Class: Immutable::Set

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

Overview

Immutable::Set is a collection of unordered values with no duplicates. Testing whether an object is present in the Set can be done in constant time. Set is also Enumerable, so you can iterate over the members of the set with #each, transform them with #map, filter them with #select, and so on. Some of the Enumerable methods are overridden to return immutable-ruby collections.

Like the Set class in Ruby’s standard library, which we will call RubySet, Immutable::Set defines equivalency of objects using #hash and #eql?. No two objects with the same #hash code, and which are also #eql?, can coexist in the same Set. If one is already in the Set, attempts to add another one will have no effect.

‘Set`s have no natural ordering and cannot be compared using `#<=>`. However, they define #<, #>, #<=, and #>= as shorthand for #proper_subset?, #proper_superset?, #subset?, and #superset? respectively.

The basic set-theoretic operations #union, #intersection, #difference, and #exclusion work with any Enumerable object.

A Set can be created in either of the following ways:

Immutable::Set.new([1, 2, 3]) # any Enumerable can be used to initialize
Immutable::Set['A', 'B', 'C', 'D']

The latter 2 forms of initialization can be used with your own, custom subclasses of Immutable::Set.

Unlike RubySet, all methods which you might expect to “modify” an Immutable::Set actually return a new set and leave the existing one unchanged.

Examples:

set1 = Immutable::Set[1, 2] # => Immutable::Set[1, 2]
set2 = Immutable::Set[1, 2] # => Immutable::Set[1, 2]
set1 == set2              # => true
set3 = set1.add("foo")    # => Immutable::Set[1, 2, "foo"]
set3 - set2               # => Immutable::Set["foo"]
set3.subset?(set1)        # => false
set1.subset?(set3)        # => true

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Enumerable

#<=>, #compact, #each_index, #grep, #grep_v, #group_by, #inspect, #join, #partition, #pretty_print, #product, #reject, #sum

Methods included from Enumerable

#to_list

Constructor Details

#initialize(items = []) ⇒ Set

Returns a new instance of Set.



2561
2562
2563
2564
2565
 
# File 'lib/immutable/_core.rb', line 2561

def initialize(items=[])
  @trie = Trie.new(0)
  items.each { |item| @trie.put!(item, nil) }
  freeze
end

Class Method Details

.[](*items) ⇒ Set

Create a new Set populated with the given items.

Returns:



2539
2540
2541
 
# File 'lib/immutable/_core.rb', line 2539

def [](*items)
  items.empty? ? empty : new(items)
end

.alloc(trie = EmptyTrie) ⇒ Set

“Raw” allocation of a new Set. Used internally to create a new instance quickly after obtaining a modified Trie.

Returns:



2556
2557
2558
 
# File 'lib/immutable/_core.rb', line 2556

def alloc(trie = EmptyTrie)
  allocate.tap { |s| s.instance_variable_set(:@trie, trie) }.freeze
end

.empty ⇒ Set

Return an empty Set. If used on a subclass, returns an empty instance of that class.

Returns:



2547
2548
2549
 
# File 'lib/immutable/_core.rb', line 2547

def empty
  @empty ||= new
end

Instance Method Details

#add(item) ⇒ Set Also known as: <<

Return a new Set with item added. If item is already in the set, return self.

Examples:

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

Parameters:

  • item (Object) —

    The object to add

Returns:



2589
2590
2591
 
# File 'lib/immutable/_core.rb', line 2589

def add(item)
  include?(item) ? self : self.class.alloc(@trie.put(item, nil))
end

#add?(item) ⇒ Set, false

If item is not a member of this Set, return a new Set with item added. Otherwise, return false.

Examples:

Immutable::Set[1, 2, 3].add?(4) # => Immutable::Set[1, 2, 4, 3]
Immutable::Set[1, 2, 3].add?(2) # => false

Parameters:

  • item (Object) —

    The object to add

Returns:



2603
2604
2605
 
# File 'lib/immutable/_core.rb', line 2603

def add?(item)
  !include?(item) && add(item)
end

#clear ⇒ Set

Return an empty Set instance, of the same class as this one. Useful if you have multiple subclasses of Set and want to treat them polymorphically.

