Class: Array

Inherits:

Object
Array

Includes:: Enumerable

Defined in:: array.c

Overview

Arrays are ordered, integer-indexed collections of any object.

Array indexing starts at 0, as in C or Java. A negative index is assumed to be relative to the end of the array---that is, an index of -1 indicates the last element of the array, -2 is the next to last element in the array, and so on.

Creating Arrays

A new array can be created by using the literal constructor []. Arrays can contain different types of objects. For example, the array below contains an Integer, a String and a Float:

ary = [1, "two", 3.0] #=> [1, "two", 3.0]

An array can also be created by explicitly calling Array.new with zero, one (the initial size of the Array) or two arguments (the initial size and a default object).

ary = Array.new    #=> []
Array.new(3)       #=> [nil, nil, nil]
Array.new(3, true) #=> [0, 0, 0]

Note that the second argument populates the array with references to the same object. Therefore, it is only recommended in cases when you need to instantiate arrays with natively immutable objects such as Symbols, numbers, true or false.

To create an array with separate objects a block can be passed instead. This method is safe to use with mutable objects such as hashes, strings or other arrays:

Array.new(4) { Hash.new } #=> [{}, {}, {}, {}]

This is also a quick way to build up multi-dimensional arrays:

empty_table = Array.new(3) { Array.new(3) }
#=> [[nil, nil, nil], [nil, nil, nil], [nil, nil, nil]]

An array can also be created by using the Array() method, provided by Kernel, which calls #to_ary or #to_a on it's argument.

Array(=> "a", :b => "b") #=> [[:a, "a"], [:b, "b"]]

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.

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]

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) #=> [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[rats live on no evil star]
str = ""
words.reverse_each { |word| str += "#{word.reverse} " }
str #=> "rats live on no evil star "

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 }     #=> [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]

Class Method Summary collapse

.[] ⇒ Object

Returns a new array populated with the given objects.
.try_convert(obj) ⇒ Array^?

Tries to convert obj into an array, using to_ary method.

Instance Method Summary collapse

#&(other_ary) ⇒ Object

Set Intersection --- Returns a new array containing elements common to the two arrays, excluding any duplicates.
#* ⇒ Object

Repetition --- With a String argument, equivalent to ary.join(str).
#+(other_ary) ⇒ Object

Concatenation --- Returns a new array built by concatenating the two arrays together to produce a third array.
#-(other_ary) ⇒ Object

Array Difference.
#<<(obj) ⇒ Object

Append---Pushes the given object on to the end of this array.
#<=>(other_ary) ⇒ -1, ...

Comparison --- Returns an integer (-1, 0, or +1) if this array is less than, equal to, or greater than other_ary.
#==(other_ary) ⇒ Boolean

Equality --- Two arrays are equal if they contain the same number of elements and if each element is equal to (according to Object#==) the corresponding element in other_ary.
#[] ⇒ Object

Element Reference --- Returns the element at index, or returns a subarray starting at the start index and continuing for length elements, or returns a subarray specified by range of indices.
#[]= ⇒ Object

Element Assignment --- Sets the element at index, or replaces a subarray from the start index for length elements, or replaces a subarray specified by the range of indices.
#assoc(obj) ⇒ nil

Searches through an array whose elements are also arrays comparing obj with the first element of each contained array using obj.==.
#at(index) ⇒ Object^?

Returns the element at index.
#bsearch {|x| ... } ⇒ Object

By using binary search, finds a value from this array which meets the given condition in O(log n) where n is the size of the array.
#clear ⇒ Object

Removes all elements from self.
#collect ⇒ Object

Invokes the given block once for each element of self.
#collect! ⇒ Object

Invokes the given block once for each element of self, replacing the element with the value returned by the block.
#combination ⇒ Object

When invoked with a block, yields all combinations of length n of elements from the array and then returns the array itself.
#compact ⇒ Object

Returns a copy of self with all nil elements removed.
#compact! ⇒ nil

Removes nil elements from the array.
#concat(other_ary) ⇒ Object

Appends the elements of other_ary to self.
#count ⇒ Object

Returns the number of elements.
#cycle ⇒ Object

Calls the given block for each element n times or forever if nil is given.
#delete ⇒ Object

Deletes all items from self that are equal to obj.
#delete_at(index) ⇒ Object^?

Deletes the element at the specified index, returning that element, or nil if the index is out of range.
#delete_if ⇒ Object

Deletes every element of self for which block evaluates to true.
#drop(n) ⇒ Object

Drops first n elements from ary and returns the rest of the elements in an array.
#drop_while ⇒ Object

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.
#each ⇒ Object

Calls the given block once for each element in self, passing that element as a parameter.
#each_index ⇒ Object

Same as Array#each, but passes the index of the element instead of the element itself.
#empty? ⇒ Boolean

Returns true if self contains no elements.
#eql?(other) ⇒ Boolean

Returns true if self and other are the same object, or are both arrays with the same content.
#fetch ⇒ Object

Tries to return the element at position index, but throws an IndexError exception if the referenced index lies outside of the array bounds.
#fill ⇒ Object

The first three forms set the selected elements of self (which may be the entire array) to obj.
#find_index ⇒ Object

Returns the index of the first object in ary such that the object is == to obj.
#first ⇒ Object

Returns the first element, or the first n elements, of the array.
#flatten ⇒ Object

Returns a new array that is a one-dimensional flattening of self (recursively).
#flatten! ⇒ Object

Flattens self in place.
#frozen? ⇒ Boolean

Return true if this array is frozen (or temporarily frozen while being sorted).
#hash ⇒ Fixnum

Compute a hash-code for this array.
#include?(object) ⇒ Boolean

Returns true if the given object is present in self (that is, if any object == object), otherwise returns false.
#index ⇒ Object

Returns the index of the first object in ary such that the object is == to obj.
#initialize ⇒ Object constructor

Returns a new array.
#replace(other_ary) ⇒ Object

Replaces the contents of self with the contents of other_ary, truncating or expanding if necessary.
#insert(index, obj...) ⇒ Object

Inserts the given values before the element with the given index.
#inspect ⇒ Object (also: #to_s)

Creates a string representation of self.
#join(separator = $,) ⇒ String

Returns a string created by converting each element of the array to a string, separated by the given separator.
#keep_if ⇒ Object

Deletes every element of self for which the given block evaluates to false.
#last ⇒ Object

Returns the last element(s) of self.
#length ⇒ Integer (also: #size)

Returns the number of elements in self.
#map ⇒ Object

Invokes the given block once for each element of self.
#map! ⇒ Object

Invokes the given block once for each element of self, replacing the element with the value returned by the block.
#pack ⇒ Object

Packs the contents of arr into a binary sequence according to the directives in aTemplateString (see the table below) Directives "A," "a," and "Z" may be followed by a count, which gives the width of the resulting field.
#permutation ⇒ Object

When invoked with a block, yield all permutations of length n of the elements of the array, then return the array itself.
#pop ⇒ Object

Removes the last element from self and returns it, or nil if the array is empty.
#product ⇒ Object

Returns an array of all combinations of elements from all arrays.
#push(obj, ...) ⇒ Object

Append --- Pushes the given object(s) on to the end of this array.
#rassoc(obj) ⇒ nil

Searches through the array whose elements are also arrays.
#reject ⇒ Object

Returns a new array containing the items in self for which the given block is not true.
#reject! ⇒ Object

Equivalent to Array#delete_if, deleting elements from self for which the block evaluates to true, but returns nil if no changes were made.
#repeated_combination ⇒ Object

When invoked with a block, yields all repeated combinations of length n of elements from the array and then returns the array itself.
#repeated_permutation ⇒ Object

When invoked with a block, yield all repeated permutations of length n of the elements of the array, then return the array itself.
#replace(other_ary) ⇒ Object

Replaces the contents of self with the contents of other_ary, truncating or expanding if necessary.
#reverse ⇒ Object

Returns a new array containing self's elements in reverse order.
#reverse! ⇒ Object

Reverses self in place.
#reverse_each ⇒ Object

Same as Array#each, but traverses self in reverse order.
#rindex ⇒ Object

Returns the index of the last object in self == to obj.
#rotate(count = 1) ⇒ Object

Returns a new array by rotating self so that the element at count is the first element of the new array.
#rotate!(count = 1) ⇒ Object

Rotates self in place so that the element at count comes first, and returns self.
#sample ⇒ Object

Choose a random element or n random elements from the array.
#select ⇒ Object

Returns a new array containing all elements of ary for which the given block returns a true value.
#select! ⇒ Object

Invokes the given block passing in successive elements from self, deleting elements for which the block returns a false value.
#shift ⇒ Object

Removes the first element of self and returns it (shifting all other elements down by one).
#shuffle ⇒ Object

Returns a new array with elements of self shuffled.
#shuffle! ⇒ Object

Shuffles elements in self in place.
#slice ⇒ Object

Element Reference --- Returns the element at index, or returns a subarray starting at the start index and continuing for length elements, or returns a subarray specified by range of indices.
#slice! ⇒ Object

Deletes the element(s) given by an index (optionally up to length elements) or by a range.
#sort ⇒ Object

Returns a new array created by sorting self.
#sort! ⇒ Object

Sorts self in place.
#sort_by! ⇒ Object

Sorts self in place using a set of keys generated by mapping the values in self through the given block.
#take(n) ⇒ Object

Returns first n elements from the array.
#take_while ⇒ Object

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.
#to_a ⇒ Object

Returns self.
#to_ary ⇒ Object

Returns self.
#transpose ⇒ Object

Assumes that self is an array of arrays and transposes the rows and columns.
#uniq ⇒ Object

Returns a new array by removing duplicate values in self.
#uniq! ⇒ Object

Removes duplicate elements from self.
#unshift(obj, ...) ⇒ Object

Prepends objects to the front of self, moving other elements upwards.
#values_at(selector, ...) ⇒ Object

Returns an array containing the elements in self corresponding to the given selector(s).
#zip ⇒ Object

Converts any arguments to arrays, then merges elements of self with corresponding elements from each argument.
#|(other_ary) ⇒ Object

Set Union --- Returns a new array by joining ary with other_ary, excluding any duplicates.

Methods included from Enumerable

#all?, #any?, #chunk, #collect_concat, #detect, #each_cons, #each_entry, #each_slice, #each_with_index, #each_with_object, #entries, #find, #find_all, #flat_map, #grep, #group_by, #inject, #lazy, #max, #max_by, #member?, #min, #min_by, #minmax, #minmax_by, #none?, #one?, #partition, #reduce, #slice_before, #sort_by

Constructor Details

#new(size = 0, obj = nil) ⇒ `Object` #new(array) ⇒ `Object` #new(size) {|index| ... } ⇒ `Object`

Returns a new array.

In the first form, if no arguments are sent, the new array will be empty. When a size and an optional obj are sent, an array is created with size copies of obj. Take notice that all elements will reference the same object obj.

The second form creates a copy of the array passed as a parameter (the array is generated by calling to_ary on the parameter).

first_array = ["Matz", "Guido"]

second_array = Array.new(first_array) #=> ["Matz", "Guido"]

first_array.equal? second_array       #=> false

In the last form, an array of the given size is created. Each element in this array is created by passing the element's index to the given block and storing the return value.

Array.new(3){ |index| index ** 2 }
# => [0, 1, 4]

Common gotchas

When sending the second parameter, the same object will be used as the value for all the array elements:

a = Array.new(2, Hash.new)
# => [{}, {}]

a[0]['cat'] = 'feline'
a # => [{"cat"=>"feline"}, {"cat"=>"feline"}]

a[1]['cat'] = 'Felix'
a # => [{"cat"=>"Felix"}, {"cat"=>"Felix"}]

Since all the Array elements store the same hash, changes to one of them will affect them all.

If multiple copies are what you want, you should use the block version which uses the result of that block each time an element of the array needs to be initialized:

a = Array.new(2) { Hash.new }
a[0]['cat'] = 'feline'
a # => [{"cat"=>"feline"}, {}]

Overloads:

#new(size) {|index| ... } ⇒ Object
Yields:
- (index)

# File 'array.c', line 644

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

    rb_ary_modify(ary);
    if (argc == 0) {
	if (ARY_OWNS_HEAP_P(ary) && RARRAY_PTR(ary)) {
	    xfree(RARRAY_PTR(ary));
	}
        rb_ary_unshare_safe(ary);
        FL_SET_EMBED(ary);
	ARY_SET_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);
    if (len < 0) {
	rb_raise(rb_eArgError, "negative array size");
    }
    if (len > ARY_MAX_SIZE) {
	rb_raise(rb_eArgError, "array size too big");
    }
    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 {
	memfill(RARRAY_PTR(ary), len, val);
	ARY_SET_LEN(ary, len);
    }
    return ary;
}

Class Method Details

.[] ⇒ `Object`

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/]

# File 'array.c', line 707

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

    return ary;
}

.try_convert(obj) ⇒ `Array`^?

Tries to convert obj into an array, using to_ary method. Returns the converted array or nil if obj cannot be converted for any reason. This method can be used to check if an argument is an array.

Array.try_convert([1])   #=> [1]
Array.try_convert("1")   #=> nil

if tmp = Array.try_convert(arg)
  # the argument is an array
elsif tmp = String.try_convert(arg)
  # the argument is a string
end

Returns:

(Array, nil)

# File 'array.c', line 582

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

Instance Method Details

#&(other_ary) ⇒ `Object`

Set Intersection --- Returns a new array containing elements common to the two arrays, excluding any duplicates.

It compares elements using their #hash and #eql? methods for efficiency.

[ 1, 1, 3, 5 ] & [ 1, 2, 3 ]                 #=> [ 1, 3 ]
[ 'a', 'b', 'b', 'z' ] & [ 'a', 'b', 'c' ]   #=> [ 'a', 'b' ]

#(int) ⇒ `Object` #(str) ⇒ `Object`

Repetition --- With a String argument, equivalent to ary.join(str).

Otherwise, returns a new array built by concatenating the int copies of self.

