Class: Set

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/set.rb

Overview

This library provides the Set class, which deals with a collection of unordered values with no duplicates. It is a hybrid of Array's intuitive inter-operation facilities and Hash's fast lookup.

The method `to_set` is added to Enumerable for convenience.

Set implements a collection of unordered values with no duplicates. This is a hybrid of Array's intuitive inter-operation facilities and Hash's fast lookup.

Set is easy to use with Enumerable objects (implementing `each`). Most of the initializer methods and binary operators accept generic Enumerable objects besides sets and arrays. 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#eql? and Object#hash. Use Set#compare_by_identity to make a set compare its elements by their identity.

  • 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.

  • When a string is to be stored, a frozen copy of the string is stored instead unless the original string is already frozen.

## Comparison

The comparison operators `<`, `>`, `<=`, and `>=` are implemented as shorthand for the proper_,subset?,superset? methods. The `<=>` operator reflects this order, or return `nil` for sets that both have distinct elements (`y` vs. `z` for example).

## Example

“`ruby require 'set' s1 = Set[1, 2] #=> #<Set: 2> s2 = [1, 2].to_set #=> #<Set: 2> s1 == s2 #=> true s1.add(“foo”) #=> #<Set: 2, “foo”> s1.merge([2, 6]) #=> #<Set: 2, “foo”, 6> s1.subset?(s2) #=> false s2.subset?(s1) #=> true “`

## Contact

Constant Summary collapse

InspectKey =

:nodoc:

:__inspect_key__

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(enum = nil, &block) ⇒ Set

Creates a new set containing the elements of the given enumerable object.

If a block is given, the elements of enum are preprocessed by the given block.

Set.new([1, 2])                       #=> #<Set: {1, 2}>
Set.new([1, 2, 1])                    #=> #<Set: {1, 2}>
Set.new([1, 'c', :s])                 #=> #<Set: {1, "c", :s}>
Set.new(1..5)                         #=> #<Set: {1, 2, 3, 4, 5}>
Set.new([1, 2, 3]) { |x| x * x }      #=> #<Set: {1, 4, 9}>

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# File 'lib/set.rb', line 88

def initialize(enum = nil, &block) # :yields: o
  @hash ||= Hash.new(false)

  enum.nil? and return

  if block
    do_with_enum(enum) { |o| add(block[o]) }
  else
    merge(enum)
  end
end

Class Method Details

.[](*ary) ⇒ Object

Creates a new set containing the given objects.

Set[1, 2]                   # => #<Set: {1, 2}>
Set[1, 2, 1]                # => #<Set: {1, 2}>
Set[1, 'c', :s]             # => #<Set: {1, "c", :s}>

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# File 'lib/set.rb', line 73

def self.[](*ary)
  new(ary)
end

Instance Method Details

#&(enum) ⇒ Object Also known as: intersection

Returns a new set containing elements common to the set and the given enumerable object.

Set[1, 3, 5] & Set[3, 2, 1]             #=> #<Set: {3, 1}>
Set['a', 'b', 'z'] & ['a', 'b', 'c']    #=> #<Set: {"a", "b"}>

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# File 'lib/set.rb', line 481

def &(enum)
  n = self.class.new
  if enum.is_a?(Set)
    if enum.size > size
      each { |o| n.add(o) if enum.include?(o) }
    else
      enum.each { |o| n.add(o) if include?(o) }
    end
  else
    do_with_enum(enum) { |o| n.add(o) if include?(o) }
  end
  n
end

#-(enum) ⇒ Object Also known as: difference

Returns a new set built by duplicating the set, removing every element that appears in the given enumerable object.

Set[1, 3, 5] - Set[1, 5]                #=> #<Set: {3}>
Set['a', 'b', 'z'] - ['a', 'c']         #=> #<Set: {"b", "z"}>

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# File 'lib/set.rb', line 471

def -(enum)
  dup.subtract(enum)
end

#<=>(set) ⇒ Object

Returns 0 if the set are equal, -1 / +1 if the set is a proper subset / superset of the given set, or nil if they both have unique elements.


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# File 'lib/set.rb', line 306

def <=>(set)
  return unless set.is_a?(Set)

  case size <=> set.size
  when -1 then -1 if proper_subset?(set)
  when +1 then +1 if proper_superset?(set)
  else 0 if self.==(set)
  end
end

#==(other) ⇒ Object

Returns true if two sets are equal. The equality of each couple of elements is defined according to Object#eql?.