Returns:



2988
2989
2990
 
# File 'lib/immutable/_core.rb', line 2988

def clear
  self.class.empty
end

#delete(item) ⇒ Set

Return a new Set with item removed. If item is not a member of the set, return self.

Examples:

Immutable::Set[1, 2, 3].delete(1)  # => Immutable::Set[2, 3]
Immutable::Set[1, 2, 3].delete(99) # => Immutable::Set[1, 2, 3]

Parameters:

  • item (Object) —

    The object to remove

Returns:



2616
2617
2618
2619
 
# File 'lib/immutable/_core.rb', line 2616

def delete(item)
  trie = @trie.delete(item)
  new_trie(trie)
end

#delete?(item) ⇒ Set, false

If item is a member of this Set, return a new Set with item removed. Otherwise, return false.

Examples:

Immutable::Set[1, 2, 3].delete?(1)  # => Immutable::Set[2, 3]
Immutable::Set[1, 2, 3].delete?(99) # => false

Parameters:

  • item (Object) —

    The object to remove

Returns:



2630
2631
2632
 
# File 'lib/immutable/_core.rb', line 2630

def delete?(item)
  include?(item) && delete(item)
end

#difference(other) ⇒ Set Also known as: subtract, -

Return a new Set with all the items in other removed. other can be any Enumerable object.

Examples:

Immutable::Set[1, 2] - Immutable::Set[2, 3] # => Immutable::Set[1]

Parameters:

  • other (Enumerable) —

    The collection to subtract from this set

Returns:



2830
2831
2832
2833
2834
2835
2836
2837
 
# File 'lib/immutable/_core.rb', line 2830

def difference(other)
  trie = if (@trie.size <= other.size) && (other.is_a?(Immutable::Set) || (defined?(::Set) && other.is_a?(::Set)))
    @trie.select { |key, _| !other.include?(key) }
  else
    @trie.bulk_delete(other)
  end
  new_trie(trie)
end

#disjoint?(other) ⇒ Boolean

Return true if this Set and other do not share any items.

Examples:

Immutable::Set[1, 2].disjoint?(Immutable::Set[8, 9]) # => true

Parameters:

Returns:

  • (Boolean) 


2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
 
# File 'lib/immutable/_core.rb', line 2932

def disjoint?(other)
  if other.size <= size
    other.each { |item| return false if include?(item) }
  else
    # See comment on #subset?
    if other.size >= 150 && @trie.size >= 190 && !(other.is_a?(Immutable::Set) || other.is_a?(::Set))
      other = ::Set.new(other)
    end
    each { |item| return false if other.include?(item) }
  end
  true
end

#dup ⇒ Set Also known as: clone

Return self. Since this is an immutable object duplicates are equivalent.

Returns:



3017
3018
3019
 
# File 'lib/immutable/_core.rb', line 3017

def dup
  self
end

#each {|item| ... } ⇒ self, Enumerator

Call the block once for each item in this Set. No specific iteration order is guaranteed, but the order will be stable for any particular Set. If no block is given, an Enumerator is returned instead.

Examples:

Immutable::Set["Dog", "Elephant", "Lion"].each { |e| puts e }
Elephant
Dog
Lion
# => Immutable::Set["Dog", "Elephant", "Lion"]

Yields:

  • (item) —

    Once for each item.

Returns:

  • (self, Enumerator) 


2647
2648
2649
2650
2651
 
# File 'lib/immutable/_core.rb', line 2647

def each
  return to_enum if not block_given?
  @trie.each { |key, _| yield(key) }
  self
end

#empty? ⇒ Boolean

Return true if this Set contains no items.

Returns:

  • (Boolean) 


2569
2570
2571
 
# File 'lib/immutable/_core.rb', line 2569

def empty?
  @trie.empty?
end

#eql?(other) ⇒ Boolean Also known as: ==

Return true if other has the same type and contents as this Set.

