Array

Class

An Array is an ordered, integer-indexed collection of objects, called elements. Any object (even another array) may be an array element, and an array can contain objects of different types.

Array Indexes

Array indexing starts at 0, as in C or Java.

A positive index is an offset from the first element:

Index 0 indicates the first element.
Index 1 indicates the second element.
…

A negative index is an offset, backwards, from the end of the array:

Index -1 indicates the last element.
Index -2 indicates the next-to-last element.
…

A non-negative index is in range if and only if it is smaller than the size of the array. For a 3-element array:

Indexes 0 through 2 are in range.
Index 3 is out of range.

A negative index is in range if and only if its absolute value is not larger than the size of the array. For a 3-element array:

Indexes -1 through -3 are in range.
Index -4 is out of range.

Although the effective index into an array is always an integer, some methods (both within and outside of class Array) accept one or more non-integer arguments that are integer-convertible objects.

Creating Arrays

You can create an Array object explicitly with:

An array literal:
```
[1, 'one', :one, [2, 'two', :two]]
```

A array literal:

%w[foo bar baz] # => ["foo", "bar", "baz"]
%w[1 % *]       # => ["1", "%", "*"]

A array literal:

%i[foo bar baz] # => [:foo, :bar, :baz]
%i[1 % *]       # => [:"1", :%, :*]

Method Kernel#Array:

Array(["a", "b"])             # => ["a", "b"]
Array(1..5)                   # => [1, 2, 3, 4, 5]
Array(key: :value)            # => [[:key, :value]]
Array(nil)                    # => []
Array(1)                      # => [1]
Array({:a => "a", :b => "b"}) # => [[:a, "a"], [:b, "b"]]

Method Array.new:
```
Array.new               # => []
Array.new(3)            # => [nil, nil, nil]
Array.new(4) {Hash.new} # => [{}, {}, {}, {}]
Array.new(3, true)      # => [true, true, true]
```
Note that the last example above populates the array with references to the same object. This is recommended only in cases where that object is a natively immutable object such as a symbol, a numeric, nil, true, or false.

Another way to create an array with various objects, using a block; this usage is safe for mutable objects such as hashes, strings or other arrays:
```
Array.new(4) {|i| i.to_s } # => ["0", "1", "2", "3"]
```
Here is a way to create a multi-dimensional array:
```
Array.new(3) {Array.new(3)}
# => [[nil, nil, nil], [nil, nil, nil], [nil, nil, nil]]
```

A number of Ruby methods, both in the core and in the standard library, provide instance method to_a, which converts an object to an array.

Example Usage

In addition to the methods it mixes in through the Enumerable module, the Array class has proprietary methods for accessing, searching and otherwise manipulating arrays.

Some of the more common ones are illustrated below.

Accessing Elements

Elements in an array can be retrieved using the Array#[] method. It can take a single integer argument (a numeric index), a pair of arguments (start and length) or a range. Negative indices start counting from the end, with -1 being the last element.

arr = [1, 2, 3, 4, 5, 6]
arr[2]    #=> 3
arr[100]  #=> nil
arr[-3]   #=> 4
arr[2, 3] #=> [3, 4, 5]
arr[1..4] #=> [2, 3, 4, 5]
arr[1..-3] #=> [2, 3, 4]

Another way to access a particular array element is by using the at method

arr.at(0) #=> 1

The slice method works in an identical manner to Array#[].

To raise an error for indices outside of the array bounds or else to provide a default value when that happens, you can use fetch.

arr = ['a', 'b', 'c', 'd', 'e', 'f']
arr.fetch(100) #=> IndexError: index 100 outside of array bounds: -6...6
arr.fetch(100, "oops") #=> "oops"

The special methods first and last will return the first and last elements of an array, respectively.

arr.first #=> 1
arr.last  #=> 6

To return the first n elements of an array, use take

arr.take(3) #=> [1, 2, 3]

drop does the opposite of take, by returning the elements after n elements have been dropped:

arr.drop(3) #=> [4, 5, 6]

Obtaining Information about an Array

Arrays keep track of their own length at all times. To query an array about the number of elements it contains, use length, count or size.

browsers = ['Chrome', 'Firefox', 'Safari', 'Opera', 'IE']
browsers.length #=> 5
browsers.count #=> 5

To check whether an array contains any elements at all

browsers.empty? #=> false

To check whether a particular item is included in the array

browsers.include?('Konqueror') #=> false

Adding Items to Arrays

Items can be added to the end of an array by using either push or <<

arr = [1, 2, 3, 4]
arr.push(5) #=> [1, 2, 3, 4, 5]
arr << 6    #=> [1, 2, 3, 4, 5, 6]

unshift will add a new item to the beginning of an array.

arr.unshift(0) #=> [0, 1, 2, 3, 4, 5, 6]

With insert you can add a new element to an array at any position.

arr.insert(3, 'apple')  #=> [0, 1, 2, 'apple', 3, 4, 5, 6]

Using the insert method, you can also insert multiple values at once:

arr.insert(3, 'orange', 'pear', 'grapefruit')
#=> [0, 1, 2, "orange", "pear", "grapefruit", "apple", 3, 4, 5, 6]

Removing Items from an Array

The method pop removes the last element in an array and returns it:

arr =  [1, 2, 3, 4, 5, 6]
arr.pop #=> 6
arr #=> [1, 2, 3, 4, 5]

To retrieve and at the same time remove the first item, use shift:

arr.shift #=> 1
arr #=> [2, 3, 4, 5]

To delete an element at a particular index:

arr.delete_at(2) #=> 4
arr #=> [2, 3, 5]

To delete a particular element anywhere in an array, use delete:

arr = [1, 2, 2, 3]
arr.delete(2) #=> 2
arr #=> [1,3]

A useful method if you need to remove nil values from an array is compact:

arr = ['foo', 0, nil, 'bar', 7, 'baz', nil]
arr.compact  #=> ['foo', 0, 'bar', 7, 'baz']
arr          #=> ['foo', 0, nil, 'bar', 7, 'baz', nil]
arr.compact! #=> ['foo', 0, 'bar', 7, 'baz']
arr          #=> ['foo', 0, 'bar', 7, 'baz']

Another common need is to remove duplicate elements from an array.

It has the non-destructive uniq, and destructive method uniq!

arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556]
arr.uniq #=> [2, 5, 6, 556, 8, 9, 0, 123]

Iterating over Arrays

Like all classes that include the Enumerable module, Array has an each method, which defines what elements should be iterated over and how. In case of Array’s each, all elements in the Array instance are yielded to the supplied block in sequence.

Note that this operation leaves the array unchanged.

arr = [1, 2, 3, 4, 5]
arr.each {|a| print a -= 10, " "}
# prints: -9 -8 -7 -6 -5
#=> [1, 2, 3, 4, 5]

Another sometimes useful iterator is reverse_each which will iterate over the elements in the array in reverse order.

words = %w[first second third fourth fifth sixth]
str = ""
words.reverse_each {|word| str += "#{word} "}
p str #=> "sixth fifth fourth third second first "

The map method can be used to create a new array based on the original array, but with the values modified by the supplied block:

arr.map {|a| 2*a}     #=> [2, 4, 6, 8, 10]
arr                   #=> [1, 2, 3, 4, 5]
arr.map! {|a| a**2}   #=> [1, 4, 9, 16, 25]
arr                   #=> [1, 4, 9, 16, 25]

Selecting Items from an Array

Elements can be selected from an array according to criteria defined in a block. The selection can happen in a destructive or a non-destructive manner. While the destructive operations will modify the array they were called on, the non-destructive methods usually return a new array with the selected elements, but leave the original array unchanged.

Non-destructive Selection

arr = [1, 2, 3, 4, 5, 6]
arr.select {|a| a > 3}       #=> [4, 5, 6]
arr.reject {|a| a < 3}       #=> [3, 4, 5, 6]
arr.drop_while {|a| a < 4}   #=> [4, 5, 6]
arr                          #=> [1, 2, 3, 4, 5, 6]

Destructive Selection

select! and reject! are the corresponding destructive methods to select and reject

Similar to select vs. reject, delete_if and keep_if have the exact opposite result when supplied with the same block:

arr.delete_if {|a| a < 4}   #=> [4, 5, 6]
arr                         #=> [4, 5, 6]

arr = [1, 2, 3, 4, 5, 6]
arr.keep_if {|a| a < 4}   #=> [1, 2, 3]
arr                       #=> [1, 2, 3]

What’s Here

First, what’s elsewhere. Class Array:

Inherits from class Object.
Includes module Enumerable, which provides dozens of additional methods.

Here, class Array provides methods that are useful for:

Methods for Creating an Array

::[]: Returns a new array populated with given objects.
::new: Returns a new array.
::try_convert: Returns a new array created from a given object.

Methods for Querying

length, size: Returns the count of elements.
include?: Returns whether any element == a given object.
empty?: Returns whether there are no elements.
all?: Returns whether all elements meet a given criterion.
any?: Returns whether any element meets a given criterion.
none?: Returns whether no element == a given object.
one?: Returns whether exactly one element == a given object.
count: Returns the count of elements that meet a given criterion.
find_index, index: Returns the index of the first element that meets a given criterion.
rindex: Returns the index of the last element that meets a given criterion.
hash: Returns the integer hash code.

Methods for Comparing

<=>: Returns -1, 0, or 1 * as self is less than, equal to, or greater than a given object.
==: Returns whether each element in self is == to the corresponding element in a given object.
eql?: Returns whether each element in self is eql? to the corresponding element in a given object.

Methods for Fetching

These methods do not modify self.

[]: Returns one or more elements.
fetch: Returns the element at a given offset.
first: Returns one or more leading elements.
last: Returns one or more trailing elements.
max: Returns one or more maximum-valued elements, as determined by <=> or a given block.
min: Returns one or more minimum-valued elements, as determined by <=> or a given block.
minmax: Returns the minimum-valued and maximum-valued elements, as determined by <=> or a given block.
assoc: Returns the first element that is an array whose first element == a given object.
rassoc: Returns the first element that is an array whose second element == a given object.
at: Returns the element at a given offset.
values_at: Returns the elements at given offsets.
dig: Returns the object in nested objects that is specified by a given index and additional arguments.
drop: Returns trailing elements as determined by a given index.
take: Returns leading elements as determined by a given index.
drop_while: Returns trailing elements as determined by a given block.
take_while: Returns leading elements as determined by a given block.
slice: Returns consecutive elements as determined by a given argument.
sort: Returns all elements in an order determined by <=> or a given block.
reverse: Returns all elements in reverse order.
compact: Returns an array containing all non-nil elements.
select, filter: Returns an array containing elements selected by a given block.
uniq: Returns an array containing non-duplicate elements.
rotate: Returns all elements with some rotated from one end to the other.
bsearch: Returns an element selected via a binary search as determined by a given block.
bsearch_index: Returns the index of an element selected via a binary search as determined by a given block.
sample: Returns one or more random elements.
shuffle: Returns elements in a random order.

Methods for Assigning

These methods add, replace, or reorder elements in self.

[]=: Assigns specified elements with a given object.
push, append, <<: Appends trailing elements.
unshift, prepend: Prepends leading elements.
insert: Inserts given objects at a given offset; does not replace elements.
concat: Appends all elements from given arrays.
fill: Replaces specified elements with specified objects.
replace: Replaces the content of self with the content of a given array.
reverse!: Replaces self with its elements reversed.
rotate!: Replaces self with its elements rotated.
shuffle!: Replaces self with its elements in random order.
sort!: Replaces self with its elements sorted, as determined by <=> or a given block.
sort_by!: Replaces self with its elements sorted, as determined by a given block.

Methods for Deleting

Each of these methods removes elements from self:

pop: Removes and returns the last element.
shift: Removes and returns the first element.
compact!: Removes all nil elements.
delete: Removes elements equal to a given object.
delete_at: Removes the element at a given offset.
delete_if: Removes elements specified by a given block.
keep_if: Removes elements not specified by a given block.
reject!: Removes elements specified by a given block.
select!, filter!: Removes elements not specified by a given block.
slice!: Removes and returns a sequence of elements.
uniq!: Removes duplicates.

Methods for Combining

&: Returns an array containing elements found both in self and a given array.
intersection: Returns an array containing elements found both in self and in each given array.
+: Returns an array containing all elements of self followed by all elements of a given array.
-: Returns an array containing all elements of self that are not found in a given array.
|: Returns an array containing all elements of self and all elements of a given array, duplicates removed.
union: Returns an array containing all elements of self and all elements of given arrays, duplicates removed.
difference: Returns an array containing all elements of self that are not found in any of the given arrays..
product: Returns or yields all combinations of elements from self and given arrays.

Methods for Iterating

each: Passes each element to a given block.
reverse_each: Passes each element, in reverse order, to a given block.
each_index: Passes each element index to a given block.
cycle: Calls a given block with each element, then does so again, for a specified number of times, or forever.
combination: Calls a given block with combinations of elements of self; a combination does not use the same element more than once.
permutation: Calls a given block with permutations of elements of self; a permutation does not use the same element more than once.
repeated_combination: Calls a given block with combinations of elements of self; a combination may use the same element more than once.
repeated_permutation: Calls a given block with permutations of elements of self; a permutation may use the same element more than once.

Methods for Converting

map, collect: Returns an array containing the block return-value for each element.
map!, collect!: Replaces each element with a block return-value.
flatten: Returns an array that is a recursive flattening of self.
flatten!: Replaces each nested array in self with the elements from that array.
inspect, to_s: Returns a new String containing the elements.
join: Returns a newsString containing the elements joined by the field separator.
to_a: Returns self or a new array containing all elements.
to_ary: Returns self.
to_h: Returns a new hash formed from the elements.
transpose: Transposes self, which must be an array of arrays.
zip: Returns a new array of arrays containing self and given arrays; follow the link for details.

Other Methods

*: Returns one of the following:
- With integer argument n, a new array that is the concatenation of n copies of self.
- With string argument field_separator, a new string that is equivalent to join(field_separator).
abbrev: Returns a hash of unambiguous abbreviations for elements.
pack: Packs the elements into a binary sequence.
sum: Returns a sum of elements according to either + or a given block.

Class Methods

[](*args)

array.c View on GitHub

          
            static VALUE
rb_ary_s_create(int argc, VALUE *argv, VALUE klass)
{
    VALUE ary = ary_new(klass, argc);
    if (argc > 0 && argv) {
        ary_memcpy(ary, 0, argc, argv);
        ARY_SET_LEN(ary, argc);
    }

    return ary;
}

Returns a new array populated with the given objects.

Array.[]( 1, 'a', /^A/)  # => [1, "a", /^A/]
Array[ 1, 'a', /^A/ ]    # => [1, "a", /^A/]
[ 1, 'a', /^A/ ]         # => [1, "a", /^A/]

Array.new → new_empty_array

Array.new(array) → new_array

Array.new(size) → new_array

Array.new(size, default_value) → new_array

Array.new(size) {|index| ... } → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_initialize(int argc, VALUE *argv, VALUE ary)
{
    long len;
    VALUE size, val;

    rb_ary_modify(ary);
    if (argc == 0) {
        rb_ary_reset(ary);
        assert(ARY_EMBED_P(ary));
        assert(ARY_EMBED_LEN(ary) == 0);
        if (rb_block_given_p()) {
            rb_warning("given block not used");
        }
        return ary;
    }
    rb_scan_args(argc, argv, "02", &size, &val);
    if (argc == 1 && !FIXNUM_P(size)) {
        val = rb_check_array_type(size);
        if (!NIL_P(val)) {
            rb_ary_replace(ary, val);
            return ary;
        }
    }

    len = NUM2LONG(size);
    /* NUM2LONG() may call size.to_int, ary can be frozen, modified, etc */
    if (len < 0) {
        rb_raise(rb_eArgError, "negative array size");
    }
    if (len > ARY_MAX_SIZE) {
        rb_raise(rb_eArgError, "array size too big");
    }
    /* recheck after argument conversion */
    rb_ary_modify(ary);
    ary_resize_capa(ary, len);
    if (rb_block_given_p()) {
        long i;

        if (argc == 2) {
            rb_warn("block supersedes default value argument");
        }
        for (i=0; i<len; i++) {
            rb_ary_store(ary, i, rb_yield(LONG2NUM(i)));
            ARY_SET_LEN(ary, i + 1);
        }
    }
    else {
        ary_memfill(ary, 0, len, val);
        ARY_SET_LEN(ary, len);
    }
    return ary;
}

Returns a new Array.

With no block and no arguments, returns a new empty Array object.

With no block and a single Array argument array, returns a new Array formed from array:

a = Array.new([:foo, 'bar', 2])
a.class # => Array
a # => [:foo, "bar", 2]

With no block and a single Integer argument size, returns a new Array of the given size whose elements are all nil:

a = Array.new(3)
a # => [nil, nil, nil]

With no block and arguments size and default_value, returns an Array of the given size; each element is that same default_value:

a = Array.new(3, 'x')
a # => ['x', 'x', 'x']

With a block and argument size, returns an Array of the given size; the block is called with each successive integer index; the element for that index is the return value from the block:

a = Array.new(3) {|index| "Element #{index}" }
a # => ["Element 0", "Element 1", "Element 2"]

Raises ArgumentError if size is negative.

With a block and no argument, or a single argument 0, ignores the block and returns a new empty Array.

Array.try_convert(object) → object, new_array, or nil

array.c View on GitHub

          
            static VALUE
rb_ary_s_try_convert(VALUE dummy, VALUE ary)
{
    return rb_check_array_type(ary);
}

If object is an Array object, returns object.

Otherwise if object responds to :to_ary, calls object.to_ary and returns the result.

Returns nil if object does not respond to :to_ary

Raises an exception unless object.to_ary returns an Array object.