Set[1, 2] == Set[2, 1]                       #=> true
Set[1, 3, 5] == Set[1, 5]                    #=> false
Set['a', 'b', 'c'] == Set['a', 'c', 'b']     #=> true
Set['a', 'b', 'c'] == ['a', 'c', 'b']        #=> false

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# File 'lib/set.rb', line 515

def ==(other)
  if self.equal?(other)
    true
  elsif other.instance_of?(self.class)
    @hash == other.instance_variable_get(:@hash)
  elsif other.is_a?(Set) && self.size == other.size
    other.all? { |o| @hash.include?(o) }
  else
    false
  end
end

#^(enum) ⇒ Object

Returns a new set containing elements exclusive between the set and the given enumerable object. `(set ^ enum)` is equivalent to `((set | enum) - (set & enum))`.

Set[1, 2] ^ Set[2, 3]                   #=> #<Set: {3, 1}>
Set[1, 'b', 'c'] ^ ['b', 'd']           #=> #<Set: {"d", 1, "c"}>

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# File 'lib/set.rb', line 502

def ^(enum)
  n = Set.new(enum)
  each { |o| n.add(o) unless n.delete?(o) }
  n
end

#add(o) ⇒ Object Also known as: <<

Adds the given object to the set and returns self. Use `merge` to add many elements at once.

Set[1, 2].add(3)                    #=> #<Set: {1, 2, 3}>
Set[1, 2].add([3, 4])               #=> #<Set: {1, 2, [3, 4]}>
Set[1, 2].add(2)                    #=> #<Set: {1, 2}>

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# File 'lib/set.rb', line 354

def add(o)
  @hash[o] = true
  self
end

#add?(o) ⇒ Boolean

Adds the given object to the set and returns self. If the object is already in the set, returns nil.

Set[1, 2].add?(3)                    #=> #<Set: {1, 2, 3}>
Set[1, 2].add?([3, 4])               #=> #<Set: {1, 2, [3, 4]}>
Set[1, 2].add?(2)                    #=> nil

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 366

def add?(o)
  add(o) unless include?(o)
end

#classifyObject

Classifies the set by the return value of the given block and returns a hash of => set of elements pairs. The block is called once for each element of the set, passing the element as parameter.

require 'set'
files = Set.new(Dir.glob("*.rb"))
hash = files.classify { |f| File.mtime(f).year }
hash       #=> {2000=>#<Set: {"a.rb", "b.rb"}>,
           #    2001=>#<Set: {"c.rb", "d.rb", "e.rb"}>,
           #    2002=>#<Set: {"f.rb"}>}

Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 584

def classify # :yields: o
  block_given? or return enum_for(__method__) { size }

  h = {}

  each { |i|
    (h[yield(i)] ||= self.class.new).add(i)
  }

  h
end

#clearObject

Removes all elements and returns self.

set = Set[1, 'c', :s]             #=> #<Set: {1, "c", :s}>
set.clear                         #=> #<Set: {}>
set                               #=> #<Set: {}>

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# File 'lib/set.rb', line 169

def clear
  @hash.clear
  self
end

#collect!Object Also known as: map!

Replaces the elements with ones returned by `collect()`. Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 407

def collect!
  block_given? or return enum_for(__method__) { size }
  set = self.class.new
  each { |o| set << yield(o) }
  replace(set)
end

#compare_by_identityObject

Makes the set compare its elements by their identity and returns self. This method may not be supported by all subclasses of Set.


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# File 'lib/set.rb', line 102

def compare_by_identity
  if @hash.respond_to?(:compare_by_identity)
    @hash.compare_by_identity
    self
  else
    raise NotImplementedError, "#{self.class.name}\##{__method__} is not implemented"
  end
end

#compare_by_identity?Boolean

Returns true if the set will compare its elements by their identity. Also see Set#compare_by_identity.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 113

def compare_by_identity?
  @hash.respond_to?(:compare_by_identity?) && @hash.compare_by_identity?
end

#delete(o) ⇒ Object

Deletes the given object from the set and returns self. Use `subtract` to delete many items at once.


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# File 'lib/set.rb', line 372

def delete(o)
  @hash.delete(o)
  self
end

#delete?(o) ⇒ Boolean

Deletes the given object from the set and returns self. If the object is not in the set, returns nil.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 379

def delete?(o)
  delete(o) if include?(o)
end

#delete_ifObject

Deletes every element of the set for which block evaluates to true, and returns self. Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 386

def delete_if
  block_given? or return enum_for(__method__) { size }
  # @hash.delete_if should be faster, but using it breaks the order
  # of enumeration in subclasses.
  select { |o| yield o }.each { |o| @hash.delete(o) }
  self
end

#disjoint?(set) ⇒ Boolean

Returns true if the set and the given set have no element in common. This method is the opposite of `intersect?`.

Set[1, 2, 3].disjoint? Set[3, 4]   #=> false
Set[1, 2, 3].disjoint? Set[4, 5]   #=> true

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 335

def disjoint?(set)
  !intersect?(set)
end

#divide(&func) ⇒ Object

Divides the set into a set of subsets according to the commonality defined by the given block.

