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  • set.rb

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Set

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.

  • 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. However, the <=> operator is intentionally left out because not every pair of sets is comparable. ({x,y} vs. {x,z} for example)

Example

require 'set'
s1 = Set.new [1, 2]                   # -> #<Set: {1, 2}>
s2 = [1, 2].to_set                    # -> #<Set: {1, 2}>
s1 == s2                              # -> true
s1.add("foo")                         # -> #<Set: {1, 2, "foo"}>
s1.merge([2, 6])                      # -> #<Set: {1, 2, "foo", 6}>
s1.subset? s2                         # -> false
s2.subset? s1                         # -> true

Contact

- Akinori MUSHA <knu@iDaemons.org> (current maintainer)

Public Class Methods

[](*ary) click to toggle source

Creates a new set containing the given objects.

 
               # File set.rb, line 71
def self.[](*ary)
  new(ary)
end
            
new(enum = nil) click to toggle source

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.

 
               # File set.rb, line 80
def initialize(enum = nil, &block) # :yields: o
  @hash ||= Hash.new

  enum.nil? and return

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

Public Instance Methods

&(enum) click to toggle source

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

 
               # File set.rb, line 385
def &(enum)
  n = self.class.new
  do_with_enum(enum) { |o| n.add(o) if include?(o) }
  n
end
            
Also aliased as: intersection
+(enum) click to toggle source
Alias for: |
-(enum) click to toggle source

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

 
               # File set.rb, line 378
def -(enum)
  dup.subtract(enum)
end
            
Also aliased as: difference
<(set) click to toggle source
Alias for: proper_subset?
<<(o) click to toggle source
Alias for: add
<=(set) click to toggle source
Alias for: subset?
==(other) click to toggle source

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

 
               # File set.rb, line 403
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
            
>(set) click to toggle source
Alias for: proper_superset?
>=(set) click to toggle source
Alias for: superset?
^(enum) click to toggle source

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

 
               # File set.rb, line 395
def ^(enum)
  n = Set.new(enum)
  each { |o| if n.include?(o) then n.delete(o) else n.add(o) end }
  n
end
            
add(o) click to toggle source

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

 
               # File set.rb, line 269
def add(o)
  @hash[o] = true
  self
end
            
Also aliased as: <<
add?(o) click to toggle source

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

 
               # File set.rb, line 277
def add?(o)
  if include?(o)
    nil
  else
    add(o)
  end
end
            
classify() click to toggle source

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

e.g.:

require 'set'
files = Set.new(Dir.glob("*.rb"))
hash = files.classify { |f| File.mtime(f).year }
p hash    # => {2000=>#<Set: {"a.rb", "b.rb"}>,
          #     2001=>#<Set: {"c.rb", "d.rb", "e.rb"}>,
          #     2002=>#<Set: {"f.rb"}>}
 
               # File set.rb, line 437
def classify # :yields: o
  block_given? or return enum_for(__method__)

  h = {}

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

  h
end
            
clear() click to toggle source

Removes all elements and returns self.

 
               # File set.rb, line 135
def clear
  @hash.clear
  self
end
            
collect!() click to toggle source

Replaces the elements with ones returned by collect().

 
               # File set.rb, line 323
def collect!
  block_given? or return enum_for(__method__)
  set = self.class.new
  each { |o| set << yield(o) }
  replace(set)
end
            
Also aliased as: map!
delete(o) click to toggle source

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

 
               # File set.rb, line 287
def delete(o)
  @hash.delete(o)
  self
end
            
delete?(o) click to toggle source

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

 
               # File set.rb, line 294
def delete?(o)
  if include?(o)
    delete(o)
  else
    nil
  end
end
            
delete_if() click to toggle source

Deletes every element of the set for which block evaluates to true, and returns self.

