Set

Class

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 ({x, y} vs. {x, z} for example).

Example 

require 'set'
s1 = Set[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

What’s Here

First, what’s elsewhere. Class Set:

In particular, class Set does not have many methods of its own for fetching or for iterating. Instead, it relies on those in Enumerable.

Here, class Set provides methods that are useful for:

Methods for Creating a Set

  • ::[] - Returns a new set containing the given objects.

  • ::new - Returns a new set containing either the given objects (if no block given) or the return values from the called block (if a block given).

Methods for Set Operations

  • | (aliased as union and +) - Returns a new set containing all elements from self and all elements from a given enumerable (no duplicates).

  • & (aliased as intersection) - Returns a new set containing all elements common to self and a given enumerable.

  • - (aliased as difference) - Returns a copy of self with all elements in a given enumerable removed.

  • ^ - Returns a new set containing all elements from self and a given enumerable except those common to both.

Methods for Comparing

  • <=> - Returns -1, 0, or 1 as self is less than, equal to, or greater than a given object.

  • == - Returns whether self and a given enumerable are equal, as determined by Object#eql?.

  • compare_by_identity? - Returns whether the set considers only identity when comparing elements.

Methods for Querying

  • length (aliased as size) - Returns the count of elements.

  • empty? - Returns whether the set has no elements.

  • include? (aliased as member? and ===) - Returns whether a given object is an element in the set.

  • subset? (aliased as <=) - Returns whether a given object is a subset of the set.

  • proper_subset? (aliased as <) - Returns whether a given enumerable is a proper subset of the set.

  • superset? (aliased as <=]) - Returns whether a given enumerable is a superset of the set.

  • proper_superset? (aliased as >) - Returns whether a given enumerable is a proper superset of the set.

  • disjoint? - Returns true if the set and a given enumerable have no common elements, false otherwise.

  • intersect? - Returns true if the set and a given enumerable - have any common elements, false otherwise.

  • compare_by_identity? - Returns whether the set considers only identity when comparing elements.

Methods for Assigning

  • add (aliased as <<) - Adds a given object to the set; returns self.

  • add? - If the given object is not an element in the set, adds it and returns self; otherwise, returns nil.

  • merge - Adds each given object to the set; returns self.

  • replace - Replaces the contents of the set with the contents of a given enumerable.

Methods for Deleting

  • clear - Removes all elements in the set; returns self.

  • delete - Removes a given object from the set; returns self.

  • delete? - If the given object is an element in the set, removes it and returns self; otherwise, returns nil.

  • subtract - Removes each given object from the set; returns self.

  • delete_if - Removes elements specified by a given block.

  • select! (aliased as filter!) - Removes elements not specified by a given block.

  • keep_if - Removes elements not specified by a given block.

  • reject! Removes elements specified by a given block.

Methods for Converting

  • classify - Returns a hash that classifies the elements, as determined by the given block.

  • collect! (aliased as map!) - Replaces each element with a block return-value.

  • divide - Returns a hash that classifies the elements, as determined by the given block; differs from classify in that the block may accept either one or two arguments.

  • flatten - Returns a new set that is a recursive flattening of self. flatten! - Replaces each nested set in self with the elements from that set.

  • inspect (aliased as to_s) - Returns a string displaying the elements.

  • join - Returns a string containing all elements, converted to strings as needed, and joined by the given record separator.

  • to_a - Returns an array containing all set elements.

  • to_set - Returns self if given no arguments and no block; with a block given, returns a new set consisting of block return values.

Methods for Iterating

  • each - Calls the block with each successive element; returns self.

Other Methods

  • reset - Resets the internal state; useful if an object has been modified while an element in the set.

Constants

InspectKey

No documentation available
Class Methods

[](*ary)
::

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}>

json_create(object)
::

Import a JSON Marshalled object.

method used for JSON marshalling support.

new(enum = nil) { |o| ... }
::

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}>
Instance Methods

&(enum)
#

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"}>

+(enum)
#
An alias for |

-(enum)
#

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"}>

<(set)
#
An alias for proper_subset?

<<(o)
#
An alias for add

<=(set)
#
An alias for subset?

<=>(set)
#

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.

==(other)
#

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

===(o)
#
An alias for include?

>(set)
#
An alias for proper_superset?

>=(set)
#
An alias for superset?

^(enum)
#

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"}>

add(o)
#

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}>

add?(o)
#

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

as_json(*)
#

Marshal the object to JSON.

method used for JSON marshalling support.

classify() { |o| ... }
#

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.

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.

clear
#

Removes all elements and returns self.

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

collect!() { |o| ... }
#

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

compare_by_identity
#

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

compare_by_identity?
#

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

delete(o)
#

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

delete?(o)
#

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

delete_if() { |o| ... }
#

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

difference(enum)
#
An alias for -

disjoint?(set)
#

Returns true if the set and the given enumerable 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
Set[1, 2, 3].disjoint? [3, 4]      #=> false
Set[1, 2, 3].disjoint? 4..5        #=> true

divide(&func)
#

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.

each(&block)
#

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

empty?
#

Returns true if the set contains no elements.

filter!(&block)
#
An alias for select!

flatten
#

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

flatten!
#

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

include?(o)
#

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?

initialize_clone(orig, **options)
#

Clone internal hash.

initialize_dup(orig)
#

Dup internal hash.

inspect
#

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

intersect?(set)
#

Returns true if the set and the given enumerable 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
Set[1, 2, 3].intersect? 4..5        #=> false
Set[1, 2, 3].intersect? [3, 4]      #=> true

intersection(enum)
#
An alias for &

join(separator=nil)
#

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

keep_if() { |o| ... }
#

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

length
#
An alias for size

map!
#
An alias for collect!

member?(o)
#
An alias for include?

merge(enum)
#

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

proper_subset?(set)
#

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

proper_superset?(set)
#

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

reject!(&block)
#

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

replace(enum)
#

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}>

reset
#

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

Elements will be reindexed and deduplicated.

select!(&block)
#

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

size
#

Returns the number of elements.

subset?(set)
#

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

subtract(enum)
#

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

superset?(set)
#

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

to_a
#

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]

to_json(*args)
#

return the JSON value

to_s
#
An alias for inspect

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

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.

union(enum)
#
An alias for |

|(enum)
#

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}>