[ 1, 2, 3 ] * 3    #=> [ 1, 2, 3, 1, 2, 3, 1, 2, 3 ]
[ 1, 2, 3 ] * ","  #=> "1,2,3"

# File 'array.c', line 3411

static VALUE
rb_ary_times(VALUE ary, VALUE times)
{
    VALUE ary2, tmp, *ptr, *ptr2;
    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_obj_class(ary), 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_obj_class(ary), len);
    ARY_SET_LEN(ary2, len);

    ptr = RARRAY_PTR(ary);
    ptr2 = RARRAY_PTR(ary2);
    t = RARRAY_LEN(ary);
    if (0 < t) {
        MEMCPY(ptr2, ptr, VALUE, t);
        while (t <= len/2) {
            MEMCPY(ptr2+t, ptr2, VALUE, t);
            t *= 2;
        }
        if (t < len) {
            MEMCPY(ptr2+t, ptr2, VALUE, len-t);
        }
    }
  out:
    OBJ_INFECT(ary2, ary);

    return ary2;
}

#+(other_ary) ⇒ `Object`

Concatenation --- Returns a new array built by concatenating the two arrays together to produce a third array.

[ 1, 2, 3 ] + [ 4, 5 ]    #=> [ 1, 2, 3, 4, 5 ]
a = [ "a", "b", "c" ]
a + [ "d", "e", "f" ]
a                         #=> [ "a", "b", "c", "d", "e", "f" ]

#-(other_ary) ⇒ `Object`

Array Difference

Returns a new array that is a copy of the original array, removing any items that also appear in other_ary.

It compares elements using their #hash and #eql? methods for efficiency.

[ 1, 1, 2, 2, 3, 3, 4, 5 ] - [ 1, 2, 4 ]  #=>  [ 3, 3, 5 ]

If you need set-like behavior, see the library class Set.

# File 'array.c', line 3813

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

    hash = ary_make_hash(to_ary(ary2));
    ary3 = rb_ary_new();

    for (i=0; i<RARRAY_LEN(ary1); i++) {
	if (st_lookup(RHASH_TBL(hash), RARRAY_PTR(ary1)[i], 0)) continue;
	rb_ary_push(ary3, rb_ary_elt(ary1, i));
    }
    ary_recycle_hash(hash);
    return ary3;
}

#<<(obj) ⇒ `Object`

Append---Pushes the given object on to the end of this array. This expression returns the array itself, so several appends may be chained together.

[ 1, 2 ] << "c" << "d" << [ 3, 4 ]
        #=>  [ 1, 2, "c", "d", [ 3, 4 ] ]

# File 'array.c', line 822

VALUE
rb_ary_push(VALUE ary, VALUE item)
{
    long idx = RARRAY_LEN(ary);

    ary_ensure_room_for_push(ary, 1);
    RARRAY_PTR(ary)[idx] = item;
    ARY_SET_LEN(ary, idx + 1);
    return ary;
}

#<=>(other_ary) ⇒ `-1`, ...

Comparison --- Returns an integer (-1, 0, or +1) if this array is less than, equal to, or greater than other_ary.

Each object in each array is compared (using the <=> operator).

Arrays are compared in an "element-wise" manner; the first two elements that are not equal will determine the return value for the whole comparison.

If all the values are equal, then the return is based on a comparison of the array lengths. Thus, two arrays are "equal" according to Array#<=> if, and only if, they have the same length and the value of each element is equal to the value of the corresponding element in the other array.

[ "a", "a", "c" ]    <=> [ "a", "b", "c" ]   #=> -1
[ 1, 2, 3, 4, 5, 6 ] <=> [ 1, 2 ]            #=> +1

Returns:

(-1, 0, +1, nil)

# File 'array.c', line 3722

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 (v != Qundef) return v;
    len = RARRAY_LEN(ary1) - RARRAY_LEN(ary2);
    if (len == 0) return INT2FIX(0);
    if (len > 0) return INT2FIX(1);
    return INT2FIX(-1);
}

#==(other_ary) ⇒ `Boolean`

Equality --- Two arrays are equal if they contain the same number of elements and if each element is equal to (according to Object#==) the corresponding element in other_ary.

[ "a", "c" ]    == [ "a", "c", 7 ]     #=> false
[ "a", "c", 7 ] == [ "a", "c", 7 ]     #=> true
[ "a", "c", 7 ] == [ "a", "d", "f" ]   #=> false

Returns:

(Boolean)

# File 'array.c', line 3573

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, rb_intern("to_ary"))) {
	    return Qfalse;
	}
	return rb_equal(ary2, ary1);
    }
    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return Qfalse;
    return rb_exec_recursive_paired(recursive_equal, ary1, ary2, ary2);
}

#[](index) ⇒ `Object`^? #[](start, length) ⇒ `nil` #[](range) ⇒ `nil` #slice(index) ⇒ `Object`^? #slice(start, length) ⇒ `nil` #slice(range) ⇒ `nil`

Element Reference --- Returns the element at index, or returns a subarray starting at the start index and continuing for length elements, or returns a subarray specified by range of indices.

Negative indices count backward from the end of the array (-1 is the last element). For start and range cases the starting index is just before an element. Additionally, an empty array is returned when the starting index for an element range is at the end of the array.

Returns nil if the index (or starting index) are out of range.

a = [ "a", "b", "c", "d", "e" ]
a[2] +  a[0] + a[1]    #=> "cab"
a[6]                   #=> nil
a[1, 2]                #=> [ "b", "c" ]
a[1..3]                #=> [ "b", "c", "d" ]
a[4..7]                #=> [ "e" ]
a[6..10]               #=> nil
a[-3, 3]               #=> [ "c", "d", "e" ]
# special cases
a[5]                   #=> nil
a[6, 1]                #=> nil
a[5, 1]                #=> []
a[5..10]               #=> []

Overloads:

#[](index) ⇒ Object^?
Returns:
- (Object, nil)
#[](start, length) ⇒ nil
Returns:
- (nil)
#[](range) ⇒ nil
Returns:
- (nil)
#slice(index) ⇒ Object^?
Returns:
- (Object, nil)
#slice(start, length) ⇒ nil
Returns:
- (nil)
#slice(range) ⇒ nil
Returns:
- (nil)

# File 'array.c', line 1163

VALUE
rb_ary_aref(int argc, VALUE *argv, VALUE ary)
{
    VALUE arg;
    long beg, len;

    if (argc == 2) {
	beg = NUM2LONG(argv[0]);
	len = NUM2LONG(argv[1]);
	if (beg < 0) {
	    beg += RARRAY_LEN(ary);
	}
	return rb_ary_subseq(ary, beg, len);
    }
    if (argc != 1) {
	rb_scan_args(argc, argv, "11", NULL, NULL);
    }
    arg = argv[0];
    /* special case - speeding up */
    if (FIXNUM_P(arg)) {
	return rb_ary_entry(ary, FIX2LONG(arg));
    }
    /* check if idx is Range */
    switch (rb_range_beg_len(arg, &beg, &len, RARRAY_LEN(ary), 0)) {
      case Qfalse:
	break;
      case Qnil:
	return Qnil;
      default:
	return rb_ary_subseq(ary, beg, len);
    }
    return rb_ary_entry(ary, NUM2LONG(arg));
}

#[]=(index) ⇒ `Object` #[]=(start, length) ⇒ `Object`^? #[]=(range) ⇒ `Object`^?

Element Assignment --- Sets the element at index, or replaces a subarray from the start index for length elements, or replaces a subarray specified by the range of indices.

If indices are greater than the current capacity of the array, the array grows automatically. Elements are inserted into the array at start if length is zero.

Negative indices will count backward from the end of the array. For start and range cases the starting index is just before an element.

An IndexError is raised if a negative index points past the beginning of the array.

#assoc(obj) ⇒ `nil`

Searches through an array whose elements are also arrays comparing obj with the first element of each contained array using obj.==.

Returns the first contained array that matches (that is, the first associated array), or nil if no match is found.

#at(index) ⇒ `Object`^?

Returns the element at index. A negative index counts from the end of self. Returns nil if the index is out of range. See also Array#[].

a = [ "a", "b", "c", "d", "e" ]
a.at(0)     #=> "a"
a.at(-1)    #=> "e"

Returns:

(Object, nil)

# File 'array.c', line 1210

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

#bsearch {|x| ... } ⇒ `Object`

By using binary search, finds a value from this array which meets the given condition in O(log n) where n is the size of the array.

You can use this method in two use cases: a find-minimum mode and a find-any mode. In either case, the elements of the array must be monotone (or sorted) with respect to the block.

In find-minimum mode (this is a good choice for typical use case), the block must return true or false, and there must be an index i (0 <= i <= ary.size) so that:

the block returns false for any element whose index is less than i, and
the block returns true for any element whose index is greater than or equal to i.

This method returns the i-th element. If i is equal to ary.size, it returns nil.

ary = [0, 4, 7, 10, 12]
ary.bsearch {|x| x >=   4 } #=> 4
ary.bsearch {|x| x >=   6 } #=> 7
ary.bsearch {|x| x >=  -1 } #=> 0
ary.bsearch {|x| x >= 100 } #=> nil

In find-any mode (this behaves like libc's bsearch(3)), the block must return a number, and there must be two indices i and j (0 <= i <= j <= ary.size) so that:

the block returns a positive number for ary if 0 <= k < i,
the block returns zero for ary if i <= k < j, and
the block returns a negative number for ary if j <= k < ary.size.

Under this condition, this method returns any element whose index is within i...j. If i is equal to j (i.e., there is no element that satisfies the block), this method returns nil.

ary = [0, 4, 7, 10, 12]
# try to find v such that 4 <= v < 8
ary.bsearch {|x| 1 - x / 4 } #=> 4 or 7
# try to find v such that 8 <= v < 10
ary.bsearch {|x| 4 - x / 2 } #=> nil

You must not mix the two modes at a time; the block must always return either true/false, or always return a number. It is undefined which value is actually picked up at each iteration.

Yields:

(x)

# File 'array.c', line 2434

static VALUE
rb_ary_bsearch(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 (FIX2INT(v) == 0) return val;
	    smaller = FIX2INT(v) < 0;
	}
	else if (v == Qtrue) {
	    satisfied = 1;
	    smaller = 1;
	}
	else if (v == Qfalse || v == Qnil) {
	    smaller = 0;
	}
	else if (rb_obj_is_kind_of(v, rb_cNumeric)) {
	    switch (rb_cmpint(rb_funcall(v, id_cmp, 1, INT2FIX(0)), v, INT2FIX(0))) {
		case 0: return val;
		case 1: smaller = 1; break;
		case -1: smaller = 0;
	    }
	}
	else {
	    rb_raise(rb_eTypeError, "wrong argument type %s"
		" (must be numeric, true, false or nil)",
		rb_obj_classname(v));
	}
	if (smaller) {
	    high = mid;
	}
	else {
	    low = mid + 1;
	}
    }
    if (low == RARRAY_LEN(ary)) return Qnil;
    if (!satisfied) return Qnil;
    return rb_ary_entry(ary, low);
}

#clear ⇒ `Object`

Removes all elements from self.

a = [ "a", "b", "c", "d", "e" ]
a.clear    #=> [ ]

# File 'array.c', line 3220

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

#collect {|item| ... } ⇒ `Object` #map {|item| ... } ⇒ `Object` #collect ⇒ `Enumerator` #map ⇒ `Enumerator`

Invokes the given block once for each element of self.

Creates a new array containing the values returned by the block.

See also Enumerable#collect.

If no block is given, an Enumerator is returned instead.

a = [ "a", "b", "c", "d" ]
a.map { |x| x + "!" }   #=> ["a!", "b!", "c!", "d!"]
a                       #=> ["a", "b", "c", "d"]

Overloads:

#collect {|item| ... } ⇒ Object
Yields:
- (item)
#map {|item| ... } ⇒ Object
Yields:
- (item)
#collect ⇒ Enumerator
Returns:
- (Enumerator)
#map ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 2533

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

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_length);
    collect = rb_ary_new2(RARRAY_LEN(ary));
    for (i = 0; i < RARRAY_LEN(ary); i++) {
	rb_ary_push(collect, rb_yield(RARRAY_PTR(ary)[i]));
    }
    return collect;
}

#collect! {|item| ... } ⇒ `Object` #map! {|item| ... } ⇒ `Object` #collect! ⇒ `Enumerator` #map! ⇒ `Enumerator`

Invokes the given block once for each element of self, replacing the element with the value returned by the block.

See also Enumerable#collect.

If no block is given, an Enumerator is returned instead.

a = [ "a", "b", "c", "d" ]
a.map! {|x| x + "!" }
a #=>  [ "a!", "b!", "c!", "d!" ]

Overloads:

#collect! {|item| ... } ⇒ Object
Yields:
- (item)
#map! {|item| ... } ⇒ Object
Yields:
- (item)
#collect! ⇒ Enumerator
Returns:
- (Enumerator)
#map! ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 2567

static VALUE
rb_ary_collect_bang(VALUE ary)
{
    long i;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_length);
    rb_ary_modify(ary);
    for (i = 0; i < RARRAY_LEN(ary); i++) {
	rb_ary_store(ary, i, rb_yield(RARRAY_PTR(ary)[i]));
    }
    return ary;
}

#combination(n) {|c| ... } ⇒ `Object` #combination(n) ⇒ `Enumerator`

When invoked with a block, yields all combinations of length n of elements from the array and then returns the array itself.

The implementation makes no guarantees about the order in which the combinations are yielded.

If no block is given, an Enumerator is returned instead.

