Set

        # Set < Object

---
# Includes:
Enumerable (from ruby core)

(from ruby core)
---

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
*   Akinori MUSHA <mailto:knu@iDaemons.org> (current maintainer)

## What's Here
First, what's elsewhere. Class Set:
*   Inherits from [class
    Object](https://docs.ruby-lang.org/en/master/Object.html#class-Objec
    t-label-What-27s+Here).
*   Includes [module
     which provides dozens of additional
    g/en/master/Enumerable.html#module-Enumerable-label-What-27s+Here),
     which provides dozens of additional methods.

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:
*   [Creating a Set](#class-Set-label-Methods+for+Creating+a+Set)
*   [Set Operations](#class-Set-label-Methods+for+Set+Operations)
*   [Comparing](#class-Set-label-Methods+for+Comparing)
*   [Querying](#class-Set-label-Methods+for+Querying)
*   [Assigning](#class-Set-label-Methods+for+Assigning)
*   [Deleting](#class-Set-label-Methods+for+Deleting)
*   [Converting](#class-Set-label-Methods+for+Converting)
*   [Iterating](#class-Set-label-Methods+for+Iterating)
*   [And more....](#class-Set-label-Other+Methods)

### 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
*   [|](#method-i-7C) (aliased as #union and #+) -
     Returns a new set containing all elements from `self`
     and all elements from a given enumerable (no duplicates).
*   [&](#method-i-26) (aliased as #intersection) -
     Returns a new set containing all elements common to `self`
     and a given enumerable.
*   [-](#method-i-2D) (aliased as #difference) -
     Returns a copy of `self` with all elements
     in a given enumerable removed.
*   [\^](#method-i-5E) -
     Returns a new set containing all elements from `self`
     and a given enumerable except those common to both.

### Methods for Comparing
*   [<=>](#method-i-3C-3D-3E) -
     Returns -1, 0, or 1 as `self` is less than, equal to,
     or greater than a given object.
*   [==](#method-i-3D-3D) -
     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 [<=](#method-i-3C-3D)) -
     Returns whether a given object is a subset of the set.
*   #proper_subset? (aliased as [<](#method-i-3C)) -
     Returns whether a given enumerable is a proper subset of the set.
*   #superset? (aliased as [<=](#method-i-3E-3D)]) -
     Returns whether a given enumerable is a superset of the set.
*   #proper_superset? (aliased as [>](#method-i-3E)) -
     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.

---
# Class methods:

    []
    json_create
    new

# Instance methods:

    &
    +
    -
    <
    <<
    <=
    <=>
    ==
    ===
    >
    >=
    ^
    add
    add?
    as_json
    classify
    clear
    collect!
    compare_by_identity
    compare_by_identity?
    delete
    delete?
    delete_if
    difference
    disjoint?
    divide
    each
    empty?
    filter!
    flatten
    flatten!
    include?
    initialize_clone
    initialize_dup
    inspect
    intersect?
    intersection
    join
    keep_if
    length
    map!
    member?
    merge
    proper_subset?
    proper_superset?
    reject!
    replace
    reset
    select!
    size
    subset?
    subtract
    superset?
    to_a
    to_json
    to_s
    to_set
    union
    |