Instance Methods

array & other_array → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_and(VALUE ary1, VALUE ary2)
{
    VALUE hash, ary3, v;
    st_data_t vv;
    long i;

    ary2 = to_ary(ary2);
    ary3 = rb_ary_new();
    if (RARRAY_LEN(ary1) == 0 || RARRAY_LEN(ary2) == 0) return ary3;

    if (RARRAY_LEN(ary1) <= SMALL_ARRAY_LEN && RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
        for (i=0; i<RARRAY_LEN(ary1); i++) {
            v = RARRAY_AREF(ary1, i);
            if (!rb_ary_includes_by_eql(ary2, v)) continue;
            if (rb_ary_includes_by_eql(ary3, v)) continue;
            rb_ary_push(ary3, v);
        }
        return ary3;
    }

    hash = ary_make_hash(ary2);

    for (i=0; i<RARRAY_LEN(ary1); i++) {
        v = RARRAY_AREF(ary1, i);
        vv = (st_data_t)v;
        if (rb_hash_stlike_delete(hash, &vv, 0)) {
            rb_ary_push(ary3, v);
        }
    }

    return ary3;
}

Returns a new Array containing each element found in both array and Array other_array; duplicates are omitted; items are compared using eql? (items must also implement hash correctly):

[0, 1, 2, 3] & [1, 2] # => [1, 2]
[0, 1, 0, 1] & [0, 1] # => [0, 1]

Preserves order from array:

[0, 1, 2] & [3, 2, 1, 0] # => [0, 1, 2]

Related: Array#intersection.

array * n → new_array

array * string_separator → new_string

array.c View on GitHub

          
            static VALUE
rb_ary_times(VALUE ary, VALUE times)
{
    VALUE ary2, tmp;
    const VALUE *ptr;
    long t, len;

    tmp = rb_check_string_type(times);
    if (!NIL_P(tmp)) {
        return rb_ary_join(ary, tmp);
    }

    len = NUM2LONG(times);
    if (len == 0) {
        ary2 = ary_new(rb_cArray, 0);
        goto out;
    }
    if (len < 0) {
        rb_raise(rb_eArgError, "negative argument");
    }
    if (ARY_MAX_SIZE/len < RARRAY_LEN(ary)) {
        rb_raise(rb_eArgError, "argument too big");
    }
    len *= RARRAY_LEN(ary);

    ary2 = ary_new(rb_cArray, len);
    ARY_SET_LEN(ary2, len);

    ptr = RARRAY_CONST_PTR(ary);
    t = RARRAY_LEN(ary);
    if (0 < t) {
        ary_memcpy(ary2, 0, t, ptr);
        while (t <= len/2) {
            ary_memcpy(ary2, t, t, RARRAY_CONST_PTR(ary2));
            t *= 2;
        }
        if (t < len) {
            ary_memcpy(ary2, t, len-t, RARRAY_CONST_PTR(ary2));
        }
    }
  out:
    return ary2;
}

When non-negative argument Integer n is given, returns a new Array built by concatenating the n copies of self:

a = ['x', 'y']
a * 3 # => ["x", "y", "x", "y", "x", "y"]

When String argument string_separator is given, equivalent to array.join(string_separator):

[0, [0, 1], {foo: 0}] * ', ' # => "0, 0, 1, {:foo=>0}"

array + other_array → new_array

array.c View on GitHub

          
            VALUE
rb_ary_plus(VALUE x, VALUE y)
{
    VALUE z;
    long len, xlen, ylen;

    y = to_ary(y);
    xlen = RARRAY_LEN(x);
    ylen = RARRAY_LEN(y);
    len = xlen + ylen;
    z = rb_ary_new2(len);

    ary_memcpy(z, 0, xlen, RARRAY_CONST_PTR(x));
    ary_memcpy(z, xlen, ylen, RARRAY_CONST_PTR(y));
    ARY_SET_LEN(z, len);
    return z;
}

Returns a new Array containing all elements of array followed by all elements of other_array:

a = [0, 1] + [2, 3]
a # => [0, 1, 2, 3]

Related: concat.

array - other_array → new_array

array.c View on GitHub

          
            VALUE
rb_ary_diff(VALUE ary1, VALUE ary2)
{
    VALUE ary3;
    VALUE hash;
    long i;

    ary2 = to_ary(ary2);
    if (RARRAY_LEN(ary2) == 0) { return ary_make_shared_copy(ary1); }
    ary3 = rb_ary_new();

    if (RARRAY_LEN(ary1) <= SMALL_ARRAY_LEN || RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
        for (i=0; i<RARRAY_LEN(ary1); i++) {
            VALUE elt = rb_ary_elt(ary1, i);
            if (rb_ary_includes_by_eql(ary2, elt)) continue;
            rb_ary_push(ary3, elt);
        }
        return ary3;
    }

    hash = ary_make_hash(ary2);
    for (i=0; i<RARRAY_LEN(ary1); i++) {
        if (rb_hash_stlike_lookup(hash, RARRAY_AREF(ary1, i), NULL)) continue;
        rb_ary_push(ary3, rb_ary_elt(ary1, i));
    }

    return ary3;
}

Returns a new Array containing only those elements from array that are not found in Array other_array; items are compared using eql?; the order from array is preserved:

[0, 1, 1, 2, 1, 1, 3, 1, 1] - [1] # => [0, 2, 3]
[0, 1, 2, 3] - [3, 0] # => [1, 2]
[0, 1, 2] - [4] # => [0, 1, 2]

Related: Array#difference.

array << object → self

array.c View on GitHub

          
            VALUE
rb_ary_push(VALUE ary, VALUE item)
{
    long idx = RARRAY_LEN((ary_verify(ary), ary));
    VALUE target_ary = ary_ensure_room_for_push(ary, 1);
    RARRAY_PTR_USE(ary, ptr, {
        RB_OBJ_WRITE(target_ary, &ptr[idx], item);
    });
    ARY_SET_LEN(ary, idx + 1);
    ary_verify(ary);
    return ary;
}

Appends object to self; returns self:

a = [:foo, 'bar', 2]
a << :baz # => [:foo, "bar", 2, :baz]

Appends object as one element, even if it is another Array:

a = [:foo, 'bar', 2]
a1 = a << [3, 4]
a1 # => [:foo, "bar", 2, [3, 4]]

array <=> other_array → -1, 0, or 1

array.c View on GitHub

          
            VALUE
rb_ary_cmp(VALUE ary1, VALUE ary2)
{
    long len;
    VALUE v;

    ary2 = rb_check_array_type(ary2);
    if (NIL_P(ary2)) return Qnil;
    if (ary1 == ary2) return INT2FIX(0);
    v = rb_exec_recursive_paired(recursive_cmp, ary1, ary2, ary2);
    if (!UNDEF_P(v)) return v;
    len = RARRAY_LEN(ary1) - RARRAY_LEN(ary2);
    if (len == 0) return INT2FIX(0);
    if (len > 0) return INT2FIX(1);
    return INT2FIX(-1);
}

Returns -1, 0, or 1 as self is less than, equal to, or greater than other_array. For each index i in self, evaluates result = self[i] <=> other_array[i].

Returns -1 if any result is -1:

[0, 1, 2] <=> [0, 1, 3] # => -1

Returns 1 if any result is 1:

[0, 1, 2] <=> [0, 1, 1] # => 1

When all results are zero:

Returns -1 if array is smaller than other_array:
```
[0, 1, 2] <=> [0, 1, 2, 3] # => -1
```
Returns 1 if array is larger than other_array:
```
[0, 1, 2] <=> [0, 1] # => 1
```
Returns 0 if array and other_array are the same size:
```
[0, 1, 2] <=> [0, 1, 2] # => 0
```

array == other_array → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_equal(VALUE ary1, VALUE ary2)
{
    if (ary1 == ary2) return Qtrue;
    if (!RB_TYPE_P(ary2, T_ARRAY)) {
        if (!rb_respond_to(ary2, idTo_ary)) {
            return Qfalse;
        }
        return rb_equal(ary2, ary1);
    }
    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return Qfalse;
    if (RARRAY_CONST_PTR(ary1) == RARRAY_CONST_PTR(ary2)) return Qtrue;
    return rb_exec_recursive_paired(recursive_equal, ary1, ary2, ary2);
}

Returns true if both array.size == other_array.size and for each index i in array, array[i] == other_array[i]:

a0 = [:foo, 'bar', 2]
a1 = [:foo, 'bar', 2.0]
a1 == a0 # => true
[] == [] # => true

Otherwise, returns false.

This method is different from method Array#eql?, which compares elements using Object#eql?.

array[index] → object or nil

array[start, length] → object or nil

array[range] → object or nil

array[aseq] → object or nil

array.c View on GitHub

          
            VALUE
rb_ary_aref(int argc, const VALUE *argv, VALUE ary)
{
    rb_check_arity(argc, 1, 2);
    if (argc == 2) {
        return rb_ary_aref2(ary, argv[0], argv[1]);
    }
    return rb_ary_aref1(ary, argv[0]);
}

Returns elements from self; does not modify self.

When a single Integer argument index is given, returns the element at offset index:

a = [:foo, 'bar', 2]
a[0] # => :foo
a[2] # => 2
a # => [:foo, "bar", 2]

If index is negative, counts relative to the end of self:

a = [:foo, 'bar', 2]
a[-1] # => 2
a[-2] # => "bar"

If index is out of range, returns nil.

When two Integer arguments start and length are given, returns a new Array of size length containing successive elements beginning at offset start:

a = [:foo, 'bar', 2]
a[0, 2] # => [:foo, "bar"]
a[1, 2] # => ["bar", 2]

If start + length is greater than self.length, returns all elements from offset start to the end:

a = [:foo, 'bar', 2]
a[0, 4] # => [:foo, "bar", 2]
a[1, 3] # => ["bar", 2]
a[2, 2] # => [2]

If start == self.size and length >= 0, returns a new empty Array.

If length is negative, returns nil.

When a single Range argument range is given, treats range.min as start above and range.size as length above:

a = [:foo, 'bar', 2]
a[0..1] # => [:foo, "bar"]
a[1..2] # => ["bar", 2]

Special case: If range.start == a.size, returns a new empty Array.

If range.end is negative, calculates the end index from the end:

a = [:foo, 'bar', 2]
a[0..-1] # => [:foo, "bar", 2]
a[0..-2] # => [:foo, "bar"]
a[0..-3] # => [:foo]

If range.start is negative, calculates the start index from the end:

a = [:foo, 'bar', 2]
a[-1..2] # => [2]
a[-2..2] # => ["bar", 2]
a[-3..2] # => [:foo, "bar", 2]

If range.start is larger than the array size, returns nil.

a = [:foo, 'bar', 2]
a[4..1] # => nil
a[4..0] # => nil
a[4..-1] # => nil

When a single Enumerator::ArithmeticSequence argument aseq is given, returns an Array of elements corresponding to the indexes produced by the sequence.

a = ['--', 'data1', '--', 'data2', '--', 'data3']
a[(1..).step(2)] # => ["data1", "data2", "data3"]

Unlike slicing with range, if the start or the end of the arithmetic sequence is larger than array size, throws RangeError.

a = ['--', 'data1', '--', 'data2', '--', 'data3']
a[(1..11).step(2)]
# RangeError (((1..11).step(2)) out of range)
a[(7..).step(2)]
# RangeError (((7..).step(2)) out of range)

If given a single argument, and its type is not one of the listed, tries to convert it to Integer, and raises if it is impossible:

a = [:foo, 'bar', 2]
# Raises TypeError (no implicit conversion of Symbol into Integer):
a[:foo]

array[index] = object → object

array[start, length] = object → object

array[range] = object → object

array.c View on GitHub

          
            static VALUE
rb_ary_aset(int argc, VALUE *argv, VALUE ary)
{
    long offset, beg, len;

    rb_check_arity(argc, 2, 3);
    rb_ary_modify_check(ary);
    if (argc == 3) {
        beg = NUM2LONG(argv[0]);
        len = NUM2LONG(argv[1]);
        return ary_aset_by_rb_ary_splice(ary, beg, len, argv[2]);
    }
    if (FIXNUM_P(argv[0])) {
        offset = FIX2LONG(argv[0]);
        return ary_aset_by_rb_ary_store(ary, offset, argv[1]);
    }
    if (rb_range_beg_len(argv[0], &beg, &len, RARRAY_LEN(ary), 1)) {
        /* check if idx is Range */
        return ary_aset_by_rb_ary_splice(ary, beg, len, argv[1]);
    }

    offset = NUM2LONG(argv[0]);
    return ary_aset_by_rb_ary_store(ary, offset, argv[1]);
}

Assigns elements in self; returns the given object.

When Integer argument index is given, assigns object to an element in self.

If index is non-negative, assigns object the element at offset index:

a = [:foo, 'bar', 2]
a[0] = 'foo' # => "foo"
a # => ["foo", "bar", 2]

If index is greater than self.length, extends the array:

a = [:foo, 'bar', 2]
a[7] = 'foo' # => "foo"
a # => [:foo, "bar", 2, nil, nil, nil, nil, "foo"]

If index is negative, counts backwards from the end of the array:

a = [:foo, 'bar', 2]
a[-1] = 'two' # => "two"
a # => [:foo, "bar", "two"]

When Integer arguments start and length are given and object is not an Array, removes length - 1 elements beginning at offset start, and assigns object at offset start:

a = [:foo, 'bar', 2]
a[0, 2] = 'foo' # => "foo"
a # => ["foo", 2]

If start is negative, counts backwards from the end of the array:

a = [:foo, 'bar', 2]
a[-2, 2] = 'foo' # => "foo"
a # => [:foo, "foo"]

If start is non-negative and outside the array ( >= self.size), extends the array with nil, assigns object at offset start, and ignores length:

a = [:foo, 'bar', 2]
a[6, 50] = 'foo' # => "foo"
a # => [:foo, "bar", 2, nil, nil, nil, "foo"]

If length is zero, shifts elements at and following offset start and assigns object at offset start:

a = [:foo, 'bar', 2]
a[1, 0] = 'foo' # => "foo"
a # => [:foo, "foo", "bar", 2]

If length is too large for the existing array, does not extend the array:

a = [:foo, 'bar', 2]
a[1, 5] = 'foo' # => "foo"
a # => [:foo, "foo"]

When Range argument range is given and object is an Array, removes length - 1 elements beginning at offset start, and assigns object at offset start:

a = [:foo, 'bar', 2]
a[0..1] = 'foo' # => "foo"
a # => ["foo", 2]

if range.begin is negative, counts backwards from the end of the array:

a = [:foo, 'bar', 2]
a[-2..2] = 'foo' # => "foo"
a # => [:foo, "foo"]

If the array length is less than range.begin, assigns object at offset range.begin, and ignores length:

a = [:foo, 'bar', 2]
a[6..50] = 'foo' # => "foo"
a # => [:foo, "bar", 2, nil, nil, nil, "foo"]

If range.end is zero, shifts elements at and following offset start and assigns object at offset start:

a = [:foo, 'bar', 2]
a[1..0] = 'foo' # => "foo"
a # => [:foo, "foo", "bar", 2]

If range.end is negative, assigns object at offset start, retains range.end.abs -1 elements past that, and removes those beyond:

a = [:foo, 'bar', 2]
a[1..-1] = 'foo' # => "foo"
a # => [:foo, "foo"]
a = [:foo, 'bar', 2]
a[1..-2] = 'foo' # => "foo"
a # => [:foo, "foo", 2]
a = [:foo, 'bar', 2]
a[1..-3] = 'foo' # => "foo"
a # => [:foo, "foo", "bar", 2]
a = [:foo, 'bar', 2]

If range.end is too large for the existing array, replaces array elements, but does not extend the array with nil values:

a = [:foo, 'bar', 2]
a[1..5] = 'foo' # => "foo"
a # => [:foo, "foo"]

abbrev(pattern = nil)

lib/abbrev.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/lib/abbrev.rb, line 130
def abbrev(pattern = nil)
  Abbrev::abbrev(self, pattern)
end

Calculates the set of unambiguous abbreviations for the strings in self.

require 'abbrev'
%w{ car cone }.abbrev
#=> {"car"=>"car", "ca"=>"car", "cone"=>"cone", "con"=>"cone", "co"=>"cone"}

The optional pattern parameter is a pattern or a string. Only input strings that match the pattern or start with the string are included in the output hash.

%w{ fast boat day }.abbrev(/^.a/)
#=> {"fast"=>"fast", "fas"=>"fast", "fa"=>"fast", "day"=>"day", "da"=>"day"}

Abbrev.abbrev(%w{car box cone}, "ca")
#=> {"car"=>"car", "ca"=>"car"}

array.all? → true or false

array.all? {|element| ... } → true or false

array.all?(obj) → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_all_p(int argc, VALUE *argv, VALUE ary)
{
    long i, len = RARRAY_LEN(ary);

    rb_check_arity(argc, 0, 1);
    if (!len) return Qtrue;
    if (argc) {
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (!RTEST(rb_funcall(argv[0], idEqq, 1, RARRAY_AREF(ary, i)))) return Qfalse;
        }
    }
    else if (!rb_block_given_p()) {
        for (i = 0; i < len; ++i) {
            if (!RTEST(RARRAY_AREF(ary, i))) return Qfalse;
        }
    }
    else {
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (!RTEST(rb_yield(RARRAY_AREF(ary, i)))) return Qfalse;
        }
    }
    return Qtrue;
}

Returns true if all elements of self meet a given criterion.

If self has no element, returns true and argument or block are not used.

With no block given and no argument, returns true if self contains only truthy elements, false otherwise:

[0, 1, :foo].all? # => true
[0, nil, 2].all? # => false
[].all? # => true

With a block given and no argument, calls the block with each element in self; returns true if the block returns only truthy values, false otherwise:

[0, 1, 2].all? { |element| element < 3 } # => true
[0, 1, 2].all? { |element| element < 2 } # => false

If argument obj is given, returns true if obj.=== every element, false otherwise:

['food', 'fool', 'foot'].all?(/foo/) # => true
['food', 'drink'].all?(/bar/) # => false
[].all?(/foo/) # => true
[0, 0, 0].all?(0) # => true
[0, 1, 2].all?(1) # => false

Related: Enumerable#all?

array.any? → true or false

array.any? {|element| ... } → true or false

array.any?(obj) → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_any_p(int argc, VALUE *argv, VALUE ary)
{
    long i, len = RARRAY_LEN(ary);

    rb_check_arity(argc, 0, 1);
    if (!len) return Qfalse;
    if (argc) {
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (RTEST(rb_funcall(argv[0], idEqq, 1, RARRAY_AREF(ary, i)))) return Qtrue;
        }
    }
    else if (!rb_block_given_p()) {
        for (i = 0; i < len; ++i) {
            if (RTEST(RARRAY_AREF(ary, i))) return Qtrue;
        }
    }
    else {
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) return Qtrue;
        }
    }
    return Qfalse;
}

Returns true if any element of self meets a given criterion.

If self has no element, returns false and argument or block are not used.

With no block given and no argument, returns true if self has any truthy element, false otherwise:

[nil, 0, false].any? # => true
[nil, false].any? # => false
[].any? # => false

With a block given and no argument, calls the block with each element in self; returns true if the block returns any truthy value, false otherwise:

[0, 1, 2].any? {|element| element > 1 } # => true
[0, 1, 2].any? {|element| element > 2 } # => false

If argument obj is given, returns true if obj.=== any element, false otherwise:

['food', 'drink'].any?(/foo/) # => true
['food', 'drink'].any?(/bar/) # => false
[].any?(/foo/) # => false
[0, 1, 2].any?(1) # => true
[0, 1, 2].any?(3) # => false

Related: Enumerable#any?

append(*args)

array.c View on GitHub

An alias for push

array.assoc(obj) → found_array or nil

array.c View on GitHub

          
            VALUE
rb_ary_assoc(VALUE ary, VALUE key)
{
    long i;
    VALUE v;

    for (i = 0; i < RARRAY_LEN(ary); ++i) {
        v = rb_check_array_type(RARRAY_AREF(ary, i));
        if (!NIL_P(v) && RARRAY_LEN(v) > 0 &&
            rb_equal(RARRAY_AREF(v, 0), key))
            return v;
    }
    return Qnil;
}

Returns the first element in self that is an Array whose first element == obj:

a = [{foo: 0}, [2, 4], [4, 5, 6], [4, 5]]
a.assoc(4) # => [4, 5, 6]

Returns nil if no such element is found.

