struct Set(T)

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.concat([6, 8])
s1.subset_of? s2 # => false
s2.subset_of? s1 # => true

json/to_json.cr
set.cr
yaml/to_yaml.cr

Constructor Detail

Returns the additive identity of this type.

This is an empty set.

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 : 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 -(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 <<(object : T) #

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

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'}

Adds object to the set and returns self.

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

def add?(object : T) : Bool #

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

s = Set{1, 5}

def clear : self #

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? : Bool #

Returns true of this Set is comparing objects by object_id.

def concat(elems) : self #

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) : 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

def dup #

Returns a new Set with all of the same elements.

def each(& : T -> ) : Nil #

Yields each element of the set, and returns nil.

def each #

Returns an iterator for each element of the set.

def empty? : Bool #

Returns true if the set is empty.

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

def hash(hasher) #

def includes?(object) : Bool #

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) : Bool #

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_of?(other : Set) : Bool #

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

def proper_superset_of?(other : Set) : Bool #

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

def size : Int32 #

Returns the number of elements in the set.

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

def subset_of?(other : Set) : Bool #

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

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_of?(other : Set) : Bool #

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

def to_a #

Returns the elements as an Array.

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

def to_json(json : JSON::Builder) : Nil #

def to_s(io : IO) : Nil #

Writes a string representation of the set to io.

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

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'}