If the arity of the block is 2, elements o1 and o2 are in common if block.call(o1, o2) is true. Otherwise, elements o1 and o2 are in common if block.call(o1) == block.call(o2).

require 'set'
numbers = Set[1, 3, 4, 6, 9, 10, 11]
set = numbers.divide { |i,j| (i - j).abs == 1 }
set        #=> #<Set: {#<Set: {1}>,
           #           #<Set: {11, 9, 10}>,
           #           #<Set: {3, 4}>,
           #           #<Set: {6}>}>

Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 612

def divide(&func)
  func or return enum_for(__method__) { size }

  if func.arity == 2
    require 'tsort'

    class << dig = {}         # :nodoc:
      include TSort

      alias tsort_each_node each_key
      def tsort_each_child(node, &block)
        fetch(node).each(&block)
      end
    end

    each { |u|
      dig[u] = a = []
      each{ |v| func.call(u, v) and a << v }
    }

    set = Set.new()
    dig.each_strongly_connected_component { |css|
      set.add(self.class.new(css))
    }
    set
  else
    Set.new(classify(&func).values)
  end
end

#each(&block) ⇒ Object

Calls the given block once for each element in the set, passing the element as parameter. Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 342

def each(&block)
  block or return enum_for(__method__) { size }
  @hash.each_key(&block)
  self
end

#empty?Boolean

Returns true if the set contains no elements.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 160

def empty?
  @hash.empty?
end

#eql?(o) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 531

def eql?(o)   # :nodoc:
  return false unless o.is_a?(Set)
  @hash.eql?(o.instance_variable_get(:@hash))
end

#flattenObject

Returns a new set that is a copy of the set, flattening each containing set recursively.


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# File 'lib/set.rb', line 230

def flatten
  self.class.new.flatten_merge(self)
end

#flatten!Object

Equivalent to Set#flatten, but replaces the receiver with the result in place. Returns nil if no modifications were made.


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# File 'lib/set.rb', line 236

def flatten!
  replace(flatten()) if any? { |e| e.is_a?(Set) }
end

#freezeObject

:nodoc:


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# File 'lib/set.rb', line 148

def freeze    # :nodoc:
  @hash.freeze
  super
end

#hashObject

:nodoc:


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# File 'lib/set.rb', line 527

def hash      # :nodoc:
  @hash.hash
end

#include?(o) ⇒ Boolean Also known as: member?, ===

Returns true if the set contains the given object.

Note that include? and member? do not test member equality using == as do other Enumerables.

See also Enumerable#include?

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 246

def include?(o)
  @hash[o]
end

#initialize_clone(orig) ⇒ Object

Clone internal hash.


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# File 'lib/set.rb', line 136

def initialize_clone(orig, **options)
  super
  @hash = orig.instance_variable_get(:@hash).clone(**options)
end

#initialize_dup(orig) ⇒ Object

Dup internal hash.


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# File 'lib/set.rb', line 129

def initialize_dup(orig)
  super
  @hash = orig.instance_variable_get(:@hash).dup
end

#inspectObject Also known as: to_s

Returns a string containing a human-readable representation of the set (“#<Set: element2, …>”).


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# File 'lib/set.rb', line 652

def inspect
  ids = (Thread.current[InspectKey] ||= [])

  if ids.include?(object_id)
    return sprintf('#<%s: {...}>', self.class.name)
  end

  ids << object_id
  begin
    return sprintf('#<%s: {%s}>', self.class, to_a.inspect[1..-2])
  ensure
    ids.pop
  end
end

#intersect?(set) ⇒ Boolean

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

Set[1, 2, 3].intersect? Set[4, 5]   #=> false
Set[1, 2, 3].intersect? Set[3, 4]   #=> true

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 321

def intersect?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  if size < set.size
    any? { |o| set.include?(o) }
  else
    set.any? { |o| include?(o) }
  end
end

#join(separator = nil) ⇒ Object

Returns a string created by converting each element of the set to a string See also: Array#join


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# File 'lib/set.rb', line 644

def join(separator=nil)
  to_a.join(separator)
end

#keep_ifObject

Deletes every element of the set for which block evaluates to false, and returns self. Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 397

def keep_if
  block_given? or return enum_for(__method__) { size }
  # @hash.keep_if should be faster, but using it breaks the order of
  # enumeration in subclasses.
  reject { |o| yield o }.each { |o| @hash.delete(o) }
  self
end

#merge(enum) ⇒ Object

Merges the elements of the given enumerable object to the set and returns self.