Related: rassoc.

array.at(index) → object

array.c View on GitHub

          
            VALUE
rb_ary_at(VALUE ary, VALUE pos)
{
    return rb_ary_entry(ary, NUM2LONG(pos));
}

Returns the element at Integer offset index; does not modify self.

a = [:foo, 'bar', 2]
a.at(0) # => :foo
a.at(2) # => 2

array.bsearch {|element| ... } → object

array.bsearch → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_bsearch(VALUE ary)
{
    VALUE index_result = rb_ary_bsearch_index(ary);

    if (FIXNUM_P(index_result)) {
        return rb_ary_entry(ary, FIX2LONG(index_result));
    }
    return index_result;
}

Returns an element from self selected by a binary search.

See Binary Searching.

array.bsearch_index {|element| ... } → integer or nil

array.bsearch_index → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_bsearch_index(VALUE ary)
{
    long low = 0, high = RARRAY_LEN(ary), mid;
    int smaller = 0, satisfied = 0;
    VALUE v, val;

    RETURN_ENUMERATOR(ary, 0, 0);
    while (low < high) {
        mid = low + ((high - low) / 2);
        val = rb_ary_entry(ary, mid);
        v = rb_yield(val);
        if (FIXNUM_P(v)) {
            if (v == INT2FIX(0)) return INT2FIX(mid);
            smaller = (SIGNED_VALUE)v < 0; /* Fixnum preserves its sign-bit */
        }
        else if (v == Qtrue) {
            satisfied = 1;
            smaller = 1;
        }
        else if (!RTEST(v)) {
            smaller = 0;
        }
        else if (rb_obj_is_kind_of(v, rb_cNumeric)) {
            const VALUE zero = INT2FIX(0);
            switch (rb_cmpint(rb_funcallv(v, id_cmp, 1, &zero), v, zero)) {
              case 0: return INT2FIX(mid);
              case 1: smaller = 0; break;
              case -1: smaller = 1;
            }
        }
        else {
            rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE
                     " (must be numeric, true, false or nil)",
                     rb_obj_class(v));
        }
        if (smaller) {
            high = mid;
        }
        else {
            low = mid + 1;
        }
    }
    if (!satisfied) return Qnil;
    return INT2FIX(low);
}

Searches self as described at method bsearch, but returns the index of the found element instead of the element itself.

array.clear → self

array.c View on GitHub

          
            VALUE
rb_ary_clear(VALUE ary)
{
    rb_ary_modify_check(ary);
    if (ARY_SHARED_P(ary)) {
        if (!ARY_EMBED_P(ary)) {
            rb_ary_unshare(ary);
            FL_SET_EMBED(ary);
            ARY_SET_EMBED_LEN(ary, 0);
        }
    }
    else {
        ARY_SET_LEN(ary, 0);
        if (ARY_DEFAULT_SIZE * 2 < ARY_CAPA(ary)) {
            ary_resize_capa(ary, ARY_DEFAULT_SIZE * 2);
        }
    }
    ary_verify(ary);
    return ary;
}

Removes all elements from self:

a = [:foo, 'bar', 2]
a.clear # => []

array.map {|element| ... } -> new_array array.map -> new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_collect(VALUE ary)
{
    long i;
    VALUE collect;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    collect = rb_ary_new2(RARRAY_LEN(ary));
    for (i = 0; i < RARRAY_LEN(ary); i++) {
        rb_ary_push(collect, rb_yield(RARRAY_AREF(ary, i)));
    }
    return collect;
}

Calls the block, if given, with each element of self; returns a new Array whose elements are the return values from the block:

a = [:foo, 'bar', 2]
a1 = a.map {|element| element.class }
a1 # => [Symbol, String, Integer]

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2]
a1 = a.map
a1 # => #<Enumerator: [:foo, "bar", 2]:map>

array.map! {|element| ... } -> self array.map! -> new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_collect_bang(VALUE ary)
{
    long i;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rb_ary_modify(ary);
    for (i = 0; i < RARRAY_LEN(ary); i++) {
        rb_ary_store(ary, i, rb_yield(RARRAY_AREF(ary, i)));
    }
    return ary;
}

Calls the block, if given, with each element; replaces the element with the block’s return value:

a = [:foo, 'bar', 2]
a.map! { |element| element.class } # => [Symbol, String, Integer]

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2]
a1 = a.map!
a1 # => #<Enumerator: [:foo, "bar", 2]:map!>

array.combination(n) {|element| ... } → self

array.combination(n) → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_combination(VALUE ary, VALUE num)
{
    long i, n, len;

    n = NUM2LONG(num);
    RETURN_SIZED_ENUMERATOR(ary, 1, &num, rb_ary_combination_size);
    len = RARRAY_LEN(ary);
    if (n < 0 || len < n) {
        /* yield nothing */
    }
    else if (n == 0) {
        rb_yield(rb_ary_new2(0));
    }
    else if (n == 1) {
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
        }
    }
    else {
        VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
        volatile VALUE t0;
        long *stack = ALLOCV_N(long, t0, n+1);

        RBASIC_CLEAR_CLASS(ary0);
        combinate0(len, n, stack, ary0);
        ALLOCV_END(t0);
        RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
    }
    return ary;
}

Calls the block, if given, with combinations of elements of self; returns self. The order of combinations is indeterminate.

When a block and an in-range positive Integer argument n (0 < n <= self.size) are given, calls the block with all n-tuple combinations of self.

Example:

a = [0, 1, 2]
a.combination(2) {|combination| p combination }

Output:

[0, 1]
[0, 2]
[1, 2]

Another example:

a = [0, 1, 2]
a.combination(3) {|combination| p combination }

Output:

[0, 1, 2]

When n is zero, calls the block once with a new empty Array:

a = [0, 1, 2]
a1 = a.combination(0) {|combination| p combination }

Output:

[]

When n is out of range (negative or larger than self.size), does not call the block:

a = [0, 1, 2]
a.combination(-1) {|combination| fail 'Cannot happen' }
a.combination(4) {|combination| fail 'Cannot happen' }

Returns a new Enumerator if no block given:

a = [0, 1, 2]
a.combination(2) # => #<Enumerator: [0, 1, 2]:combination(2)>

array.compact → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_compact(VALUE ary)
{
    ary = rb_ary_dup(ary);
    rb_ary_compact_bang(ary);
    return ary;
}

Returns a new Array containing all non-nil elements from self:

a = [nil, 0, nil, 1, nil, 2, nil]
a.compact # => [0, 1, 2]

array.compact! → self or nil

array.c View on GitHub

          
            static VALUE
rb_ary_compact_bang(VALUE ary)
{
    VALUE *p, *t, *end;
    long n;

    rb_ary_modify(ary);
    p = t = (VALUE *)RARRAY_CONST_PTR(ary); /* WB: no new reference */
    end = p + RARRAY_LEN(ary);

    while (t < end) {
        if (NIL_P(*t)) t++;
        else *p++ = *t++;
    }
    n = p - RARRAY_CONST_PTR(ary);
    if (RARRAY_LEN(ary) == n) {
        return Qnil;
    }
    ary_resize_smaller(ary, n);

    return ary;
}

Removes all nil elements from self.

Returns self if any elements removed, otherwise nil.

array.concat(*other_arrays) → self

array.c View on GitHub

          
            static VALUE
rb_ary_concat_multi(int argc, VALUE *argv, VALUE ary)
{
    rb_ary_modify_check(ary);

    if (argc == 1) {
        rb_ary_concat(ary, argv[0]);
    }
    else if (argc > 1) {
        int i;
        VALUE args = rb_ary_hidden_new(argc);
        for (i = 0; i < argc; i++) {
            rb_ary_concat(args, argv[i]);
        }
        ary_append(ary, args);
    }

    ary_verify(ary);
    return ary;
}

Adds to array all elements from each Array in other_arrays; returns self:

a = [0, 1]
a.concat([2, 3], [4, 5]) # => [0, 1, 2, 3, 4, 5]

array.count → an_integer

array.count(obj) → an_integer

array.count {|element| ... } → an_integer

array.c View on GitHub

          
            static VALUE
rb_ary_count(int argc, VALUE *argv, VALUE ary)
{
    long i, n = 0;

    if (rb_check_arity(argc, 0, 1) == 0) {
        VALUE v;

        if (!rb_block_given_p())
            return LONG2NUM(RARRAY_LEN(ary));

        for (i = 0; i < RARRAY_LEN(ary); i++) {
            v = RARRAY_AREF(ary, i);
            if (RTEST(rb_yield(v))) n++;
        }
    }
    else {
        VALUE obj = argv[0];

        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            if (rb_equal(RARRAY_AREF(ary, i), obj)) n++;
        }
    }

    return LONG2NUM(n);
}

Returns a count of specified elements.

With no argument and no block, returns the count of all elements:

[0, 1, 2].count # => 3
[].count # => 0

With argument obj, returns the count of elements == to obj:

[0, 1, 2, 0.0].count(0) # => 2
[0, 1, 2].count(3) # => 0

With no argument and a block given, calls the block with each element; returns the count of elements for which the block returns a truthy value:

[0, 1, 2, 3].count {|element| element > 1} # => 2

With argument obj and a block given, issues a warning, ignores the block, and returns the count of elements == to obj.

array.cycle {|element| ... } → nil

array.cycle(count) {|element| ... } → nil

array.cycle → new_enumerator

array.cycle(count) → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_cycle(int argc, VALUE *argv, VALUE ary)
{
    long n, i;

    rb_check_arity(argc, 0, 1);

    RETURN_SIZED_ENUMERATOR(ary, argc, argv, rb_ary_cycle_size);
    if (argc == 0 || NIL_P(argv[0])) {
        n = -1;
    }
    else {
        n = NUM2LONG(argv[0]);
        if (n <= 0) return Qnil;
    }

    while (RARRAY_LEN(ary) > 0 && (n < 0 || 0 < n--)) {
        for (i=0; i<RARRAY_LEN(ary); i++) {
            rb_yield(RARRAY_AREF(ary, i));
        }
    }
    return Qnil;
}

When called with positive Integer argument count and a block, calls the block with each element, then does so again, until it has done so count times; returns nil:

output = []
[0, 1].cycle(2) {|element| output.push(element) } # => nil
output # => [0, 1, 0, 1]

If count is zero or negative, does not call the block:

[0, 1].cycle(0) {|element| fail 'Cannot happen' } # => nil
[0, 1].cycle(-1) {|element| fail 'Cannot happen' } # => nil

When a block is given, and argument is omitted or nil, cycles forever:

# Prints 0 and 1 forever.
[0, 1].cycle {|element| puts element }
[0, 1].cycle(nil) {|element| puts element }

When no block is given, returns a new Enumerator:

[0, 1].cycle(2) # => #<Enumerator: [0, 1]:cycle(2)>
[0, 1].cycle # => # => #<Enumerator: [0, 1]:cycle>
[0, 1].cycle.first(5) # => [0, 1, 0, 1, 0]

array.delete(obj) → deleted_object

array.delete(obj) {|nosuch| ... } → deleted_object or block_return

array.c View on GitHub

          
            VALUE
rb_ary_delete(VALUE ary, VALUE item)
{
    VALUE v = item;
    long i1, i2;

    for (i1 = i2 = 0; i1 < RARRAY_LEN(ary); i1++) {
        VALUE e = RARRAY_AREF(ary, i1);

        if (rb_equal(e, item)) {
            v = e;
            continue;
        }
        if (i1 != i2) {
            rb_ary_store(ary, i2, e);
        }
        i2++;
    }
    if (RARRAY_LEN(ary) == i2) {
        if (rb_block_given_p()) {
            return rb_yield(item);
        }
        return Qnil;
    }

    ary_resize_smaller(ary, i2);

    ary_verify(ary);
    return v;
}

Removes zero or more elements from self.

When no block is given, removes from self each element ele such that ele == obj; returns the last deleted element:

s1 = 'bar'; s2 = 'bar'
a = [:foo, s1, 2, s2]
a.delete('bar') # => "bar"
a # => [:foo, 2]

Returns nil if no elements removed.

When a block is given, removes from self each element ele such that ele == obj.

If any such elements are found, ignores the block and returns the last deleted element:

s1 = 'bar'; s2 = 'bar'
a = [:foo, s1, 2, s2]
deleted_obj = a.delete('bar') {|obj| fail 'Cannot happen' }
a # => [:foo, 2]

If no such elements are found, returns the block’s return value:

a = [:foo, 'bar', 2]
a.delete(:nosuch) {|obj| "#{obj} not found" } # => "nosuch not found"

array.delete_at(index) → deleted_object or nil

array.c View on GitHub

          
            static VALUE
rb_ary_delete_at_m(VALUE ary, VALUE pos)
{
    return rb_ary_delete_at(ary, NUM2LONG(pos));
}

Deletes an element from self, per the given Integer index.

When index is non-negative, deletes the element at offset index:

a = [:foo, 'bar', 2]
a.delete_at(1) # => "bar"
a # => [:foo, 2]

If index is too large, returns nil.

When index is negative, counts backward from the end of the array:

a = [:foo, 'bar', 2]
a.delete_at(-2) # => "bar"
a # => [:foo, 2]

If index is too small (far from zero), returns nil.

array.delete_if {|element| ... } → self

array.delete_if → Enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_delete_if(VALUE ary)
{
    ary_verify(ary);
    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    ary_reject_bang(ary);
    return ary;
}

Removes each element in self for which the block returns a truthy value; returns self:

a = [:foo, 'bar', 2, 'bat']
a.delete_if {|element| element.to_s.start_with?('b') } # => [:foo, 2]

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2]
a.delete_if # => #<Enumerator: [:foo, "bar", 2]:delete_if>

array.difference(*other_arrays) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_difference_multi(int argc, VALUE *argv, VALUE ary)
{
    VALUE ary_diff;
    long i, length;
    volatile VALUE t0;
    bool *is_hash = ALLOCV_N(bool, t0, argc);
    ary_diff = rb_ary_new();
    length = RARRAY_LEN(ary);

    for (i = 0; i < argc; i++) {
        argv[i] = to_ary(argv[i]);
        is_hash[i] = (length > SMALL_ARRAY_LEN && RARRAY_LEN(argv[i]) > SMALL_ARRAY_LEN);
        if (is_hash[i]) argv[i] = ary_make_hash(argv[i]);
    }

    for (i = 0; i < RARRAY_LEN(ary); i++) {
        int j;
        VALUE elt = rb_ary_elt(ary, i);
        for (j = 0; j < argc; j++) {
            if (is_hash[j]) {
                if (rb_hash_stlike_lookup(argv[j], RARRAY_AREF(ary, i), NULL))
                    break;
            }
            else {
                if (rb_ary_includes_by_eql(argv[j], elt)) break;
            }
        }
        if (j == argc) rb_ary_push(ary_diff, elt);
    }

    ALLOCV_END(t0);

    return ary_diff;
}

Returns a new Array containing only those elements from self that are not found in any of the Arrays other_arrays; items are compared using eql?; order from self is preserved:

[0, 1, 1, 2, 1, 1, 3, 1, 1].difference([1]) # => [0, 2, 3]
[0, 1, 2, 3].difference([3, 0], [1, 3]) # => [2]
[0, 1, 2].difference([4]) # => [0, 1, 2]

Returns a copy of self if no arguments given.

Related: Array#-.

array.dig(index, *identifiers) → object

array.c View on GitHub

          
            static VALUE
rb_ary_dig(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    self = rb_ary_at(self, *argv);
    if (!--argc) return self;
    ++argv;
    return rb_obj_dig(argc, argv, self, Qnil);
}

Finds and returns the object in nested objects that is specified by index and identifiers. The nested objects may be instances of various classes. See Dig Methods.

Examples:

a = [:foo, [:bar, :baz, [:bat, :bam]]]
a.dig(1) # => [:bar, :baz, [:bat, :bam]]
a.dig(1, 2) # => [:bat, :bam]
a.dig(1, 2, 0) # => :bat
a.dig(1, 2, 3) # => nil

array.drop(n) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_drop(VALUE ary, VALUE n)
{
    VALUE result;
    long pos = NUM2LONG(n);
    if (pos < 0) {
        rb_raise(rb_eArgError, "attempt to drop negative size");
    }

    result = rb_ary_subseq(ary, pos, RARRAY_LEN(ary));
    if (NIL_P(result)) result = rb_ary_new();
    return result;
}

Returns a new Array containing all but the first n element of self, where n is a non-negative Integer; does not modify self.

Examples:

a = [0, 1, 2, 3, 4, 5]
a.drop(0) # => [0, 1, 2, 3, 4, 5]
a.drop(1) # => [1, 2, 3, 4, 5]
a.drop(2) # => [2, 3, 4, 5]

array.drop_while {|element| ... } → new_array

array.drop_while → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_drop_while(VALUE ary)
{
    long i;

    RETURN_ENUMERATOR(ary, 0, 0);
    for (i = 0; i < RARRAY_LEN(ary); i++) {
        if (!RTEST(rb_yield(RARRAY_AREF(ary, i)))) break;
    }
    return rb_ary_drop(ary, LONG2FIX(i));
}

Returns a new Array containing zero or more trailing elements of self; does not modify self.

With a block given, calls the block with each successive element of self; stops if the block returns false or nil; returns a new Array omitting those elements for which the block returned a truthy value:

a = [0, 1, 2, 3, 4, 5]
a.drop_while {|element| element < 3 } # => [3, 4, 5]

With no block given, returns a new Enumerator:

[0, 1].drop_while # => # => #<Enumerator: [0, 1]:drop_while>

array.each {|element| ... } → self

array.each → Enumerator

array.c View on GitHub

          
            VALUE
rb_ary_each(VALUE ary)
{
    long i;
    ary_verify(ary);
    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    for (i=0; i<RARRAY_LEN(ary); i++) {
        rb_yield(RARRAY_AREF(ary, i));
    }
    return ary;
}

Iterates over array elements.

When a block given, passes each successive array element to the block; returns self:

a = [:foo, 'bar', 2]
a.each {|element|  puts "#{element.class} #{element}" }

Output:

Symbol foo
String bar
Integer 2

Allows the array to be modified during iteration:

a = [:foo, 'bar', 2]
a.each {|element| puts element; a.clear if element.to_s.start_with?('b') }

Output:

foo
bar

When no block given, returns a new Enumerator:

a = [:foo, 'bar', 2]

e = a.each
e # => #<Enumerator: [:foo, "bar", 2]:each>
a1 = e.each {|element|  puts "#{element.class} #{element}" }

Output:

Symbol foo
String bar
Integer 2

Related: each_index, reverse_each.

array.each_index {|index| ... } → self

array.each_index → Enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_each_index(VALUE ary)
{
    long i;
    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);

    for (i=0; i<RARRAY_LEN(ary); i++) {
        rb_yield(LONG2NUM(i));
    }
    return ary;
}

Iterates over array indexes.

