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In Files

  • hash.c

Hash

A Hash is a collection of key-value pairs. It is similar to an Array, except that indexing is done via arbitrary keys of any object type, not an integer index. The order in which you traverse a hash by either key or value may seem arbitrary, and will generally not be in the insertion order.

Hashes have a default value that is returned when accessing keys that do not exist in the hash. By default, that value is nil.

Hash uses key.eql? to test keys for equality. If you need to use instances of your own classes as keys in a Hash, it is recommended that you define both the eql? and hash methods. The hash method must have the property that a.eql?(b) implies a.hash == b.hash.

class MyClass
  attr_reader :str
  def initialize(str)
    @str = str
  end
  def eql?(o)
    o.is_a?(MyClass) && str == o.str
  end
  def hash
    @str.hash
  end
end

a = MyClass.new("some string")
b = MyClass.new("some string")
a.eql? b  #=> true

h = {}

h[a] = 1
h[a]      #=> 1
h[b]      #=> 1

h[b] = 2
h[a]      #=> 2
h[b]      #=> 2

Public Class Methods

Hash[ [key =>|, value]* ] => hash click to toggle source

Creates a new hash populated with the given objects. Equivalent to the literal { key, value, ... }. Keys and values occur in pairs, so there must be an even number of arguments.

Hash["a", 100, "b", 200]       #=> {"a"=>100, "b"=>200}
Hash["a" => 100, "b" => 200]   #=> {"a"=>100, "b"=>200}
{ "a" => 100, "b" => 200 }     #=> {"a"=>100, "b"=>200}
 
               static VALUE
rb_hash_s_create(argc, argv, klass)
    int argc;
    VALUE *argv;
    VALUE klass;
{
    VALUE hash, tmp;
    int i;

    if (argc == 1) {
        tmp = rb_check_convert_type(argv[0], T_HASH, "Hash", "to_hash");
        if (!NIL_P(tmp)) {
            hash = hash_alloc0(klass);
            RHASH(hash)->tbl = st_copy(RHASH(tmp)->tbl);
            return hash;
        }

        tmp = rb_check_array_type(argv[0]);
        if (!NIL_P(tmp)) {
            long i;

            hash = hash_alloc(klass);
            for (i = 0; i < RARRAY_LEN(tmp); ++i) {
                VALUE v = rb_check_array_type(RARRAY_PTR(tmp)[i]);
                VALUE key, val = Qnil;

                if (NIL_P(v)) continue;
                switch (RARRAY_LEN(v)) {
                  case 2:
                    val = RARRAY_PTR(v)[1];
                  case 1:
                    key = RARRAY_PTR(v)[0];
                    rb_hash_aset(hash, key, val);
                }
            }
            return hash;
        }
    }
    if (argc % 2 != 0) {
        rb_raise(rb_eArgError, "odd number of arguments for Hash");
    }

    hash = hash_alloc(klass);
    for (i=0; i<argc; i+=2) {
        rb_hash_aset(hash, argv[i], argv[i + 1]);
    }

    return hash;
}
            
new => hash click to toggle source
new(obj) => aHash
new {|hash, key| block } => aHash

Returns a new, empty hash. If this hash is subsequently accessed by a key that doesn’t correspond to a hash entry, the value returned depends on the style of new used to create the hash. In the first form, the access returns nil. If obj is specified, this single object will be used for all default values. If a block is specified, it will be called with the hash object and the key, and should return the default value. It is the block’s responsibility to store the value in the hash if required.

h = Hash.new("Go Fish")
h["a"] = 100
h["b"] = 200
h["a"]           #=> 100
h["c"]           #=> "Go Fish"
# The following alters the single default object
h["c"].upcase!   #=> "GO FISH"
h["d"]           #=> "GO FISH"
h.keys           #=> ["a", "b"]

