# struct Set(T)

- Set(T)
- Struct
- Value
- Object

##
Overview

`Set` implements a collection of unordered values with no duplicates.

An `Enumerable` object can be converted to `Set` using the `#to_set` method.

`Set` uses `Hash` as storage, so you must note the following points:

- Equality of elements is determined according to `Object#==` and `Object#hash`.
- `Set` assumes that the identity of each element does not change while it is stored. Modifying an element of a set will render the set to an unreliable state.

###
Example

    s1 = Set{1, 2}
    s2 = [1, 2].to_set
    s3 = Set.new [1, 2]
    s1 == s2 # => true
    s1 == s3 # => true
    s1.add(2)
    s1.concat([6, 8])
    s1.subset? s2 # => false
    s2.subset? s1 # => true

##
Included Modules

- Enumerable(T)
- Iterable(T)

##
Defined in:

##
Constructors

- .new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
- .new(other : Indexable(T))

  Optimized version of `.new` used when other is also an `Indexable`

- .new(enumerable : Enumerable(T))

  Creates a new set from the elements in enumerable.

- .new(pull : JSON::PullParser)
- .new(initial_capacity = nil)

  Creates a new, empty `Set`.

- .new(ctx : YAML::ParseContext, node : YAML::Nodes::Node, &)

##
Instance Method Summary

- #&(other : Set)

  Intersection: returns a new set containing elements common to both sets.

- #+(other : Set(U)) forall U

  Addition: returns a new set containing the unique elements from both sets.

- #-(other : Enumerable)

  Difference: returns a new set containing elements in this set that are not present in the other enumerable.

- #-(other : Set)

  Difference: returns a new set containing elements in this set that are not present in the other.

- #<<(object : T)

  Alias for `#add`

- #==(other : Set)

  Returns `true` if both sets have the same elements.

- #===(object : T)

  Same as `#includes?`.

- #^(other : Set(U)) forall U

  Symmetric Difference: returns a new set `(self - other) | (other - self)`.

- #^(other : Enumerable(U)) forall U

  Symmetric Difference: returns a new set `(self - other) | (other - self)`.

- #add(object : T)

  Adds object to the set and returns `self`.

- #add?(object : T)

  Adds object to the set and returns `true` on success and `false` if the value was already in the set.

- #clear

  Removes all elements in the set, and returns `self`.

- #clone

  Returns a new `Set` with all of the elements cloned.

- #compare_by_identity

  Makes this set compare objects using their object identity (`object_id)` for types that define such method (`Reference` types, but also structs that might wrap other `Reference` types and delegate the `object_id` method to them).

- #compare_by_identity?

  Returns `true` of this Set is comparing objects by `object_id`.

- #concat(elems)

  Adds `#each` element of elems to the set and returns `self`.

- #delete(object)

  Removes the object from the set and returns `self`.

- #dup

  Returns a new `Set` with all of the same elements.

- #each

  Returns an iterator for each element of the set.

- #each(&)

  Yields each element of the set, and returns `self`.

- #empty?

  Returns `true` if the set is empty.

- #hash(hasher)

  See `Object#hash(hasher)`

- #includes?(object)

  Returns `true` if object exists in the set.

- #inspect(io : IO) : Nil

  Alias of `#to_s`.

- #intersects?(other : Set)

  Returns `true` if the set and the given set have at least one element in common.

- #pretty_print(pp) : Nil
- #proper_subset?(other : Set)

  Returns `true` if the set is a proper subset of the other set.

- #proper_superset?(other : Set)

  Returns `true` if the set is a superset of the other set.

- #size

  Returns the number of elements in the set.

- #subset?(other : Set)

  Returns `true` if the set is a subset of the other set.

- #subtract(other : Enumerable)

  Returns `self` after removing from it those elements that are present in the given enumerable.

- #superset?(other : Set)

  Returns `true` if the set is a superset of the other set.

- #to_a

  Returns the elements as an `Array`.

- #to_json(json : JSON::Builder)
- #to_s(io : IO) : Nil

  Writes a string representation of the set to io.

- #to_yaml(yaml : YAML::Nodes::Builder)
- #|(other : Set(U)) forall U

  Union: returns a new set containing all unique elements from both sets.

