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# class Set

The Set class implements a collection of unordered values with no duplicates. It 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 a data structure similar to `Hash` for storage, except that it only has keys and no values.

- 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 returns `nil` for sets that both have distinct elements (`{x, y}` vs. `{x, z}` for example).

## Example

    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)

## Inheriting from Set

Before Ruby 4.0 (released December 2025), Set had a different, less efficient implementation. It was reimplemented in C, and the behavior of some of the core methods were adjusted.

To keep backward compatibility, when a class is inherited from Set, additional module `Set::SubclassCompatible` is included, which makes the inherited class behavior, as well as internal method names, closer to what it was before Ruby 4.0.

It can be easily seen, for example, in the `inspect` method behavior:

    p Set[1, 2, 3]
    # prints "Set[1, 2, 3]"

    class MySet < Set
    end
    p MySet[1, 2, 3]
    # prints "#<MySet: {1, 2, 3}>", like it was in Ruby 3.4

For new code, if backward compatibility is not necessary, it is recommended to instead inherit from `Set::CoreSet`, which avoids including the “compatibility” layer:

    class MyCoreSet < Set::CoreSet
    end
    p MyCoreSet[1, 2, 3]
    # prints "MyCoreSet[1, 2, 3]"

## Set’s methods

First, what’s elsewhere. Class Set:

- Inherits from class Object.

- Includes module Enumerable, 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

- Set Operations

- Comparing

- Querying

- Assigning

- Deleting

- Converting

- Iterating

- And more.…

### 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`: Merges the elements of each given enumerable 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.

### Public Class Methods

Set[*objects] → new_set
Source

    static VALUE
    set_s_create(int argc, VALUE *argv, VALUE klass)
    {
        VALUE set = set_alloc_with_size(klass, argc);
        set_table *table = RSET_TABLE(set);
        int i;

        for (i=0; i < argc; i++) {
            set_table_insert_wb(table, set, argv[i], NULL);
        }

        return set;
    }

Returns a new Set object populated with the given objects, See `Set::new`.

json_create (object)
Source

    # File ext/json/lib/json/add/set.rb, line 9
    def self.json_create(object)
      new object['a']
    end

See `as_json`.

new → new_set
new(enum) → new_set
new(enum) { |elem| ... } → new_set
Source

    static VALUE
    set_i_initialize(int argc, VALUE *argv, VALUE set)
    {
        if (RBASIC(set)->flags & RSET_INITIALIZED) {
            rb_raise(rb_eRuntimeError, "cannot reinitialize set");
        }
        RBASIC(set)->flags |= RSET_INITIALIZED;

        VALUE other;
        rb_check_arity(argc, 0, 1);

        if (argc > 0 && (other = argv[0]) != Qnil) {
            if (RB_TYPE_P(other, T_ARRAY)) {
                long i;
                int block_given = rb_block_given_p();
                set_table *into = RSET_TABLE(set);
                for (i=0; i<RARRAY_LEN(other); i++) {
                    VALUE key = RARRAY_AREF(other, i);
                    if (block_given) key = rb_yield(key);
                    set_table_insert_wb(into, set, key, NULL);
                }
            }
            else {
                rb_block_call(other, enum_method_id(other), 0, 0,
                    rb_block_given_p() ? set_initialize_with_block : set_initialize_without_block,
                    set);
            }
        }

        return set;
    }

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]

