class Set

set/subclass_compatible.rb - Provides compatibility for set subclasses

Documentation by Akinori MUSHA and Gavin Sinclair.

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:

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

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

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;
}

new → new_set

new(enum) → new_set

new(enum) { |elem| ... } → new_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]

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;
}

Public Instance Methods

set & enum → 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"]

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;
}

Also aliased as: intersection

Alias for: |

set - enum → new_set

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"]

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

Also aliased as: difference

Alias for: proper_subset?

Alias for: add

Alias for: subset?

set <=> other → -1, 0, 1, or nil

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.

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;
}

set == other → true or false

Returns true if two sets are equal.

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);
}

Also aliased as: eql?

===

Alias for: include?

Alias for: proper_superset?

Alias for: superset?

set ^ enum → 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"]

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;
}

set | enum → new_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]

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

Also aliased as: +, union

add(obj) → self

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]

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;
}

Also aliased as: <<

add?(obj) → self or nil

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

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;
    }
}

classify { |o| ... } → hash

classify → enumerator

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.

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];
}

clear → self

Removes all elements and returns self.

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

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;
}

collect! { |o| ... } → self

collect! → enumerator

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

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;
}

Also aliased as: map!

compare_by_identity → self

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

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);
}

compare_by_identity? → true or false

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

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

delete(obj) → self

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

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;
}

delete?(obj) → self or nil

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

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;
}

delete_if { |o| ... } → self

delete_if → enumerator

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

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;
}

difference

Alias for: -

disjoint?(set) → true or false

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

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

divide { |o1, o2| ... } → set

divide { |o| ... } → set

divide → enumerator

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.

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;
}

each { |o| ... } → self

each → enumerator

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

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;
}

empty? → true or false

Returns true if the set contains no elements.

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

encode_with (coder)

# 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

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

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;
}

flatten! → self

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

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));
}

hash → integer

Returns hash code for set.

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);
}

include?(item) → true or false

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?

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

Also aliased as: member?, ===

init_with (coder)

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

inspect → new_string

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.

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

Also aliased as: to_s

intersect?(set) → true or false

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

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");
    }
}

intersection

Alias for: &

join(separator=nil)→ new_string

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

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]);
}

keep_if { |o| ... } → self

keep_if → enumerator

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

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;
}

length

Alias for: size

map!

Alias for: collect!

member?

Alias for: include?

merge(*enums, **nil) → self

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

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;
}

proper_subset?(set) → true or false

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

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);
}

Also aliased as: <

proper_superset?(set) → true or false

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

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);
}

Also aliased as: >

reject! { |o| ... } → self

reject! → enumerator

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

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;
}

replace(enum) → self

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]

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;
}

reset → self

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

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);
}

select! { |o| ... } → self

select! → enumerator

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

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;
}

Also aliased as: filter!

size → integer

Returns the number of elements.

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

Also aliased as: length

subset?(set) → true or false

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

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);
}

Also aliased as: <=

subtract(enum) → self

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

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

superset?(set) → true or false

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

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);
}

Also aliased as: >=

to_a → array

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]

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;
}

to_s

Alias for: inspect

to_set(klass = Set, *args, &block) → self or new_set

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).

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);
}

union

Alias for: |