# While this creates a new default object each time
h = Hash.new { |hash, key| hash[key] = "Go Fish: #{key}" }
h["c"]           #=> "Go Fish: c"
h["c"].upcase!   #=> "GO FISH: C"
h["d"]           #=> "Go Fish: d"
h.keys           #=> ["c", "d"]
 
               static VALUE
rb_hash_initialize(argc, argv, hash)
    int argc;
    VALUE *argv;
    VALUE hash;
{
    VALUE ifnone;

    rb_hash_modify(hash);
    if (rb_block_given_p()) {
        if (argc > 0) {
            rb_raise(rb_eArgError, "wrong number of arguments");
        }
        RHASH(hash)->ifnone = rb_block_proc();
        FL_SET(hash, HASH_PROC_DEFAULT);
    }
    else {
        rb_scan_args(argc, argv, "01", &ifnone);
        RHASH(hash)->ifnone = ifnone;
    }

    return hash;
}
            

Public Instance Methods

hsh == other_hash => true or false click to toggle source

Equality—Two hashes are equal if they each contain the same number of keys and if each key-value pair is equal to (according to Object#==) the corresponding elements in the other hash.

h1 = { "a" => 1, "c" => 2 }
h2 = { 7 => 35, "c" => 2, "a" => 1 }
h3 = { "a" => 1, "c" => 2, 7 => 35 }
h4 = { "a" => 1, "d" => 2, "f" => 35 }
h1 == h2   #=> false
h2 == h3   #=> true
h3 == h4   #=> false
 
               static VALUE
rb_hash_equal(hash1, hash2)
    VALUE hash1, hash2;
{
    return hash_equal(hash1, hash2, Qfalse);
}
            
hsh[key] => value click to toggle source

Element Reference—Retrieves the value object corresponding to the key object. If not found, returns the a default value (see Hash::new for details).

h = { "a" => 100, "b" => 200 }
h["a"]   #=> 100
h["c"]   #=> nil
 
               VALUE
rb_hash_aref(hash, key)
    VALUE hash, key;
{
    VALUE val;

    if (!st_lookup(RHASH(hash)->tbl, key, &val)) {
        return rb_funcall(hash, id_default, 1, key);
    }
    return val;
}
            
hsh[key] = value => value click to toggle source

Element Assignment—Associates the value given by value with the key given by key. key should not have its value changed while it is in use as a key (a String passed as a key will be duplicated and frozen).

h = { "a" => 100, "b" => 200 }
h["a"] = 9
h["c"] = 4
h   #=> {"a"=>9, "b"=>200, "c"=>4}
 
               VALUE
rb_hash_aset(hash, key, val)
    VALUE hash, key, val;
{
    rb_hash_modify(hash);
    if (TYPE(key) != T_STRING || st_lookup(RHASH(hash)->tbl, key, 0)) {
        st_insert(RHASH(hash)->tbl, key, val);
    }
    else {
        st_add_direct(RHASH(hash)->tbl, rb_str_new4(key), val);
    }
    return val;
}
            
clear → hsh click to toggle source

Removes all key-value pairs from hsh.

h = { "a" => 100, "b" => 200 }   #=> {"a"=>100, "b"=>200}
h.clear                          #=> {}
 
               static VALUE
rb_hash_clear(hash)
    VALUE hash;
{
    rb_hash_modify(hash);
    if (RHASH(hash)->tbl->num_entries > 0) {
        rb_hash_foreach(hash, clear_i, 0);
    }

    return hash;
}
            
default(key=nil) => obj click to toggle source

Returns the default value, the value that would be returned by hsh if key did not exist in hsh. See also Hash::new and Hash#default=.

h = Hash.new                            #=> {}
h.default                               #=> nil
h.default(2)                            #=> nil

h = Hash.new("cat")                     #=> {}
h.default                               #=> "cat"
h.default(2)                            #=> "cat"

h = Hash.new {|h,k| h[k] = k.to_i*10}   #=> {}
h.default                               #=> nil
h.default(2)                            #=> 20
 
               static VALUE
rb_hash_default(argc, argv, hash)
    int argc;
    VALUE *argv;
    VALUE hash;
{
    VALUE key;

    rb_scan_args(argc, argv, "01", &key);
    if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
        if (argc == 0) return Qnil;
        return rb_funcall(RHASH(hash)->ifnone, id_call, 2, hash, key);
    }
    return RHASH(hash)->ifnone;
}
            
default = obj => hsh click to toggle source

Sets the default value, the value returned for a key that does not exist in the hash. It is not possible to set the a default to a Proc that will be executed on each key lookup.

