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struct Set(T)
inherits Struct

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_of? s2 # => false
s2.subset_of? s1 # => true

Included modules

Enumerable Iterable

Class methods

.additive_identity : self

Returns the additive identity of this type.

This is an empty set.

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

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.new(other : Indexable(T))

Optimized version of new used when other is also an Indexable

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.new(enumerable : Enumerable(T))

Creates a new set from the elements in enumerable.

a = [1, 3, 5]
s = Set.new a
s.empty? # => false
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.new(pull : JSON::PullParser)

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.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.

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.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node

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Methods

#&(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'}
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#+(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}
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#-(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'}
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#-(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'}
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#<<(object : T)

Alias for add

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#==(other : Set)

Returns true if both sets have the same elements.

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

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#^(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'}
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#^(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'}
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#add(object : T)

Adds object to the set and returns self.

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

Removes all elements in the set, and returns self.

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

Returns a new Set with all of the elements cloned.

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#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
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#compare_by_identity?

Returns true of this Set is comparing objects by object_id.

See compare_by_identity.

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#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.

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#delete(object) : Bool

Removes the object from the set and returns true if it was present, otherwise returns false.

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

Returns a new Set with all of the same elements.

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#each

Returns an iterator for each element of the set.

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#each(&) : Nil

Yields each element of the set, and returns nil.

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#empty?

Returns true if the set is empty.

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

See Object#hash(hasher)

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#includes?(object)

Returns true if object exists in the set.

s = Set{1, 5}
s.includes? 5 # => true
s.includes? 9 # => false
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#inspect(io : IO) : Nil

Alias of #to_s.

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#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
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#pretty_print(pp) : Nil

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#proper_subset_of?(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_of? Set{1, 3, 5}    # => true
Set{1, 3, 5}.proper_subset_of? Set{1, 3, 5} # => false
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#proper_superset_of?(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_of? Set{1, 5}    # => true
Set{1, 3, 5}.proper_superset_of? Set{1, 3, 5} # => false
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#size

Returns the number of elements in the set.

s = Set{1, 5}
s.size # => 2
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#subset_of?(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_of? Set{1, 3, 5}    # => true
Set{1, 3, 5}.subset_of? Set{1, 3, 5} # => true
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#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}
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#superset_of?(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_of? Set{1, 5}    # => true
Set{1, 3, 5}.superset_of? Set{1, 3, 5} # => true
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#to_a

Returns the elements as an Array.

Set{1, 5}.to_a # => [1,5]
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#to_json(json : JSON::Builder)

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#to_s(io : IO) : Nil

Writes a string representation of the set to io.

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#to_yaml(yaml : YAML::Nodes::Builder)

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#|(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.

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