### Public Instance Methods

set & enum → new_set
Source

    static VALUE
    set_i_intersection(VALUE set, VALUE other)
    {
        VALUE new_set = set_s_alloc(rb_obj_class(set));
        set_table *stable = RSET_TABLE(set);
        set_table *ntable = RSET_TABLE(new_set);

        if (rb_obj_is_kind_of(other, rb_cSet)) {
            set_table *otable = RSET_TABLE(other);
            if (set_table_size(stable) >= set_table_size(otable)) {
                /* Swap so we iterate over the smaller set */
                otable = stable;
                set = other;
            }

            struct set_intersection_data data = {
                .set = new_set,
                .into = ntable,
                .other = otable
            };
            set_iter(set, set_intersection_i, (st_data_t)&data);
        }
        else {
            struct set_intersection_data data = {
                .set = new_set,
                .into = ntable,
                .other = stable
            };
            rb_block_call(other, enum_method_id(other), 0, 0, set_intersection_block, (VALUE)&data);
        }

        return new_set;
    }

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"]

Also aliased as: intersection
+
Alias for: |
set - enum → new_set
Source

    static VALUE
    set_i_difference(VALUE set, VALUE other)
    {
        return set_i_subtract(rb_obj_dup(set), other);
    }

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"]

Also aliased as: difference
<
Alias for: proper_subset?
<<
Alias for: add
<=
Alias for: subset?
set <=> other → -1, 0, 1, or nil
Source

    static VALUE
    set_i_compare(VALUE set, VALUE other)
    {
        if (rb_obj_is_kind_of(other, rb_cSet)) {
            size_t set_size = RSET_SIZE(set);
            size_t other_size = RSET_SIZE(other);

            if (set_size < other_size) {
                if (set_le(set, other) == Qtrue) {
                    return INT2NUM(-1);
                }
            }
            else if (set_size > other_size) {
                if (set_le(other, set) == Qtrue) {
                    return INT2NUM(1);
                }
            }
            else if (set_le(set, other) == Qtrue) {
                return INT2NUM(0);
            }
        }

        return Qnil;
    }

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.

set == other → true or false
Source

    static VALUE
    set_i_eq(VALUE set, VALUE other)
    {
        if (!rb_obj_is_kind_of(other, rb_cSet)) return Qfalse;
        if (set == other) return Qtrue;

        set_table *stable = RSET_TABLE(set);
        set_table *otable = RSET_TABLE(other);
        size_t ssize = set_table_size(stable);
        size_t osize = set_table_size(otable);

        if (ssize != osize) return Qfalse;
        if (ssize == 0 && osize == 0) return Qtrue;
        if (stable->type != otable->type) return Qfalse;

        struct set_equal_data data;
        data.set = other;
        return rb_exec_recursive_paired(set_recursive_eql, set, other, (VALUE)&data);
    }

Returns true if two sets are equal.

Also aliased as: eql?
===
Alias for: include?
>
Alias for: proper_superset?
>=
Alias for: superset?
set ^ enum → new_set
Source

    static VALUE
    set_i_xor(VALUE set, VALUE other)
    {
        VALUE new_set = rb_obj_dup(set);

        if (rb_obj_is_kind_of(other, rb_cSet)) {
            set_iter(other, set_xor_i, (st_data_t)new_set);
        }
        else {
            VALUE tmp = set_s_alloc(rb_cSet);
            set_merge_enum_into(tmp, other);
            set_iter(tmp, set_xor_i, (st_data_t)new_set);
        }

        return new_set;
    }

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"]

set | enum → new_set
Source

    static VALUE
    set_i_union(VALUE set, VALUE other)
    {
        set = rb_obj_dup(set);
        set_merge_enum_into(set, other);
        return set;
    }

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]

Also aliased as: +, union
add(obj) → self
Source

    static VALUE
    set_i_add(VALUE set, VALUE item)
    {
        rb_check_frozen(set);
        if (set_iterating_p(set)) {
            if (!set_table_lookup(RSET_TABLE(set), (st_data_t)item)) {
                no_new_item();
            }
        }
        else {
            set_insert_wb(set, item, NULL);
        }
        return set;
    }

Adds the given object to the set and returns self. Use `Set#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]