h = { "a" => 100, "b" => 200 }
h.default = "Go fish"
h["a"]     #=> 100
h["z"]     #=> "Go fish"
# This doesn't do what you might hope...
h.default = proc do |hash, key|
  hash[key] = key + key
end
h[2]       #=> #<Proc:0x401b3948@-:6>
h["cat"]   #=> #<Proc:0x401b3948@-:6>
 
               static VALUE
rb_hash_set_default(hash, ifnone)
    VALUE hash, ifnone;
{
    rb_hash_modify(hash);
    RHASH(hash)->ifnone = ifnone;
    FL_UNSET(hash, HASH_PROC_DEFAULT);
    return ifnone;
}
            
default_proc → anObject click to toggle source

If Hash::new was invoked with a block, return that block, otherwise return nil.

h = Hash.new {|h,k| h[k] = k*k }   #=> {}
p = h.default_proc                 #=> #<Proc:0x401b3d08@-:1>
a = []                             #=> []
p.call(a, 2)
a                                  #=> [nil, nil, 4]
 
               static VALUE
rb_hash_default_proc(hash)
    VALUE hash;
{
    if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
        return RHASH(hash)->ifnone;
    }
    return Qnil;
}
            
delete(key) => value click to toggle source
delete(key) {| key | block } => value

Deletes and returns a key-value pair from hsh whose key is equal to key. If the key is not found, returns nil. If the optional code block is given and the key is not found, pass in the key and return the result of block.

h = { "a" => 100, "b" => 200 }
h.delete("a")                              #=> 100
h.delete("z")                              #=> nil
h.delete("z") { |el| "#{el} not found" }   #=> "z not found"
 
               VALUE
rb_hash_delete(hash, key)
    VALUE hash, key;
{
    VALUE val;

    rb_hash_modify(hash);
    val = rb_hash_delete_key(hash, key);
    if (val != Qundef) return val;
    if (rb_block_given_p()) {
        return rb_yield(key);
    }
    return Qnil;
}
            
delete_if {| key, value | block } → hsh click to toggle source

Deletes every key-value pair from hsh for which block evaluates to true.

h = { "a" => 100, "b" => 200, "c" => 300 }
h.delete_if {|key, value| key >= "b" }   #=> {"a"=>100}
 
               VALUE
rb_hash_delete_if(hash)
    VALUE hash;
{
    RETURN_ENUMERATOR(hash, 0, 0);
    rb_hash_modify(hash);
    rb_hash_foreach(hash, delete_if_i, hash);
    return hash;
}
            
each {| key, value | block } → hsh click to toggle source

Calls block once for each key in hsh, passing the key and value to the block as a two-element array. Because of the assignment semantics of block parameters, these elements will be split out if the block has two formal parameters. Also see Hash.each_pair, which will be marginally more efficient for blocks with two parameters.

h = { "a" => 100, "b" => 200 }
h.each {|key, value| puts "#{key} is #{value}" }

produces:

a is 100
b is 200
 
               static VALUE
rb_hash_each(hash)
    VALUE hash;
{
    RETURN_ENUMERATOR(hash, 0, 0);
    rb_hash_foreach(hash, each_i, 0);
    return hash;
}
            
each_key {| key | block } → hsh click to toggle source

Calls block once for each key in hsh, passing the key as a parameter.

h = { "a" => 100, "b" => 200 }
h.each_key {|key| puts key }

produces:

a
b
 
               static VALUE
rb_hash_each_key(hash)
    VALUE hash;
{
    RETURN_ENUMERATOR(hash, 0, 0);
    rb_hash_foreach(hash, each_key_i, 0);
    return hash;
}
            
each_pair {| key_value_array | block } → hsh click to toggle source

Calls block once for each key in hsh, passing the key and value as parameters.

h = { "a" => 100, "b" => 200 }
h.each_pair {|key, value| puts "#{key} is #{value}" }

produces:

a is 100
b is 200
 
               static VALUE
rb_hash_each_pair(hash)
    VALUE hash;
{
    RETURN_ENUMERATOR(hash, 0, 0);
    rb_hash_foreach(hash, each_pair_i, 0);
    return hash;
}
            
each_value {| value | block } → hsh click to toggle source

Calls block once for each key in hsh, passing the value as a parameter.

h = { "a" => 100, "b" => 200 }
h.each_value {|value| puts value }

produces:

100
200
 
               static VALUE
rb_hash_each_value(hash)
    VALUE hash;
{
    RETURN_ENUMERATOR(hash, 0, 0);
    rb_hash_foreach(hash, each_value_i, 0);
    return hash;
}
            
empty? => true or false click to toggle source

Returns true if hsh contains no key-value pairs.