Examples:

a = [1, 2, 3, 4]
a.combination(1).to_a  #=> [[1],[2],[3],[4]]
a.combination(2).to_a  #=> [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]
a.combination(3).to_a  #=> [[1,2,3],[1,2,4],[1,3,4],[2,3,4]]
a.combination(4).to_a  #=> [[1,2,3,4]]
a.combination(0).to_a  #=> [[]] # one combination of length 0
a.combination(5).to_a  #=> []   # no combinations of length 5

Overloads:

#combination(n) {|c| ... } ⇒ Object
Yields:
- (c)
#combination(n) ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 4723

static VALUE
rb_ary_combination(VALUE ary, VALUE num)
{
    long n, i, 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 < len; i++) {
	    rb_yield(rb_ary_new3(1, RARRAY_PTR(ary)[i]));
	}
    }
    else {
	volatile VALUE t0 = tmpbuf(n+1, sizeof(long));
	long *stack = (long*)RSTRING_PTR(t0);
	volatile VALUE cc = tmpary(n);
	VALUE *chosen = RARRAY_PTR(cc);
	long lev = 0;

	MEMZERO(stack, long, n);
	stack[0] = -1;
	for (;;) {
	    chosen[lev] = RARRAY_PTR(ary)[stack[lev+1]];
	    for (lev++; lev < n; lev++) {
		chosen[lev] = RARRAY_PTR(ary)[stack[lev+1] = stack[lev]+1];
	    }
	    rb_yield(rb_ary_new4(n, chosen));
	    if (RBASIC(t0)->klass) {
		rb_raise(rb_eRuntimeError, "combination reentered");
	    }
	    do {
		if (lev == 0) goto done;
		stack[lev--]++;
	    } while (stack[lev+1]+n == len+lev+1);
	}
    done:
	tmpbuf_discard(t0);
	tmpary_discard(cc);
    }
    return ary;
}

#compact ⇒ `Object`

Returns a copy of self with all nil elements removed.

[ "a", nil, "b", nil, "c", nil ].compact
                  #=> [ "a", "b", "c" ]

# File 'array.c', line 4081

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

#compact! ⇒ `nil`

Removes nil elements from the array.

Returns nil if no changes were made, otherwise returns the array.

[ "a", nil, "b", nil, "c" ].compact! #=> [ "a", "b", "c" ]
[ "a", "b", "c" ].compact!           #=> nil

Returns:

(nil)

# File 'array.c', line 4045

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

    rb_ary_modify(ary);
    p = t = RARRAY_PTR(ary);
    end = p + RARRAY_LEN(ary);

    while (t < end) {
	if (NIL_P(*t)) t++;
	else *p++ = *t++;
    }
    n = p - RARRAY_PTR(ary);
    if (RARRAY_LEN(ary) == n) {
	return Qnil;
    }
    ARY_SET_LEN(ary, n);
    if (n * 2 < ARY_CAPA(ary) && ARY_DEFAULT_SIZE * 2 < ARY_CAPA(ary)) {
	ary_resize_capa(ary, n * 2);
    }

    return ary;
}

#concat(other_ary) ⇒ `Object`

Appends the elements of other_ary to self.

[ "a", "b" ].concat( ["c", "d"] ) #=> [ "a", "b", "c", "d" ]
a = [ 1, 2, 3 ]
a.concat( [ 4, 5 ] )
a                                 #=> [ 1, 2, 3, 4, 5 ]

#count ⇒ `Integer` #count(obj) ⇒ `Integer` #count {|item| ... } ⇒ `Integer`

Returns the number of elements.

If an argument is given, counts the number of elements which equal obj using ===.

If a block is given, counts the number of elements for which the block returns a true value.

ary = [1, 2, 4, 2]
ary.count                  #=> 4
ary.count(2)               #=> 2
ary.count { |x| x%2 == 0 } #=> 3

Overloads:

#count ⇒ Integer
Returns:
- (Integer)
#count(obj) ⇒ Integer
Returns:
- (Integer)
#count {|item| ... } ⇒ Integer
Yields:
- (item)
Returns:
- (Integer)

# File 'array.c', line 4110

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

    if (argc == 0) {
	VALUE *p, *pend;

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

	for (p = RARRAY_PTR(ary), pend = p + RARRAY_LEN(ary); p < pend; p++) {
	    if (RTEST(rb_yield(*p))) n++;
	}
    }
    else {
	VALUE obj, *p, *pend;

	rb_scan_args(argc, argv, "1", &obj);
	if (rb_block_given_p()) {
	    rb_warn("given block not used");
	}
	for (p = RARRAY_PTR(ary), pend = p + RARRAY_LEN(ary); p < pend; p++) {
	    if (rb_equal(*p, obj)) n++;
	}
    }

    return LONG2NUM(n);
}

#cycle(n = nil) {|obj| ... } ⇒ `nil` #cycle(n = nil) ⇒ `Enumerator`

Calls the given block for each element n times or forever if nil is given.

Does nothing if a non-positive number is given or the array is empty.

Returns nil if the loop has finished without getting interrupted.

If no block is given, an Enumerator is returned instead.

a = ["a", "b", "c"]
a.cycle { |x| puts x }     # print, a, b, c, a, b, c,.. forever.
a.cycle(2) { |x| puts x }  # print, a, b, c, a, b, c.

Overloads:

#cycle(n = nil) {|obj| ... } ⇒ nil
Yields:
- (obj)
Returns:
- (nil)
#cycle(n = nil) ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 4510

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

    rb_scan_args(argc, argv, "01", &nv);

    RETURN_SIZED_ENUMERATOR(ary, argc, argv, rb_ary_cycle_size);
    if (NIL_P(nv)) {
        n = -1;
    }
    else {
        n = NUM2LONG(nv);
        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_PTR(ary)[i]);
        }
    }
    return Qnil;
}

#delete(obj) ⇒ `nil` #delete(obj) { ... } ⇒ `Object`

Deletes all items from self that are equal to obj.

Returns the last deleted item, or nil if no matching item is found.

If the optional code block is given, the result of the block is returned if the item is not found. (To remove nil elements and get an informative return value, use Array#compact!)

a = [ "a", "b", "b", "b", "c" ]
a.delete("b")                   #=> "b"
a                               #=> ["a", "c"]
a.delete("z")                   #=> nil
a.delete("z") { "not found" }   #=> "not found"

Overloads:

#delete(obj) ⇒ nil
Returns:
- (nil)
#delete(obj) { ... } ⇒ Object
Yields:

# File 'array.c', line 2760

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_PTR(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);

    return v;
}

#delete_at(index) ⇒ `Object`^?

Deletes the element at the specified index, returning that element, or nil if the index is out of range.

#delete_if {|item| ... } ⇒ `Object` #delete_if ⇒ `Enumerator`

Deletes every element of self for which block evaluates to true.

The array is changed instantly every time the block is called, not after the iteration is over.

#drop(n) ⇒ `Object`

Drops first n elements from ary and returns the rest of the elements in an array.

If a negative number is given, raises an ArgumentError.

#drop_while {|arr| ... } ⇒ `Object` #drop_while ⇒ `Enumerator`

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.

If no block is given, an Enumerator is returned instead.

#each {|item| ... } ⇒ `Object` #each ⇒ `Enumerator`

Calls the given block once for each element in self, passing that element as a parameter.

An Enumerator is returned if no block is given.

a = [ "a", "b", "c" ]
a.each {|x| print x, " -- " }

produces:

a -- b -- c --

Overloads:

#each {|item| ... } ⇒ Object
Yields:
- (item)
#each ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 1670

VALUE
rb_ary_each(VALUE array)
{
    long i;
    volatile VALUE ary = array;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_length);
    for (i=0; i<RARRAY_LEN(ary); i++) {
	rb_yield(RARRAY_PTR(ary)[i]);
    }
    return ary;
}

#each_index {|index| ... } ⇒ `Object` #each_index ⇒ `Enumerator`

Same as Array#each, but passes the index of the element instead of the element itself.

An Enumerator is returned if no block is given.

a = [ "a", "b", "c" ]
a.each_index {|x| print x, " -- " }

produces:

0 -- 1 -- 2 --

Overloads:

#each_index {|index| ... } ⇒ Object
Yields:
- (index)
#each_index ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 1701

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

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

#empty? ⇒ `Boolean`

Returns true if self contains no elements.

[].empty?   #=> true

Returns:

(Boolean)

Returns:

(Boolean)

# File 'array.c', line 1770

static VALUE
rb_ary_empty_p(VALUE ary)
{
    if (RARRAY_LEN(ary) == 0)
	return Qtrue;
    return Qfalse;
}

#eql?(other) ⇒ `Boolean`

Returns true if self and other are the same object, or are both arrays with the same content.

Returns:

(Boolean)

Returns:

(Boolean)

# File 'array.c', line 3608

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;
    return rb_exec_recursive_paired(recursive_eql, ary1, ary2, ary2);
}

#fetch(index) ⇒ `Object` #fetch(index, default) ⇒ `Object` #fetch(index) {|index| ... } ⇒ `Object`

Tries to return the element at position index, but throws an IndexError exception if the referenced index lies outside of the array bounds. This error can be prevented by supplying a second argument, which will act as a default value.

Alternatively, if a block is given it will only be executed when an invalid index is referenced. Negative values of index count from the end of the array.

a = [ 11, 22, 33, 44 ]
a.fetch(1)               #=> 22
a.fetch(-1)              #=> 44
a.fetch(4, 'cat')        #=> "cat"
a.fetch(100) { |i| puts "#{i} is out of bounds" }
                         #=> "100 is out of bounds"

Overloads:

#fetch(index) ⇒ Object
Returns:
- (Object)
#fetch(index, default) ⇒ Object
Returns:
- (Object)
#fetch(index) {|index| ... } ⇒ Object
Yields:
- (index)
Returns:
- (Object)

# File 'array.c', line 1293

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_PTR(ary)[idx];
}

#fill(obj) ⇒ `Object` #fill(obj, start[, length]) ⇒ `Object` #fill(obj, range) ⇒ `Object` #fill {|index| ... } ⇒ `Object` #fill(start[, length]) {|index| ... } ⇒ `Object` #fill(range) {|index| ... } ⇒ `Object`

The first three forms set the selected elements of self (which may be the entire array) to obj.

A start of nil is equivalent to zero.

A length of nil is equivalent to the length of the array.

The last three forms fill the array with the value of the given block, which is passed the absolute index of each element to be filled.

Negative values of start count from the end of the array, where -1 is the last element.

a = [ "a", "b", "c", "d" ]
a.fill("x")              #=> ["x", "x", "x", "x"]
a.fill("z", 2, 2)        #=> ["x", "x", "z", "z"]
a.fill("y", 0..1)        #=> ["y", "y", "z", "z"]
a.fill { |i| i*i }       #=> [0, 1, 4, 9]
a.fill(-2) { |i| i*i*i } #=> [0, 1, 8, 27]

Overloads:

#fill {|index| ... } ⇒ Object
Yields:
- (index)
#fill(start[, length]) {|index| ... } ⇒ Object
Yields:
- (index)
#fill(range) {|index| ... } ⇒ Object
Yields:
- (index)

# File 'array.c', line 3267

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

    if (rb_block_given_p()) {
	block_p = TRUE;
	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);
	}
	rb_mem_clear(RARRAY_PTR(ary) + RARRAY_LEN(ary), end - RARRAY_LEN(ary));
	ARY_SET_LEN(ary, end);
    }

    if (block_p) {
	VALUE v;
	long i;

	for (i=beg; i<end; i++) {
	    v = rb_yield(LONG2NUM(i));
	    if (i>=RARRAY_LEN(ary)) break;
	    RARRAY_PTR(ary)[i] = v;
	}
    }
    else {
	p = RARRAY_PTR(ary) + beg;
	pend = p + len;
	while (p < pend) {
	    *p++ = item;
	}
    }
    return ary;
}

#index(obj) ⇒ `Integer`^? #index {|item| ... } ⇒ `Integer`^? #index ⇒ `Enumerator`

Returns the index of the first object in ary such that the object is == to obj.

If a block is given instead of an argument, returns the index of the first object for which the block returns true. Returns nil if no match is found.

#first ⇒ `Object`^? #first(n) ⇒ `Object`

Returns the first element, or the first n elements, of the array. If the array is empty, the first form returns nil, and the second form returns an empty array. See also Array#last for the opposite effect.

a = [ "q", "r", "s", "t" ]
a.first     #=> "q"
a.first(2)  #=> ["q", "r"]

Overloads:

#first ⇒ Object^?
Returns:
- (Object, nil)

# File 'array.c', line 1231

static VALUE
rb_ary_first(int argc, VALUE *argv, VALUE ary)
{
    if (argc == 0) {
	if (RARRAY_LEN(ary) == 0) return Qnil;
	return RARRAY_PTR(ary)[0];
    }
    else {
	return ary_take_first_or_last(argc, argv, ary, ARY_TAKE_FIRST);
    }
}

#flatten ⇒ `Object` #flatten(level) ⇒ `Object`

Returns a new array that is a one-dimensional flattening of self (recursively).

That is, for every element that is an array, extract its elements into the new array.

The optional level argument determines the level of recursion to flatten.

s = [ 1, 2, 3 ]           #=> [1, 2, 3]
t = [ 4, 5, 6, [7, 8] ]   #=> [4, 5, 6, [7, 8]]
a = [ s, t, 9, 10 ]       #=> [[1, 2, 3], [4, 5, 6, [7, 8]], 9, 10]
a.flatten                 #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a = [ 1, 2, [3, [4, 5] ] ]
a.flatten(1)              #=> [1, 2, 3, [4, 5]]

# File 'array.c', line 4259

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

    rb_scan_args(argc, argv, "01", &lv);
    if (!NIL_P(lv)) level = NUM2INT(lv);
    if (level == 0) return ary_make_shared_copy(ary);

    result = flatten(ary, level, &mod);
    OBJ_INFECT(result, ary);

    return result;
}

#flatten! ⇒ `nil` #flatten!(level) ⇒ `nil`

Flattens self in place.

Returns nil if no modifications were made (i.e., the array contains no subarrays.)

The optional level argument determines the level of recursion to flatten.

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

Overloads:

#flatten! ⇒ nil
Returns:
- (nil)
#flatten!(level) ⇒ nil
Returns:
- (nil)

# File 'array.c', line 4214

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

    rb_scan_args(argc, argv, "01", &lv);
    rb_ary_modify_check(ary);
    if (!NIL_P(lv)) level = NUM2INT(lv);
    if (level == 0) return Qnil;

    result = flatten(ary, level, &mod);
    if (mod == 0) {
	ary_discard(result);
	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;
}

#frozen? ⇒ `Boolean`

Return true if this array is frozen (or temporarily frozen while being sorted). See also Object#frozen?