Also aliased as: <<
add?(obj) → self or nil
Source

    static VALUE
    set_i_add_p(VALUE set, VALUE item)
    {
        rb_check_frozen(set);
        if (set_iterating_p(set)) {
            if (!set_table_lookup(RSET_TABLE(set), (st_data_t)item)) {
                no_new_item();
            }
            return Qnil;
        }
        else {
            return set_insert_wb(set, item, NULL) ? Qnil : set;
        }
    }

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 (*)
Source

    # File ext/json/lib/json/add/set.rb, line 28
    def as_json(*)
      {
        JSON.create_id => self.class.name,
        'a'            => to_a,
      }
    end

Methods `Set#as_json` and `Set.json_create` may be used to serialize and deserialize a Set object; see `Marshal`.

Method `Set#as_json` serializes `self`, returning a 2-element hash representing `self`:

    require 'json/add/set'
    x = Set.new(%w/foo bar baz/).as_json
    # => {"json_class"=>"Set", "a"=>["foo", "bar", "baz"]}

Method `JSON.create` deserializes such a hash, returning a Set object:

    Set.json_create(x) # => #<Set: {"foo", "bar", "baz"}>

classify { |o| ... } → hash
classify → enumerator
Source

    static VALUE
    set_i_classify(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        VALUE args[2];
        args[0] = rb_hash_new();
        args[1] = rb_obj_class(set);
        set_iter(set, set_classify_i, (st_data_t)args);
        return args[0];
    }

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.

    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 → self
Source

    static VALUE
    set_i_clear(VALUE set)
    {
        rb_check_frozen(set);
        if (RSET_SIZE(set) == 0) return set;
        if (set_iterating_p(set)) {
            set_iter(set, set_clear_i, 0);
        }
        else {
            set_table_clear(RSET_TABLE(set));
            set_compact_after_delete(set);
        }
        return set;
    }

Removes all elements and returns self.

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

collect! { |o| ... } → self
collect! → enumerator
Source

    static VALUE
    set_i_collect(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        rb_check_frozen(set);

        VALUE new_set = set_s_alloc(rb_obj_class(set));
        set_iter(set, set_collect_i, (st_data_t)new_set);
        set_i_initialize_copy(set, new_set);

        return set;
    }

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

Also aliased as: map!
compare_by_identity → self
Source

    static VALUE
    set_i_compare_by_identity(VALUE set)
    {
        if (RSET_COMPARE_BY_IDENTITY(set)) return set;

        if (set_iterating_p(set)) {
            rb_raise(rb_eRuntimeError, "compare_by_identity during iteration");
        }

        return set_reset_table_with_type(set, &identhash);
    }

Makes the set compare its elements by their identity and returns self.

compare_by_identity? → true or false
Source

    static VALUE
    set_i_compare_by_identity_p(VALUE set)
    {
        return RBOOL(RSET_COMPARE_BY_IDENTITY(set));
    }

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

delete(obj) → self
Source

    static VALUE
    set_i_delete(VALUE set, VALUE item)
    {
        rb_check_frozen(set);
        if (set_table_delete(RSET_TABLE(set), (st_data_t *)&item)) {
            set_compact_after_delete(set);
        }
        return set;
    }

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

delete?(obj) → self or nil
Source

    static VALUE
    set_i_delete_p(VALUE set, VALUE item)
    {
        rb_check_frozen(set);
        if (set_table_delete(RSET_TABLE(set), (st_data_t *)&item)) {
            set_compact_after_delete(set);
            return set;
        }
        return Qnil;
    }

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

delete_if { |o| ... } → self
delete_if → enumerator
Source

    static VALUE
    set_i_delete_if(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        rb_check_frozen(set);
        set_iter(set, set_delete_if_i, 0);
        set_compact_after_delete(set);
        return set;
    }

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

difference
Alias for: -
disjoint?(set) → true or false
Source

    static VALUE
    set_i_disjoint(VALUE set, VALUE other)
    {
        return RBOOL(!RTEST(set_i_intersect(set, other)));
    }