Parameters:

  • other (Object) —

    The object to compare with

Returns:

  • (Boolean) 


2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
 
# File 'lib/immutable/_core.rb', line 2996

def eql?(other)
  return true if other.equal?(self)
  return false if not instance_of?(other.class)
  other_trie = other.instance_variable_get(:@trie)
  return false if @trie.size != other_trie.size
  @trie.each do |key, _|
    return false if !other_trie.key?(key)
  end
  true
end

#exclusion(other) ⇒ Set Also known as: ^

Return a new Set which contains all the items which are members of this Set or of other, but not both. other can be any Enumerable object.

Examples:

Immutable::Set[1, 2] ^ Immutable::Set[2, 3] # => Immutable::Set[1, 3]

Parameters:

  • other (Enumerable) —

    The collection to take the exclusive disjunction of

Returns:



2849
2850
2851
 
# File 'lib/immutable/_core.rb', line 2849

def exclusion(other)
  ((self | other) - (self & other))
end

#first ⇒ Object

Return a member of this Set. The member chosen will be the first one which would be yielded by #each. If the set is empty, return nil.

Examples:

Immutable::Set["A", "B", "C"].first # => "C"

Returns:

  • (Object) 


2726
2727
2728
 
# File 'lib/immutable/_core.rb', line 2726

def first
  (entry = @trie.at(0)) && entry[0]
end

#flatten ⇒ Set

Recursively insert the contents of any nested ‘Set`s into this Set, and remove them.

Examples:

Immutable::Set[Immutable::Set[1, 2], Immutable::Set[3, 4]].flatten
# => Immutable::Set[1, 2, 3, 4]

Returns:



2964
2965
2966
2967
2968
2969
 
# File 'lib/immutable/_core.rb', line 2964

def flatten
  reduce(self.class.empty) do |set, item|
    next set.union(item.flatten) if item.is_a?(Set)
    set.add(item)
  end
end

#hash ⇒ Integer

See ‘Object#hash`.

Returns:

  • (Integer) 


3010
3011
3012
 
# File 'lib/immutable/_core.rb', line 3010

def hash
  reduce(0) { |hash, item| (hash << 5) - hash + item.hash }
end

#include?(object) ⇒ Boolean Also known as: member?

Return true if the given item is present in this Set. More precisely, return true if an object with the same #hash code, and which is also #eql? to the given object is present.

Examples:

Immutable::Set["A", "B", "C"].include?("B") # => true
Immutable::Set["A", "B", "C"].include?("Z") # => false

Parameters:

  • object (Object) —

    The object to check for

Returns:

  • (Boolean) 


2714
2715
2716
 
# File 'lib/immutable/_core.rb', line 2714

def include?(object)
  @trie.key?(object)
end

#intersect?(other) ⇒ Boolean

Return true if this Set and other have at least one item in common.

Examples:

Immutable::Set[1, 2].intersect?(Immutable::Set[2, 3]) # => true

Parameters:

Returns:

  • (Boolean) 


2952
2953
2954
 
# File 'lib/immutable/_core.rb', line 2952

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

#intersection(other) ⇒ Set Also known as: &

Return a new Set which contains all the items which are members of both this Set and other. other can be any Enumerable object.

Examples:

Immutable::Set[1, 2] & Immutable::Set[2, 3] # => Immutable::Set[2]

Parameters:

  • other (Enumerable) —

    The collection to intersect with

Returns:



2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
 
# File 'lib/immutable/_core.rb', line 2807

def intersection(other)
  if other.size < @trie.size
    if other.is_a?(Immutable::Set)
      trie = other.instance_variable_get(:@trie).select { |key, _| include?(key) }
    else
      trie = Trie.new(0)
      other.each { |obj| trie.put!(obj, nil) if include?(obj) }
    end
  else
    trie = @trie.select { |key, _| other.include?(key) }
  end
  new_trie(trie)
end

#map {|item| ... } ⇒ Set Also known as: collect

Call the block once for each item in this Set. All the values returned from the block will be gathered into a new Set. If no block is given, an Enumerator is returned instead.

Examples:

Immutable::Set["Cat", "Elephant", "Dog", "Lion"].map { |e| e.size }
# => Immutable::Set[8, 4, 3]

Yields:

  • (item) —

    Once for each item.