Returns:

(Boolean)

Returns:

(Boolean)

# File 'array.c', line 344

static VALUE
rb_ary_frozen_p(VALUE ary)
{
    if (OBJ_FROZEN(ary)) return Qtrue;
    return Qfalse;
}

#hash ⇒ `Fixnum`

Compute a hash-code for this array.

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

Returns:

(Fixnum)

# File 'array.c', line 3648

static VALUE
rb_ary_hash(VALUE ary)
{
    return rb_exec_recursive_outer(recursive_hash, ary, 0);
}

#include?(object) ⇒ `Boolean`

Returns true if the given object is present in self (that is, if any object == object), otherwise returns false.

a = [ "a", "b", "c" ]
a.include?("b")   #=> true
a.include?("z")   #=> false

Returns:

(Boolean)

Returns:

(Boolean)

# File 'array.c', line 3666

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

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

#index(obj) ⇒ `Integer`^? #index {|item| ... } ⇒ `Integer`^? #index ⇒ `Enumerator`

Returns the index of the first object in ary such that the object is == to obj.

If a block is given instead of an argument, returns the index of the first object for which the block returns true. Returns nil if no match is found.

#replace(other_ary) ⇒ `Object`

Replaces the contents of self with the contents of other_ary, truncating or expanding if necessary.

a = [ "a", "b", "c", "d", "e" ]
a.replace([ "x", "y", "z" ])   #=> ["x", "y", "z"]
a                              #=> ["x", "y", "z"]

# File 'array.c', line 3168

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

    if (RARRAY_LEN(orig) <= RARRAY_EMBED_LEN_MAX) {
        VALUE *ptr;
        VALUE shared = 0;

        if (ARY_OWNS_HEAP_P(copy)) {
            xfree(RARRAY_PTR(copy));
        }
        else if (ARY_SHARED_P(copy)) {
            shared = ARY_SHARED(copy);
            FL_UNSET_SHARED(copy);
        }
        FL_SET_EMBED(copy);
        ptr = RARRAY_PTR(orig);
        MEMCPY(RARRAY_PTR(copy), ptr, VALUE, RARRAY_LEN(orig));
        if (shared) {
            rb_ary_decrement_share(shared);
        }
        ARY_SET_LEN(copy, RARRAY_LEN(orig));
    }
    else {
        VALUE shared = ary_make_shared(orig);
        if (ARY_OWNS_HEAP_P(copy)) {
            xfree(RARRAY_PTR(copy));
        }
        else {
            rb_ary_unshare_safe(copy);
        }
        FL_UNSET_EMBED(copy);
        ARY_SET_PTR(copy, RARRAY_PTR(orig));
        ARY_SET_LEN(copy, RARRAY_LEN(orig));
        rb_ary_set_shared(copy, shared);
    }
    return copy;
}

#insert(index, obj...) ⇒ `Object`

Inserts the given values before the element with the given index.

Negative indices count backwards from the end of the array, where -1 is the last element.

a = %w{ a b c d }
a.insert(2, 99)         #=> ["a", "b", 99, "c", "d"]
a.insert(-2, 1, 2, 3)   #=> ["a", "b", 99, "c", 1, 2, 3, "d"]

# File 'array.c', line 1630

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);
    if (argc == 1) return ary;
    pos = NUM2LONG(argv[0]);
    if (pos == -1) {
	pos = RARRAY_LEN(ary);
    }
    if (pos < 0) {
	pos++;
    }
    rb_ary_splice(ary, pos, 0, rb_ary_new4(argc - 1, argv + 1));
    return ary;
}

#inspect ⇒ `String` #to_s ⇒ `String` Also known as: to_s

Creates a string representation of self.

[ "a", "b", "c" ].to_s     #=> "[\"a\", \"b\", \"c\"]"

Overloads:

#inspect ⇒ String
Returns:
- (String)
#to_s ⇒ String
Returns:
- (String)

# File 'array.c', line 1987

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);
}

#join(separator = $,) ⇒ `String`

Returns a string created by converting each element of the array to a string, separated by the given separator. If the separator is nil, it uses current $,. If both the separator and $, are nil, it uses empty string.

[ "a", "b", "c" ].join        #=> "abc"
[ "a", "b", "c" ].join("-")   #=> "a-b-c"

Returns:

(String)

# File 'array.c', line 1942

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

    rb_scan_args(argc, argv, "01", &sep);
    if (NIL_P(sep)) sep = rb_output_fs;

    return rb_ary_join(ary, sep);
}

#keep_if {|item| ... } ⇒ `Object` #keep_if ⇒ `Enumerator`

Deletes every element of self for which the given block evaluates to false.

#last ⇒ `Object`^? #last(n) ⇒ `Object`

Returns the last element(s) of self. If the array is empty, the first form returns nil.

See also Array#first for the opposite effect.

a = [ "w", "x", "y", "z" ]
a.last     #=> "z"
a.last(2)  #=> ["y", "z"]

Overloads:

#last ⇒ Object^?
Returns:
- (Object, nil)

# File 'array.c', line 1258

VALUE
rb_ary_last(int argc, VALUE *argv, VALUE ary)
{
    if (argc == 0) {
	if (RARRAY_LEN(ary) == 0) return Qnil;
	return RARRAY_PTR(ary)[RARRAY_LEN(ary)-1];
    }
    else {
	return ary_take_first_or_last(argc, argv, ary, ARY_TAKE_LAST);
    }
}

#length ⇒ `Integer` Also known as: size

Returns the number of elements in self. May be zero.

[ 1, 2, 3, 4, 5 ].length   #=> 5
[].length                  #=> 0

Returns:

(Integer)

# File 'array.c', line 1754

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

#collect {|item| ... } ⇒ `Object` #map {|item| ... } ⇒ `Object` #collect ⇒ `Enumerator` #map ⇒ `Enumerator`

Invokes the given block once for each element of self.

Creates a new array containing the values returned by the block.

See also Enumerable#collect.

If no block is given, an Enumerator is returned instead.

a = [ "a", "b", "c", "d" ]
a.map { |x| x + "!" }   #=> ["a!", "b!", "c!", "d!"]
a                       #=> ["a", "b", "c", "d"]

Overloads:

#collect {|item| ... } ⇒ Object
Yields:
- (item)
#map {|item| ... } ⇒ Object
Yields:
- (item)
#collect ⇒ Enumerator
Returns:
- (Enumerator)
#map ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 2533

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

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_length);
    collect = rb_ary_new2(RARRAY_LEN(ary));
    for (i = 0; i < RARRAY_LEN(ary); i++) {
	rb_ary_push(collect, rb_yield(RARRAY_PTR(ary)[i]));
    }
    return collect;
}

#collect! {|item| ... } ⇒ `Object` #map! {|item| ... } ⇒ `Object` #collect! ⇒ `Enumerator` #map! ⇒ `Enumerator`

Invokes the given block once for each element of self, replacing the element with the value returned by the block.

See also Enumerable#collect.

If no block is given, an Enumerator is returned instead.

a = [ "a", "b", "c", "d" ]
a.map! {|x| x + "!" }
a #=>  [ "a!", "b!", "c!", "d!" ]

Overloads:

#collect! {|item| ... } ⇒ Object
Yields:
- (item)
#map! {|item| ... } ⇒ Object
Yields:
- (item)
#collect! ⇒ Enumerator
Returns:
- (Enumerator)
#map! ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 2567

static VALUE
rb_ary_collect_bang(VALUE ary)
{
    long i;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_length);
    rb_ary_modify(ary);
    for (i = 0; i < RARRAY_LEN(ary); i++) {
	rb_ary_store(ary, i, rb_yield(RARRAY_PTR(ary)[i]));
    }
    return ary;
}

#pack ⇒ `Object`

Packs the contents of arr into a binary sequence according to the directives in aTemplateString (see the table below) Directives "A," "a," and "Z" may be followed by a count, which gives the width of the resulting field. The remaining directives also may take a count, indicating the number of array elements to convert. If the count is an asterisk ("*"), all remaining array elements will be converted. Any of the directives "sSiIlL" may be followed by an underscore ("_") or exclamation mark ("!") to use the underlying platform's native size for the specified type; otherwise, they use a platform-independent size. Spaces are ignored in the template string. See also String#unpack.

a = [ "a", "b", "c" ]
n = [ 65, 66, 67 ]
a.pack("A3A3A3")   #=> "a  b  c  "
a.pack("a3a3a3")   #=> "a\000\000b\000\000c\000\000"
n.pack("ccc")      #=> "ABC"

Directives for pack.

Integer      | Array   |
Directive    | Element | Meaning
---------------------------------------------------------------------------
   C         | Integer | 8-bit unsigned (unsigned char)
   S         | Integer | 16-bit unsigned, native endian (uint16_t)
   L         | Integer | 32-bit unsigned, native endian (uint32_t)
   Q         | Integer | 64-bit unsigned, native endian (uint64_t)
             |         |
   c         | Integer | 8-bit signed (signed char)
   s         | Integer | 16-bit signed, native endian (int16_t)
   l         | Integer | 32-bit signed, native endian (int32_t)
   q         | Integer | 64-bit signed, native endian (int64_t)
             |         |
   S_, S!    | Integer | unsigned short, native endian
   I, I_, I! | Integer | unsigned int, native endian
   L_, L!    | Integer | unsigned long, native endian
             |         |
   s_, s!    | Integer | signed short, native endian
   i, i_, i! | Integer | signed int, native endian
   l_, l!    | Integer | signed long, native endian
             |         |
   S> L> Q>  | Integer | same as the directives without ">" except
   s> l> q>  |         | big endian
   S!> I!>   |         | (available since Ruby 1.9.3)
   L!>       |         | "S>" is same as "n"
   s!> i!>   |         | "L>" is same as "N"
   l!>       |         |
             |         |
   S< L< Q<  | Integer | same as the directives without "<" except
   s< l< q<  |         | little endian
   S!< I!<   |         | (available since Ruby 1.9.3)
   L!<       |         | "S<" is same as "v"
   s!< i!<   |         | "L<" is same as "V"
   l!<       |         |
             |         |
   n         | Integer | 16-bit unsigned, network (big-endian) byte order
   N         | Integer | 32-bit unsigned, network (big-endian) byte order
   v         | Integer | 16-bit unsigned, VAX (little-endian) byte order
   V         | Integer | 32-bit unsigned, VAX (little-endian) byte order
             |         |
   U         | Integer | UTF-8 character
   w         | Integer | BER-compressed integer

Float        |         |
Directive    |         | Meaning
---------------------------------------------------------------------------
   D, d      | Float   | double-precision, native format
   F, f      | Float   | single-precision, native format
   E         | Float   | double-precision, little-endian byte order
   e         | Float   | single-precision, little-endian byte order
   G         | Float   | double-precision, network (big-endian) byte order
   g         | Float   | single-precision, network (big-endian) byte order

String       |         |
Directive    |         | Meaning
---------------------------------------------------------------------------
   A         | String  | arbitrary binary string (space padded, count is width)
   a         | String  | arbitrary binary string (null padded, count is width)
   Z         | String  | same as ``a'', except that null is added with *
   B         | String  | bit string (MSB first)
   b         | String  | bit string (LSB first)
   H         | String  | hex string (high nibble first)
   h         | String  | hex string (low nibble first)
   u         | String  | UU-encoded string
   M         | String  | quoted printable, MIME encoding (see RFC2045)
   m         | String  | base64 encoded string (see RFC 2045, count is width)
             |         | (if count is 0, no line feed are added, see RFC 4648)
   P         | String  | pointer to a structure (fixed-length string)
   p         | String  | pointer to a null-terminated string

Misc.        |         |
Directive    |         | Meaning
---------------------------------------------------------------------------
   @         | ---     | moves to absolute position
   X         | ---     | back up a byte
   x         | ---     | null byte

# File 'pack.c', line 368

static VALUE
pack_pack(VALUE ary, VALUE fmt)
{
    static const char nul10[] = "\0\0\0\0\0\0\0\0\0\0";
    static const char spc10[] = "          ";
    const char *p, *pend;
    VALUE res, from, associates = 0;
    char type;
    long items, len, idx, plen;
    const char *ptr;
    int enc_info = 1;		/* 0 - BINARY, 1 - US-ASCII, 2 - UTF-8 */
#ifdef NATINT_PACK
    int natint;		/* native integer */
#endif
    int integer_size, bigendian_p;

    StringValue(fmt);
    p = RSTRING_PTR(fmt);
    pend = p + RSTRING_LEN(fmt);
    res = rb_str_buf_new(0);

    items = RARRAY_LEN(ary);
    idx = 0;

#define TOO_FEW (rb_raise(rb_eArgError, toofew), 0)
#define THISFROM (items > 0 ? RARRAY_PTR(ary)[idx] : TOO_FEW)
#define NEXTFROM (items-- > 0 ? RARRAY_PTR(ary)[idx++] : TOO_FEW)

    while (p < pend) {
	int explicit_endian = 0;
	if (RSTRING_PTR(fmt) + RSTRING_LEN(fmt) != pend) {
	    rb_raise(rb_eRuntimeError, "format string modified");
	}
	type = *p++;		/* get data type */
#ifdef NATINT_PACK
	natint = 0;
#endif

	if (ISSPACE(type)) continue;
	if (type == '#') {
	    while ((p < pend) && (*p != '\n')) {
		p++;
	    }
	    continue;
	}