### Instance methods inherited from module `Iterable(T)`

chunk(reuse = false, &block : T -> U) forall U chunk, chunk_while(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B chunk_while, cycle(n)
cycle cycle, each each, each_cons(count : Int, reuse = false) each_cons, each_slice(count : Int, reuse = false) each_slice, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object, slice_after(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_after(pattern, reuse : Bool | Array(T) = false) slice_after, slice_before(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_before(pattern, reuse : Bool | Array(T) = false) slice_before, slice_when(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B slice_when

### Instance methods inherited from module `Enumerable(T)`

all?(&)
all?(pattern)
all? all?, any?(&)
any?(pattern)
any? any?, chunks(&block : T -> U) forall U chunks, compact_map(&) compact_map, count(&)
count(item) count, cycle(n, &)
cycle(&) cycle, each(&block : T -> _) each, each_cons(count : Int, reuse = false, &) each_cons, each_cons_pair(& : T, T -> _) : Nil each_cons_pair, each_slice(count : Int, reuse = false, &) each_slice, each_with_index(offset = 0, &) each_with_index, each_with_object(obj, &) each_with_object, find(if_none = nil, &) find, first(count : Int)
first first, first? first?, flat_map(&block : T -> Array(U) | Iterator(U) | U) forall U flat_map, grep(pattern) grep, group_by(&block : T -> U) forall U group_by, in_groups_of(size : Int, filled_up_with : U = nil) forall U
in_groups_of(size : Int, filled_up_with : U = nil, reuse = false, &) forall U in_groups_of, includes?(obj) includes?, index(&)
index(obj) index, index_by(&block : T -> U) forall U index_by, join(separator = "", &)
join(separator, io, &)
join(separator, io)
join(separator = "") join, map(&block : T -> U) forall U map, map_with_index(offset = 0, &block : T, Int32 -> U) forall U map_with_index, max max, max? max?, max_by(&block : T -> U) forall U max_by, max_by?(&block : T -> U) forall U max_by?, max_of(&block : T -> U) forall U max_of, max_of?(&block : T -> U) forall U max_of?, min min, min? min?, min_by(&block : T -> U) forall U min_by, min_by?(&block : T -> U) forall U min_by?, min_of(&block : T -> U) forall U min_of, min_of?(&block : T -> U) forall U min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : T -> U) forall U minmax_by, minmax_by?(&block : T -> U) forall U minmax_by?, minmax_of(&block : T -> U) forall U minmax_of, minmax_of?(&block : T -> U) forall U minmax_of?, none?
none?(pattern)
none?(&) none?, one?(&)
one?(pattern)
one? one?, partition(&) partition, product(&)
product(initial : Number, &)
product
product(initial : Number) product, reduce(memo, &)
reduce(&) reduce, reduce?(&) reduce?, reject(&block : T -> )
reject(type : U.class) forall U
reject(pattern) reject, select(pattern)
select(type : U.class) forall U
select(&block : T -> ) select, size size, skip(count : Int) skip, skip_while(&) skip_while, sum(initial)
sum
sum(initial, &)
sum(&) sum, take_while(&) take_while, tally : Hash(T, Int32) tally, to_a to_a, to_h
to_h(&block : T -> Tuple(K, V)) forall K, V to_h, to_set to_set, zip(*others : Indexable | Iterable | Iterator, &)
zip(*others : Indexable | Iterable | Iterator) zip, zip?(*others : Indexable | Iterable | Iterator, &)
zip?(*others : Indexable | Iterable | Iterator) zip?