When a block given, passes each successive array index to the block; returns self:

a = [:foo, 'bar', 2]
a.each_index {|index|  puts "#{index} #{a[index]}" }

Output:

0 foo
1 bar
2 2

Allows the array to be modified during iteration:

a = [:foo, 'bar', 2]
a.each_index {|index| puts index; a.clear if index > 0 }

Output:

0
1

When no block given, returns a new Enumerator:

a = [:foo, 'bar', 2]
e = a.each_index
e # => #<Enumerator: [:foo, "bar", 2]:each_index>
a1 = e.each {|index|  puts "#{index} #{a[index]}"}

Output:

0 foo
1 bar
2 2

Related: each, reverse_each.

array.empty? → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_empty_p(VALUE ary)
{
    return RBOOL(RARRAY_LEN(ary) == 0);
}

Returns true if the count of elements in self is zero, false otherwise.

array.eql? other_array → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_eql(VALUE ary1, VALUE ary2)
{
    if (ary1 == ary2) return Qtrue;
    if (!RB_TYPE_P(ary2, T_ARRAY)) return Qfalse;
    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return Qfalse;
    if (RARRAY_CONST_PTR(ary1) == RARRAY_CONST_PTR(ary2)) return Qtrue;
    return rb_exec_recursive_paired(recursive_eql, ary1, ary2, ary2);
}

Returns true if self and other_array are the same size, and if, for each index i in self, self[i].eql? other_array[i]:

a0 = [:foo, 'bar', 2]
a1 = [:foo, 'bar', 2]
a1.eql?(a0) # => true

Otherwise, returns false.

This method is different from method Array#==, which compares using method Object#==.

array.fetch(index) → element

array.fetch(index, default_value) → element

array.fetch(index) {|index| ... } → element

array.c View on GitHub

          
            static VALUE
rb_ary_fetch(int argc, VALUE *argv, VALUE ary)
{
    VALUE pos, ifnone;
    long block_given;
    long idx;

    rb_scan_args(argc, argv, "11", &pos, &ifnone);
    block_given = rb_block_given_p();
    if (block_given && argc == 2) {
        rb_warn("block supersedes default value argument");
    }
    idx = NUM2LONG(pos);

    if (idx < 0) {
        idx +=  RARRAY_LEN(ary);
    }
    if (idx < 0 || RARRAY_LEN(ary) <= idx) {
        if (block_given) return rb_yield(pos);
        if (argc == 1) {
            rb_raise(rb_eIndexError, "index %ld outside of array bounds: %ld...%ld",
                        idx - (idx < 0 ? RARRAY_LEN(ary) : 0), -RARRAY_LEN(ary), RARRAY_LEN(ary));
        }
        return ifnone;
    }
    return RARRAY_AREF(ary, idx);
}

Returns the element at offset index.

With the single Integer argument index, returns the element at offset index:

a = [:foo, 'bar', 2]
a.fetch(1) # => "bar"

If index is negative, counts from the end of the array:

a = [:foo, 'bar', 2]
a.fetch(-1) # => 2
a.fetch(-2) # => "bar"

With arguments index and default_value, returns the element at offset index if index is in range, otherwise returns default_value:

a = [:foo, 'bar', 2]
a.fetch(1, nil) # => "bar"

With argument index and a block, returns the element at offset index if index is in range (and the block is not called); otherwise calls the block with index and returns its return value:

a = [:foo, 'bar', 2]
a.fetch(1) {|index| raise 'Cannot happen' } # => "bar"
a.fetch(50) {|index| "Value for #{index}" } # => "Value for 50"

array.fill(obj) → self

array.fill(obj, start) → self

array.fill(obj, start, length) → self

array.fill(obj, range) → self

array.fill {|index| ... } → self

array.fill(start) {|index| ... } → self

array.fill(start, length) {|index| ... } → self

array.fill(range) {|index| ... } → self

array.c View on GitHub

          
            static VALUE
rb_ary_fill(int argc, VALUE *argv, VALUE ary)
{
    VALUE item = Qundef, arg1, arg2;
    long beg = 0, end = 0, len = 0;

    if (rb_block_given_p()) {
        rb_scan_args(argc, argv, "02", &arg1, &arg2);
        argc += 1;              /* hackish */
    }
    else {
        rb_scan_args(argc, argv, "12", &item, &arg1, &arg2);
    }
    switch (argc) {
      case 1:
        beg = 0;
        len = RARRAY_LEN(ary);
        break;
      case 2:
        if (rb_range_beg_len(arg1, &beg, &len, RARRAY_LEN(ary), 1)) {
            break;
        }
        /* fall through */
      case 3:
        beg = NIL_P(arg1) ? 0 : NUM2LONG(arg1);
        if (beg < 0) {
            beg = RARRAY_LEN(ary) + beg;
            if (beg < 0) beg = 0;
        }
        len = NIL_P(arg2) ? RARRAY_LEN(ary) - beg : NUM2LONG(arg2);
        break;
    }
    rb_ary_modify(ary);
    if (len < 0) {
        return ary;
    }
    if (beg >= ARY_MAX_SIZE || len > ARY_MAX_SIZE - beg) {
        rb_raise(rb_eArgError, "argument too big");
    }
    end = beg + len;
    if (RARRAY_LEN(ary) < end) {
        if (end >= ARY_CAPA(ary)) {
            ary_resize_capa(ary, end);
        }
        ary_mem_clear(ary, RARRAY_LEN(ary), end - RARRAY_LEN(ary));
        ARY_SET_LEN(ary, end);
    }

    if (UNDEF_P(item)) {
        VALUE v;
        long i;

        for (i=beg; i<end; i++) {
            v = rb_yield(LONG2NUM(i));
            if (i>=RARRAY_LEN(ary)) break;
            ARY_SET(ary, i, v);
        }
    }
    else {
        ary_memfill(ary, beg, len, item);
    }
    return ary;
}

Replaces specified elements in self with specified objects; returns self.

With argument obj and no block given, replaces all elements with that one object:

a = ['a', 'b', 'c', 'd']
a # => ["a", "b", "c", "d"]
a.fill(:X) # => [:X, :X, :X, :X]

With arguments obj and Integer start, and no block given, replaces elements based on the given start.

If start is in range (0 <= start < array.size), replaces all elements from offset start through the end:

a = ['a', 'b', 'c', 'd']
a.fill(:X, 2) # => ["a", "b", :X, :X]

If start is too large (start >= array.size), does nothing:

a = ['a', 'b', 'c', 'd']
a.fill(:X, 4) # => ["a", "b", "c", "d"]
a = ['a', 'b', 'c', 'd']
a.fill(:X, 5) # => ["a", "b", "c", "d"]

If start is negative, counts from the end (starting index is start + array.size):

a = ['a', 'b', 'c', 'd']
a.fill(:X, -2) # => ["a", "b", :X, :X]

If start is too small (less than and far from zero), replaces all elements:

a = ['a', 'b', 'c', 'd']
a.fill(:X, -6) # => [:X, :X, :X, :X]
a = ['a', 'b', 'c', 'd']
a.fill(:X, -50) # => [:X, :X, :X, :X]

With arguments obj, Integer start, and Integer length, and no block given, replaces elements based on the given start and length.

If start is in range, replaces length elements beginning at offset start:

a = ['a', 'b', 'c', 'd']
a.fill(:X, 1, 1) # => ["a", :X, "c", "d"]

If start is negative, counts from the end:

a = ['a', 'b', 'c', 'd']
a.fill(:X, -2, 1) # => ["a", "b", :X, "d"]

If start is large (start >= array.size), extends self with nil:

a = ['a', 'b', 'c', 'd']
a.fill(:X, 5, 0) # => ["a", "b", "c", "d", nil]
a = ['a', 'b', 'c', 'd']
a.fill(:X, 5, 2) # => ["a", "b", "c", "d", nil, :X, :X]

If length is zero or negative, replaces no elements:

a = ['a', 'b', 'c', 'd']
a.fill(:X, 1, 0) # => ["a", "b", "c", "d"]
a.fill(:X, 1, -1) # => ["a", "b", "c", "d"]

With arguments obj and Range range, and no block given, replaces elements based on the given range.

If the range is positive and ascending (0 < range.begin <= range.end), replaces elements from range.begin to range.end:

a = ['a', 'b', 'c', 'd']
a.fill(:X, (1..1)) # => ["a", :X, "c", "d"]

If range.first is negative, replaces no elements:

a = ['a', 'b', 'c', 'd']
a.fill(:X, (-1..1)) # => ["a", "b", "c", "d"]

If range.last is negative, counts from the end:

a = ['a', 'b', 'c', 'd']
a.fill(:X, (0..-2)) # => [:X, :X, :X, "d"]
a = ['a', 'b', 'c', 'd']
a.fill(:X, (1..-2)) # => ["a", :X, :X, "d"]

If range.last and range.last are both negative, both count from the end of the array:

a = ['a', 'b', 'c', 'd']
a.fill(:X, (-1..-1)) # => ["a", "b", "c", :X]
a = ['a', 'b', 'c', 'd']
a.fill(:X, (-2..-2)) # => ["a", "b", :X, "d"]

With no arguments and a block given, calls the block with each index; replaces the corresponding element with the block’s return value:

a = ['a', 'b', 'c', 'd']
a.fill { |index| "new_#{index}" } # => ["new_0", "new_1", "new_2", "new_3"]

With argument start and a block given, calls the block with each index from offset start to the end; replaces the corresponding element with the block’s return value.

If start is in range (0 <= start < array.size), replaces from offset start to the end:

a = ['a', 'b', 'c', 'd']
a.fill(1) { |index| "new_#{index}" } # => ["a", "new_1", "new_2", "new_3"]

If start is too large(start >= array.size), does nothing:

a = ['a', 'b', 'c', 'd']
a.fill(4) { |index| fail 'Cannot happen' } # => ["a", "b", "c", "d"]
a = ['a', 'b', 'c', 'd']
a.fill(4) { |index| fail 'Cannot happen' } # => ["a", "b", "c", "d"]

If start is negative, counts from the end:

a = ['a', 'b', 'c', 'd']
a.fill(-2) { |index| "new_#{index}" } # => ["a", "b", "new_2", "new_3"]

If start is too small (start <= -array.size, replaces all elements:

a = ['a', 'b', 'c', 'd']
a.fill(-6) { |index| "new_#{index}" } # => ["new_0", "new_1", "new_2", "new_3"]
a = ['a', 'b', 'c', 'd']
a.fill(-50) { |index| "new_#{index}" } # => ["new_0", "new_1", "new_2", "new_3"]

With arguments start and length, and a block given, calls the block for each index specified by start length; replaces the corresponding element with the block’s return value.

If start is in range, replaces length elements beginning at offset start:

a = ['a', 'b', 'c', 'd']
a.fill(1, 1) { |index| "new_#{index}" } # => ["a", "new_1", "c", "d"]

If start is negative, counts from the end:

a = ['a', 'b', 'c', 'd']
a.fill(-2, 1) { |index| "new_#{index}" } # => ["a", "b", "new_2", "d"]

If start is large (start >= array.size), extends self with nil:

a = ['a', 'b', 'c', 'd']
a.fill(5, 0) { |index| "new_#{index}" } # => ["a", "b", "c", "d", nil]
a = ['a', 'b', 'c', 'd']
a.fill(5, 2) { |index| "new_#{index}" } # => ["a", "b", "c", "d", nil, "new_5", "new_6"]

If length is zero or less, replaces no elements:

a = ['a', 'b', 'c', 'd']
a.fill(1, 0) { |index| "new_#{index}" } # => ["a", "b", "c", "d"]
a.fill(1, -1) { |index| "new_#{index}" } # => ["a", "b", "c", "d"]

With arguments obj and range, and a block given, calls the block with each index in the given range; replaces the corresponding element with the block’s return value.

If the range is positive and ascending (range 0 < range.begin <= range.end, replaces elements from range.begin to range.end:

a = ['a', 'b', 'c', 'd']
a.fill(1..1) { |index| "new_#{index}" } # => ["a", "new_1", "c", "d"]

If range.first is negative, does nothing:

a = ['a', 'b', 'c', 'd']
a.fill(-1..1) { |index| fail 'Cannot happen' } # => ["a", "b", "c", "d"]

If range.last is negative, counts from the end:

a = ['a', 'b', 'c', 'd']
a.fill(0..-2) { |index| "new_#{index}" } # => ["new_0", "new_1", "new_2", "d"]
a = ['a', 'b', 'c', 'd']
a.fill(1..-2) { |index| "new_#{index}" } # => ["a", "new_1", "new_2", "d"]

If range.first and range.last are both negative, both count from the end:

a = ['a', 'b', 'c', 'd']
a.fill(-1..-1) { |index| "new_#{index}" } # => ["a", "b", "c", "new_3"]
a = ['a', 'b', 'c', 'd']
a.fill(-2..-2) { |index| "new_#{index}" } # => ["a", "b", "new_2", "d"]

filter

array.c View on GitHub

An alias for select

filter!

array.c View on GitHub

An alias for select!

array.index(object) -> integer or nil array.index {|element| ... } -> integer or nil array.index -> new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_index(int argc, VALUE *argv, VALUE ary)
{
    VALUE val;
    long i;

    if (argc == 0) {
        RETURN_ENUMERATOR(ary, 0, 0);
        for (i=0; i<RARRAY_LEN(ary); i++) {
            if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) {
                return LONG2NUM(i);
            }
        }
        return Qnil;
    }
    rb_check_arity(argc, 0, 1);
    val = argv[0];
    if (rb_block_given_p())
        rb_warn("given block not used");
    for (i=0; i<RARRAY_LEN(ary); i++) {
        VALUE e = RARRAY_AREF(ary, i);
        if (rb_equal(e, val)) {
            return LONG2NUM(i);
        }
    }
    return Qnil;
}

Returns the index of a specified element.

When argument object is given but no block, returns the index of the first element element for which object == element:

a = [:foo, 'bar', 2, 'bar']
a.index('bar') # => 1

Returns nil if no such element found.

When both argument object and a block are given, calls the block with each successive element; returns the index of the first element for which the block returns a truthy value:

a = [:foo, 'bar', 2, 'bar']
a.index {|element| element == 'bar' } # => 1

Returns nil if the block never returns a truthy value.

When neither an argument nor a block is given, returns a new Enumerator:

a = [:foo, 'bar', 2]
e = a.index
e # => #<Enumerator: [:foo, "bar", 2]:index>
e.each {|element| element == 'bar' } # => 1

Related: rindex.

array.first → object or nil

array.first(n) → new_array

array.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/array.rb, line 101
def first n = unspecified = true
  if Primitive.mandatory_only?
    Primitive.attr! :leaf
    Primitive.cexpr! %q{ ary_first(self) }
  else
    if unspecified
      Primitive.cexpr! %q{ ary_first(self) }
    else
      Primitive.cexpr! %q{  ary_take_first_or_last_n(self, NUM2LONG(n), ARY_TAKE_FIRST) }
    end
  end
end

Returns elements from self; does not modify self.

When no argument is given, returns the first element:

a = [:foo, 'bar', 2]
a.first # => :foo
a # => [:foo, "bar", 2]

If self is empty, returns nil.

When non-negative Integer argument n is given, returns the first n elements in a new Array:

a = [:foo, 'bar', 2]
a.first(2) # => [:foo, "bar"]

If n >= array.size, returns all elements:

a = [:foo, 'bar', 2]
a.first(50) # => [:foo, "bar", 2]

If n == 0 returns an new empty Array:

a = [:foo, 'bar', 2]
a.first(0) # []

Related: last.

array.flatten → new_array

array.flatten(level) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_flatten(int argc, VALUE *argv, VALUE ary)
{
    int level = -1;
    VALUE result;

    if (rb_check_arity(argc, 0, 1) && !NIL_P(argv[0])) {
        level = NUM2INT(argv[0]);
        if (level == 0) return ary_make_shared_copy(ary);
    }

    result = flatten(ary, level);
    if (result == ary) {
        result = ary_make_shared_copy(ary);
    }

    return result;
}

Returns a new Array that is a recursive flattening of self:

Each non-Array element is unchanged.
Each Array is replaced by its individual elements.

With non-negative Integer argument level, flattens recursively through level levels:

a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten(0) # => [0, [1, [2, 3], 4], 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten(1) # => [0, 1, [2, 3], 4, 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten(2) # => [0, 1, 2, 3, 4, 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten(3) # => [0, 1, 2, 3, 4, 5]

With no argument, a nil argument, or with negative argument level, flattens all levels:

a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten # => [0, 1, 2, 3, 4, 5]
[0, 1, 2].flatten # => [0, 1, 2]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten(-1) # => [0, 1, 2, 3, 4, 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten(-2) # => [0, 1, 2, 3, 4, 5]
[0, 1, 2].flatten(-1) # => [0, 1, 2]

array.flatten! → self or nil

array.flatten!(level) → self or nil

array.c View on GitHub

          
            static VALUE
rb_ary_flatten_bang(int argc, VALUE *argv, VALUE ary)
{
    int mod = 0, level = -1;
    VALUE result, lv;

    lv = (rb_check_arity(argc, 0, 1) ? argv[0] : Qnil);
    rb_ary_modify_check(ary);
    if (!NIL_P(lv)) level = NUM2INT(lv);
    if (level == 0) return Qnil;

    result = flatten(ary, level);
    if (result == ary) {
        return Qnil;
    }
    if (!(mod = ARY_EMBED_P(result))) rb_obj_freeze(result);
    rb_ary_replace(ary, result);
    if (mod) ARY_SET_EMBED_LEN(result, 0);

    return ary;
}

Replaces each nested Array in self with the elements from that Array; returns self if any changes, nil otherwise.

With non-negative Integer argument level, flattens recursively through level levels:

a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten!(1) # => [0, 1, [2, 3], 4, 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten!(2) # => [0, 1, 2, 3, 4, 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten!(3) # => [0, 1, 2, 3, 4, 5]
[0, 1, 2].flatten!(1) # => nil

With no argument, a nil argument, or with negative argument level, flattens all levels:

a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten! # => [0, 1, 2, 3, 4, 5]
[0, 1, 2].flatten! # => nil
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten!(-1) # => [0, 1, 2, 3, 4, 5]
a = [ 0, [ 1, [2, 3], 4 ], 5 ]
a.flatten!(-2) # => [0, 1, 2, 3, 4, 5]
[0, 1, 2].flatten!(-1) # => nil

array.hash → integer

array.c View on GitHub

          
            static VALUE
rb_ary_hash(VALUE ary)
{
    return rb_ary_hash_values(RARRAY_LEN(ary), RARRAY_CONST_PTR(ary));
}

Returns the integer hash value for self.