	{
	    static const char natstr[] = "sSiIlL";
	    static const char endstr[] = "sSiIlLqQ";

          modifiers:
	    switch (*p) {
	      case '_':
	      case '!':
		if (strchr(natstr, type)) {
#ifdef NATINT_PACK
		    natint = 1;
#endif
		    p++;
		}
		else {
		    rb_raise(rb_eArgError, "'%c' allowed only after types %s", *p, natstr);
		}
		goto modifiers;

	      case '<':
	      case '>':
		if (!strchr(endstr, type)) {
		    rb_raise(rb_eArgError, "'%c' allowed only after types %s", *p, endstr);
		}
		if (explicit_endian) {
		    rb_raise(rb_eRangeError, "Can't use both '<' and '>'");
		}
		explicit_endian = *p++;
		goto modifiers;
	    }
	}

	if (*p == '*') {	/* set data length */
	    len = strchr("@Xxu", type) ? 0
                : strchr("PMm", type) ? 1
                : items;
	    p++;
	}
	else if (ISDIGIT(*p)) {
	    errno = 0;
	    len = STRTOUL(p, (char**)&p, 10);
	    if (errno) {
		rb_raise(rb_eRangeError, "pack length too big");
	    }
	}
	else {
	    len = 1;
	}

	switch (type) {
	  case 'U':
	    /* if encoding is US-ASCII, upgrade to UTF-8 */
	    if (enc_info == 1) enc_info = 2;
	    break;
	  case 'm': case 'M': case 'u':
	    /* keep US-ASCII (do nothing) */
	    break;
	  default:
	    /* fall back to BINARY */
	    enc_info = 0;
	    break;
	}
	switch (type) {
	  case 'A': case 'a': case 'Z':
	  case 'B': case 'b':
	  case 'H': case 'h':
	    from = NEXTFROM;
	    if (NIL_P(from)) {
		ptr = "";
		plen = 0;
	    }
	    else {
		StringValue(from);
		ptr = RSTRING_PTR(from);
		plen = RSTRING_LEN(from);
		OBJ_INFECT(res, from);
	    }

	    if (p[-1] == '*')
		len = plen;

	    switch (type) {
	      case 'a':		/* arbitrary binary string (null padded)  */
	      case 'A':         /* arbitrary binary string (ASCII space padded) */
	      case 'Z':         /* null terminated string  */
		if (plen >= len) {
		    rb_str_buf_cat(res, ptr, len);
		    if (p[-1] == '*' && type == 'Z')
			rb_str_buf_cat(res, nul10, 1);
		}
		else {
		    rb_str_buf_cat(res, ptr, plen);
		    len -= plen;
		    while (len >= 10) {
			rb_str_buf_cat(res, (type == 'A')?spc10:nul10, 10);
			len -= 10;
		    }
		    rb_str_buf_cat(res, (type == 'A')?spc10:nul10, len);
		}
		break;

#define castchar(from) (char)((from) & 0xff)

	      case 'b':		/* bit string (ascending) */
		{
		    int byte = 0;
		    long i, j = 0;

		    if (len > plen) {
			j = (len - plen + 1)/2;
			len = plen;
		    }
		    for (i=0; i++ < len; ptr++) {
			if (*ptr & 1)
			    byte |= 128;
			if (i & 7)
			    byte >>= 1;
			else {
			    char c = castchar(byte);
			    rb_str_buf_cat(res, &c, 1);
			    byte = 0;
			}
		    }
		    if (len & 7) {
			char c;
			byte >>= 7 - (len & 7);
			c = castchar(byte);
			rb_str_buf_cat(res, &c, 1);
		    }
		    len = j;
		    goto grow;
		}
		break;

	      case 'B':		/* bit string (descending) */
		{
		    int byte = 0;
		    long i, j = 0;

		    if (len > plen) {
			j = (len - plen + 1)/2;
			len = plen;
		    }
		    for (i=0; i++ < len; ptr++) {
			byte |= *ptr & 1;
			if (i & 7)
			    byte <<= 1;
			else {
			    char c = castchar(byte);
			    rb_str_buf_cat(res, &c, 1);
			    byte = 0;
			}
		    }
		    if (len & 7) {
			char c;
			byte <<= 7 - (len & 7);
			c = castchar(byte);
			rb_str_buf_cat(res, &c, 1);
		    }
		    len = j;
		    goto grow;
		}
		break;

	      case 'h':		/* hex string (low nibble first) */
		{
		    int byte = 0;
		    long i, j = 0;

		    if (len > plen) {
			j = (len + 1) / 2 - (plen + 1) / 2;
			len = plen;
		    }
		    for (i=0; i++ < len; ptr++) {
			if (ISALPHA(*ptr))
			    byte |= (((*ptr & 15) + 9) & 15) << 4;
			else
			    byte |= (*ptr & 15) << 4;
			if (i & 1)
			    byte >>= 4;
			else {
			    char c = castchar(byte);
			    rb_str_buf_cat(res, &c, 1);
			    byte = 0;
			}
		    }
		    if (len & 1) {
			char c = castchar(byte);
			rb_str_buf_cat(res, &c, 1);
		    }
		    len = j;
		    goto grow;
		}
		break;

	      case 'H':		/* hex string (high nibble first) */
		{
		    int byte = 0;
		    long i, j = 0;

		    if (len > plen) {
			j = (len + 1) / 2 - (plen + 1) / 2;
			len = plen;
		    }
		    for (i=0; i++ < len; ptr++) {
			if (ISALPHA(*ptr))
			    byte |= ((*ptr & 15) + 9) & 15;
			else
			    byte |= *ptr & 15;
			if (i & 1)
			    byte <<= 4;
			else {
			    char c = castchar(byte);
			    rb_str_buf_cat(res, &c, 1);
			    byte = 0;
			}
		    }
		    if (len & 1) {
			char c = castchar(byte);
			rb_str_buf_cat(res, &c, 1);
		    }
		    len = j;
		    goto grow;
		}
		break;
	    }
	    break;

	  case 'c':		/* signed char */
	  case 'C':		/* unsigned char */
	    while (len-- > 0) {
		char c;

		from = NEXTFROM;
		c = (char)num2i32(from);
		rb_str_buf_cat(res, &c, sizeof(char));
	    }
	    break;

	  case 's':		/* signed short */
            integer_size = NATINT_LEN(short, 2);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'S':		/* unsigned short */
            integer_size = NATINT_LEN(short, 2);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'i':		/* signed int */
            integer_size = (int)sizeof(int);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'I':		/* unsigned int */
            integer_size = (int)sizeof(int);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'l':		/* signed long */
            integer_size = NATINT_LEN(long, 4);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'L':		/* unsigned long */
            integer_size = NATINT_LEN(long, 4);
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'q':		/* signed quad (64bit) int */
	    integer_size = 8;
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'Q':		/* unsigned quad (64bit) int */
	    integer_size = 8;
            bigendian_p = BIGENDIAN_P();
            goto pack_integer;

	  case 'n':		/* unsigned short (network byte-order)  */
            integer_size = 2;
            bigendian_p = 1;
            goto pack_integer;

	  case 'N':		/* unsigned long (network byte-order) */
            integer_size = 4;
            bigendian_p = 1;
            goto pack_integer;

	  case 'v':		/* unsigned short (VAX byte-order) */
            integer_size = 2;
            bigendian_p = 0;
            goto pack_integer;

	  case 'V':		/* unsigned long (VAX byte-order) */
            integer_size = 4;
            bigendian_p = 0;
            goto pack_integer;

          pack_integer:
	    if (explicit_endian) {
		bigendian_p = explicit_endian == '>';
	    }

            switch (integer_size) {
#if defined(HAVE_INT16_T) && !defined(FORCE_BIG_PACK)
              case SIZEOF_INT16_T:
		while (len-- > 0) {
                    union {
                        int16_t i;
                        char a[sizeof(int16_t)];
                    } v;

		    from = NEXTFROM;
		    v.i = (int16_t)num2i32(from);
		    if (bigendian_p != BIGENDIAN_P()) v.i = swap16(v.i);
		    rb_str_buf_cat(res, v.a, sizeof(int16_t));
		}
		break;
#endif

#if defined(HAVE_INT32_T) && !defined(FORCE_BIG_PACK)
              case SIZEOF_INT32_T:
		while (len-- > 0) {
		    union {
                        int32_t i;
                        char a[sizeof(int32_t)];
                    } v;

		    from = NEXTFROM;
		    v.i = (int32_t)num2i32(from);
		    if (bigendian_p != BIGENDIAN_P()) v.i = swap32(v.i);
		    rb_str_buf_cat(res, v.a, sizeof(int32_t));
		}
		break;
#endif

#if defined(HAVE_INT64_T) && SIZEOF_LONG == SIZEOF_INT64_T && !defined(FORCE_BIG_PACK)
              case SIZEOF_INT64_T:
		while (len-- > 0) {
		    union {
                        int64_t i;
                        char a[sizeof(int64_t)];
                    } v;

		    from = NEXTFROM;
		    v.i = num2i32(from); /* can return 64bit value if SIZEOF_LONG == SIZEOF_INT64_T */
		    if (bigendian_p != BIGENDIAN_P()) v.i = swap64(v.i);
		    rb_str_buf_cat(res, v.a, sizeof(int64_t));
		}
		break;
#endif

	      default:
                if (integer_size > MAX_INTEGER_PACK_SIZE)
                    rb_bug("unexpected intger size for pack: %d", integer_size);
                while (len-- > 0) {
                    union {
                        unsigned long i[(MAX_INTEGER_PACK_SIZE+SIZEOF_LONG-1)/SIZEOF_LONG];
                        char a[(MAX_INTEGER_PACK_SIZE+SIZEOF_LONG-1)/SIZEOF_LONG*SIZEOF_LONG];
                    } v;
                    int num_longs = (integer_size+SIZEOF_LONG-1)/SIZEOF_LONG;
                    int i;

                    from = NEXTFROM;
                    rb_big_pack(from, v.i, num_longs);
                    if (bigendian_p) {
                        for (i = 0; i < num_longs/2; i++) {
                            unsigned long t = v.i[i];
                            v.i[i] = v.i[num_longs-1-i];
                            v.i[num_longs-1-i] = t;
                        }
                    }
		    if (bigendian_p != BIGENDIAN_P()) {
                        for (i = 0; i < num_longs; i++)
                            v.i[i] = swapl(v.i[i]);
                    }
                    rb_str_buf_cat(res,
                                   bigendian_p ?
                                     v.a + sizeof(long)*num_longs - integer_size :
                                     v.a,
                                   integer_size);
                }
                break;
	    }
	    break;

	  case 'f':		/* single precision float in native format */
	  case 'F':		/* ditto */
	    while (len-- > 0) {
		float f;

		from = NEXTFROM;
		f = (float)RFLOAT_VALUE(rb_to_float(from));
		rb_str_buf_cat(res, (char*)&f, sizeof(float));
	    }
	    break;

	  case 'e':		/* single precision float in VAX byte-order */
	    while (len-- > 0) {
		float f;
		FLOAT_CONVWITH(ftmp);

		from = NEXTFROM;
		f = (float)RFLOAT_VALUE(rb_to_float(from));
		f = HTOVF(f,ftmp);
		rb_str_buf_cat(res, (char*)&f, sizeof(float));
	    }
	    break;

	  case 'E':		/* double precision float in VAX byte-order */
	    while (len-- > 0) {
		double d;
		DOUBLE_CONVWITH(dtmp);

		from = NEXTFROM;
		d = RFLOAT_VALUE(rb_to_float(from));
		d = HTOVD(d,dtmp);
		rb_str_buf_cat(res, (char*)&d, sizeof(double));
	    }
	    break;

	  case 'd':		/* double precision float in native format */
	  case 'D':		/* ditto */
	    while (len-- > 0) {
		double d;

		from = NEXTFROM;
		d = RFLOAT_VALUE(rb_to_float(from));
		rb_str_buf_cat(res, (char*)&d, sizeof(double));
	    }
	    break;

	  case 'g':		/* single precision float in network byte-order */
	    while (len-- > 0) {
		float f;
		FLOAT_CONVWITH(ftmp);

		from = NEXTFROM;
		f = (float)RFLOAT_VALUE(rb_to_float(from));
		f = HTONF(f,ftmp);
		rb_str_buf_cat(res, (char*)&f, sizeof(float));
	    }
	    break;

	  case 'G':		/* double precision float in network byte-order */
	    while (len-- > 0) {
		double d;
		DOUBLE_CONVWITH(dtmp);

		from = NEXTFROM;
		d = RFLOAT_VALUE(rb_to_float(from));
		d = HTOND(d,dtmp);
		rb_str_buf_cat(res, (char*)&d, sizeof(double));
	    }
	    break;

	  case 'x':		/* null byte */
	  grow:
	    while (len >= 10) {
		rb_str_buf_cat(res, nul10, 10);
		len -= 10;
	    }
	    rb_str_buf_cat(res, nul10, len);
	    break;

	  case 'X':		/* back up byte */
	  shrink:
	    plen = RSTRING_LEN(res);
	    if (plen < len)
		rb_raise(rb_eArgError, "X outside of string");
	    rb_str_set_len(res, plen - len);
	    break;

	  case '@':		/* null fill to absolute position */
	    len -= RSTRING_LEN(res);
	    if (len > 0) goto grow;
	    len = -len;
	    if (len > 0) goto shrink;
	    break;

	  case '%':
	    rb_raise(rb_eArgError, "%% is not supported");
	    break;

	  case 'U':		/* Unicode character */
	    while (len-- > 0) {
		SIGNED_VALUE l;
		char buf[8];
		int le;

		from = NEXTFROM;
		from = rb_to_int(from);
		l = NUM2LONG(from);
		if (l < 0) {
		    rb_raise(rb_eRangeError, "pack(U): value out of range");
		}
		le = rb_uv_to_utf8(buf, l);
		rb_str_buf_cat(res, (char*)buf, le);
	    }
	    break;

	  case 'u':		/* uuencoded string */
	  case 'm':		/* base64 encoded string */
	    from = NEXTFROM;
	    StringValue(from);
	    ptr = RSTRING_PTR(from);
	    plen = RSTRING_LEN(from);

	    if (len == 0 && type == 'm') {
		encodes(res, ptr, plen, type, 0);
		ptr += plen;
		break;
	    }
	    if (len <= 2)
		len = 45;
	    else if (len > 63 && type == 'u')
		len = 63;
	    else
		len = len / 3 * 3;
	    while (plen > 0) {
		long todo;

		if (plen > len)
		    todo = len;
		else
		    todo = plen;
		encodes(res, ptr, todo, type, 1);
		plen -= todo;
		ptr += todo;
	    }
	    break;

	  case 'M':		/* quoted-printable encoded string */
	    from = rb_obj_as_string(NEXTFROM);
	    if (len <= 1)
		len = 72;
	    qpencode(res, from, len);
	    break;

	  case 'P':		/* pointer to packed byte string */
	    from = THISFROM;
	    if (!NIL_P(from)) {
		StringValue(from);
		if (RSTRING_LEN(from) < len) {
		    rb_raise(rb_eArgError, "too short buffer for P(%ld for %ld)",
			     RSTRING_LEN(from), len);
		}
	    }
	    len = 1;
	    /* FALL THROUGH */
	  case 'p':		/* pointer to string */
	    while (len-- > 0) {
		char *t;
		from = NEXTFROM;
		if (NIL_P(from)) {
		    t = 0;
		}
		else {
		    t = StringValuePtr(from);
		}
		if (!associates) {
		    associates = rb_ary_new();
		}
		rb_ary_push(associates, from);
		rb_obj_taint(from);
		rb_str_buf_cat(res, (char*)&t, sizeof(char*));
	    }
	    break;

	  case 'w':		/* BER compressed integer  */
	    while (len-- > 0) {
		unsigned long ul;
		VALUE buf = rb_str_new(0, 0);
		char c, *bufs, *bufe;

		from = NEXTFROM;
		if (RB_TYPE_P(from, T_BIGNUM)) {
		    VALUE big128 = rb_uint2big(128);
		    while (RB_TYPE_P(from, T_BIGNUM)) {
			from = rb_big_divmod(from, big128);
			c = castchar(NUM2INT(RARRAY_PTR(from)[1]) | 0x80); /* mod */
			rb_str_buf_cat(buf, &c, sizeof(char));
			from = RARRAY_PTR(from)[0]; /* div */
		    }
		}