Returns:



2697
2698
2699
2700
2701
 
# File 'lib/immutable/_core.rb', line 2697

def map
  return enum_for(:map) if not block_given?
  return self if empty?
  self.class.new(super)
end

#marshal_dump ⇒ Object 



3033
3034
3035
3036
3037
3038
3039
 
# File 'lib/immutable/_core.rb', line 3033

def marshal_dump
  output = {}
  each do |key|
    output[key] = nil
  end
  output
end

#marshal_load(dictionary) ⇒ Object 



3042
3043
3044
3045
3046
 
# File 'lib/immutable/_core.rb', line 3042

def marshal_load(dictionary)
  @trie = dictionary.reduce(EmptyTrie) do |trie, key_value|
    trie.put(key_value.first, nil)
  end
end

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

Returns true if other contains all the items in this Set, plus at least one item which is not in this set.

Examples:

Immutable::Set[2, 3].proper_subset?(Immutable::Set[1, 2, 3])    # => true
Immutable::Set[1, 2, 3].proper_subset?(Immutable::Set[1, 2, 3]) # => false

Parameters:

Returns:

  • (Boolean) 


2901
2902
2903
2904
2905
2906
2907
2908
 
# File 'lib/immutable/_core.rb', line 2901

def proper_subset?(other)
  return false if other.size <= size
  # See comments above
  if other.size >= 150 && @trie.size >= 190 && !(other.is_a?(Immutable::Set) || other.is_a?(::Set))
    other = ::Set.new(other)
  end
  all? { |item| other.include?(item) }
end

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

Returns true if this Set contains all the items in other, plus at least one item which is not in other.

Examples:

Immutable::Set[1, 2, 3].proper_superset?(Immutable::Set[2, 3])    # => true
Immutable::Set[1, 2, 3].proper_superset?(Immutable::Set[1, 2, 3]) # => false

Parameters:

Returns:

  • (Boolean) 


2920
2921
2922
 
# File 'lib/immutable/_core.rb', line 2920

def proper_superset?(other)
  other.proper_subset?(self)
end

#reverse_each {|item| ... } ⇒ self

Call the block once for each item in this Set. Iteration order will be the opposite of #each. If no block is given, an Enumerator is returned instead.

Examples:

Immutable::Set["Dog", "Elephant", "Lion"].reverse_each { |e| puts e }
Lion
Dog
Elephant
# => Immutable::Set["Dog", "Elephant", "Lion"]

Yields:

  • (item) —

    Once for each item.

Returns:

  • (self) 


2666
2667
2668
2669
2670
 
# File 'lib/immutable/_core.rb', line 2666

def reverse_each
  return enum_for(:reverse_each) if not block_given?
  @trie.reverse_each { |key, _| yield(key) }
  self
end

#sample ⇒ Object

Return a randomly chosen item from this Set. If the set is empty, return nil.

Examples:

Immutable::Set[1, 2, 3, 4, 5].sample # => 3

Returns:

  • (Object) 


2980
2981
2982
 
# File 'lib/immutable/_core.rb', line 2980

def sample
  empty? ? nil : @trie.at(rand(size))[0]
end

#select {|item| ... } ⇒ Set Also known as: find_all, keep_if

Return a new Set with all the items for which the block returns true.

Examples:

Immutable::Set["Elephant", "Dog", "Lion"].select { |e| e.size >= 4 }
# => Immutable::Set["Elephant", "Lion"]

Yields:

  • (item) —

    Once for each item.

Returns:



2679
2680
2681
2682
2683
 
# File 'lib/immutable/_core.rb', line 2679

def select
  return enum_for(:select) unless block_given?
  trie = @trie.select { |key, _| yield(key) }
  new_trie(trie)
end

#size ⇒ Integer Also known as: length

Return the number of items in this Set.

Returns:

  • (Integer) 


2575
2576
2577
 
# File 'lib/immutable/_core.rb', line 2575

def size
  @trie.size
end

#sort {|a, b| ... } ⇒ SortedSet

Return a Immutable::SortedSet which contains the same items as this Set, ordered by the given comparator block.