Two arrays with the same content will have the same hash code (and will compare using eql?):

[0, 1, 2].hash == [0, 1, 2].hash # => true
[0, 1, 2].hash == [0, 1, 3].hash # => false

array.include?(obj) → true or false

array.c View on GitHub

          
            VALUE
rb_ary_includes(VALUE ary, VALUE item)
{
    long i;
    VALUE e;

    for (i=0; i<RARRAY_LEN(ary); i++) {
        e = RARRAY_AREF(ary, i);
        if (rb_equal(e, item)) {
            return Qtrue;
        }
    }
    return Qfalse;
}

Returns true if for some index i in self, obj == self[i]; otherwise false:

[0, 1, 2].include?(2) # => true
[0, 1, 2].include?(3) # => false

array.index(object) → integer or nil

array.index {|element| ... } → integer or nil

array.index → new_enumerator

array.c View on GitHub

An alias for find_index

array.replace(other_array) -> self

array.c View on GitHub

          
            VALUE
rb_ary_replace(VALUE copy, VALUE orig)
{
    rb_ary_modify_check(copy);
    orig = to_ary(orig);
    if (copy == orig) return copy;

    rb_ary_reset(copy);

    /* orig has enough space to embed the contents of orig. */
    if (RARRAY_LEN(orig) <= ary_embed_capa(copy)) {
        assert(ARY_EMBED_P(copy));
        ary_memcpy(copy, 0, RARRAY_LEN(orig), RARRAY_CONST_PTR(orig));
        ARY_SET_EMBED_LEN(copy, RARRAY_LEN(orig));
    }
    /* orig is embedded but copy does not have enough space to embed the
     * contents of orig. */
    else if (ARY_EMBED_P(orig)) {
        long len = ARY_EMBED_LEN(orig);
        VALUE *ptr = ary_heap_alloc(len);

        FL_UNSET_EMBED(copy);
        ARY_SET_PTR(copy, ptr);
        ARY_SET_LEN(copy, len);
        ARY_SET_CAPA(copy, len);

        // No allocation and exception expected that could leave `copy` in a
        // bad state from the edits above.
        ary_memcpy(copy, 0, len, RARRAY_CONST_PTR(orig));
    }
    /* Otherwise, orig is on heap and copy does not have enough space to embed
     * the contents of orig. */
    else {
        VALUE shared_root = ary_make_shared(orig);
        FL_UNSET_EMBED(copy);
        ARY_SET_PTR(copy, ARY_HEAP_PTR(orig));
        ARY_SET_LEN(copy, ARY_HEAP_LEN(orig));
        rb_ary_set_shared(copy, shared_root);
    }
    ary_verify(copy);
    return copy;
}

Replaces the content of self with the content of other_array; returns self:

a = [:foo, 'bar', 2]
a.replace(['foo', :bar, 3]) # => ["foo", :bar, 3]

array.insert(index, *objects) → self

array.c View on GitHub

          
            static VALUE
rb_ary_insert(int argc, VALUE *argv, VALUE ary)
{
    long pos;

    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    rb_ary_modify_check(ary);
    pos = NUM2LONG(argv[0]);
    if (argc == 1) return ary;
    if (pos == -1) {
        pos = RARRAY_LEN(ary);
    }
    else if (pos < 0) {
        long minpos = -RARRAY_LEN(ary) - 1;
        if (pos < minpos) {
            rb_raise(rb_eIndexError, "index %ld too small for array; minimum: %ld",
                     pos, minpos);
        }
        pos++;
    }
    rb_ary_splice(ary, pos, 0, argv + 1, argc - 1);
    return ary;
}

Inserts given objects before or after the element at Integer index offset; returns self.

When index is non-negative, inserts all given objects before the element at offset index:

a = [:foo, 'bar', 2]
a.insert(1, :bat, :bam) # => [:foo, :bat, :bam, "bar", 2]

Extends the array if index is beyond the array (index >= self.size):

a = [:foo, 'bar', 2]
a.insert(5, :bat, :bam)
a # => [:foo, "bar", 2, nil, nil, :bat, :bam]

Does nothing if no objects given:

a = [:foo, 'bar', 2]
a.insert(1)
a.insert(50)
a.insert(-50)
a # => [:foo, "bar", 2]

When index is negative, inserts all given objects after the element at offset index+self.size:

a = [:foo, 'bar', 2]
a.insert(-2, :bat, :bam)
a # => [:foo, "bar", :bat, :bam, 2]

array.inspect → new_string

array.c View on GitHub

          
            static VALUE
rb_ary_inspect(VALUE ary)
{
    if (RARRAY_LEN(ary) == 0) return rb_usascii_str_new2("[]");
    return rb_exec_recursive(inspect_ary, ary, 0);
}

Returns the new String formed by calling method #inspect on each array element:

a = [:foo, 'bar', 2]
a.inspect # => "[:foo, \"bar\", 2]"

ary.intersect?(other_ary) → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_intersect_p(VALUE ary1, VALUE ary2)
{
    VALUE hash, v, result, shorter, longer;
    st_data_t vv;
    long i;

    ary2 = to_ary(ary2);
    if (RARRAY_LEN(ary1) == 0 || RARRAY_LEN(ary2) == 0) return Qfalse;

    if (RARRAY_LEN(ary1) <= SMALL_ARRAY_LEN && RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
        for (i=0; i<RARRAY_LEN(ary1); i++) {
            v = RARRAY_AREF(ary1, i);
            if (rb_ary_includes_by_eql(ary2, v)) return Qtrue;
        }
        return Qfalse;
    }

    shorter = ary1;
    longer = ary2;
    if (RARRAY_LEN(ary1) > RARRAY_LEN(ary2)) {
        longer = ary1;
        shorter = ary2;
    }

    hash = ary_make_hash(shorter);
    result = Qfalse;

    for (i=0; i<RARRAY_LEN(longer); i++) {
        v = RARRAY_AREF(longer, i);
        vv = (st_data_t)v;
        if (rb_hash_stlike_lookup(hash, vv, 0)) {
            result = Qtrue;
            break;
        }
    }

    return result;
}

Returns true if the array and other_ary have at least one element in common, otherwise returns false:

a = [ 1, 2, 3 ]
b = [ 3, 4, 5 ]
c = [ 5, 6, 7 ]
a.intersect?(b)   #=> true
a.intersect?(c)   #=> false

Array elements are compared using eql? (items must also implement hash correctly).

array.intersection(*other_arrays) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_intersection_multi(int argc, VALUE *argv, VALUE ary)
{
    VALUE result = rb_ary_dup(ary);
    int i;

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

    return result;
}

Returns a new Array containing each element found both in self and in all of the given Arrays other_arrays; duplicates are omitted; items are compared using eql? (items must also implement hash correctly):

[0, 1, 2, 3].intersection([0, 1, 2], [0, 1, 3]) # => [0, 1]
[0, 0, 1, 1, 2, 3].intersection([0, 1, 2], [0, 1, 3]) # => [0, 1]

Preserves order from self:

[0, 1, 2].intersection([2, 1, 0]) # => [0, 1, 2]

Returns a copy of self if no arguments given.

Related: Array#&.

array.join →new_string

array.join(separator = $,) → new_string

array.c View on GitHub

          
            static VALUE
rb_ary_join_m(int argc, VALUE *argv, VALUE ary)
{
    VALUE sep;

    if (rb_check_arity(argc, 0, 1) == 0 || NIL_P(sep = argv[0])) {
        sep = rb_output_fs;
        if (!NIL_P(sep)) {
            rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "$, is set to non-nil value");
        }
    }

    return rb_ary_join(ary, sep);
}

Returns the new String formed by joining the array elements after conversion. For each element element:

Uses element.to_s if element is not a kind_of?(Array).
Uses recursive element.join(separator) if element is a kind_of?(Array).

With no argument, joins using the output field separator, $,:

a = [:foo, 'bar', 2]
$, # => nil
a.join # => "foobar2"

With string argument separator, joins using that separator:

a = [:foo, 'bar', 2]
a.join("\n") # => "foo\nbar\n2"

Joins recursively for nested Arrays:

a = [:foo, [:bar, [:baz, :bat]]]
a.join # => "foobarbazbat"

array.keep_if {|element| ... } → self

array.keep_if → new_enumeration

array.c View on GitHub

          
            static VALUE
rb_ary_keep_if(VALUE ary)
{
    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rb_ary_select_bang(ary);
    return ary;
}

Retains those elements for which the block returns a truthy value; deletes all other elements; returns self:

a = [:foo, 'bar', 2, :bam]
a.keep_if {|element| element.to_s.start_with?('b') } # => ["bar", :bam]

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2, :bam]
a.keep_if # => #<Enumerator: [:foo, "bar", 2, :bam]:keep_if>

array.last → object or nil

array.last(n) → new_array

array.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/array.rb, line 145
def last n = unspecified = true
  if Primitive.mandatory_only?
    Primitive.attr! :leaf
    Primitive.cexpr! %q{ ary_last(self) }
  else
    if unspecified
      Primitive.cexpr! %q{ ary_last(self) }
    else
      Primitive.cexpr! %q{ ary_take_first_or_last_n(self, NUM2LONG(n), ARY_TAKE_LAST) }
    end
  end
end

Returns elements from self; self is not modified.

When no argument is given, returns the last element:

a = [:foo, 'bar', 2]
a.last # => 2
a # => [:foo, "bar", 2]

If self is empty, returns nil.

When non-negative Integer argument n is given, returns the last n elements in a new Array:

a = [:foo, 'bar', 2]
a.last(2) # => ["bar", 2]

If n >= array.size, returns all elements:

a = [:foo, 'bar', 2]
a.last(50) # => [:foo, "bar", 2]

If n == 0, returns an new empty Array:

a = [:foo, 'bar', 2]
a.last(0) # []

Related: first.

array.length → an_integer

array.c View on GitHub

          
            static VALUE
rb_ary_length(VALUE ary)
{
    long len = RARRAY_LEN(ary);
    return LONG2NUM(len);
}

Returns the count of elements in self.

array.map {|element| ... } → new_array

array.map → new_enumerator

array.c View on GitHub

An alias for collect

array.map! {|element| ... } → self

array.map! → new_enumerator

array.c View on GitHub

An alias for collect!

array.max → element

array.max {|a, b| ... } → element

array.max(n) → new_array

array.max(n) {|a, b| ... } → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_max(int argc, VALUE *argv, VALUE ary)
{
    VALUE result = Qundef, v;
    VALUE num;
    long i;

    if (rb_check_arity(argc, 0, 1) && !NIL_P(num = argv[0]))
       return rb_nmin_run(ary, num, 0, 1, 1);

    const long n = RARRAY_LEN(ary);
    if (rb_block_given_p()) {
        for (i = 0; i < RARRAY_LEN(ary); i++) {
           v = RARRAY_AREF(ary, i);
           if (UNDEF_P(result) || rb_cmpint(rb_yield_values(2, v, result), v, result) > 0) {
               result = v;
           }
        }
    }
    else if (n > 0) {
        result = RARRAY_AREF(ary, 0);
        if (n > 1) {
            if (FIXNUM_P(result) && CMP_OPTIMIZABLE(INTEGER)) {
                return ary_max_opt_fixnum(ary, 1, result);
            }
            else if (STRING_P(result) && CMP_OPTIMIZABLE(STRING)) {
                return ary_max_opt_string(ary, 1, result);
            }
            else if (RB_FLOAT_TYPE_P(result) && CMP_OPTIMIZABLE(FLOAT)) {
                return ary_max_opt_float(ary, 1, result);
            }
            else {
                return ary_max_generic(ary, 1, result);
            }
        }
    }
    if (UNDEF_P(result)) return Qnil;
    return result;
}

Returns one of the following:

The maximum-valued element from self.
A new Array of maximum-valued elements selected from self.

When no block is given, each element in self must respond to method <=> with an Integer.

With no argument and no block, returns the element in self having the maximum value per method <=>:

[0, 1, 2].max # => 2

With an argument Integer n and no block, returns a new Array with at most n elements, in descending order per method <=>:

[0, 1, 2, 3].max(3) # => [3, 2, 1]
[0, 1, 2, 3].max(6) # => [3, 2, 1, 0]

When a block is given, the block must return an Integer.

With a block and no argument, calls the block self.size-1 times to compare elements; returns the element having the maximum value per the block:

['0', '00', '000'].max {|a, b| a.size <=> b.size } # => "000"

With an argument n and a block, returns a new Array with at most n elements, in descending order per the block:

['0', '00', '000'].max(2) {|a, b| a.size <=> b.size } # => ["000", "00"]

array.min → element

array.min { |a, b| ... } → element

array.min(n) → new_array

array.min(n) { |a, b| ... } → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_min(int argc, VALUE *argv, VALUE ary)
{
    VALUE result = Qundef, v;
    VALUE num;
    long i;

    if (rb_check_arity(argc, 0, 1) && !NIL_P(num = argv[0]))
       return rb_nmin_run(ary, num, 0, 0, 1);

    const long n = RARRAY_LEN(ary);
    if (rb_block_given_p()) {
        for (i = 0; i < RARRAY_LEN(ary); i++) {
           v = RARRAY_AREF(ary, i);
           if (UNDEF_P(result) || rb_cmpint(rb_yield_values(2, v, result), v, result) < 0) {
               result = v;
           }
        }
    }
    else if (n > 0) {
        result = RARRAY_AREF(ary, 0);
        if (n > 1) {
            if (FIXNUM_P(result) && CMP_OPTIMIZABLE(INTEGER)) {
                return ary_min_opt_fixnum(ary, 1, result);
            }
            else if (STRING_P(result) && CMP_OPTIMIZABLE(STRING)) {
                return ary_min_opt_string(ary, 1, result);
            }
            else if (RB_FLOAT_TYPE_P(result) && CMP_OPTIMIZABLE(FLOAT)) {
                return ary_min_opt_float(ary, 1, result);
            }
            else {
                return ary_min_generic(ary, 1, result);
            }
        }
    }
    if (UNDEF_P(result)) return Qnil;
    return result;
}

Returns one of the following:

The minimum-valued element from self.
A new Array of minimum-valued elements selected from self.

When no block is given, each element in self must respond to method <=> with an Integer.

With no argument and no block, returns the element in self having the minimum value per method <=>:

[0, 1, 2].min # => 0

With Integer argument n and no block, returns a new Array with at most n elements, in ascending order per method <=>:

[0, 1, 2, 3].min(3) # => [0, 1, 2]
[0, 1, 2, 3].min(6) # => [0, 1, 2, 3]

When a block is given, the block must return an Integer.

With a block and no argument, calls the block self.size-1 times to compare elements; returns the element having the minimum value per the block:

['0', '00', '000'].min { |a, b| a.size <=> b.size } # => "0"

With an argument n and a block, returns a new Array with at most n elements, in ascending order per the block:

['0', '00', '000'].min(2) {|a, b| a.size <=> b.size } # => ["0", "00"]

array.minmax → [min_val, max_val]

array.minmax {|a, b| ... } → [min_val, max_val]

array.c View on GitHub

          
            static VALUE
rb_ary_minmax(VALUE ary)
{
    if (rb_block_given_p()) {
        return rb_call_super(0, NULL);
    }
    return rb_assoc_new(rb_ary_min(0, 0, ary), rb_ary_max(0, 0, ary));
}

Returns a new 2-element Array containing the minimum and maximum values from self, either per method <=> or per a given block:.

When no block is given, each element in self must respond to method <=> with an Integer; returns a new 2-element Array containing the minimum and maximum values from self, per method <=>:

[0, 1, 2].minmax # => [0, 2]

When a block is given, the block must return an Integer; the block is called self.size-1 times to compare elements; returns a new 2-element Array containing the minimum and maximum values from self, per the block:

['0', '00', '000'].minmax {|a, b| a.size <=> b.size } # => ["0", "000"]

array.none? → true or false

array.none? {|element| ... } → true or false

array.none?(obj) → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_none_p(int argc, VALUE *argv, VALUE ary)
{
    long i, len = RARRAY_LEN(ary);

    rb_check_arity(argc, 0, 1);
    if (!len) return Qtrue;
    if (argc) {
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (RTEST(rb_funcall(argv[0], idEqq, 1, RARRAY_AREF(ary, i)))) return Qfalse;
        }
    }
    else if (!rb_block_given_p()) {
        for (i = 0; i < len; ++i) {
            if (RTEST(RARRAY_AREF(ary, i))) return Qfalse;
        }
    }
    else {
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) return Qfalse;
        }
    }
    return Qtrue;
}

Returns true if no element of self meet a given criterion.

With no block given and no argument, returns true if self has no truthy elements, false otherwise:

[nil, false].none? # => true
[nil, 0, false].none? # => false
[].none? # => true

With a block given and no argument, calls the block with each element in self; returns true if the block returns no truthy value, false otherwise:

[0, 1, 2].none? {|element| element > 3 } # => true
[0, 1, 2].none? {|element| element > 1 } # => false

If argument obj is given, returns true if obj.=== no element, false otherwise:

['food', 'drink'].none?(/bar/) # => true
['food', 'drink'].none?(/foo/) # => false
[].none?(/foo/) # => true
[0, 1, 2].none?(3) # => true
[0, 1, 2].none?(1) # => false

Related: Enumerable#none?

array.one? → true or false

array.one? {|element| ... } → true or false

array.one?(obj) → true or false

array.c View on GitHub

          
            static VALUE
rb_ary_one_p(int argc, VALUE *argv, VALUE ary)
{
    long i, len = RARRAY_LEN(ary);
    VALUE result = Qfalse;

    rb_check_arity(argc, 0, 1);
    if (!len) return Qfalse;
    if (argc) {
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (RTEST(rb_funcall(argv[0], idEqq, 1, RARRAY_AREF(ary, i)))) {
                if (result) return Qfalse;
                result = Qtrue;
            }
        }
    }
    else if (!rb_block_given_p()) {
        for (i = 0; i < len; ++i) {
            if (RTEST(RARRAY_AREF(ary, i))) {
                if (result) return Qfalse;
                result = Qtrue;
            }
        }
    }
    else {
        for (i = 0; i < RARRAY_LEN(ary); ++i) {
            if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) {
                if (result) return Qfalse;
                result = Qtrue;
            }
        }
    }
    return result;
}

Returns true if exactly one element of self meets a given criterion.