{}.empty?   #=> true
 
               static VALUE
rb_hash_empty_p(hash)
    VALUE hash;
{
    if (RHASH(hash)->tbl->num_entries == 0)
        return Qtrue;
    return Qfalse;
}
            
eql?(other) → true or false click to toggle source

Returns true if hash and other are both hashes with the same content.

 
               static VALUE
rb_hash_eql(hash1, hash2)
    VALUE hash1, hash2;
{
    return hash_equal(hash1, hash2, Qtrue);
}
            
fetch(key [, default] ) => obj click to toggle source
fetch(key) {| key | block } => obj

Returns a value from the hash for the given key. If the key can’t be found, there are several options: With no other arguments, it will raise an IndexError exception; if default is given, then that will be returned; if the optional code block is specified, then that will be run and its result returned.

h = { "a" => 100, "b" => 200 }
h.fetch("a")                            #=> 100
h.fetch("z", "go fish")                 #=> "go fish"
h.fetch("z") { |el| "go fish, #{el}"}   #=> "go fish, z"

The following example shows that an exception is raised if the key is not found and a default value is not supplied.

h = { "a" => 100, "b" => 200 }
h.fetch("z")

produces:

prog.rb:2:in `fetch': key not found (IndexError)
 from prog.rb:2
 
               static VALUE
rb_hash_fetch(argc, argv, hash)
    int argc;
    VALUE *argv;
    VALUE hash;
{
    VALUE key, if_none;
    VALUE val;
    long block_given;

    rb_scan_args(argc, argv, "11", &key, &if_none);

    block_given = rb_block_given_p();
    if (block_given && argc == 2) {
        rb_warn("block supersedes default value argument");
    }
    if (!st_lookup(RHASH(hash)->tbl, key, &val)) {
        if (block_given) return rb_yield(key);
        if (argc == 1) {
            rb_raise(rb_eIndexError, "key not found");
        }
        return if_none;
    }
    return val;
}
            
has_key?(key) => true or false click to toggle source

Returns true if the given key is present in hsh.

h = { "a" => 100, "b" => 200 }
h.has_key?("a")   #=> true
h.has_key?("z")   #=> false
 
               static VALUE
rb_hash_has_key(hash, key)
    VALUE hash;
    VALUE key;
{
    if (st_lookup(RHASH(hash)->tbl, key, 0)) {
        return Qtrue;
    }
    return Qfalse;
}
            
has_value?(value) => true or false click to toggle source

Returns true if the given value is present for some key in hsh.

h = { "a" => 100, "b" => 200 }
h.has_value?(100)   #=> true
h.has_value?(999)   #=> false
 
               static VALUE
rb_hash_has_value(hash, val)
    VALUE hash;
    VALUE val;
{
    VALUE data[2];

    data[0] = Qfalse;
    data[1] = val;
    rb_hash_foreach(hash, rb_hash_search_value, (st_data_t)data);
    return data[0];
}
            
hash → fixnum click to toggle source

Compute a hash-code for this array. Two arrays with the same content will have the same hash code (and will compare using eql?).

 
               static VALUE
rb_hash_hash(hash)
    VALUE hash;
{
    return rb_exec_recursive(recursive_hash, hash, 0);
}
            
include?(key) => true or false click to toggle source

Returns true if the given key is present in hsh.

h = { "a" => 100, "b" => 200 }
h.has_key?("a")   #=> true
h.has_key?("z")   #=> false
 
               static VALUE
rb_hash_has_key(hash, key)
    VALUE hash;
    VALUE key;
{
    if (st_lookup(RHASH(hash)->tbl, key, 0)) {
        return Qtrue;
    }
    return Qfalse;
}
            
index(value) => key click to toggle source

Returns the key for a given value. If not found, returns nil.

