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

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

Summary

Functions

delete(set, value): Deletes value from set
difference(mapset1, mapset2): Returns a set that is set1 without the members of set2
disjoint?(map_set1, map_set2): Checks if set1 and set2 have no members in common
equal?(map_set1, map_set2): Checks if two sets are equal
intersection(map_set1, map_set2): Returns a set containing only members that set1 and set2 have in common
member?(map_set, value): Checks if set contains value
new(): Returns a new set
new(mapset): Creates a set from an enumerable
new(enumerable, transform): Creates a mapset from an enumerable via the transformation function
put(set, value): Inserts value into set if set doesn’t already contain it
size(map_set): Returns the number of elements in set
subset?(map_set1, map_set2): Checks if set1’s members are all contained in set2
to_list(map_set): Converts set to a list
union(map_set1, map_set2): Returns a set containing all members of set1 and set2

Types

t()

t() :: t(term)

t(value)

t(value)

value()

value() :: term

Functions

delete(set, value)

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

Deletes value from set.

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

Examples

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

difference(mapset1, mapset2)

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

Returns a set that is set1 without the members of 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 set1 and 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_set1, map_set2)

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

Returns a set containing only members that set1 and 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 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(mapset)

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 mapset from an enumerable via the transformation function.

Examples

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

put(set, value)

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

Inserts value into set if 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 set.

Examples

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

subset?(map_set1, map_set2)

subset?(t, t) :: boolean

Checks if set1’s members are all contained in set2.

This function checks if set1 is a subset of 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 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 set1 and set2.

Examples

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