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 { |o1, o2| ... } → set
divide { |o| ... } → set
divide → enumerator
Source

    static VALUE
    set_i_divide(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);

        if (rb_block_arity() == 2) {
            return set_divide_arity2(set);
        }

        VALUE values = rb_hash_values(set_i_classify(set));
        set = set_alloc_with_size(rb_cSet, RARRAY_LEN(values));
        set_merge_enum_into(set, values);
        return set;
    }

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 both block.call(o1, o2) and block.call(o2, o1) are true. Otherwise, elements o1 and o2 are in common if block.call(o1) == block.call(o2).

    numbers = Set[1, 3, 4, 6, 9, 10, 11]
    set = numbers.divide { |i,j| (i - j).abs == 1 }
    set        #=> Set[Set[1],
               #       Set[3, 4],
               #       Set[6],
               #       Set[9, 10, 11]]

Returns an enumerator if no block is given.

each { |o| ... } → self
each → enumerator
Source

    static VALUE
    set_i_each(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        set_iter(set, set_each_i, 0);
        return set;
    }

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? → true or false
Source

    static VALUE
    set_i_empty(VALUE set)
    {
        return RBOOL(RSET_EMPTY(set));
    }

Returns true if the set contains no elements.

encode_with (coder)
Source

    # File ext/psych/lib/psych/core_ext.rb, line 23
    def encode_with(coder)
      hash = {}
      each do |m|
        hash[m] = true
      end
      coder["hash"] = hash
      coder
    end

eql?
Alias for: ==
filter!
Alias for: select!
flatten → set
Source

    static VALUE
    set_i_flatten(VALUE set)
    {
        VALUE new_set = set_s_alloc(rb_obj_class(set));
        set_flatten_merge(new_set, set, rb_hash_new());
        return new_set;
    }

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

flatten! → self
Source

    static VALUE
    set_i_flatten_bang(VALUE set)
    {
        bool contains_set = false;
        set_iter(set, set_contains_set_i, (st_data_t)&contains_set);
        if (!contains_set) return Qnil;
        rb_check_frozen(set);
        return set_i_replace(set, set_i_flatten(set));
    }

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

hash → integer
Source

    static VALUE
    set_i_hash(VALUE set)
    {
        st_index_t size = RSET_SIZE(set);
        st_index_t hval = rb_st_hash_start(size);
        hval = rb_hash_uint(hval, (st_index_t)set_i_hash);
        if (size) {
            set_iter(set, set_hash_i, (VALUE)&hval);
        }
        hval = rb_st_hash_end(hval);
        return ST2FIX(hval);
    }

Returns hash code for set.

include?(item) → true or false
Source

    static VALUE
    set_i_include(VALUE set, VALUE item)
    {
        return RBOOL(RSET_IS_MEMBER(set, item));
    }

Returns true if the set contains the given object:

    Set[1, 2, 3].include? 2   #=> true
    Set[1, 2, 3].include? 4   #=> false

Note that `include?` and `member?` do not test member equality using `==` as do other Enumerables.

This is aliased to `===`, so it is usable in `case` expressions:

    case :apple
    when Set[:potato, :carrot]
      "vegetable"
    when Set[:apple, :banana]
      "fruit"
    end
    # => "fruit"

See also `Enumerable#include?`

Also aliased as: member?, ===
init_with (coder)
Source

    # File ext/psych/lib/psych/core_ext.rb, line 32
    def init_with(coder)
      replace(coder["hash"].keys)
    end

inspect → new_string
Source

    static VALUE
    set_i_inspect(VALUE set)
    {
        return rb_exec_recursive(set_inspect, set, 0);
    }

Returns a new string containing the set entries:

    s = Set.new
    s.inspect # => "Set[]"
    s.add(1)
    s.inspect # => "Set[1]"
    s.add(2)
    s.inspect # => "Set[1, 2]"

Related: see Methods for Converting.