h = { "a" => 100, "b" => 200 }
h.index(200)   #=> "b"
h.index(999)   #=> nil
 
               static VALUE
rb_hash_index(hash, value)
    VALUE hash, value;
{
    VALUE args[2];

    args[0] = value;
    args[1] = Qnil;

    rb_hash_foreach(hash, index_i, (st_data_t)args);

    return args[1];
}
            
indexes(key, ...) => array click to toggle source

Deprecated in favor of Hash#select.

 
               static VALUE
rb_hash_indexes(argc, argv, hash)
    int argc;
    VALUE *argv;
    VALUE hash;
{
    VALUE indexes;
    int i;

    rb_warn("Hash#%s is deprecated; use Hash#values_at",
            rb_id2name(rb_frame_last_func()));
    indexes = rb_ary_new2(argc);
    for (i=0; i<argc; i++) {
        RARRAY(indexes)->ptr[i] = rb_hash_aref(hash, argv[i]);
        RARRAY(indexes)->len++;
    }
    return indexes;
}
            
indices(key, ...) => array click to toggle source

Deprecated in favor of Hash#select.

 
               static VALUE
rb_hash_indexes(argc, argv, hash)
    int argc;
    VALUE *argv;
    VALUE hash;
{
    VALUE indexes;
    int i;

    rb_warn("Hash#%s is deprecated; use Hash#values_at",
            rb_id2name(rb_frame_last_func()));
    indexes = rb_ary_new2(argc);
    for (i=0; i<argc; i++) {
        RARRAY(indexes)->ptr[i] = rb_hash_aref(hash, argv[i]);
        RARRAY(indexes)->len++;
    }
    return indexes;
}
            
replace(other_hash) → hsh click to toggle source

Replaces the contents of hsh with the contents of other_hash.

h = { "a" => 100, "b" => 200 }
h.replace({ "c" => 300, "d" => 400 })   #=> {"c"=>300, "d"=>400}
 
               static VALUE
rb_hash_replace(hash, hash2)
    VALUE hash, hash2;
{
    hash2 = to_hash(hash2);
    if (hash == hash2) return hash;
    rb_hash_clear(hash);
    rb_hash_foreach(hash2, replace_i, hash);
    RHASH(hash)->ifnone = RHASH(hash2)->ifnone;
    if (FL_TEST(hash2, HASH_PROC_DEFAULT)) {
        FL_SET(hash, HASH_PROC_DEFAULT);
    }
    else {
        FL_UNSET(hash, HASH_PROC_DEFAULT);
    }

    return hash;
}
            
inspect => string click to toggle source

Return the contents of this hash as a string.

 
               static VALUE
rb_hash_inspect(hash)
    VALUE hash;
{
    if (RHASH(hash)->tbl == 0 || RHASH(hash)->tbl->num_entries == 0)
        return rb_str_new2("{}");
    if (rb_inspecting_p(hash)) return rb_str_new2("{...}");
    return rb_protect_inspect(inspect_hash, hash, 0);
}
            
invert → aHash click to toggle source

Returns a new hash created by using hsh’s values as keys, and the keys as values.

h = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 }
h.invert   #=> {0=>"a", 100=>"n", 200=>"d", 300=>"y"}
 
               static VALUE
rb_hash_invert(hash)
    VALUE hash;
{
    VALUE h = rb_hash_new();

    rb_hash_foreach(hash, rb_hash_invert_i, h);
    return h;
}
            
key?(key) => true or false click to toggle source

Returns true if the given key is present in hsh.

h = { "a" => 100, "b" => 200 }
h.has_key?("a")   #=> true
h.has_key?("z")   #=> false
 
               static VALUE
rb_hash_has_key(hash, key)
    VALUE hash;
    VALUE key;
{
    if (st_lookup(RHASH(hash)->tbl, key, 0)) {
        return Qtrue;
    }
    return Qfalse;
}
            
keys => array click to toggle source

Returns a new array populated with the keys from this hash. See also Hash#values.

h = { "a" => 100, "b" => 200, "c" => 300, "d" => 400 }
h.keys   #=> ["a", "b", "c", "d"]
 
               static VALUE
rb_hash_keys(hash)
    VALUE hash;
{
    VALUE ary;

    ary = rb_ary_new();
    rb_hash_foreach(hash, keys_i, ary);

    return ary;
}
            
length => fixnum click to toggle source

Returns the number of key-value pairs in the hash.