		{
		    long l = NUM2LONG(from);
		    if (l < 0) {
			rb_raise(rb_eArgError, "can't compress negative numbers");
		    }
		    ul = l;
		}

		while (ul) {
		    c = castchar((ul & 0x7f) | 0x80);
		    rb_str_buf_cat(buf, &c, sizeof(char));
		    ul >>=  7;
		}

		if (RSTRING_LEN(buf)) {
		    bufs = RSTRING_PTR(buf);
		    bufe = bufs + RSTRING_LEN(buf) - 1;
		    *bufs &= 0x7f; /* clear continue bit */
		    while (bufs < bufe) { /* reverse */
			c = *bufs;
			*bufs++ = *bufe;
			*bufe-- = c;
		    }
		    rb_str_buf_cat(res, RSTRING_PTR(buf), RSTRING_LEN(buf));
		}
		else {
		    c = 0;
		    rb_str_buf_cat(res, &c, sizeof(char));
		}
	    }
	    break;

	  default:
	    rb_warning("unknown pack directive '%c' in '%s'",
		type, RSTRING_PTR(fmt));
	    break;
	}
    }

    if (associates) {
	rb_str_associate(res, associates);
    }
    OBJ_INFECT(res, fmt);
    switch (enc_info) {
      case 1:
	ENCODING_CODERANGE_SET(res, rb_usascii_encindex(), ENC_CODERANGE_7BIT);
	break;
      case 2:
	rb_enc_set_index(res, rb_utf8_encindex());
	break;
      default:
	/* do nothing, keep ASCII-8BIT */
	break;
    }
    return res;
}

#permutation {|p| ... } ⇒ `Object` #permutation ⇒ `Enumerator` #permutation(n) {|p| ... } ⇒ `Object` #permutation(n) ⇒ `Enumerator`

When invoked with a block, yield all permutations of length n of the elements of the array, then return the array itself.

If n is not specified, yield all permutations of all elements.

The implementation makes no guarantees about the order in which the permutations are yielded.

If no block is given, an Enumerator is returned instead.

Examples:

a = [1, 2, 3]
a.permutation.to_a    #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
a.permutation(1).to_a #=> [[1],[2],[3]]
a.permutation(2).to_a #=> [[1,2],[1,3],[2,1],[2,3],[3,1],[3,2]]
a.permutation(3).to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
a.permutation(0).to_a #=> [[]] # one permutation of length 0
a.permutation(4).to_a #=> []   # no permutations of length 4

Overloads:

#permutation {|p| ... } ⇒ Object
Yields:
- (p)
#permutation ⇒ Enumerator
Returns:
- (Enumerator)
#permutation(n) {|p| ... } ⇒ Object
Yields:
- (p)
#permutation(n) ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 4649

static VALUE
rb_ary_permutation(int argc, VALUE *argv, VALUE ary)
{
    VALUE num;
    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 */
    rb_scan_args(argc, argv, "01", &num);
    r = NIL_P(num) ? n : NUM2LONG(num);   /* 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_PTR(ary)[i]));
	}
    }
    else {             /* this is the general case */
	volatile VALUE t0 = tmpbuf(n,sizeof(long));
	long *p = (long*)RSTRING_PTR(t0);
	volatile VALUE t1 = tmpbuf(n,sizeof(char));
	char *used = (char*)RSTRING_PTR(t1);
	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
	RBASIC(ary0)->klass = 0;

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

	permute0(n, r, p, 0, used, ary0); /* compute and yield permutations */
	tmpbuf_discard(t0);
	tmpbuf_discard(t1);
	RBASIC(ary0)->klass = rb_cArray;
    }
    return ary;
}

#pop ⇒ `Object`^? #pop(n) ⇒ `Object`

Removes the last element from self and returns it, or nil if the array is empty.

If a number n is given, returns an array of the last n elements (or less) just like array.slice!(-n, n) does. See also Array#push for the opposite effect.

a = [ "a", "b", "c", "d" ]
a.pop     #=> "d"
a.pop(2)  #=> ["b", "c"]
a         #=> ["a"]

Overloads:

#pop ⇒ Object^?
Returns:
- (Object, nil)

# File 'array.c', line 914

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));
    return result;
}

#product(other_ary, ...) ⇒ `Object` #product(other_ary, ...) {|p| ... } ⇒ `Object`

Returns an array of all combinations of elements from all arrays.

The length of the returned array is the product of the length of self and the argument arrays.

If given a block, #product will yield all combinations and return self instead.

[1,2,3].product([4,5])     #=> [[1,4],[1,5],[2,4],[2,5],[3,4],[3,5]]
[1,2].product([1,2])       #=> [[1,1],[1,2],[2,1],[2,2]]
[1,2].product([3,4],[5,6]) #=> [[1,3,5],[1,3,6],[1,4,5],[1,4,6],
                           #     [2,3,5],[2,3,6],[2,4,5],[2,4,6]]
[1,2].product()            #=> [[1],[2]]
[1,2].product([])          #=> []

Overloads:

#product(other_ary, ...) {|p| ... } ⇒ Object
Yields:
- (p)

# File 'array.c', line 4999

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 = tmpary(n);
    volatile VALUE t1 = tmpbuf(n, sizeof(int));
    VALUE *arrays = RARRAY_PTR(t0); /* The arrays we're computing the product of */
    int *counters = (int*)RSTRING_PTR(t1); /* 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(t0)->klass = 0;
    RBASIC(t1)->klass = 0;

    /* 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]), l = resultlen;
	    if (k == 0) {
		result = rb_ary_new2(0);
		goto done;
	    }
	    resultlen *= k;
	    if (resultlen < k || resultlen < l || resultlen / k != l) {
		rb_raise(rb_eRangeError, "too big to product");
	    }
	}
	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, FL_USER5);
	    rb_yield(subarray);
	    if (! FL_TEST(t0, FL_USER5)) {
		rb_raise(rb_eRuntimeError, "product reentered");
	    }
	    else {
		FL_UNSET(t0, FL_USER5);
	    }
	}
	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:
    tmpary_discard(t0);
    tmpbuf_discard(t1);

    return NIL_P(result) ? ary : result;
}

#push(obj, ...) ⇒ `Object`

Append --- Pushes the given object(s) on to the end of this array. This expression returns the array itself, so several appends may be chained together. See also Array#pop for the opposite effect.

a = [ "a", "b", "c" ]
a.push("d", "e", "f")
        #=> ["a", "b", "c", "d", "e", "f"]
[1, 2, 3,].push(4).push(5)
        #=> [1, 2, 3, 4, 5]

# File 'array.c', line 873

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

#rassoc(obj) ⇒ `nil`

Searches through the array whose elements are also arrays.

Compares obj with the second element of each contained array using obj.==.

Returns the first contained array that matches obj.

#reject {|item| ... } ⇒ `Object` #reject ⇒ `Enumerator`

Returns a new array containing the items in self for which the given block is not true.

#reject! {|item| ... } ⇒ `nil` #reject! ⇒ `Enumerator`

Equivalent to Array#delete_if, deleting elements from self for which the block evaluates to true, but returns nil if no changes were made.

The array is changed instantly every time the block is called, not after the iteration is over.

See also Enumerable#reject and Array#delete_if.

If no block is given, an Enumerator is returned instead.

Overloads:

#reject! {|item| ... } ⇒ nil
Yields:
- (item)
Returns:
- (nil)
#reject! ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 2977

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

#repeated_combination(n) {|c| ... } ⇒ `Object` #repeated_combination(n) ⇒ `Enumerator`

When invoked with a block, yields all repeated combinations of length n of elements from the array and then returns the array itself.

The implementation makes no guarantees about the order in which the repeated combinations are yielded.

If no block is given, an Enumerator is returned instead.

Examples:

a = [1, 2, 3]
a.repeated_combination(1).to_a  #=> [[1], [2], [3]]
a.repeated_combination(2).to_a  #=> [[1,1],[1,2],[1,3],[2,2],[2,3],[3,3]]
a.repeated_combination(3).to_a  #=> [[1,1,1],[1,1,2],[1,1,3],[1,2,2],[1,2,3],
                                #    [1,3,3],[2,2,2],[2,2,3],[2,3,3],[3,3,3]]
a.repeated_combination(4).to_a  #=> [[1,1,1,1],[1,1,1,2],[1,1,1,3],[1,1,2,2],[1,1,2,3],
                                #    [1,1,3,3],[1,2,2,2],[1,2,2,3],[1,2,3,3],[1,3,3,3],
                                #    [2,2,2,2],[2,2,2,3],[2,2,3,3],[2,3,3,3],[3,3,3,3]]
a.repeated_combination(0).to_a  #=> [[]] # one combination of length 0

Overloads:

#repeated_combination(n) {|c| ... } ⇒ Object
Yields:
- (c)
#repeated_combination(n) ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 4943

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 < len; i++) {
	    rb_yield(rb_ary_new3(1, RARRAY_PTR(ary)[i]));
	}
    }
    else if (len == 0) {
	/* yield nothing */
    }
    else {
	volatile VALUE t0 = tmpbuf(n, sizeof(long));
	long *p = (long*)RSTRING_PTR(t0);
	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
	RBASIC(ary0)->klass = 0;

	rcombinate0(len, n, p, 0, n, ary0); /* compute and yield repeated combinations */
	tmpbuf_discard(t0);
	RBASIC(ary0)->klass = rb_cArray;
    }
    return ary;
}

#repeated_permutation(n) {|p| ... } ⇒ `Object` #repeated_permutation(n) ⇒ `Enumerator`

When invoked with a block, yield all repeated permutations of length n of the elements of the array, then return the array itself.

The implementation makes no guarantees about the order in which the repeated permutations are yielded.

If no block is given, an Enumerator is returned instead.

Examples:

a = [1, 2]
a.repeated_permutation(1).to_a  #=> [[1], [2]]
a.repeated_permutation(2).to_a  #=> [[1,1],[1,2],[2,1],[2,2]]
a.repeated_permutation(3).to_a  #=> [[1,1,1],[1,1,2],[1,2,1],[1,2,2],
                                #    [2,1,1],[2,1,2],[2,2,1],[2,2,2]]
a.repeated_permutation(0).to_a  #=> [[]] # one permutation of length 0

Overloads:

#repeated_permutation(n) {|p| ... } ⇒ Object
Yields:
- (p)
#repeated_permutation(n) ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 4848

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_PTR(ary)[i]));
	}
    }
    else {             /* this is the general case */
	volatile VALUE t0 = tmpbuf(r, sizeof(long));
	long *p = (long*)RSTRING_PTR(t0);
	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
	RBASIC(ary0)->klass = 0;

	rpermute0(n, r, p, 0, ary0); /* compute and yield repeated permutations */
	tmpbuf_discard(t0);
	RBASIC(ary0)->klass = rb_cArray;
    }
    return ary;
}

#replace(other_ary) ⇒ `Object`

Replaces the contents of self with the contents of other_ary, truncating or expanding if necessary.

a = [ "a", "b", "c", "d", "e" ]
a.replace([ "x", "y", "z" ])   #=> ["x", "y", "z"]
a                              #=> ["x", "y", "z"]

# File 'array.c', line 3168

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

    if (RARRAY_LEN(orig) <= RARRAY_EMBED_LEN_MAX) {
        VALUE *ptr;
        VALUE shared = 0;

        if (ARY_OWNS_HEAP_P(copy)) {
            xfree(RARRAY_PTR(copy));
        }
        else if (ARY_SHARED_P(copy)) {
            shared = ARY_SHARED(copy);
            FL_UNSET_SHARED(copy);
        }
        FL_SET_EMBED(copy);
        ptr = RARRAY_PTR(orig);
        MEMCPY(RARRAY_PTR(copy), ptr, VALUE, RARRAY_LEN(orig));
        if (shared) {
            rb_ary_decrement_share(shared);
        }
        ARY_SET_LEN(copy, RARRAY_LEN(orig));
    }
    else {
        VALUE shared = ary_make_shared(orig);
        if (ARY_OWNS_HEAP_P(copy)) {
            xfree(RARRAY_PTR(copy));
        }
        else {
            rb_ary_unshare_safe(copy);
        }
        FL_UNSET_EMBED(copy);
        ARY_SET_PTR(copy, RARRAY_PTR(orig));
        ARY_SET_LEN(copy, RARRAY_LEN(orig));
        rb_ary_set_shared(copy, shared);
    }
    return copy;
}

#reverse ⇒ `Object`

Returns a new array containing self's elements in reverse order.