Examples:

Immutable::Set["Elephant", "Dog", "Lion"].sort
# => Immutable::SortedSet["Dog", "Elephant", "Lion"]
Immutable::Set["Elephant", "Dog", "Lion"].sort { |a,b| a.size <=> b.size }
# => Immutable::SortedSet["Dog", "Lion", "Elephant"]

Yields:

  • (a, b) —

    Any number of times with different pairs of elements.

Yield Returns:

  • (Integer) —

    Negative if the first element should be sorted lower, positive if the latter element, or 0 if equal.

Returns:



2744
2745
2746
 
# File 'lib/immutable/_core.rb', line 2744

def sort(&comparator)
  SortedSet.new(to_a, &comparator)
end

#sort_by {|item| ... } ⇒ SortedSet

Return a Immutable::SortedSet which contains the same items as this Set, ordered by mapping each item through the provided block to obtain sort keys, and then sorting the keys.

Examples:

Immutable::Set["Elephant", "Dog", "Lion"].sort_by { |e| e.size }
# => Immutable::SortedSet["Dog", "Lion", "Elephant"]

Yields:

  • (item) —

    Once for each item to create the set, and then potentially again depending on what operations are performed on the returned Immutable::SortedSet. As such, it is recommended that the block be a pure function.

Yield Returns:

  • (Object) —

    sort key for the item

Returns:



2762
2763
2764
 
# File 'lib/immutable/_core.rb', line 2762

def sort_by(&mapper)
  SortedSet.new(to_a, &mapper)
end

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

Return true if all items in this Set are also in other.

Examples:

Immutable::Set[2, 3].subset?(Immutable::Set[1, 2, 3]) # => true

Parameters:

Returns:

  • (Boolean) 


2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
 
# File 'lib/immutable/_core.rb', line 2861

def subset?(other)
  return false if other.size < size

  # This method has the potential to be very slow if 'other' is a large Array, so to avoid that,
  #   we convert those Arrays to Sets before checking presence of items
  # Time to convert Array -> Set is linear in array.size
  # Time to check for presence of all items in an Array is proportional to set.size * array.size
  # Note that both sides of that equation have array.size -- hence those terms cancel out,
  #   and the break-even point is solely dependent on the size of this collection
  # After doing some benchmarking to estimate the constants, it appears break-even is at ~190 items
  # We also check other.size, to avoid the more expensive #is_a? checks in cases where it doesn't matter
  #
  if other.size >= 150 && @trie.size >= 190 && !(other.is_a?(Immutable::Set) || other.is_a?(::Set))
    other = ::Set.new(other)
  end
  all? { |item| other.include?(item) }
end

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

Return true if all items in other are also in this Set.

Examples:

Immutable::Set[1, 2, 3].superset?(Immutable::Set[2, 3]) # => true

Parameters:

Returns:

  • (Boolean) 


2887
2888
2889
 
# File 'lib/immutable/_core.rb', line 2887

def superset?(other)
  other.subset?(self)
end

#to_set ⇒ self

Return self.

Returns:

  • (self) 


3028
3029
3030
 
# File 'lib/immutable/_core.rb', line 3028

def to_set
  self
end

#union(other) ⇒ Set Also known as: |, +, merge

Return a new Set which contains all the members of both this Set and other. other can be any Enumerable object.

Examples:

Immutable::Set[1, 2] | Immutable::Set[2, 3] # => Immutable::Set[1, 2, 3]

Parameters:

  • other (Enumerable) —

    The collection to merge with

Returns:



2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
 
# File 'lib/immutable/_core.rb', line 2774

def union(other)
  if other.is_a?(Immutable::Set)
    if other.size > size
      small_set_pairs = @trie
      large_set_trie = other.instance_variable_get(:@trie)
    else
      small_set_pairs = other.instance_variable_get(:@trie)
      large_set_trie = @trie
    end
  else
    if other.respond_to?(:lazy)
      small_set_pairs = other.lazy.map { |e| [e, nil] }
    else
      small_set_pairs = other.map { |e| [e, nil] }
    end
    large_set_trie = @trie
  end

  trie = large_set_trie.bulk_put(small_set_pairs)
  new_trie(trie)
end