subset?(map_set1, map_set2)

subset?(t(), t()) :: boolean()

Checks if map_set1’s members are all contained in map_set2.

This function checks if map_set1 is a subset of map_set2.

Examples

iex> MapSet.subset?(MapSet.new([1, 2]), MapSet.new([1, 2, 3]))
true
iex> MapSet.subset?(MapSet.new([1, 2, 3]), MapSet.new([1, 2]))
false

to_list(map_set)

to_list(t(val)) :: [val] when val: value()

Converts map_set to a list.

Examples

iex> MapSet.to_list(MapSet.new([1, 2, 3]))
[1, 2, 3]

union(map_set1, map_set2)

union(t(val1), t(val2)) :: t(val1 | val2)
when val1: value(), val2: value()

Returns a set containing all members of map_set1 and map_set2.

Examples

iex> MapSet.union(MapSet.new([1, 2]), MapSet.new([2, 3, 4]))
#MapSet<[1, 2, 3, 4]>