[ "a", "b", "c" ].reverse   #=> ["c", "b", "a"]
[ 1 ].reverse               #=> [1]

# File 'array.c', line 2084

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

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

#reverse! ⇒ `Object`

Reverses self in place.

a = [ "a", "b", "c" ]
a.reverse!       #=> ["c", "b", "a"]
a                #=> ["c", "b", "a"]

# File 'array.c', line 2068

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

#reverse_each {|item| ... } ⇒ `Object` #reverse_each ⇒ `Enumerator`

Same as Array#each, but traverses self in reverse order.

a = [ "a", "b", "c" ]
a.reverse_each {|x| print x, " " }

produces:

c b a

Overloads:

#reverse_each {|item| ... } ⇒ Object
Yields:
- (item)
#reverse_each ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 1728

static VALUE
rb_ary_reverse_each(VALUE ary)
{
    long len;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_length);
    len = RARRAY_LEN(ary);
    while (len--) {
	rb_yield(RARRAY_PTR(ary)[len]);
	if (RARRAY_LEN(ary) < len) {
	    len = RARRAY_LEN(ary);
	}
    }
    return ary;
}

#rindex(obj) ⇒ `Integer`^? #rindex {|item| ... } ⇒ `Integer`^? #rindex ⇒ `Enumerator`

Returns the index of the last object in self == to obj.

If a block is given instead of an argument, returns the index of the first object for which the block returns true, starting from the last object.

Returns nil if no match is found.

#rotate(count = 1) ⇒ `Object`

Returns a new array by rotating self so that the element at count is the first element of the new array.

If count is negative then it rotates in the opposite direction, starting from the end of self where -1 is the last element.

a = [ "a", "b", "c", "d" ]
a.rotate         #=> ["b", "c", "d", "a"]
a                #=> ["a", "b", "c", "d"]
a.rotate(2)      #=> ["c", "d", "a", "b"]
a.rotate(-3)     #=> ["b", "c", "d", "a"]

# File 'array.c', line 2174

static VALUE
rb_ary_rotate_m(int argc, VALUE *argv, VALUE ary)
{
    VALUE rotated, *ptr, *ptr2;
    long len, cnt = 1;

    switch (argc) {
      case 1: cnt = NUM2LONG(argv[0]);
      case 0: break;
      default: rb_scan_args(argc, argv, "01", NULL);
    }

    len = RARRAY_LEN(ary);
    rotated = rb_ary_new2(len);
    if (len > 0) {
	cnt = rotate_count(cnt, len);
	ptr = RARRAY_PTR(ary);
	ptr2 = RARRAY_PTR(rotated);
	len -= cnt;
	MEMCPY(ptr2, ptr + cnt, VALUE, len);
	MEMCPY(ptr2 + len, ptr, VALUE, cnt);
    }
    ARY_SET_LEN(rotated, RARRAY_LEN(ary));
    return rotated;
}

#rotate!(count = 1) ⇒ `Object`

Rotates self in place so that the element at count comes first, and returns self.

If count is negative then it rotates in the opposite direction, starting from the end of the array where -1 is the last element.

a = [ "a", "b", "c", "d" ]
a.rotate!        #=> ["b", "c", "d", "a"]
a                #=> ["b", "c", "d", "a"]
a.rotate!(2)     #=> ["d", "a", "b", "c"]
a.rotate!(-3)    #=> ["a", "b", "c", "d"]

# File 'array.c', line 2143

static VALUE
rb_ary_rotate_bang(int argc, VALUE *argv, VALUE ary)
{
    long n = 1;

    switch (argc) {
      case 1: n = NUM2LONG(argv[0]);
      case 0: break;
      default: rb_scan_args(argc, argv, "01", NULL);
    }
    rb_ary_rotate(ary, n);
    return ary;
}

#sample ⇒ `Object` #sample(random:rng) ⇒ `Object` #sample(n) ⇒ `Object` #sample(n, random:rng) ⇒ `Object`

Choose a random element or n random elements from the array.

The elements are chosen by using random and unique indices into the array in order to ensure that an element doesn't repeat itself unless the array already contained duplicate elements.

If the array is empty the first form returns nil and the second form returns an empty array.

The optional rng argument will be used as the random number generator.

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

Overloads:

#sample ⇒ Object
Returns:
- (Object)
#sample(random:rng) ⇒ Object
Returns:
- (Object)

# File 'array.c', line 4368

static VALUE
rb_ary_sample(int argc, VALUE *argv, VALUE ary)
{
    VALUE nv, result, *ptr;
    VALUE opts, randgen = rb_cRandom;
    long n, len, i, j, k, idx[10];
    long rnds[numberof(idx)];

    if (OPTHASH_GIVEN_P(opts)) {
	randgen = rb_hash_lookup2(opts, sym_random, randgen);
    }
    ptr = RARRAY_PTR(ary);
    len = RARRAY_LEN(ary);
    if (argc == 0) {
	if (len == 0) return Qnil;
	if (len == 1) {
	    i = 0;
	}
	else {
	    i = RAND_UPTO(len);
	    if ((len = RARRAY_LEN(ary)) <= i) return Qnil;
	    ptr = RARRAY_PTR(ary);
	}
	return ptr[i];
    }
    rb_scan_args(argc, argv, "1", &nv);
    n = NUM2LONG(nv);
    if (n < 0) rb_raise(rb_eArgError, "negative sample number");
    if (n > len) n = len;
    if (n <= numberof(idx)) {
	for (i = 0; i < n; ++i) {
	    rnds[i] = RAND_UPTO(len - i);
	}
    }
    k = len;
    len = RARRAY_LEN(ary);
    ptr = RARRAY_PTR(ary);
    if (len < k) {
	if (n <= numberof(idx)) {
	    for (i = 0; i < n; ++i) {
		if (rnds[i] >= len) {
		    return rb_ary_new2(0);
		}
	    }
	}
    }
    if (n > len) n = len;
    switch (n) {
      case 0:
	return rb_ary_new2(0);
      case 1:
	i = rnds[0];
	return rb_ary_new4(1, &ptr[i]);
      case 2:
	i = rnds[0];
	j = rnds[1];
	if (j >= i) j++;
	return rb_ary_new3(2, ptr[i], ptr[j]);
      case 3:
	i = rnds[0];
	j = rnds[1];
	k = rnds[2];
	{
	    long l = j, g = i;
	    if (j >= i) l = i, g = ++j;
	    if (k >= l && (++k >= g)) ++k;
	}
	return rb_ary_new3(3, ptr[i], ptr[j], ptr[k]);
    }
    if (n <= numberof(idx)) {
	VALUE *ptr_result;
	long sorted[numberof(idx)];
	sorted[0] = idx[0] = rnds[0];
	for (i=1; i<n; i++) {
	    k = rnds[i];
	    for (j = 0; j < i; ++j) {
		if (k < sorted[j]) break;
		++k;
	    }
	    memmove(&sorted[j+1], &sorted[j], sizeof(sorted[0])*(i-j));
	    sorted[j] = idx[i] = k;
	}
	result = rb_ary_new2(n);
	ptr_result = RARRAY_PTR(result);
	for (i=0; i<n; i++) {
	    ptr_result[i] = ptr[idx[i]];
	}
    }
    else {
	VALUE *ptr_result;
	result = rb_ary_new4(len, ptr);
	RBASIC(result)->klass = 0;
	ptr_result = RARRAY_PTR(result);
	RB_GC_GUARD(ary);
	for (i=0; i<n; i++) {
	    j = RAND_UPTO(len-i) + i;
	    nv = ptr_result[j];
	    ptr_result[j] = ptr_result[i];
	    ptr_result[i] = nv;
	}
	RBASIC(result)->klass = rb_cArray;
    }
    ARY_SET_LEN(result, n);

    return result;
}

#select {|item| ... } ⇒ `Object` #select ⇒ `Enumerator`

Returns a new array containing all elements of ary for which the given block returns a true value.

If no block is given, an Enumerator is returned instead.

[1,2,3,4,5].select { |num|  num.even?  }   #=> [2, 4]

a = %w{ a b c d e f }
a.select { |v| v =~ /[aeiou]/ }  #=> ["a", "e"]

#select! {|item| ... } ⇒ `nil` #select! ⇒ `Enumerator`

Invokes the given block passing in successive elements from self, deleting elements for which the block returns a false value.

If changes were made, it will return self, otherwise it returns nil.

#shift ⇒ `Object`^? #shift(n) ⇒ `Object`

Removes the first element of self and returns it (shifting all other elements down by one). Returns nil if the array is empty.

If a number n is given, returns an array of the first n elements (or less) just like array.slice!(0, n) does. With ary containing only the remainder elements, not including what was shifted to new_ary. See also Array#unshift for the opposite effect.

args = [ "-m", "-q", "filename" ]
args.shift     #=> "-m"
args           #=> ["-q", "filename"]

args = [ "-m", "-q", "filename" ]
args.shift(2)  #=> ["-m", "-q"]
args           #=> ["filename"]

Overloads:

#shift ⇒ Object^?
Returns:
- (Object, nil)

# File 'array.c', line 980

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);
    if (ARY_SHARED_P(ary)) {
	if (ARY_SHARED_NUM(ARY_SHARED(ary)) == 1) {
	    rb_mem_clear(RARRAY_PTR(ary), n);
	}
        ARY_INCREASE_PTR(ary, n);
    }
    else {
	MEMMOVE(RARRAY_PTR(ary), RARRAY_PTR(ary)+n, VALUE, RARRAY_LEN(ary)-n);
    }
    ARY_INCREASE_LEN(ary, -n);

    return result;
}

#shuffle ⇒ `Object` #shuffle(random:rng) ⇒ `Object`

Returns a new array with elements of self shuffled.

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

The optional rng argument will be used as the random number generator.

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

# File 'array.c', line 4335

static VALUE
rb_ary_shuffle(int argc, VALUE *argv, VALUE ary)
{
    ary = rb_ary_dup(ary);
    rb_ary_shuffle_bang(argc, argv, ary);
    return ary;
}

#shuffle! ⇒ `Object` #shuffle!(random:rng) ⇒ `Object`

Shuffles elements in self in place.

The optional rng argument will be used as the random number generator.

# File 'array.c', line 4291

static VALUE
rb_ary_shuffle_bang(int argc, VALUE *argv, VALUE ary)
{
    VALUE *ptr, opts, *snap_ptr, randgen = rb_cRandom;
    long i, snap_len;

    if (OPTHASH_GIVEN_P(opts)) {
	randgen = rb_hash_lookup2(opts, sym_random, randgen);
    }
    rb_check_arity(argc, 0, 0);
    rb_ary_modify(ary);
    i = RARRAY_LEN(ary);
    ptr = RARRAY_PTR(ary);
    snap_len = i;
    snap_ptr = ptr;
    while (i) {
	long j = RAND_UPTO(i);
	VALUE tmp;
	if (snap_len != RARRAY_LEN(ary) || snap_ptr != RARRAY_PTR(ary)) {
	    rb_raise(rb_eRuntimeError, "modified during shuffle");
	}
	tmp = ptr[--i];
	ptr[i] = ptr[j];
	ptr[j] = tmp;
    }
    return ary;
}

#[](index) ⇒ `Object`^? #[](start, length) ⇒ `nil` #[](range) ⇒ `nil` #slice(index) ⇒ `Object`^? #slice(start, length) ⇒ `nil` #slice(range) ⇒ `nil`

Element Reference --- Returns the element at index, or returns a subarray starting at the start index and continuing for length elements, or returns a subarray specified by range of indices.

Returns nil if the index (or starting index) are out of range.

a = [ "a", "b", "c", "d", "e" ]
a[2] +  a[0] + a[1]    #=> "cab"
a[6]                   #=> nil
a[1, 2]                #=> [ "b", "c" ]
a[1..3]                #=> [ "b", "c", "d" ]
a[4..7]                #=> [ "e" ]
a[6..10]               #=> nil
a[-3, 3]               #=> [ "c", "d", "e" ]
# special cases
a[5]                   #=> nil
a[6, 1]                #=> nil
a[5, 1]                #=> []
a[5..10]               #=> []

Overloads:

#[](index) ⇒ Object^?
Returns:
- (Object, nil)
#[](start, length) ⇒ nil
Returns:
- (nil)
#[](range) ⇒ nil
Returns:
- (nil)
#slice(index) ⇒ Object^?
Returns:
- (Object, nil)
#slice(start, length) ⇒ nil
Returns:
- (nil)
#slice(range) ⇒ nil
Returns:
- (nil)

# File 'array.c', line 1163

VALUE
rb_ary_aref(int argc, VALUE *argv, VALUE ary)
{
    VALUE arg;
    long beg, len;

    if (argc == 2) {
	beg = NUM2LONG(argv[0]);
	len = NUM2LONG(argv[1]);
	if (beg < 0) {
	    beg += RARRAY_LEN(ary);
	}
	return rb_ary_subseq(ary, beg, len);
    }
    if (argc != 1) {
	rb_scan_args(argc, argv, "11", NULL, NULL);
    }
    arg = argv[0];
    /* special case - speeding up */
    if (FIXNUM_P(arg)) {
	return rb_ary_entry(ary, FIX2LONG(arg));
    }
    /* check if idx is Range */
    switch (rb_range_beg_len(arg, &beg, &len, RARRAY_LEN(ary), 0)) {
      case Qfalse:
	break;
      case Qnil:
	return Qnil;
      default:
	return rb_ary_subseq(ary, beg, len);
    }
    return rb_ary_entry(ary, NUM2LONG(arg));
}

#slice!(index) ⇒ `Object`^? #slice!(start, length) ⇒ `nil` #slice!(range) ⇒ `nil`

Deletes the element(s) given by an index (optionally up to length elements) or by a range.