 
               # File set.rb, line 304
def delete_if
  block_given? or return enum_for(__method__)
  # @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
            
difference(enum) click to toggle source
Alias for: -
disjoint?(set) click to toggle source

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

 
               # File set.rb, line 254
def disjoint?(set)
  !intersect?(set)
end
            
divide(&func) click to toggle source

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).

e.g.:

require 'set'
numbers = Set[1, 3, 4, 6, 9, 10, 11]
set = numbers.divide { |i,j| (i - j).abs == 1 }
p set     # => #<Set: {#<Set: {1}>,
          #            #<Set: {11, 9, 10}>,
          #            #<Set: {3, 4}>,
          #            #<Set: {6}>}>
 
               # File set.rb, line 466
def divide(&func)
  func or return enum_for(__method__)

  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) click to toggle source

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

 
               # File set.rb, line 261
def each(&block)
  block or return enum_for(__method__)
  @hash.each_key(&block)
  self
end
            
empty?() click to toggle source

Returns true if the set contains no elements.

 
               # File set.rb, line 130
def empty?
  @hash.empty?
end
            
flatten() click to toggle source

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

 
               # File set.rb, line 189
def flatten
  self.class.new.flatten_merge(self)
end
            
flatten!() click to toggle source

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

 
               # File set.rb, line 195
def flatten!
  if detect { |e| e.is_a?(Set) }
    replace(flatten())
  else
    nil
  end
end
            
include?(o) click to toggle source

Returns true if the set contains the given object.

 
               # File set.rb, line 204
def include?(o)
  @hash.include?(o)
end
            
Also aliased as: member?
initialize_copy(orig) click to toggle source

Copy internal hash.

 
               # File set.rb, line 104
def initialize_copy(orig)
  @hash = orig.instance_variable_get(:@hash).dup
end
            
inspect() click to toggle source

Returns a string containing a human-readable representation of the set. (“#<Set: {element1, element2, …}>”)

 
               # File set.rb, line 500
def inspect
  ids = (Thread.current[InspectKey] ||= [])

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

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

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

 
               # File set.rb, line 243
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
            
intersection(enum) click to toggle source
Alias for: &
keep_if() click to toggle source

Deletes every element of the set for which block evaluates to false, and returns self.

 
               # File set.rb, line 314
def keep_if
  block_given? or return enum_for(__method__)
  # @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
            
length() click to toggle source
Alias for: size
map!() click to toggle source
Alias for: collect!
member?(o) click to toggle source
Alias for: include?
merge(enum) click to toggle source

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

 
               # File set.rb, line 351
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
            
proper_subset?(set) click to toggle source

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

 
               # File set.rb, line 234
def proper_subset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if set.size <= size
  all? { |o| set.include?(o) }
end
            
Also aliased as: <
proper_superset?(set) click to toggle source

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

 
               # File set.rb, line 218
def proper_superset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if size <= set.size
  set.all? { |o| include?(o) }
end
            
Also aliased as: >
reject!(&block) click to toggle source

Equivalent to #delete_if, but returns nil if no changes were made.

 
               # File set.rb, line 333
def reject!(&block)
  block or return enum_for(__method__)
  n = size
  delete_if(&block)
  size == n ? nil : self
end
            
replace(enum) click to toggle source

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

 
               # File set.rb, line 142
def replace(enum)
  if enum.instance_of?(self.class)
    @hash.replace(enum.instance_variable_get(:@hash))
  else
    clear
    merge(enum)
  end

  self
end
            
select!(&block) click to toggle source

Equivalent to #keep_if, but returns nil if no changes were made.

 
               # File set.rb, line 342
def select!(&block)
  block or return enum_for(__method__)
  n = size
  keep_if(&block)
  size == n ? nil : self
end
            
size() click to toggle source

Returns the number of elements.

 
               # File set.rb, line 124
def size
  @hash.size
end
            
Also aliased as: length
subset?(set) click to toggle source

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

 
               # File set.rb, line 226
def subset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if set.size < size
  all? { |o| set.include?(o) }
end
            
Also aliased as: <=
subtract(enum) click to toggle source

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

 
               # File set.rb, line 363
def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end
            
superset?(set) click to toggle source

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

 
               # File set.rb, line 210
def superset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if size < set.size
  set.all? { |o| include?(o) }
end
            
Also aliased as: >=
to_a() click to toggle source

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

 
               # File set.rb, line 154
def to_a
  @hash.keys
end
            
to_set(klass = Set, *args, &block) click to toggle source

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.

 
               # File set.rb, line 163
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
            
union(enum) click to toggle source
Alias for: |
|(enum) click to toggle source

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

 
               # File set.rb, line 370
def |(enum)
  dup.merge(enum)
end
            
Also aliased as: +, union

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