With no block given and no argument, returns true if self has exactly one truthy element, false otherwise:

[nil, 0].one? # => true
[0, 0].one? # => false
[nil, nil].one? # => false
[].one? # => false

With a block given and no argument, calls the block with each element in self; returns true if the block a truthy value for exactly one element, false otherwise:

[0, 1, 2].one? {|element| element > 0 } # => false
[0, 1, 2].one? {|element| element > 1 } # => true
[0, 1, 2].one? {|element| element > 2 } # => false

If argument obj is given, returns true if obj.=== exactly one element, false otherwise:

[0, 1, 2].one?(0) # => true
[0, 0, 1].one?(0) # => false
[1, 1, 2].one?(0) # => false
['food', 'drink'].one?(/bar/) # => false
['food', 'drink'].one?(/foo/) # => true
[].one?(/foo/) # => false

Related: Enumerable#one?

pack(template, buffer: nil) → string

pack.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/pack.rb, line 7
def pack(fmt, buffer: nil)
  Primitive.pack_pack(fmt, buffer)
end

Formats each element in self into a binary string; returns that string. See Packed Data.

array.permutation {|element| ... } → self

array.permutation(n) {|element| ... } → self

array.permutation → new_enumerator

array.permutation(n) → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_permutation(int argc, VALUE *argv, VALUE ary)
{
    long r, n, i;

    n = RARRAY_LEN(ary);                  /* Array length */
    RETURN_SIZED_ENUMERATOR(ary, argc, argv, rb_ary_permutation_size);   /* Return enumerator if no block */
    r = n;
    if (rb_check_arity(argc, 0, 1) && !NIL_P(argv[0]))
        r = NUM2LONG(argv[0]);            /* Permutation size from argument */

    if (r < 0 || n < r) {
        /* no permutations: yield nothing */
    }
    else if (r == 0) { /* exactly one permutation: the zero-length array */
        rb_yield(rb_ary_new2(0));
    }
    else if (r == 1) { /* this is a special, easy case */
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
        }
    }
    else {             /* this is the general case */
        volatile VALUE t0;
        long *p = ALLOCV_N(long, t0, r+roomof(n, sizeof(long)));
        char *used = (char*)(p + r);
        VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
        RBASIC_CLEAR_CLASS(ary0);

        MEMZERO(used, char, n); /* initialize array */

        permute0(n, r, p, used, ary0); /* compute and yield permutations */
        ALLOCV_END(t0);
        RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
    }
    return ary;
}

When invoked with a block, yield all permutations of elements of self; returns self. The order of permutations is indeterminate.

When a block and an in-range positive Integer argument n (0 < n <= self.size) are given, calls the block with all n-tuple permutations of self.

Example:

a = [0, 1, 2]
a.permutation(2) {|permutation| p permutation }

Output:

[0, 1]
[0, 2]
[1, 0]
[1, 2]
[2, 0]
[2, 1]

Another example:

a = [0, 1, 2]
a.permutation(3) {|permutation| p permutation }

Output:

[0, 1, 2]
[0, 2, 1]
[1, 0, 2]
[1, 2, 0]
[2, 0, 1]
[2, 1, 0]

When n is zero, calls the block once with a new empty Array:

a = [0, 1, 2]
a.permutation(0) {|permutation| p permutation }

Output:

[]

When n is out of range (negative or larger than self.size), does not call the block:

a = [0, 1, 2]
a.permutation(-1) {|permutation| fail 'Cannot happen' }
a.permutation(4) {|permutation| fail 'Cannot happen' }

When a block given but no argument, behaves the same as a.permutation(a.size):

a = [0, 1, 2]
a.permutation {|permutation| p permutation }

Output:

[0, 1, 2]
[0, 2, 1]
[1, 0, 2]
[1, 2, 0]
[2, 0, 1]
[2, 1, 0]

Returns a new Enumerator if no block given:

a = [0, 1, 2]
a.permutation # => #<Enumerator: [0, 1, 2]:permutation>
a.permutation(2) # => #<Enumerator: [0, 1, 2]:permutation(2)>

array.pop → object or nil

array.pop(n) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_pop_m(int argc, VALUE *argv, VALUE ary)
{
    VALUE result;

    if (argc == 0) {
        return rb_ary_pop(ary);
    }

    rb_ary_modify_check(ary);
    result = ary_take_first_or_last(argc, argv, ary, ARY_TAKE_LAST);
    ARY_INCREASE_LEN(ary, -RARRAY_LEN(result));
    ary_verify(ary);
    return result;
}

Removes and returns trailing elements.

When no argument is given and self is not empty, removes and returns the last element:

a = [:foo, 'bar', 2]
a.pop # => 2
a # => [:foo, "bar"]

Returns nil if the array is empty.

When a non-negative Integer argument n is given and is in range,

removes and returns the last n elements in a new Array:

a = [:foo, 'bar', 2]
a.pop(2) # => ["bar", 2]

If n is positive and out of range, removes and returns all elements:

a = [:foo, 'bar', 2]
a.pop(50) # => [:foo, "bar", 2]

Related: push, shift, unshift.

prepend(*args)

array.c View on GitHub

An alias for unshift

array.product(*other_arrays) → new_array

array.product(*other_arrays) {|combination| ... } → self

array.c View on GitHub

          
            static VALUE
rb_ary_product(int argc, VALUE *argv, VALUE ary)
{
    int n = argc+1;    /* How many arrays we're operating on */
    volatile VALUE t0 = rb_ary_hidden_new(n);
    volatile VALUE t1 = Qundef;
    VALUE *arrays = RARRAY_PTR(t0); /* The arrays we're computing the product of */
    int *counters = ALLOCV_N(int, t1, n); /* The current position in each one */
    VALUE result = Qnil;      /* The array we'll be returning, when no block given */
    long i,j;
    long resultlen = 1;

    RBASIC_CLEAR_CLASS(t0);

    /* initialize the arrays of arrays */
    ARY_SET_LEN(t0, n);
    arrays[0] = ary;
    for (i = 1; i < n; i++) arrays[i] = Qnil;
    for (i = 1; i < n; i++) arrays[i] = to_ary(argv[i-1]);

    /* initialize the counters for the arrays */
    for (i = 0; i < n; i++) counters[i] = 0;

    /* Otherwise, allocate and fill in an array of results */
    if (rb_block_given_p()) {
        /* Make defensive copies of arrays; exit if any is empty */
        for (i = 0; i < n; i++) {
            if (RARRAY_LEN(arrays[i]) == 0) goto done;
            arrays[i] = ary_make_shared_copy(arrays[i]);
        }
    }
    else {
        /* Compute the length of the result array; return [] if any is empty */
        for (i = 0; i < n; i++) {
            long k = RARRAY_LEN(arrays[i]);
            if (k == 0) {
                result = rb_ary_new2(0);
                goto done;
            }
            if (MUL_OVERFLOW_LONG_P(resultlen, k))
                rb_raise(rb_eRangeError, "too big to product");
            resultlen *= k;
        }
        result = rb_ary_new2(resultlen);
    }
    for (;;) {
        int m;
        /* fill in one subarray */
        VALUE subarray = rb_ary_new2(n);
        for (j = 0; j < n; j++) {
            rb_ary_push(subarray, rb_ary_entry(arrays[j], counters[j]));
        }

        /* put it on the result array */
        if (NIL_P(result)) {
            FL_SET(t0, RARRAY_SHARED_ROOT_FLAG);
            rb_yield(subarray);
            if (!FL_TEST(t0, RARRAY_SHARED_ROOT_FLAG)) {
                rb_raise(rb_eRuntimeError, "product reentered");
            }
            else {
                FL_UNSET(t0, RARRAY_SHARED_ROOT_FLAG);
            }
        }
        else {
            rb_ary_push(result, subarray);
        }

        /*
         * Increment the last counter.  If it overflows, reset to 0
         * and increment the one before it.
         */
        m = n-1;
        counters[m]++;
        while (counters[m] == RARRAY_LEN(arrays[m])) {
            counters[m] = 0;
            /* If the first counter overflows, we are done */
            if (--m < 0) goto done;
            counters[m]++;
        }
    }

done:
    ALLOCV_END(t1);

    return NIL_P(result) ? ary : result;
}

Computes and returns or yields all combinations of elements from all the Arrays, including both self and other_arrays:

The number of combinations is the product of the sizes of all the arrays, including both self and other_arrays.
The order of the returned combinations is indeterminate.

When no block is given, returns the combinations as an Array of Arrays:

a = [0, 1, 2]
a1 = [3, 4]
a2 = [5, 6]
p = a.product(a1)
p.size # => 6 # a.size * a1.size
p # => [[0, 3], [0, 4], [1, 3], [1, 4], [2, 3], [2, 4]]
p = a.product(a1, a2)
p.size # => 12 # a.size * a1.size * a2.size
p # => [[0, 3, 5], [0, 3, 6], [0, 4, 5], [0, 4, 6], [1, 3, 5], [1, 3, 6], [1, 4, 5], [1, 4, 6], [2, 3, 5], [2, 3, 6], [2, 4, 5], [2, 4, 6]]

If any argument is an empty Array, returns an empty Array.

If no argument is given, returns an Array of 1-element Arrays, each containing an element of self:

a.product # => [[0], [1], [2]]

When a block is given, yields each combination as an Array; returns self:

a.product(a1) {|combination| p combination }

Output:

[0, 3]
[0, 4]
[1, 3]
[1, 4]
[2, 3]
[2, 4]

If any argument is an empty Array, does not call the block:

a.product(a1, a2, []) {|combination| fail 'Cannot happen' }

If no argument is given, yields each element of self as a 1-element Array:

a.product {|combination| p combination }

Output:

[0]
[1]
[2]

array.push(*objects) → self

array.c View on GitHub

          
            static VALUE
rb_ary_push_m(int argc, VALUE *argv, VALUE ary)
{
    return rb_ary_cat(ary, argv, argc);
}

Appends trailing elements.

Appends each argument in objects to self; returns self:

a = [:foo, 'bar', 2]
a.push(:baz, :bat) # => [:foo, "bar", 2, :baz, :bat]

Appends each argument as one element, even if it is another Array:

a = [:foo, 'bar', 2]
a1 = a.push([:baz, :bat], [:bam, :bad])
a1 # => [:foo, "bar", 2, [:baz, :bat], [:bam, :bad]]

Related: pop, shift, unshift.

array.rassoc(obj) → found_array or nil

array.c View on GitHub

          
            VALUE
rb_ary_rassoc(VALUE ary, VALUE value)
{
    long i;
    VALUE v;

    for (i = 0; i < RARRAY_LEN(ary); ++i) {
        v = rb_check_array_type(RARRAY_AREF(ary, i));
        if (RB_TYPE_P(v, T_ARRAY) &&
            RARRAY_LEN(v) > 1 &&
            rb_equal(RARRAY_AREF(v, 1), value))
            return v;
    }
    return Qnil;
}

Returns the first element in self that is an Array whose second element == obj:

a = [{foo: 0}, [2, 4], [4, 5, 6], [4, 5]]
a.rassoc(4) # => [2, 4]

Returns nil if no such element is found.

Related: assoc.

array.reject {|element| ... } → new_array

array.reject → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_reject(VALUE ary)
{
    VALUE rejected_ary;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rejected_ary = rb_ary_new();
    ary_reject(ary, rejected_ary);
    return rejected_ary;
}

Returns a new Array whose elements are all those from self for which the block returns false or nil:

a = [:foo, 'bar', 2, 'bat']
a1 = a.reject {|element| element.to_s.start_with?('b') }
a1 # => [:foo, 2]

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2]
a.reject # => #<Enumerator: [:foo, "bar", 2]:reject>

array.reject! {|element| ... } → self or nil

array.reject! → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_reject_bang(VALUE ary)
{
    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rb_ary_modify(ary);
    return ary_reject_bang(ary);
}

Removes each element for which the block returns a truthy value.

Returns self if any elements removed:

a = [:foo, 'bar', 2, 'bat']
a.reject! {|element| element.to_s.start_with?('b') } # => [:foo, 2]

Returns nil if no elements removed.

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2]
a.reject! # => #<Enumerator: [:foo, "bar", 2]:reject!>

array.repeated_combination(n) {|combination| ... } → self

array.repeated_combination(n) → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_repeated_combination(VALUE ary, VALUE num)
{
    long n, i, len;

    n = NUM2LONG(num);                 /* Combination size from argument */
    RETURN_SIZED_ENUMERATOR(ary, 1, &num, rb_ary_repeated_combination_size);   /* Return enumerator if no block */
    len = RARRAY_LEN(ary);
    if (n < 0) {
        /* yield nothing */
    }
    else if (n == 0) {
        rb_yield(rb_ary_new2(0));
    }
    else if (n == 1) {
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
        }
    }
    else if (len == 0) {
        /* yield nothing */
    }
    else {
        volatile VALUE t0;
        long *p = ALLOCV_N(long, t0, n);
        VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
        RBASIC_CLEAR_CLASS(ary0);

        rcombinate0(len, n, p, n, ary0); /* compute and yield repeated combinations */
        ALLOCV_END(t0);
        RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
    }
    return ary;
}

Calls the block with each repeated combination of length n of the elements of self; each combination is an Array; returns self. The order of the combinations is indeterminate.

When a block and a positive Integer argument n are given, calls the block with each n-tuple repeated combination of the elements of self. The number of combinations is (n+1)(n+2)/2.

n = 1:

a = [0, 1, 2]
a.repeated_combination(1) {|combination| p combination }

Output:

[0]
[1]
[2]

n = 2:

a.repeated_combination(2) {|combination| p combination }

Output:

[0, 0]
[0, 1]
[0, 2]
[1, 1]
[1, 2]
[2, 2]

If n is zero, calls the block once with an empty Array.

If n is negative, does not call the block:

a.repeated_combination(-1) {|combination| fail 'Cannot happen' }

Returns a new Enumerator if no block given:

a = [0, 1, 2]
a.repeated_combination(2) # => #<Enumerator: [0, 1, 2]:combination(2)>

Using Enumerators, it’s convenient to show the combinations and counts for some values of n:

e = a.repeated_combination(0)
e.size # => 1
e.to_a # => [[]]
e = a.repeated_combination(1)
e.size # => 3
e.to_a # => [[0], [1], [2]]
e = a.repeated_combination(2)
e.size # => 6
e.to_a # => [[0, 0], [0, 1], [0, 2], [1, 1], [1, 2], [2, 2]]

array.repeated_permutation(n) {|permutation| ... } → self

array.repeated_permutation(n) → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_repeated_permutation(VALUE ary, VALUE num)
{
    long r, n, i;

    n = RARRAY_LEN(ary);                  /* Array length */
    RETURN_SIZED_ENUMERATOR(ary, 1, &num, rb_ary_repeated_permutation_size);      /* Return Enumerator if no block */
    r = NUM2LONG(num);                    /* Permutation size from argument */

    if (r < 0) {
        /* no permutations: yield nothing */
    }
    else if (r == 0) { /* exactly one permutation: the zero-length array */
        rb_yield(rb_ary_new2(0));
    }
    else if (r == 1) { /* this is a special, easy case */
        for (i = 0; i < RARRAY_LEN(ary); i++) {
            rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
        }
    }
    else {             /* this is the general case */
        volatile VALUE t0;
        long *p = ALLOCV_N(long, t0, r);
        VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
        RBASIC_CLEAR_CLASS(ary0);

        rpermute0(n, r, p, ary0); /* compute and yield repeated permutations */
        ALLOCV_END(t0);
        RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
    }
    return ary;
}

Calls the block with each repeated permutation of length n of the elements of self; each permutation is an Array; returns self. The order of the permutations is indeterminate.

When a block and a positive Integer argument n are given, calls the block with each n-tuple repeated permutation of the elements of self. The number of permutations is self.size**n.

n = 1:

a = [0, 1, 2]
a.repeated_permutation(1) {|permutation| p permutation }

Output:

[0]
[1]
[2]

n = 2:

a.repeated_permutation(2) {|permutation| p permutation }

Output:

[0, 0]
[0, 1]
[0, 2]
[1, 0]
[1, 1]
[1, 2]
[2, 0]
[2, 1]
[2, 2]

If n is zero, calls the block once with an empty Array.

If n is negative, does not call the block:

a.repeated_permutation(-1) {|permutation| fail 'Cannot happen' }

Returns a new Enumerator if no block given:

a = [0, 1, 2]
a.repeated_permutation(2) # => #<Enumerator: [0, 1, 2]:permutation(2)>

Using Enumerators, it’s convenient to show the permutations and counts for some values of n:

e = a.repeated_permutation(0)
e.size # => 1
e.to_a # => [[]]
e = a.repeated_permutation(1)
e.size # => 3
e.to_a # => [[0], [1], [2]]
e = a.repeated_permutation(2)
e.size # => 9
e.to_a # => [[0, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 0], [2, 1], [2, 2]]

array.replace(other_array) → self

array.c View on GitHub

An alias for initialize_copy

array.reverse → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_reverse_m(VALUE ary)
{
    long len = RARRAY_LEN(ary);
    VALUE dup = rb_ary_new2(len);

    if (len > 0) {
        const VALUE *p1 = RARRAY_CONST_PTR(ary);
        VALUE *p2 = (VALUE *)RARRAY_CONST_PTR(dup) + len - 1;
        do *p2-- = *p1++; while (--len > 0);
    }
    ARY_SET_LEN(dup, RARRAY_LEN(ary));
    return dup;
}

Returns a new Array with the elements of self in reverse order:

a = ['foo', 'bar', 'two']
a1 = a.reverse
a1 # => ["two", "bar", "foo"]

array.reverse! → self

array.c View on GitHub

          
            static VALUE
rb_ary_reverse_bang(VALUE ary)
{
    return rb_ary_reverse(ary);
}

Reverses self in place:

a = ['foo', 'bar', 'two']
a.reverse! # => ["two", "bar", "foo"]

array.reverse_each {|element| ... } → self

array.reverse_each → Enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_reverse_each(VALUE ary)
{
    long len;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    len = RARRAY_LEN(ary);
    while (len--) {
        long nlen;
        rb_yield(RARRAY_AREF(ary, len));
        nlen = RARRAY_LEN(ary);
        if (nlen < len) {
            len = nlen;
        }
    }
    return ary;
}

Iterates backwards over array elements.

When a block given, passes, in reverse order, each element to the block; returns self:

a = [:foo, 'bar', 2]
a.reverse_each {|element|  puts "#{element.class} #{element}" }

Output:

Integer 2
String bar
Symbol foo

Allows the array to be modified during iteration:

a = [:foo, 'bar', 2]
a.reverse_each {|element| puts element; a.clear if element.to_s.start_with?('b') }

Output:

2
bar

When no block given, returns a new Enumerator:

a = [:foo, 'bar', 2]
e = a.reverse_each
e # => #<Enumerator: [:foo, "bar", 2]:reverse_each>
a1 = e.each {|element|  puts "#{element.class} #{element}" }

Output:

Integer 2
String bar
Symbol foo

Related: each, each_index.

array.rindex(object) → integer or nil

array.rindex {|element| ... } → integer or nil

array.rindex → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_rindex(int argc, VALUE *argv, VALUE ary)
{
    VALUE val;
    long i = RARRAY_LEN(ary), len;

    if (argc == 0) {
        RETURN_ENUMERATOR(ary, 0, 0);
        while (i--) {
            if (RTEST(rb_yield(RARRAY_AREF(ary, i))))
                return LONG2NUM(i);
            if (i > (len = RARRAY_LEN(ary))) {
                i = len;
            }
        }
        return Qnil;
    }
    rb_check_arity(argc, 0, 1);
    val = argv[0];
    if (rb_block_given_p())
        rb_warn("given block not used");
    while (i--) {
        VALUE e = RARRAY_AREF(ary, i);
        if (rb_equal(e, val)) {
            return LONG2NUM(i);
        }
        if (i > RARRAY_LEN(ary)) {
            break;
        }
    }
    return Qnil;
}

Returns the index of the last element for which object == element.

When argument object is given but no block, returns the index of the last such element found:

a = [:foo, 'bar', 2, 'bar']
a.rindex('bar') # => 3

Returns nil if no such object found.