h = { "d" => 100, "a" => 200, "v" => 300, "e" => 400 }
h.length        #=> 4
h.delete("a")   #=> 200
h.length        #=> 3
 
               static VALUE
rb_hash_size(hash)
    VALUE hash;
{
    return INT2FIX(RHASH(hash)->tbl->num_entries);
}
            
member?(key) => true or false click to toggle source

Returns true if the given key is present in hsh.

h = { "a" => 100, "b" => 200 }
h.has_key?("a")   #=> true
h.has_key?("z")   #=> false
 
               static VALUE
rb_hash_has_key(hash, key)
    VALUE hash;
    VALUE key;
{
    if (st_lookup(RHASH(hash)->tbl, key, 0)) {
        return Qtrue;
    }
    return Qfalse;
}
            
merge(other_hash) → a_hash click to toggle source
merge(other_hash){|key, oldval, newval| block} → a_hash

Returns a new hash containing the contents of other_hash and the contents of hsh, overwriting entries in hsh with duplicate keys with those from other_hash.

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge(h2)   #=> {"a"=>100, "b"=>254, "c"=>300}
h1             #=> {"a"=>100, "b"=>200}
 
               static VALUE
rb_hash_merge(hash1, hash2)
    VALUE hash1, hash2;
{
    return rb_hash_update(rb_obj_dup(hash1), hash2);
}
            
merge!(other_hash) => hsh click to toggle source
merge!(other_hash){|key, oldval, newval| block} => hsh

Adds the contents of other_hash to hsh. If no block is specified entries with duplicate keys are overwritten with the values from other_hash, otherwise the value of each duplicate key is determined by calling the block with the key, its value in hsh and its value in other_hash.

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge!(h2)   #=> {"a"=>100, "b"=>254, "c"=>300}

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge!(h2) { |key, v1, v2| v1 }
                #=> {"a"=>100, "b"=>200, "c"=>300}
 
               static VALUE
rb_hash_update(hash1, hash2)
    VALUE hash1, hash2;
{
    hash2 = to_hash(hash2);
    if (rb_block_given_p()) {
        rb_hash_foreach(hash2, rb_hash_update_block_i, hash1);
    }
    else {
        rb_hash_foreach(hash2, rb_hash_update_i, hash1);
    }
    return hash1;
}
            
rehash → hsh click to toggle source

Rebuilds the hash based on the current hash values for each key. If values of key objects have changed since they were inserted, this method will reindex hsh. If Hash#rehash is called while an iterator is traversing the hash, an IndexError will be raised in the iterator.

a = [ "a", "b" ]
c = [ "c", "d" ]
h = { a => 100, c => 300 }
h[a]       #=> 100
a[0] = "z"
h[a]       #=> nil
h.rehash   #=> {["z", "b"]=>100, ["c", "d"]=>300}
h[a]       #=> 100
 
               static VALUE
rb_hash_rehash(hash)
    VALUE hash;
{
    st_table *tbl;

    rb_hash_modify(hash);
    tbl = st_init_table_with_size(&objhash, RHASH(hash)->tbl->num_entries);
    rb_hash_foreach(hash, rb_hash_rehash_i, (st_data_t)tbl);
    st_free_table(RHASH(hash)->tbl);
    RHASH(hash)->tbl = tbl;

    return hash;
}
            
reject {| key, value | block } → a_hash click to toggle source

Same as Hash#delete_if, but works on (and returns) a copy of the hsh. Equivalent to hsh.dup.delete_if.

 
               static VALUE
rb_hash_reject(hash)
    VALUE hash;
{
    return rb_hash_delete_if(rb_obj_dup(hash));
}
            
reject! {| key, value | block } → hsh or nil click to toggle source

Equivalent to Hash#delete_if, but returns nil if no changes were made.

