Set

Class

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. 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[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)
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?

==(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 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

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)
#

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 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

intersection(enum)
#
An alias for &

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}>