Also aliased as: to_s
intersect?(set) → true or false
Source

    static VALUE
    set_i_intersect(VALUE set, VALUE other)
    {
        if (rb_obj_is_kind_of(other, rb_cSet)) {
            size_t set_size = RSET_SIZE(set);
            size_t other_size = RSET_SIZE(other);
            VALUE args[2];
            args[1] = Qfalse;
            VALUE iter_arg;

            if (set_size < other_size) {
                iter_arg = set;
                args[0] = (VALUE)RSET_TABLE(other);
            }
            else {
                iter_arg = other;
                args[0] = (VALUE)RSET_TABLE(set);
            }
            set_iter(iter_arg, set_intersect_i, (st_data_t)args);
            return args[1];
        }
        else if (rb_obj_is_kind_of(other, rb_mEnumerable)) {
            return rb_funcall(other, id_any_p, 1, set);
        }
        else {
            rb_raise(rb_eArgError, "value must be enumerable");
        }
    }

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
Alias for: &
join(separator=nil)→ new_string
Source

    static VALUE
    set_i_join(int argc, VALUE *argv, VALUE set)
    {
        rb_check_arity(argc, 0, 1);
        return rb_ary_join(set_i_to_a(set), argc == 0 ? Qnil : argv[0]);
    }

Returns a string created by converting each element of the set to a string.

keep_if { |o| ... } → self
keep_if → enumerator
Source

    static VALUE
    set_i_keep_if(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        rb_check_frozen(set);

        set_iter(set, set_keep_if_i, (st_data_t)RSET_TABLE(set));

        return set;
    }

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

length
Alias for: size
map!
Alias for: collect!
member?
Alias for: include?
merge(*enums, **nil) → self
Source

    static VALUE
    set_i_merge(int argc, VALUE *argv, VALUE set)
    {
        if (rb_keyword_given_p()) {
            rb_raise(rb_eArgError, "no keywords accepted");
        }

        if (set_iterating_p(set)) {
            rb_raise(rb_eRuntimeError, "cannot add to set during iteration");
        }

        rb_check_frozen(set);

        int i;

        for (i=0; i < argc; i++) {
            set_merge_enum_into(set, argv[i]);
        }

        return set;
    }

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

proper_subset?(set) → true or false
Source

    static VALUE
    set_i_proper_subset(VALUE set, VALUE other)
    {
        check_set(other);
        if (RSET_SIZE(set) >= RSET_SIZE(other)) return Qfalse;
        return set_le(set, other);
    }

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

Also aliased as: <
proper_superset?(set) → true or false
Source

    static VALUE
    set_i_proper_superset(VALUE set, VALUE other)
    {
        check_set(other);
        if (RSET_SIZE(set) <= RSET_SIZE(other)) return Qfalse;
        return set_le(other, set);
    }

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

Also aliased as: >
reject! { |o| ... } → self
reject! → enumerator
Source

    static VALUE
    set_i_reject(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        rb_check_frozen(set);

        set_table *table = RSET_TABLE(set);
        size_t n = set_table_size(table);
        set_iter(set, set_delete_if_i, 0);

        if (n == set_table_size(table)) return Qnil;

        set_compact_after_delete(set);
        return set;
    }

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

replace(enum) → self
Source

    static VALUE
    set_i_replace(VALUE set, VALUE other)
    {
        rb_check_frozen(set);

        if (rb_obj_is_kind_of(other, rb_cSet)) {
            set_i_initialize_copy(set, other);
        }
        else {
            if (set_iterating_p(set)) {
                rb_raise(rb_eRuntimeError, "cannot replace set during iteration");
            }