### Instance methods inherited from struct `Struct`

==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

### Instance methods inherited from struct `Value`

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, __crystal_pseudo_! : Bool __crystal_pseudo_!, __crystal_pseudo_as(type : Class) __crystal_pseudo_as, __crystal_pseudo_as?(type : Class) __crystal_pseudo_as?, __crystal_pseudo_is_a?(type : Class) : Bool __crystal_pseudo_is_a?, __crystal_pseudo_nil? : Bool __crystal_pseudo_nil?, __crystal_pseudo_responds_to?(name : Symbol) : Bool __crystal_pseudo_responds_to?, class class, dup dup, hash(hasher)
hash hash, inspect : String
inspect(io : IO) : Nil inspect, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&) tap, to_json(io : IO)
to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s : String
to_s(io : IO) : Nil to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

##
Constructor Detail

def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node) #
def self.new(other : Indexable(T)) #

Optimized version of `.new` used when other is also an `Indexable`

def self.new(enumerable : Enumerable(T)) #

Creates a new set from the elements in enumerable.

    a = [1, 3, 5]
    s = Set.new a
    s.empty? # => false

def self.new(pull : JSON::PullParser) #
def self.new(initial_capacity = nil) #

Creates a new, empty `Set`.

    s = Set(Int32).new
    s.empty? # => true

An initial capacity can be specified, and it will be set as the initial capacity of the internal `Hash`.

def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node, &) #

##
Instance Method Detail

def &(other : Set) #

Intersection: returns a new set containing elements common to both sets.

    Set{1, 1, 3, 5} & Set{1, 2, 3}               # => Set{1, 3}
    Set{'a', 'b', 'b', 'z'} & Set{'a', 'b', 'c'} # => Set{'a', 'b'}

def +(other : Set(U)) forall U #

Addition: returns a new set containing the unique elements from both sets.

    Set{1, 1, 2, 3} + Set{3, 4, 5} # => Set{1, 2, 3, 4, 5}

def -(other : Enumerable) #

Difference: returns a new set containing elements in this set that are not present in the other enumerable.

    Set{1, 2, 3, 4, 5} - [2, 4]               # => Set{1, 3, 5}
    Set{'a', 'b', 'b', 'z'} - ['a', 'b', 'c'] # => Set{'z'}

def -(other : Set) #

Difference: returns a new set containing elements in this set that are not present in the other.

    Set{1, 2, 3, 4, 5} - Set{2, 4}               # => Set{1, 3, 5}
    Set{'a', 'b', 'b', 'z'} - Set{'a', 'b', 'c'} # => Set{'z'}

def <<(object : T) #

Alias for `#add`

def ==(other : Set) #

Returns `true` if both sets have the same elements.

    Set{1, 5} == Set{1, 5} # => true

def ===(object : T) #

Same as `#includes?`.

It is for convenience with using on `case` statement.

    red_like = Set{"red", "pink", "violet"}
    blue_like = Set{"blue", "azure", "violet"}

    case "violet"
    when red_like & blue_like
      puts "red & blue like color!"
    when red_like
      puts "red like color!"
    when blue_like
      puts "blue like color!"
    end

See also: `Object#===`.

def ^(other : Set(U)) forall U #

Symmetric Difference: returns a new set `(self - other) | (other - self)`. Equivalently, returns `(self | other) - (self & other)`.

    Set{1, 2, 3, 4, 5} ^ Set{2, 4, 6}            # => Set{1, 3, 5, 6}
    Set{'a', 'b', 'b', 'z'} ^ Set{'a', 'b', 'c'} # => Set{'z', 'c'}

def ^(other : Enumerable(U)) forall U #

Symmetric Difference: returns a new set `(self - other) | (other - self)`. Equivalently, returns `(self | other) - (self & other)`.

    Set{1, 2, 3, 4, 5} ^ [2, 4, 6]            # => Set{1, 3, 5, 6}
    Set{'a', 'b', 'b', 'z'} ^ ['a', 'b', 'c'] # => Set{'z', 'c'}

def add(object : T) #

Adds object to the set and returns `self`.

    s = Set{1, 5}
    s.includes? 8 # => false
    s << 8
    s.includes? 8 # => true

def add?(object : T) #

Adds object to the set and returns `true` on success and `false` if the value was already in the set.

    s = Set{1, 5}
    s.add? 8 # => true
    s.add? 8 # => false

def clear #

Removes all elements in the set, and returns `self`.

    s = Set{1, 5}
    s.size # => 2
    s.clear
    s.size # => 0

def clone #

Returns a new `Set` with all of the elements cloned.

def compare_by_identity #

Makes this set compare objects using their object identity (`object_id)` for types that define such method (`Reference` types, but also structs that might wrap other `Reference` types and delegate the `object_id` method to them).

    s = Set{"foo", "bar"}
    s.includes?("fo" + "o") # => true

    s.compare_by_identity
    s.compare_by_identity?  # => true
    s.includes?("fo" + "o") # => false # not the same String instance

def compare_by_identity? #

Returns `true` of this Set is comparing objects by `object_id`.