 
               VALUE
rb_hash_reject_bang(hash)
    VALUE hash;
{
    int n;

    RETURN_ENUMERATOR(hash, 0, 0);
    n = RHASH(hash)->tbl->num_entries;
    rb_hash_delete_if(hash);
    if (n == RHASH(hash)->tbl->num_entries) return Qnil;
    return hash;
}
            
replace(other_hash) → hsh click to toggle source

Replaces the contents of hsh with the contents of other_hash.

h = { "a" => 100, "b" => 200 }
h.replace({ "c" => 300, "d" => 400 })   #=> {"c"=>300, "d"=>400}
 
               static VALUE
rb_hash_replace(hash, hash2)
    VALUE hash, hash2;
{
    hash2 = to_hash(hash2);
    if (hash == hash2) return hash;
    rb_hash_clear(hash);
    rb_hash_foreach(hash2, replace_i, hash);
    RHASH(hash)->ifnone = RHASH(hash2)->ifnone;
    if (FL_TEST(hash2, HASH_PROC_DEFAULT)) {
        FL_SET(hash, HASH_PROC_DEFAULT);
    }
    else {
        FL_UNSET(hash, HASH_PROC_DEFAULT);
    }

    return hash;
}
            
select {|key, value| block} => array click to toggle source

Returns a new array consisting of [key,value] pairs for which the block returns true. Also see Hash.values_at.

h = { "a" => 100, "b" => 200, "c" => 300 }
h.select {|k,v| k > "a"}  #=> [["b", 200], ["c", 300]]
h.select {|k,v| v < 200}  #=> [["a", 100]]
 
               VALUE
rb_hash_select(hash)
    VALUE hash;
{
    VALUE result;

    RETURN_ENUMERATOR(hash, 0, 0);
    result = rb_ary_new();
    rb_hash_foreach(hash, select_i, result);
    return result;
}
            
shift → anArray or obj click to toggle source

Removes a key-value pair from hsh and returns it as the two-item array [ key, value ], or the hash’s default value if the hash is empty.

h = { 1 => "a", 2 => "b", 3 => "c" }
h.shift   #=> [1, "a"]
h         #=> {2=>"b", 3=>"c"}
 
               static VALUE
rb_hash_shift(hash)
    VALUE hash;
{
    struct shift_var var;

    rb_hash_modify(hash);
    var.key = Qundef;
    if (RHASH(hash)->iter_lev > 0) {
        rb_hash_foreach(hash, shift_i_safe, (st_data_t)&var);
        if (var.key != Qundef) {
            st_data_t key = var.key;
            if (st_delete_safe(RHASH(hash)->tbl, &key, 0, Qundef)) {
                FL_SET(hash, HASH_DELETED);
            }
        }
    }
    else {
        rb_hash_foreach(hash, shift_i, (st_data_t)&var);
    }

    if (var.key != Qundef) {
        return rb_assoc_new(var.key, var.val);
    }
    else if (FL_TEST(hash, HASH_PROC_DEFAULT)) {
        return rb_funcall(RHASH(hash)->ifnone, id_call, 2, hash, Qnil);
    }
    else {
        return RHASH(hash)->ifnone;
    }
}
            
size => fixnum click to toggle source

Returns the number of key-value pairs in the hash.

h = { "d" => 100, "a" => 200, "v" => 300, "e" => 400 }
h.length        #=> 4
h.delete("a")   #=> 200
h.length        #=> 3
 
               static VALUE
rb_hash_size(hash)
    VALUE hash;
{
    return INT2FIX(RHASH(hash)->tbl->num_entries);
}
            
sort => array click to toggle source
sort {| a, b | block } => array

Converts hsh to a nested array of [ key, value ] arrays and sorts it, using Array#sort.

h = { "a" => 20, "b" => 30, "c" => 10  }
h.sort                       #=> [["a", 20], ["b", 30], ["c", 10]]
h.sort {|a,b| a[1]<=>b[1]}   #=> [["c", 10], ["a", 20], ["b", 30]]
 
               static VALUE
rb_hash_sort(hash)
    VALUE hash;
{
    VALUE entries = rb_hash_to_a(hash);
    rb_ary_sort_bang(entries);
    return entries;
}
            
store(key, value) => value click to toggle source

Element Assignment—Associates the value given by value with the key given by key. key should not have its value changed while it is in use as a key (a String passed as a key will be duplicated and frozen).

h = { "a" => 100, "b" => 200 }
h["a"] = 9
h["c"] = 4
h   #=> {"a"=>9, "b"=>200, "c"=>4}
 