            // make sure enum is enumerable before calling clear
            enum_method_id(other);

            set_table_clear(RSET_TABLE(set));
            set_merge_enum_into(set, other);
        }

        return set;
    }

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 → self
Source

    static VALUE
    set_i_reset(VALUE set)
    {
        if (set_iterating_p(set)) {
            rb_raise(rb_eRuntimeError, "reset during iteration");
        }

        return set_reset_table_with_type(set, RSET_TABLE(set)->type);
    }

Resets the internal state after modification to existing elements and returns self. Elements will be reindexed and deduplicated.

select! { |o| ... } → self
select! → enumerator
Source

    static VALUE
    set_i_select(VALUE set)
    {
        RETURN_SIZED_ENUMERATOR(set, 0, 0, set_enum_size);
        rb_check_frozen(set);

        set_table *table = RSET_TABLE(set);
        size_t n = set_table_size(table);
        set_iter(set, set_keep_if_i, (st_data_t)table);

        return (n == set_table_size(table)) ? Qnil : set;
    }

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

Also aliased as: filter!
size → integer
Source

    static VALUE
    set_i_size(VALUE set)
    {
        return RSET_SIZE_NUM(set);
    }

Returns the number of elements.

Also aliased as: length
subset?(set) → true or false
Source

    static VALUE
    set_i_subset(VALUE set, VALUE other)
    {
        check_set(other);
        if (RSET_SIZE(set) > RSET_SIZE(other)) return Qfalse;
        return set_le(set, other);
    }

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

Also aliased as: <=
subtract(enum) → self
Source

    static VALUE
    set_i_subtract(VALUE set, VALUE other)
    {
        rb_check_frozen(set);
        set_remove_enum_from(set, other);
        return set;
    }

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

superset?(set) → true or false
Source

    static VALUE
    set_i_superset(VALUE set, VALUE other)
    {
        check_set(other);
        if (RSET_SIZE(set) < RSET_SIZE(other)) return Qfalse;
        return set_le(other, set);
    }

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

Also aliased as: >=
to_a → array
Source

    static VALUE
    set_i_to_a(VALUE set)
    {
        st_index_t size = RSET_SIZE(set);
        VALUE ary = rb_ary_new_capa(size);

        if (size == 0) return ary;

        if (ST_DATA_COMPATIBLE_P(VALUE)) {
            RARRAY_PTR_USE(ary, ptr, {
                size = set_keys(RSET_TABLE(set), ptr, size);
            });
            rb_gc_writebarrier_remember(ary);
            rb_ary_set_len(ary, size);
        }
        else {
            set_iter(set, set_to_a_i, (st_data_t)ary);
        }
        return ary;
    }

Returns an array containing all elements in the set.

    Set[1, 2].to_a                    #=> [1, 2]
    Set[1, 'c', :s].to_a              #=> [1, "c", :s]

to_json (*args)
Source

    # File ext/json/lib/json/add/set.rb, line 44
    def to_json(*args)
      as_json.to_json(*args)
    end

Returns a `JSON` string representing `self`:

    require 'json/add/set'
    puts Set.new(%w/foo bar baz/).to_json

Output:

    {"json_class":"Set","a":["foo","bar","baz"]}

to_s
Alias for: inspect
to_set(klass = Set, *args, &block) → self or new_set
Source

    static VALUE
    set_i_to_set(int argc, VALUE *argv, VALUE set)
    {
        VALUE klass;

        if (argc == 0) {
            klass = rb_cSet;
            argv = &set;
            argc = 1;
        }
        else {
            rb_warn_deprecated("passing arguments to Set#to_set", NULL);
            klass = argv[0];
            argv[0] = set;
        }

        if (klass == rb_cSet && rb_obj_is_instance_of(set, rb_cSet) &&
                argc == 1 && !rb_block_given_p()) {
            return set;
        }

        return rb_funcall_passing_block(klass, id_new, argc, argv);
    }

Without arguments, returns `self` (for duck-typing in methods that accept “set, or set-convertible” arguments).

A form with arguments is deprecated. It converts the set to another with `klass.new(self, *args, &block)`.

union
Alias for: |