When a block is given but no argument, calls the block with each successive element; returns the index of the last element for which the block returns a truthy value:

a = [:foo, 'bar', 2, 'bar']
a.rindex {|element| element == 'bar' } # => 3

Returns nil if the block never returns a truthy value.

When neither an argument nor a block is given, returns a new Enumerator:

a = [:foo, 'bar', 2, 'bar']
e = a.rindex
e # => #<Enumerator: [:foo, "bar", 2, "bar"]:rindex>
e.each {|element| element == 'bar' } # => 3

Related: index.

array.rotate → new_array

array.rotate(count) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_rotate_m(int argc, VALUE *argv, VALUE ary)
{
    VALUE rotated;
    const VALUE *ptr;
    long len;
    long cnt = (rb_check_arity(argc, 0, 1) ? NUM2LONG(argv[0]) : 1);

    len = RARRAY_LEN(ary);
    rotated = rb_ary_new2(len);
    if (len > 0) {
        cnt = rotate_count(cnt, len);
        ptr = RARRAY_CONST_PTR(ary);
        len -= cnt;
        ary_memcpy(rotated, 0, len, ptr + cnt);
        ary_memcpy(rotated, len, cnt, ptr);
    }
    ARY_SET_LEN(rotated, RARRAY_LEN(ary));
    return rotated;
}

Returns a new Array formed from self with elements rotated from one end to the other.

When no argument given, returns a new Array that is like self, except that the first element has been rotated to the last position:

a = [:foo, 'bar', 2, 'bar']
a1 = a.rotate
a1 # => ["bar", 2, "bar", :foo]

When given a non-negative Integer count, returns a new Array with count elements rotated from the beginning to the end:

a = [:foo, 'bar', 2]
a1 = a.rotate(2)
a1 # => [2, :foo, "bar"]

If count is large, uses count % array.size as the count:

a = [:foo, 'bar', 2]
a1 = a.rotate(20)
a1 # => [2, :foo, "bar"]

If count is zero, returns a copy of self, unmodified:

a = [:foo, 'bar', 2]
a1 = a.rotate(0)
a1 # => [:foo, "bar", 2]

When given a negative Integer count, rotates in the opposite direction, from end to beginning:

a = [:foo, 'bar', 2]
a1 = a.rotate(-2)
a1 # => ["bar", 2, :foo]

If count is small (far from zero), uses count % array.size as the count:

a = [:foo, 'bar', 2]
a1 = a.rotate(-5)
a1 # => ["bar", 2, :foo]

array.rotate! → self

array.rotate!(count) → self

array.c View on GitHub

          
            static VALUE
rb_ary_rotate_bang(int argc, VALUE *argv, VALUE ary)
{
    long n = (rb_check_arity(argc, 0, 1) ? NUM2LONG(argv[0]) : 1);
    rb_ary_rotate(ary, n);
    return ary;
}

Rotates self in place by moving elements from one end to the other; returns self.

When no argument given, rotates the first element to the last position:

a = [:foo, 'bar', 2, 'bar']
a.rotate! # => ["bar", 2, "bar", :foo]

When given a non-negative Integer count, rotates count elements from the beginning to the end:

a = [:foo, 'bar', 2]
a.rotate!(2)
a # => [2, :foo, "bar"]

If count is large, uses count % array.size as the count:

a = [:foo, 'bar', 2]
a.rotate!(20)
a # => [2, :foo, "bar"]

If count is zero, returns self unmodified:

a = [:foo, 'bar', 2]
a.rotate!(0)
a # => [:foo, "bar", 2]

When given a negative Integer count, rotates in the opposite direction, from end to beginning:

a = [:foo, 'bar', 2]
a.rotate!(-2)
a # => ["bar", 2, :foo]

If count is small (far from zero), uses count % array.size as the count:

a = [:foo, 'bar', 2]
a.rotate!(-5)
a # => ["bar", 2, :foo]

array.sample(random: Random) → object

array.sample(n, random: Random) → new_ary

array.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/array.rb, line 60
def sample(n = (ary = false), random: Random)
  if Primitive.mandatory_only?
    # Primitive.cexpr! %{ rb_ary_sample(self, rb_cRandom, Qfalse, Qfalse) }
    Primitive.ary_sample0
  else
    # Primitive.cexpr! %{ rb_ary_sample(self, random, n, ary) }
    Primitive.ary_sample(random, n, ary)
  end
end

Returns random elements from self.

When no arguments are given, returns a random element from self:

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a.sample # => 3
a.sample # => 8

If self is empty, returns nil.

When argument n is given, returns a new Array containing n random elements from self:

a.sample(3) # => [8, 9, 2]
a.sample(6) # => [9, 6, 10, 3, 1, 4]

Returns no more than a.size elements (because no new duplicates are introduced):

a.sample(a.size * 2) # => [6, 4, 1, 8, 5, 9, 10, 2, 3, 7]

But self may contain duplicates:

a = [1, 1, 1, 2, 2, 3]
a.sample(a.size * 2) # => [1, 1, 3, 2, 1, 2]

The argument n must be a non-negative numeric value. The order of the result array is unrelated to the order of self. Returns a new empty Array if self is empty.

The optional random argument will be used as the random number generator:

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a.sample(random: Random.new(1))     #=> 6
a.sample(4, random: Random.new(1))  #=> [6, 10, 9, 2]

array.select {|element| ... } → new_array

array.select → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_select(VALUE ary)
{
    VALUE result;
    long i;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    result = rb_ary_new2(RARRAY_LEN(ary));
    for (i = 0; i < RARRAY_LEN(ary); i++) {
        if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) {
            rb_ary_push(result, rb_ary_elt(ary, i));
        }
    }
    return result;
}

Calls the block, if given, with each element of self; returns a new Array containing those elements of self for which the block returns a truthy value:

a = [:foo, 'bar', 2, :bam]
a1 = a.select {|element| element.to_s.start_with?('b') }
a1 # => ["bar", :bam]

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2, :bam]
a.select # => #<Enumerator: [:foo, "bar", 2, :bam]:select>

array.select! {|element| ... } → self or nil

array.select! → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_select_bang(VALUE ary)
{
    struct select_bang_arg args;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rb_ary_modify(ary);

    args.ary = ary;
    args.len[0] = args.len[1] = 0;
    return rb_ensure(select_bang_i, (VALUE)&args, select_bang_ensure, (VALUE)&args);
}

Calls the block, if given with each element of self; removes from self those elements for which the block returns false or nil.

Returns self if any elements were removed:

a = [:foo, 'bar', 2, :bam]
a.select! {|element| element.to_s.start_with?('b') } # => ["bar", :bam]

Returns nil if no elements were removed.

Returns a new Enumerator if no block given:

a = [:foo, 'bar', 2, :bam]
a.select! # => #<Enumerator: [:foo, "bar", 2, :bam]:select!>

array.shelljoin => string

lib/shellwords.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/lib/shellwords.rb, line 239
def shelljoin
  Shellwords.join(self)
end

Builds a command line string from an argument list array joining all elements escaped for the Bourne shell and separated by a space.

See Shellwords.shelljoin for details.

array.shift → object or nil

array.shift(n) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_shift_m(int argc, VALUE *argv, VALUE ary)
{
    VALUE result;
    long n;

    if (argc == 0) {
        return rb_ary_shift(ary);
    }

    rb_ary_modify_check(ary);
    result = ary_take_first_or_last(argc, argv, ary, ARY_TAKE_FIRST);
    n = RARRAY_LEN(result);
    rb_ary_behead(ary,n);

    return result;
}

Removes and returns leading elements.

When no argument is given, removes and returns the first element:

a = [:foo, 'bar', 2]
a.shift # => :foo
a # => ['bar', 2]

Returns nil if self is empty.

When positive Integer argument n is given, removes the first n elements; returns those elements in a new Array:

a = [:foo, 'bar', 2]
a.shift(2) # => [:foo, 'bar']
a # => [2]

If n is as large as or larger than self.length, removes all elements; returns those elements in a new Array:

a = [:foo, 'bar', 2]
a.shift(3) # => [:foo, 'bar', 2]

If n is zero, returns a new empty Array; self is unmodified.

Related: push, pop, unshift.

array.shuffle(random: Random) → new_ary

array.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/array.rb, line 26
def shuffle(random: Random)
  Primitive.rb_ary_shuffle(random)
end

Returns a new array with elements of self shuffled.

a = [1, 2, 3] #=> [1, 2, 3]
a.shuffle     #=> [2, 3, 1]
a             #=> [1, 2, 3]

The optional random argument will be used as the random number generator:

a.shuffle(random: Random.new(1))  #=> [1, 3, 2]

array.shuffle!(random: Random) → array

array.rb View on GitHub

          
            # File tmp/rubies/ruby-3.3.0/array.rb, line 12
def shuffle!(random: Random)
  Primitive.rb_ary_shuffle_bang(random)
end

Shuffles the elements of self in place.

a = [1, 2, 3] #=> [1, 2, 3]
a.shuffle!    #=> [2, 3, 1]
a             #=> [2, 3, 1]

The optional random argument will be used as the random number generator:

a.shuffle!(random: Random.new(1))  #=> [1, 3, 2]

size

array.c View on GitHub

An alias for length

array.slice(index) → object or nil

array.slice(start, length) → object or nil

array.slice(range) → object or nil

array.slice(aseq) → object or nil

array.c View on GitHub

An alias for []

array.slice!(n) → object or nil

array.slice!(start, length) → new_array or nil

array.slice!(range) → new_array or nil

array.c View on GitHub

          
            static VALUE
rb_ary_slice_bang(int argc, VALUE *argv, VALUE ary)
{
    VALUE arg1;
    long pos, len;

    rb_ary_modify_check(ary);
    rb_check_arity(argc, 1, 2);
    arg1 = argv[0];

    if (argc == 2) {
        pos = NUM2LONG(argv[0]);
        len = NUM2LONG(argv[1]);
        return ary_slice_bang_by_rb_ary_splice(ary, pos, len);
    }

    if (!FIXNUM_P(arg1)) {
        switch (rb_range_beg_len(arg1, &pos, &len, RARRAY_LEN(ary), 0)) {
          case Qtrue:
            /* valid range */
            return ary_slice_bang_by_rb_ary_splice(ary, pos, len);
          case Qnil:
            /* invalid range */
            return Qnil;
          default:
            /* not a range */
            break;
        }
    }

    return rb_ary_delete_at(ary, NUM2LONG(arg1));
}

Removes and returns elements from self.

When the only argument is an Integer n, removes and returns the nth element in self:

a = [:foo, 'bar', 2]
a.slice!(1) # => "bar"
a # => [:foo, 2]

If n is negative, counts backwards from the end of self:

a = [:foo, 'bar', 2]
a.slice!(-1) # => 2
a # => [:foo, "bar"]

If n is out of range, returns nil.

When the only arguments are Integers start and length, removes length elements from self beginning at offset start; returns the deleted objects in a new Array:

a = [:foo, 'bar', 2]
a.slice!(0, 2) # => [:foo, "bar"]
a # => [2]

If start + length exceeds the array size, removes and returns all elements from offset start to the end:

a = [:foo, 'bar', 2]
a.slice!(1, 50) # => ["bar", 2]
a # => [:foo]

If start == a.size and length is non-negative, returns a new empty Array.

If length is negative, returns nil.

When the only argument is a Range object range, treats range.min as start above and range.size as length above:

a = [:foo, 'bar', 2]
a.slice!(1..2) # => ["bar", 2]
a # => [:foo]

If range.start == a.size, returns a new empty Array.

If range.start is larger than the array size, returns nil.

If range.end is negative, counts backwards from the end of the array:

a = [:foo, 'bar', 2]
a.slice!(0..-2) # => [:foo, "bar"]
a # => [2]

If range.start is negative, calculates the start index backwards from the end of the array:

a = [:foo, 'bar', 2]
a.slice!(-2..2) # => ["bar", 2]
a # => [:foo]

array.sort → new_array

array.sort {|a, b| ... } → new_array

array.c View on GitHub

          
            VALUE
rb_ary_sort(VALUE ary)
{
    ary = rb_ary_dup(ary);
    rb_ary_sort_bang(ary);
    return ary;
}

Returns a new Array whose elements are those from self, sorted.

With no block, compares elements using operator <=> (see Comparable):

a = 'abcde'.split('').shuffle
a # => ["e", "b", "d", "a", "c"]
a1 = a.sort
a1 # => ["a", "b", "c", "d", "e"]

With a block, calls the block with each element pair; for each element pair a and b, the block should return an integer:

Negative when b is to follow a.
Zero when a and b are equivalent.
Positive when a is to follow b.

Example:

a = 'abcde'.split('').shuffle
a # => ["e", "b", "d", "a", "c"]
a1 = a.sort {|a, b| a <=> b }
a1 # => ["a", "b", "c", "d", "e"]
a2 = a.sort {|a, b| b <=> a }
a2 # => ["e", "d", "c", "b", "a"]

When the block returns zero, the order for a and b is indeterminate, and may be unstable:

a = 'abcde'.split('').shuffle
a # => ["e", "b", "d", "a", "c"]
a1 = a.sort {|a, b| 0 }
a1 # =>  ["c", "e", "b", "d", "a"]

Related: Enumerable#sort_by.

array.sort! → self

array.sort! {|a, b| ... } → self

array.c View on GitHub

          
            VALUE
rb_ary_sort_bang(VALUE ary)
{
    rb_ary_modify(ary);
    assert(!ARY_SHARED_P(ary));
    if (RARRAY_LEN(ary) > 1) {
        VALUE tmp = ary_make_substitution(ary); /* only ary refers tmp */
        struct ary_sort_data data;
        long len = RARRAY_LEN(ary);
        RBASIC_CLEAR_CLASS(tmp);
        data.ary = tmp;
        data.receiver = ary;
        RARRAY_PTR_USE(tmp, ptr, {
            ruby_qsort(ptr, len, sizeof(VALUE),
                       rb_block_given_p()?sort_1:sort_2, &data);
        }); /* WB: no new reference */
        rb_ary_modify(ary);
        if (ARY_EMBED_P(tmp)) {
            if (ARY_SHARED_P(ary)) { /* ary might be destructively operated in the given block */
                rb_ary_unshare(ary);
                FL_SET_EMBED(ary);
            }
            ary_memcpy(ary, 0, ARY_EMBED_LEN(tmp), ARY_EMBED_PTR(tmp));
            ARY_SET_LEN(ary, ARY_EMBED_LEN(tmp));
        }
        else {
            if (!ARY_EMBED_P(ary) && ARY_HEAP_PTR(ary) == ARY_HEAP_PTR(tmp)) {
                FL_UNSET_SHARED(ary);
                ARY_SET_CAPA(ary, RARRAY_LEN(tmp));
            }
            else {
                assert(!ARY_SHARED_P(tmp));
                if (ARY_EMBED_P(ary)) {
                    FL_UNSET_EMBED(ary);
                }
                else if (ARY_SHARED_P(ary)) {
                    /* ary might be destructively operated in the given block */
                    rb_ary_unshare(ary);
                }
                else {
                    ary_heap_free(ary);
                }
                ARY_SET_PTR(ary, ARY_HEAP_PTR(tmp));
                ARY_SET_HEAP_LEN(ary, len);
                ARY_SET_CAPA(ary, ARY_HEAP_LEN(tmp));
            }
            /* tmp was lost ownership for the ptr */
            FL_UNSET(tmp, FL_FREEZE);
            FL_SET_EMBED(tmp);
            ARY_SET_EMBED_LEN(tmp, 0);
            FL_SET(tmp, FL_FREEZE);
        }
        /* tmp will be GC'ed. */
        RBASIC_SET_CLASS_RAW(tmp, rb_cArray); /* rb_cArray must be marked */
    }
    ary_verify(ary);
    return ary;
}

Returns self with its elements sorted in place.

With no block, compares elements using operator <=> (see Comparable):

a = 'abcde'.split('').shuffle
a # => ["e", "b", "d", "a", "c"]
a.sort!
a # => ["a", "b", "c", "d", "e"]

With a block, calls the block with each element pair; for each element pair a and b, the block should return an integer:

Negative when b is to follow a.
Zero when a and b are equivalent.
Positive when a is to follow b.

Example:

a = 'abcde'.split('').shuffle
a # => ["e", "b", "d", "a", "c"]
a.sort! {|a, b| a <=> b }
a # => ["a", "b", "c", "d", "e"]
a.sort! {|a, b| b <=> a }
a # => ["e", "d", "c", "b", "a"]

When the block returns zero, the order for a and b is indeterminate, and may be unstable:

a = 'abcde'.split('').shuffle
a # => ["e", "b", "d", "a", "c"]
a.sort! {|a, b| 0 }
a # => ["d", "e", "c", "a", "b"]

array.sort_by! {|element| ... } → self

array.sort_by! → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_sort_by_bang(VALUE ary)
{
    VALUE sorted;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rb_ary_modify(ary);
    sorted = rb_block_call(ary, rb_intern("sort_by"), 0, 0, sort_by_i, 0);
    rb_ary_replace(ary, sorted);
    return ary;
}

Sorts the elements of self in place, using an ordering determined by the block; returns self.

Calls the block with each successive element; sorts elements based on the values returned from the block.

For duplicates returned by the block, the ordering is indeterminate, and may be unstable.