               VALUE
rb_hash_aset(hash, key, val)
    VALUE hash, key, val;
{
    rb_hash_modify(hash);
    if (TYPE(key) != T_STRING || st_lookup(RHASH(hash)->tbl, key, 0)) {
        st_insert(RHASH(hash)->tbl, key, val);
    }
    else {
        st_add_direct(RHASH(hash)->tbl, rb_str_new4(key), val);
    }
    return val;
}
            
to_a → array click to toggle source

Converts hsh to a nested array of [ key, value ] arrays.

h = { "c" => 300, "a" => 100, "d" => 400, "c" => 300  }
h.to_a   #=> [["a", 100], ["c", 300], ["d", 400]]
 
               static VALUE
rb_hash_to_a(hash)
    VALUE hash;
{
    VALUE ary;

    ary = rb_ary_new();
    rb_hash_foreach(hash, to_a_i, ary);
    if (OBJ_TAINTED(hash)) OBJ_TAINT(ary);

    return ary;
}
            
to_hash => hsh click to toggle source

Returns self.

 
               static VALUE
rb_hash_to_hash(hash)
    VALUE hash;
{
    return hash;
}
            
to_s => string click to toggle source

Converts hsh to a string by converting the hash to an array of [ key, value ] pairs and then converting that array to a string using Array#join with the default separator.

h = { "c" => 300, "a" => 100, "d" => 400, "c" => 300  }
h.to_s   #=> "a100c300d400"
 
               static VALUE
rb_hash_to_s(hash)
    VALUE hash;
{
    if (rb_inspecting_p(hash)) return rb_str_new2("{...}");
    return rb_protect_inspect(to_s_hash, hash, 0);
}
            
update(other_hash) => hsh click to toggle source
update(other_hash){|key, oldval, newval| block} => hsh

Adds the contents of other_hash to hsh. If no block is specified entries with duplicate keys are overwritten with the values from other_hash, otherwise the value of each duplicate key is determined by calling the block with the key, its value in hsh and its value in other_hash.

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge!(h2)   #=> {"a"=>100, "b"=>254, "c"=>300}

h1 = { "a" => 100, "b" => 200 }
h2 = { "b" => 254, "c" => 300 }
h1.merge!(h2) { |key, v1, v2| v1 }
                #=> {"a"=>100, "b"=>200, "c"=>300}
 
               static VALUE
rb_hash_update(hash1, hash2)
    VALUE hash1, hash2;
{
    hash2 = to_hash(hash2);
    if (rb_block_given_p()) {
        rb_hash_foreach(hash2, rb_hash_update_block_i, hash1);
    }
    else {
        rb_hash_foreach(hash2, rb_hash_update_i, hash1);
    }
    return hash1;
}
            
value?(value) => true or false click to toggle source

Returns true if the given value is present for some key in hsh.

h = { "a" => 100, "b" => 200 }
h.has_value?(100)   #=> true
h.has_value?(999)   #=> false
 
               static VALUE
rb_hash_has_value(hash, val)
    VALUE hash;
    VALUE val;
{
    VALUE data[2];

    data[0] = Qfalse;
    data[1] = val;
    rb_hash_foreach(hash, rb_hash_search_value, (st_data_t)data);
    return data[0];
}
            
values => array click to toggle source

Returns a new array populated with the values from hsh. See also Hash#keys.

h = { "a" => 100, "b" => 200, "c" => 300 }
h.values   #=> [100, 200, 300]
 
               static VALUE
rb_hash_values(hash)
    VALUE hash;
{
    VALUE ary;

    ary = rb_ary_new();
    rb_hash_foreach(hash, values_i, ary);

    return ary;
}
            
values_at(key, ...) => array click to toggle source

Return an array containing the values associated with the given keys. Also see Hash.select.

h = { "cat" => "feline", "dog" => "canine", "cow" => "bovine" }
h.values_at("cow", "cat")  #=> ["bovine", "feline"]
 
               VALUE
rb_hash_values_at(argc, argv, hash)
    int argc;
    VALUE *argv;
    VALUE hash;
{
    VALUE result = rb_ary_new();
    long i;

    for (i=0; i<argc; i++) {
        rb_ary_push(result, rb_hash_aref(hash, argv[i]));
    }
    return result;
}
            

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