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# File 'lib/set.rb', line 438

def merge(enum)
  if enum.instance_of?(self.class)
    @hash.update(enum.instance_variable_get(:@hash))
  else
    do_with_enum(enum) { |o| add(o) }
  end

  self
end

#pretty_print(pp) ⇒ Object

:nodoc:


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# File 'lib/set.rb', line 669

def pretty_print(pp)  # :nodoc:
  pp.text sprintf('#<%s: {', self.class.name)
  pp.nest(1) {
    pp.seplist(self) { |o|
      pp.pp o
    }
  }
  pp.text "}>"
end

#pretty_print_cycle(pp) ⇒ Object

:nodoc:


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# File 'lib/set.rb', line 679

def pretty_print_cycle(pp)    # :nodoc:
  pp.text sprintf('#<%s: {%s}>', self.class.name, empty? ? '' : '...')
end

#proper_subset?(set) ⇒ Boolean Also known as: <

Returns true if the set is a proper subset of the given set.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 291

def proper_subset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:<)
    @hash < set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size < set.size && all? { |o| set.include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

#proper_superset?(set) ⇒ Boolean Also known as: >

Returns true if the set is a proper superset of the given set.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 265

def proper_superset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:>)
    @hash > set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size > set.size && set.all? { |o| include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

#reject!(&block) ⇒ Object

Equivalent to Set#delete_if, but returns nil if no changes were made. Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 417

def reject!(&block)
  block or return enum_for(__method__) { size }
  n = size
  delete_if(&block)
  self if size != n
end

#replace(enum) ⇒ Object

Replaces the contents of the set with the contents of the given enumerable object and returns self.

set = Set[1, 'c', :s]             #=> #<Set: {1, "c", :s}>
set.replace([1, 2])               #=> #<Set: {1, 2}>
set                               #=> #<Set: {1, 2}>

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# File 'lib/set.rb', line 180

def replace(enum)
  if enum.instance_of?(self.class)
    @hash.replace(enum.instance_variable_get(:@hash))
    self
  else
    do_with_enum(enum)  # make sure enum is enumerable before calling clear
    clear
    merge(enum)
  end
end

#resetObject

Resets the internal state after modification to existing elements and returns self.

Elements will be reindexed and deduplicated.


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# File 'lib/set.rb', line 540

def reset
  if @hash.respond_to?(:rehash)
    @hash.rehash # This should perform frozenness check.
  else
    raise FrozenError, "can't modify frozen #{self.class.name}" if frozen?
  end
  self
end

#select!(&block) ⇒ Object Also known as: filter!

Equivalent to Set#keep_if, but returns nil if no changes were made. Returns an enumerator if no block is given.


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# File 'lib/set.rb', line 426

def select!(&block)
  block or return enum_for(__method__) { size }
  n = size
  keep_if(&block)
  self if size != n
end

#sizeObject Also known as: length

Returns the number of elements.


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# File 'lib/set.rb', line 154

def size
  @hash.size
end

#subset?(set) ⇒ Boolean Also known as: <=

Returns true if the set is a subset of the given set.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 278

def subset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:<=)
    @hash <= set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size <= set.size && all? { |o| set.include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

#subtract(enum) ⇒ Object

Deletes every element that appears in the given enumerable object and returns self.


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# File 'lib/set.rb', line 450

def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end

#superset?(set) ⇒ Boolean Also known as: >=

Returns true if the set is a superset of the given set.

Returns:

  • (Boolean)

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# File 'lib/set.rb', line 252

def superset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:>=)
    @hash >= set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size >= set.size && set.all? { |o| include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

#to_aObject

Converts the set to an array. The order of elements is uncertain.

Set[1, 2].to_a                    #=> [1, 2]
Set[1, 'c', :s].to_a              #=> [1, "c", :s]

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# File 'lib/set.rb', line 195

def to_a
  @hash.keys
end

#to_set(klass = Set, *args, &block) ⇒ Object

Returns self if no arguments are given. Otherwise, converts the set to another with `klass.new(self, *args, &block)`.

In subclasses, returns `klass.new(self, *args, &block)` unless overridden.


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# File 'lib/set.rb', line 204

def to_set(klass = Set, *args, &block)
  return self if instance_of?(Set) && klass == Set && block.nil? && args.empty?
  klass.new(self, *args, &block)
end

#|(enum) ⇒ Object Also known as: +, union

Returns a new set built by merging the set and the elements of the given enumerable object.

Set[1, 2, 3] | Set[2, 4, 5]         #=> #<Set: {1, 2, 3, 4, 5}>
Set[1, 5, 'z'] | (1..6)             #=> #<Set: {1, 5, "z", 2, 3, 4, 6}>

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# File 'lib/set.rb', line 460

def |(enum)
  dup.merge(enum)
end