This example sorts strings based on their sizes:

a = ['aaaa', 'bbb', 'cc', 'd']
a.sort_by! {|element| element.size }
a # => ["d", "cc", "bbb", "aaaa"]

Returns a new Enumerator if no block given:

a = ['aaaa', 'bbb', 'cc', 'd']
a.sort_by! # => #<Enumerator: ["aaaa", "bbb", "cc", "d"]:sort_by!>

array.sum(init = 0) → object

array.sum(init = 0) {|element| ... } → object

array.c View on GitHub

          
            static VALUE
rb_ary_sum(int argc, VALUE *argv, VALUE ary)
{
    VALUE e, v, r;
    long i, n;
    int block_given;

    v = (rb_check_arity(argc, 0, 1) ? argv[0] : LONG2FIX(0));

    block_given = rb_block_given_p();

    if (RARRAY_LEN(ary) == 0)
        return v;

    n = 0;
    r = Qundef;

    if (!FIXNUM_P(v) && !RB_BIGNUM_TYPE_P(v) && !RB_TYPE_P(v, T_RATIONAL)) {
        i = 0;
        goto init_is_a_value;
    }

    for (i = 0; i < RARRAY_LEN(ary); i++) {
        e = RARRAY_AREF(ary, i);
        if (block_given)
            e = rb_yield(e);
        if (FIXNUM_P(e)) {
            n += FIX2LONG(e); /* should not overflow long type */
            if (!FIXABLE(n)) {
                v = rb_big_plus(LONG2NUM(n), v);
                n = 0;
            }
        }
        else if (RB_BIGNUM_TYPE_P(e))
            v = rb_big_plus(e, v);
        else if (RB_TYPE_P(e, T_RATIONAL)) {
            if (UNDEF_P(r))
                r = e;
            else
                r = rb_rational_plus(r, e);
        }
        else
            goto not_exact;
    }
    v = finish_exact_sum(n, r, v, argc!=0);
    return v;

  not_exact:
    v = finish_exact_sum(n, r, v, i!=0);

    if (RB_FLOAT_TYPE_P(e)) {
        /*
         * Kahan-Babuska balancing compensated summation algorithm
         * See https://link.springer.com/article/10.1007/s00607-005-0139-x
         */
        double f, c;
        double x, t;

        f = NUM2DBL(v);
        c = 0.0;
        goto has_float_value;
        for (; i < RARRAY_LEN(ary); i++) {
            e = RARRAY_AREF(ary, i);
            if (block_given)
                e = rb_yield(e);
            if (RB_FLOAT_TYPE_P(e))
              has_float_value:
                x = RFLOAT_VALUE(e);
            else if (FIXNUM_P(e))
                x = FIX2LONG(e);
            else if (RB_BIGNUM_TYPE_P(e))
                x = rb_big2dbl(e);
            else if (RB_TYPE_P(e, T_RATIONAL))
                x = rb_num2dbl(e);
            else
                goto not_float;

            if (isnan(f)) continue;
            if (isnan(x)) {
                f = x;
                continue;
            }
            if (isinf(x)) {
                if (isinf(f) && signbit(x) != signbit(f))
                    f = NAN;
                else
                    f = x;
                continue;
            }
            if (isinf(f)) continue;

            t = f + x;
            if (fabs(f) >= fabs(x))
                c += ((f - t) + x);
            else
                c += ((x - t) + f);
            f = t;
        }
        f += c;
        return DBL2NUM(f);

      not_float:
        v = DBL2NUM(f);
    }

    goto has_some_value;
    init_is_a_value:
    for (; i < RARRAY_LEN(ary); i++) {
        e = RARRAY_AREF(ary, i);
        if (block_given)
            e = rb_yield(e);
      has_some_value:
        v = rb_funcall(v, idPLUS, 1, e);
    }
    return v;
}

When no block is given, returns the object equivalent to:

sum = init
array.each {|element| sum += element }
sum

For example, [e1, e2, e3].sum returns init + e1 + e2 + e3.

Examples:

a = [0, 1, 2, 3]
a.sum # => 6
a.sum(100) # => 106

The elements need not be numeric, but must be +-compatible with each other and with init:

a = ['abc', 'def', 'ghi']
a.sum('jkl') # => "jklabcdefghi"

When a block is given, it is called with each element and the block’s return value (instead of the element itself) is used as the addend:

a = ['zero', 1, :two]
s = a.sum('Coerced and concatenated: ') {|element| element.to_s }
s # => "Coerced and concatenated: zero1two"

Notes:

Array#join and Array#flatten may be faster than Array#sum for an Array of Strings or an Array of Arrays.
Array#sum method may not respect method redefinition of “+” methods such as Integer#+.

array.take(n) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_take(VALUE obj, VALUE n)
{
    long len = NUM2LONG(n);
    if (len < 0) {
        rb_raise(rb_eArgError, "attempt to take negative size");
    }
    return rb_ary_subseq(obj, 0, len);
}

Returns a new Array containing the first n element of self, where n is a non-negative Integer; does not modify self.

Examples:

a = [0, 1, 2, 3, 4, 5]
a.take(1) # => [0]
a.take(2) # => [0, 1]
a.take(50) # => [0, 1, 2, 3, 4, 5]
a # => [0, 1, 2, 3, 4, 5]

array.take_while {|element| ... } → new_array

array.take_while → new_enumerator

array.c View on GitHub

          
            static VALUE
rb_ary_take_while(VALUE ary)
{
    long i;

    RETURN_ENUMERATOR(ary, 0, 0);
    for (i = 0; i < RARRAY_LEN(ary); i++) {
        if (!RTEST(rb_yield(RARRAY_AREF(ary, i)))) break;
    }
    return rb_ary_take(ary, LONG2FIX(i));
}

Returns a new Array containing zero or more leading elements of self; does not modify self.

With a block given, calls the block with each successive element of self; stops if the block returns false or nil; returns a new Array containing those elements for which the block returned a truthy value:

a = [0, 1, 2, 3, 4, 5]
a.take_while {|element| element < 3 } # => [0, 1, 2]
a.take_while {|element| true } # => [0, 1, 2, 3, 4, 5]
a # => [0, 1, 2, 3, 4, 5]

With no block given, returns a new Enumerator:

[0, 1].take_while # => #<Enumerator: [0, 1]:take_while>

to_a → self or new_array

array.c View on GitHub

          
            static VALUE
rb_ary_to_a(VALUE ary)
{
    if (rb_obj_class(ary) != rb_cArray) {
        VALUE dup = rb_ary_new2(RARRAY_LEN(ary));
        rb_ary_replace(dup, ary);
        return dup;
    }
    return ary;
}

When self is an instance of Array, returns self:

a = [:foo, 'bar', 2]
a.to_a # => [:foo, "bar", 2]

Otherwise, returns a new Array containing the elements of self:

class MyArray < Array; end
a = MyArray.new(['foo', 'bar', 'two'])
a.instance_of?(Array) # => false
a.kind_of?(Array) # => true
a1 = a.to_a
a1 # => ["foo", "bar", "two"]
a1.class # => Array # Not MyArray

array.to_ary → self

array.c View on GitHub

          
            static VALUE
rb_ary_to_ary_m(VALUE ary)
{
    return ary;
}

Returns self.

array.to_h → new_hash

array.to_h {|item| ... } → new_hash

array.c View on GitHub

          
            static VALUE
rb_ary_to_h(VALUE ary)
{
    long i;
    VALUE hash = rb_hash_new_with_size(RARRAY_LEN(ary));
    int block_given = rb_block_given_p();

    for (i=0; i<RARRAY_LEN(ary); i++) {
        const VALUE e = rb_ary_elt(ary, i);
        const VALUE elt = block_given ? rb_yield_force_blockarg(e) : e;
        const VALUE key_value_pair = rb_check_array_type(elt);
        if (NIL_P(key_value_pair)) {
            rb_raise(rb_eTypeError, "wrong element type %"PRIsVALUE" at %ld (expected array)",
                     rb_obj_class(elt), i);
        }
        if (RARRAY_LEN(key_value_pair) != 2) {
            rb_raise(rb_eArgError, "wrong array length at %ld (expected 2, was %ld)",
                i, RARRAY_LEN(key_value_pair));
        }
        rb_hash_aset(hash, RARRAY_AREF(key_value_pair, 0), RARRAY_AREF(key_value_pair, 1));
    }
    return hash;
}

Returns a new Hash formed from self.

When a block is given, calls the block with each array element; the block must return a 2-element Array whose two elements form a key-value pair in the returned Hash:

a = ['foo', :bar, 1, [2, 3], {baz: 4}]
h = a.to_h {|item| [item, item] }
h # => {"foo"=>"foo", :bar=>:bar, 1=>1, [2, 3]=>[2, 3], {:baz=>4}=>{:baz=>4}}

When no block is given, self must be an Array of 2-element sub-arrays, each sub-array is formed into a key-value pair in the new Hash:

[].to_h # => {}
a = [['foo', 'zero'], ['bar', 'one'], ['baz', 'two']]
h = a.to_h
h # => {"foo"=>"zero", "bar"=>"one", "baz"=>"two"}

to_s

array.c View on GitHub

An alias for inspect

array.transpose → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_transpose(VALUE ary)
{
    long elen = -1, alen, i, j;
    VALUE tmp, result = 0;

    alen = RARRAY_LEN(ary);
    if (alen == 0) return rb_ary_dup(ary);
    for (i=0; i<alen; i++) {
        tmp = to_ary(rb_ary_elt(ary, i));
        if (elen < 0) {         /* first element */
            elen = RARRAY_LEN(tmp);
            result = rb_ary_new2(elen);
            for (j=0; j<elen; j++) {
                rb_ary_store(result, j, rb_ary_new2(alen));
            }
        }
        else if (elen != RARRAY_LEN(tmp)) {
            rb_raise(rb_eIndexError, "element size differs (%ld should be %ld)",
                     RARRAY_LEN(tmp), elen);
        }
        for (j=0; j<elen; j++) {
            rb_ary_store(rb_ary_elt(result, j), i, rb_ary_elt(tmp, j));
        }
    }
    return result;
}

Transposes the rows and columns in an Array of Arrays; the nested Arrays must all be the same size:

a = [[:a0, :a1], [:b0, :b1], [:c0, :c1]]
a.transpose # => [[:a0, :b0, :c0], [:a1, :b1, :c1]]

array.union(*other_arrays) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_union_multi(int argc, VALUE *argv, VALUE ary)
{
    int i;
    long sum;
    VALUE hash;

    sum = RARRAY_LEN(ary);
    for (i = 0; i < argc; i++) {
        argv[i] = to_ary(argv[i]);
        sum += RARRAY_LEN(argv[i]);
    }

    if (sum <= SMALL_ARRAY_LEN) {
        VALUE ary_union = rb_ary_new();

        rb_ary_union(ary_union, ary);
        for (i = 0; i < argc; i++) rb_ary_union(ary_union, argv[i]);

        return ary_union;
    }

    hash = ary_make_hash(ary);
    for (i = 0; i < argc; i++) rb_ary_union_hash(hash, argv[i]);

    return rb_hash_values(hash);
}

Returns a new Array that is the union of self and all given Arrays other_arrays; duplicates are removed; order is preserved; items are compared using eql?:

[0, 1, 2, 3].union([4, 5], [6, 7]) # => [0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 1].union([2, 1], [3, 1]) # => [0, 1, 2, 3]
[0, 1, 2, 3].union([3, 2], [1, 0]) # => [0, 1, 2, 3]

Returns a copy of self if no arguments given.

Related: Array#|.

array.uniq → new_array

array.uniq {|element| ... } → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_uniq(VALUE ary)
{
    VALUE hash, uniq;

    if (RARRAY_LEN(ary) <= 1) {
        hash = 0;
        uniq = rb_ary_dup(ary);
    }
    else if (rb_block_given_p()) {
        hash = ary_make_hash_by(ary);
        uniq = rb_hash_values(hash);
    }
    else {
        hash = ary_make_hash(ary);
        uniq = rb_hash_values(hash);
    }

    return uniq;
}

Returns a new Array containing those elements from self that are not duplicates, the first occurrence always being retained.

With no block given, identifies and omits duplicates using method eql? to compare:

a = [0, 0, 1, 1, 2, 2]
a.uniq # => [0, 1, 2]

With a block given, calls the block for each element; identifies (using method eql?) and omits duplicate values, that is, those elements for which the block returns the same value:

a = ['a', 'aa', 'aaa', 'b', 'bb', 'bbb']
a.uniq {|element| element.size } # => ["a", "aa", "aaa"]

array.uniq! → self or nil

array.uniq! {|element| ... } → self or nil

array.c View on GitHub

          
            static VALUE
rb_ary_uniq_bang(VALUE ary)
{
    VALUE hash;
    long hash_size;

    rb_ary_modify_check(ary);
    if (RARRAY_LEN(ary) <= 1)
        return Qnil;
    if (rb_block_given_p())
        hash = ary_make_hash_by(ary);
    else
        hash = ary_make_hash(ary);

    hash_size = RHASH_SIZE(hash);
    if (RARRAY_LEN(ary) == hash_size) {
        return Qnil;
    }
    rb_ary_modify_check(ary);
    ARY_SET_LEN(ary, 0);
    if (ARY_SHARED_P(ary) && !ARY_EMBED_P(ary)) {
        rb_ary_unshare(ary);
        FL_SET_EMBED(ary);
    }
    ary_resize_capa(ary, hash_size);
    rb_hash_foreach(hash, push_value, ary);

    return ary;
}

Removes duplicate elements from self, the first occurrence always being retained; returns self if any elements removed, nil otherwise.

With no block given, identifies and removes elements using method eql? to compare.

Returns self if any elements removed:

a = [0, 0, 1, 1, 2, 2]
a.uniq! # => [0, 1, 2]

Returns nil if no elements removed.

With a block given, calls the block for each element; identifies (using method eql?) and removes elements for which the block returns duplicate values.

Returns self if any elements removed:

a = ['a', 'aa', 'aaa', 'b', 'bb', 'bbb']
a.uniq! {|element| element.size } # => ['a', 'aa', 'aaa']

Returns nil if no elements removed.

array.unshift(*objects) → self

array.c View on GitHub

          
            VALUE
rb_ary_unshift_m(int argc, VALUE *argv, VALUE ary)
{
    long len = RARRAY_LEN(ary);
    VALUE target_ary;

    if (argc == 0) {
        rb_ary_modify_check(ary);
        return ary;
    }

    target_ary = ary_ensure_room_for_unshift(ary, argc);
    ary_memcpy0(ary, 0, argc, argv, target_ary);
    ARY_SET_LEN(ary, len + argc);
    return ary;
}

Prepends the given objects to self:

a = [:foo, 'bar', 2]
a.unshift(:bam, :bat) # => [:bam, :bat, :foo, "bar", 2]

Related: push, pop, shift.

array.values_at(*indexes) → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_values_at(int argc, VALUE *argv, VALUE ary)
{
    long i, olen = RARRAY_LEN(ary);
    VALUE result = rb_ary_new_capa(argc);
    for (i = 0; i < argc; ++i) {
        append_values_at_single(result, ary, olen, argv[i]);
    }
    RB_GC_GUARD(ary);
    return result;
}

Returns a new Array whose elements are the elements of self at the given Integer or Range indexes.

For each positive index, returns the element at offset index:

a = [:foo, 'bar', 2]
a.values_at(0, 2) # => [:foo, 2]
a.values_at(0..1) # => [:foo, "bar"]

The given indexes may be in any order, and may repeat:

a = [:foo, 'bar', 2]
a.values_at(2, 0, 1, 0, 2) # => [2, :foo, "bar", :foo, 2]
a.values_at(1, 0..2) # => ["bar", :foo, "bar", 2]

Assigns nil for an index that is too large:

a = [:foo, 'bar', 2]
a.values_at(0, 3, 1, 3) # => [:foo, nil, "bar", nil]

Returns a new empty Array if no arguments given.

For each negative index, counts backward from the end of the array:

a = [:foo, 'bar', 2]
a.values_at(-1, -3) # => [2, :foo]

Assigns nil for an index that is too small:

a = [:foo, 'bar', 2]
a.values_at(0, -5, 1, -6, 2) # => [:foo, nil, "bar", nil, 2]

The given indexes may have a mixture of signs:

a = [:foo, 'bar', 2]
a.values_at(0, -2, 1, -1) # => [:foo, "bar", "bar", 2]

array.zip(*other_arrays) → new_array

array.zip(*other_arrays) {|other_array| ... } → nil

array.c View on GitHub

          
            static VALUE
rb_ary_zip(int argc, VALUE *argv, VALUE ary)
{
    int i, j;
    long len = RARRAY_LEN(ary);
    VALUE result = Qnil;

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

    if (rb_block_given_p()) {
        int arity = rb_block_arity();

        if (arity > 1) {
            VALUE work, *tmp;

            tmp = ALLOCV_N(VALUE, work, argc+1);

            for (i=0; i<RARRAY_LEN(ary); i++) {
                tmp[0] = RARRAY_AREF(ary, i);
                for (j=0; j<argc; j++) {
                    tmp[j+1] = rb_ary_elt(argv[j], i);
                }
                rb_yield_values2(argc+1, tmp);
            }

            if (work) ALLOCV_END(work);
        }
        else {
            for (i=0; i<RARRAY_LEN(ary); i++) {
                VALUE tmp = rb_ary_new2(argc+1);

                rb_ary_push(tmp, RARRAY_AREF(ary, i));
                for (j=0; j<argc; j++) {
                    rb_ary_push(tmp, rb_ary_elt(argv[j], i));
                }
                rb_yield(tmp);
            }
        }
    }
    else {
        result = rb_ary_new_capa(len);

        for (i=0; i<len; i++) {
            VALUE tmp = rb_ary_new_capa(argc+1);

            rb_ary_push(tmp, RARRAY_AREF(ary, i));
            for (j=0; j<argc; j++) {
                rb_ary_push(tmp, rb_ary_elt(argv[j], i));
            }
            rb_ary_push(result, tmp);
        }
    }

    return result;
}

When no block given, returns a new Array new_array of size self.size whose elements are Arrays.

Each nested array new_array[n] is of size other_arrays.size+1, and contains:

The nth element of self.
The nth element of each of the other_arrays.

If all other_arrays and self are the same size:

a = [:a0, :a1, :a2, :a3]
b = [:b0, :b1, :b2, :b3]
c = [:c0, :c1, :c2, :c3]
d = a.zip(b, c)
d # => [[:a0, :b0, :c0], [:a1, :b1, :c1], [:a2, :b2, :c2], [:a3, :b3, :c3]]

If any array in other_arrays is smaller than self, fills to self.size with nil:

a = [:a0, :a1, :a2, :a3]
b = [:b0, :b1, :b2]
c = [:c0, :c1]
d = a.zip(b, c)
d # => [[:a0, :b0, :c0], [:a1, :b1, :c1], [:a2, :b2, nil], [:a3, nil, nil]]

If any array in other_arrays is larger than self, its trailing elements are ignored:

a = [:a0, :a1, :a2, :a3]
b = [:b0, :b1, :b2, :b3, :b4]
c = [:c0, :c1, :c2, :c3, :c4, :c5]
d = a.zip(b, c)
d # => [[:a0, :b0, :c0], [:a1, :b1, :c1], [:a2, :b2, :c2], [:a3, :b3, :c3]]

When a block is given, calls the block with each of the sub-arrays (formed as above); returns nil:

a = [:a0, :a1, :a2, :a3]
b = [:b0, :b1, :b2, :b3]
c = [:c0, :c1, :c2, :c3]
a.zip(b, c) {|sub_array| p sub_array} # => nil

Output:

[:a0, :b0, :c0]
[:a1, :b1, :c1]
[:a2, :b2, :c2]
[:a3, :b3, :c3]

array | other_array → new_array

array.c View on GitHub

          
            static VALUE
rb_ary_or(VALUE ary1, VALUE ary2)
{
    VALUE hash;

    ary2 = to_ary(ary2);
    if (RARRAY_LEN(ary1) + RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
        VALUE ary3 = rb_ary_new();
        rb_ary_union(ary3, ary1);
        rb_ary_union(ary3, ary2);
        return ary3;
    }

    hash = ary_make_hash(ary1);
    rb_ary_union_hash(hash, ary2);

    return rb_hash_values(hash);
}

Returns the union of array and Array other_array; duplicates are removed; order is preserved; items are compared using eql?:

[0, 1] | [2, 3] # => [0, 1, 2, 3]
[0, 1, 1] | [2, 2, 3] # => [0, 1, 2, 3]
[0, 1, 2] | [3, 2, 1, 0] # => [0, 1, 2, 3]

Related: Array#union.