See `#compare_by_identity`.

def concat(elems) #

Adds `#each` element of elems to the set and returns `self`.

    s = Set{1, 5}
    s.concat [5, 5, 8, 9]
    s.size # => 4

See also: `#|` to merge two sets and return a new one.

def delete(object) #

Removes the object from the set and returns `self`.

    s = Set{1, 5}
    s.includes? 5 # => true
    s.delete 5
    s.includes? 5 # => false

def dup #

Returns a new `Set` with all of the same elements.

def each #

Returns an iterator for each element of the set.

def each(&) #

Yields each element of the set, and returns `self`.

def empty? #

Returns `true` if the set is empty.

    s = Set(Int32).new
    s.empty? # => true
    s << 3
    s.empty? # => false

def hash(hasher) #

See `Object#hash(hasher)`

def includes?(object) #

Returns `true` if object exists in the set.

    s = Set{1, 5}
    s.includes? 5 # => true
    s.includes? 9 # => false

def inspect(io : IO) : Nil #

Alias of `#to_s`.

def intersects?(other : Set) #

Returns `true` if the set and the given set have at least one element in common.

    Set{1, 2, 3}.intersects? Set{4, 5} # => false
    Set{1, 2, 3}.intersects? Set{3, 4} # => true

def pretty_print(pp) : Nil #
def proper_subset?(other : Set) #

Returns `true` if the set is a proper subset of the other set.

This set must have fewer elements than the other set, and all of elements in this set must be present in the other set.

    Set{1, 5}.proper_subset? Set{1, 3, 5}    # => true
    Set{1, 3, 5}.proper_subset? Set{1, 3, 5} # => false

def proper_superset?(other : Set) #

Returns `true` if the set is a superset of the other set.

The other must have the same or fewer elements than this set, and all of elements in the other set must be present in this set.

    Set{1, 3, 5}.proper_superset? Set{1, 5}    # => true
    Set{1, 3, 5}.proper_superset? Set{1, 3, 5} # => false

def size #

Returns the number of elements in the set.

    s = Set{1, 5}
    s.size # => 2

def subset?(other : Set) #

Returns `true` if the set is a subset of the other set.

This set must have the same or fewer elements than the other set, and all of elements in this set must be present in the other set.

    Set{1, 5}.subset? Set{1, 3, 5}    # => true
    Set{1, 3, 5}.subset? Set{1, 3, 5} # => true

def subtract(other : Enumerable) #

Returns `self` after removing from it those elements that are present in the given enumerable.

    Set{'a', 'b', 'b', 'z'}.subtract Set{'a', 'b', 'c'} # => Set{'z'}
    Set{1, 2, 3, 4, 5}.subtract [2, 4, 6]               # => Set{1, 3, 5}

def superset?(other : Set) #

Returns `true` if the set is a superset of the other set.

The other must have the same or fewer elements than this set, and all of elements in the other set must be present in this set.

    Set{1, 3, 5}.superset? Set{1, 5}    # => true
    Set{1, 3, 5}.superset? Set{1, 3, 5} # => true

def to_a #

Returns the elements as an `Array`.

    Set{1, 5}.to_a # => [1,5]

def to_json(json : JSON::Builder) #
def to_s(io : IO) : Nil #

Writes a string representation of the set to io.

def to_yaml(yaml : YAML::Nodes::Builder) #
def |(other : Set(U)) forall U #

Union: returns a new set containing all unique elements from both sets.

    Set{1, 1, 3, 5} | Set{1, 2, 3}               # => Set{1, 3, 5, 2}
    Set{'a', 'b', 'b', 'z'} | Set{'a', 'b', 'c'} # => Set{'a', 'b', 'z', 'c'}

See also: `#concat` to add elements from a set to `self`.