Returns the deleted object (or objects), or nil if the index is out of range.

a = [ "a", "b", "c" ]
a.slice!(1)     #=> "b"
a               #=> ["a", "c"]
a.slice!(-1)    #=> "c"
a               #=> ["a"]
a.slice!(100)   #=> nil
a               #=> ["a"]

Overloads:

#slice!(index) ⇒ Object^?
Returns:
- (Object, nil)
#slice!(start, length) ⇒ nil
Returns:
- (nil)
#slice!(range) ⇒ nil
Returns:
- (nil)

# File 'array.c', line 2876

static VALUE
rb_ary_slice_bang(int argc, VALUE *argv, VALUE ary)
{
    VALUE arg1, arg2;
    long pos, len, orig_len;

    rb_ary_modify_check(ary);
    if (argc == 2) {
	pos = NUM2LONG(argv[0]);
	len = NUM2LONG(argv[1]);
      delete_pos_len:
	if (len < 0) return Qnil;
	orig_len = RARRAY_LEN(ary);
	if (pos < 0) {
	    pos += orig_len;
	    if (pos < 0) return Qnil;
	}
	else if (orig_len < pos) return Qnil;
	if (orig_len < pos + len) {
	    len = orig_len - pos;
	}
	if (len == 0) return rb_ary_new2(0);
	arg2 = rb_ary_new4(len, RARRAY_PTR(ary)+pos);
	RBASIC(arg2)->klass = rb_obj_class(ary);
	rb_ary_splice(ary, pos, len, Qundef);
	return arg2;
    }

    if (argc != 1) {
	/* error report */
	rb_scan_args(argc, argv, "11", NULL, NULL);
    }
    arg1 = argv[0];

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

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

#sort ⇒ `Object` #sort {|a, b| ... } ⇒ `Object`

Returns a new array created by sorting self.

Comparisons for the sort will be done using the <=> operator or using an optional code block.

The block must implement a comparison between a and b, and return -1, when a follows b, 0 when a and b are equivalent, or +1 if b follows a.

#sort! ⇒ `Object` #sort! {|a, b| ... } ⇒ `Object`

Sorts self in place.

Comparisons for the sort will be done using the <=> operator or using an optional code block.

The block must implement a comparison between a and b, and return -1, when a follows b, 0 when a and b are equivalent, or +1 if b follows a.

#sort_by! {|obj| ... } ⇒ `Object` #sort_by! ⇒ `Enumerator`

Sorts self in place using a set of keys generated by mapping the values in self through the given block.

If no block is given, an Enumerator is returned instead.

Overloads:

#sort_by! {|obj| ... } ⇒ Object
Yields:
- (obj)
#sort_by! ⇒ Enumerator
Returns:
- (Enumerator)

# File 'array.c', line 2500

static VALUE
rb_ary_sort_by_bang(VALUE ary)
{
    VALUE sorted;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, rb_ary_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;
}

#take(n) ⇒ `Object`

Returns first n elements from the array.

If a negative number is given, raises an ArgumentError.

#take_while {|arr| ... } ⇒ `Object` #take_while ⇒ `Enumerator`

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.

If no block is given, an Enumerator is returned instead.

#to_a ⇒ `Object`

Returns self.

If called on a subclass of Array, converts the receiver to an Array object.

# File 'array.c', line 2009

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;
}

#to_ary ⇒ `Object`

Returns self.

# File 'array.c', line 2027

static VALUE
rb_ary_to_ary_m(VALUE ary)
{
    return ary;
}

#transpose ⇒ `Object`

Assumes that self is an array of arrays and transposes the rows and columns.

a = [[1,2], [3,4], [5,6]]
a.transpose   #=> [[1, 3, 5], [2, 4, 6]]

If the length of the subarrays don't match, an IndexError is raised.

# File 'array.c', line 3128

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;
}

#uniq ⇒ `Object` #uniq {|item| ... } ⇒ `Object`

Returns a new array by removing duplicate values in self.

If a block is given, it will use the return value of the block for comparison.

It compares values using their #hash and #eql? methods for efficiency.

a = [ "a", "a", "b", "b", "c" ]
a.uniq   # => ["a", "b", "c"]

b = [["student","sam"], ["student","george"], ["teacher","matz"]]
b.uniq { |s| s.first } # => [["student", "sam"], ["teacher", "matz"]]

Overloads:

#uniq {|item| ... } ⇒ Object
Yields:
- (item)

# File 'array.c', line 4005

static VALUE
rb_ary_uniq(VALUE ary)
{
    VALUE hash, uniq, v;
    long i;

    if (RARRAY_LEN(ary) <= 1)
        return rb_ary_dup(ary);
    if (rb_block_given_p()) {
	hash = ary_make_hash_by(ary);
	uniq = ary_new(rb_obj_class(ary), RHASH_SIZE(hash));
	st_foreach(RHASH_TBL(hash), push_value, uniq);
    }
    else {
	hash = ary_make_hash(ary);
	uniq = ary_new(rb_obj_class(ary), RHASH_SIZE(hash));
	for (i=0; i<RARRAY_LEN(ary); i++) {
	    st_data_t vv = (st_data_t)(v = rb_ary_elt(ary, i));
	    if (st_delete(RHASH_TBL(hash), &vv, 0)) {
		rb_ary_push(uniq, v);
	    }
	}
    }
    ary_recycle_hash(hash);

    return uniq;
}

#uniq! ⇒ `nil` #uniq! {|item| ... } ⇒ `nil`

Removes duplicate elements from self.

If a block is given, it will use the return value of the block for comparison.

It compares values using their #hash and #eql? methods for efficiency.

Returns nil if no changes are made (that is, no duplicates are found).

a = [ "a", "a", "b", "b", "c" ]
a.uniq!   # => ["a", "b", "c"]

b = [ "a", "b", "c" ]
b.uniq!   # => nil

c = [["student","sam"], ["student","george"], ["teacher","matz"]]
c.uniq! { |s| s.first } # => [["student", "sam"], ["teacher", "matz"]]

Overloads:

#uniq! ⇒ nil
Returns:
- (nil)
#uniq! {|item| ... } ⇒ nil
Yields:
- (item)
Returns:
- (nil)

# File 'array.c', line 3946

static VALUE
rb_ary_uniq_bang(VALUE ary)
{
    VALUE hash, v;
    long i, j;

    rb_ary_modify_check(ary);
    if (RARRAY_LEN(ary) <= 1)
        return Qnil;
    if (rb_block_given_p()) {
	hash = ary_make_hash_by(ary);
	if (RARRAY_LEN(ary) == (i = RHASH_SIZE(hash))) {
	    return Qnil;
	}
	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, i);
	st_foreach(RHASH_TBL(hash), push_value, ary);
    }
    else {
	hash = ary_make_hash(ary);
	if (RARRAY_LEN(ary) == (long)RHASH_SIZE(hash)) {
	    return Qnil;
	}
	for (i=j=0; i<RARRAY_LEN(ary); i++) {
	    st_data_t vv = (st_data_t)(v = rb_ary_elt(ary, i));
	    if (st_delete(RHASH_TBL(hash), &vv, 0)) {
		rb_ary_store(ary, j++, v);
	    }
	}
	ARY_SET_LEN(ary, j);
    }
    ary_recycle_hash(hash);

    return ary;
}

#unshift(obj, ...) ⇒ `Object`

Prepends objects to the front of self, moving other elements upwards. See also Array#shift for the opposite effect.

a = [ "b", "c", "d" ]
a.unshift("a")   #=> ["a", "b", "c", "d"]
a.unshift(1, 2)  #=> [ 1, 2, "a", "b", "c", "d"]

# File 'array.c', line 1068

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

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

    ary_ensure_room_for_unshift(ary, argc);
    MEMCPY(RARRAY_PTR(ary), argv, VALUE, argc);
    ARY_SET_LEN(ary, len + argc);
    return ary;
}

#values_at(selector, ...) ⇒ `Object`

Returns an array containing the elements in self corresponding to the given selector(s).

The selectors may be either integer indices or ranges.

#zip(arg, ...) ⇒ `Object` #zip(arg, ...) {|arr| ... } ⇒ `nil`

Converts any arguments to arrays, then merges elements of self with corresponding elements from each argument.

This generates a sequence of ary.size n-element arrays, where n is one more that the count of arguments.

If the size of any argument is less than the size of the initial array, nil values are supplied.

If a block is given, it is invoked for each output array, otherwise an array of arrays is returned.

a = [ 4, 5, 6 ]
b = [ 7, 8, 9 ]
[1, 2, 3].zip(a, b)   #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
[1, 2].zip(a, b)      #=> [[1, 4, 7], [2, 5, 8]]
a.zip([1, 2], [8])    #=> [[4, 1, 8], [5, 2, nil], [6, nil, nil]]

Overloads:

#zip(arg, ...) {|arr| ... } ⇒ nil
Yields:
- (arr)
Returns:
- (nil)

# File 'array.c', line 3083

static VALUE
rb_ary_zip(int argc, VALUE *argv, VALUE ary)
{
    int i, j;
    long len;
    VALUE result = Qnil;

    len = RARRAY_LEN(ary);
    for (i=0; i<argc; i++) {
	argv[i] = take_items(argv[i], len);
    }
    if (!rb_block_given_p()) {
	result = rb_ary_new2(len);
    }

    for (i=0; i<RARRAY_LEN(ary); i++) {
	VALUE tmp = rb_ary_new2(argc+1);

	rb_ary_push(tmp, rb_ary_elt(ary, i));
	for (j=0; j<argc; j++) {
	    rb_ary_push(tmp, rb_ary_elt(argv[j], i));
	}
	if (NIL_P(result)) {
	    rb_yield(tmp);
	}
	else {
	    rb_ary_push(result, tmp);
	}
    }
    return result;
}

#|(other_ary) ⇒ `Object`

Set Union --- Returns a new array by joining ary with other_ary, excluding any duplicates.

It compares elements using their #hash and #eql? methods for efficiency.

[ "a", "b", "c" ] | [ "c", "d", "a" ]    #=> [ "a", "b", "c", "d" ]

Class: Array

Overview

Creating Arrays

Example Usage

Accessing Elements

Obtaining Information about an Array

Adding Items to Arrays

Removing Items from an Array

Iterating over Arrays

Selecting Items from an Array

Non-destructive Selection

Destructive Selection

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Enumerable

Constructor Details

#new(size = 0, obj = nil) ⇒ Object #new(array) ⇒ Object #new(size) {|index| ... } ⇒ Object

Common gotchas

Class Method Details

.[] ⇒ Object

.try_convert(obj) ⇒ Array?

Instance Method Details

#&(other_ary) ⇒ Object

#*(int) ⇒ Object #*(str) ⇒ Object

#+(other_ary) ⇒ Object

#-(other_ary) ⇒ Object

#<<(obj) ⇒ Object

#<=>(other_ary) ⇒ -1, ...

#==(other_ary) ⇒ Boolean

#[](index) ⇒ Object? #[](start, length) ⇒ nil #[](range) ⇒ nil #slice(index) ⇒ Object? #slice(start, length) ⇒ nil #slice(range) ⇒ nil

#[]=(index) ⇒ Object #[]=(start, length) ⇒ Object? #[]=(range) ⇒ Object?

#assoc(obj) ⇒ nil

#at(index) ⇒ Object?

#bsearch {|x| ... } ⇒ Object

#clear ⇒ Object

#collect {|item| ... } ⇒ Object #map {|item| ... } ⇒ Object #collect ⇒ Enumerator #map ⇒ Enumerator

#collect! {|item| ... } ⇒ Object #map! {|item| ... } ⇒ Object #collect! ⇒ Enumerator #map! ⇒ Enumerator

#combination(n) {|c| ... } ⇒ Object #combination(n) ⇒ Enumerator

#compact ⇒ Object

#compact! ⇒ nil

#concat(other_ary) ⇒ Object

#count ⇒ Integer #count(obj) ⇒ Integer #count {|item| ... } ⇒ Integer

#cycle(n = nil) {|obj| ... } ⇒ nil #cycle(n = nil) ⇒ Enumerator

#delete(obj) ⇒ nil #delete(obj) { ... } ⇒ Object

#delete_at(index) ⇒ Object?

#delete_if {|item| ... } ⇒ Object #delete_if ⇒ Enumerator

#drop(n) ⇒ Object

#drop_while {|arr| ... } ⇒ Object #drop_while ⇒ Enumerator

#each {|item| ... } ⇒ Object #each ⇒ Enumerator

#each_index {|index| ... } ⇒ Object #each_index ⇒ Enumerator

#empty? ⇒ Boolean

#eql?(other) ⇒ Boolean

#fetch(index) ⇒ Object #fetch(index, default) ⇒ Object #fetch(index) {|index| ... } ⇒ Object

#fill(obj) ⇒ Object #fill(obj, start[, length]) ⇒ Object #fill(obj, range) ⇒ Object #fill {|index| ... } ⇒ Object #fill(start[, length]) {|index| ... } ⇒ Object #fill(range) {|index| ... } ⇒ Object

#index(obj) ⇒ Integer? #index {|item| ... } ⇒ Integer? #index ⇒ Enumerator

#first ⇒ Object? #first(n) ⇒ Object

#flatten ⇒ Object #flatten(level) ⇒ Object

#flatten! ⇒ nil #flatten!(level) ⇒ nil

#frozen? ⇒ Boolean

#hash ⇒ Fixnum

#include?(object) ⇒ Boolean

#index(obj) ⇒ Integer? #index {|item| ... } ⇒ Integer? #index ⇒ Enumerator

#replace(other_ary) ⇒ Object

#insert(index, obj...) ⇒ Object

#inspect ⇒ String #to_s ⇒ String Also known as: to_s

#join(separator = $,) ⇒ String

#keep_if {|item| ... } ⇒ Object #keep_if ⇒ Enumerator

#last ⇒ Object? #last(n) ⇒ Object

#length ⇒ Integer Also known as: size

#collect {|item| ... } ⇒ Object #map {|item| ... } ⇒ Object #collect ⇒ Enumerator #map ⇒ Enumerator

#collect! {|item| ... } ⇒ Object #map! {|item| ... } ⇒ Object #collect! ⇒ Enumerator #map! ⇒ Enumerator

#pack ⇒ Object

#permutation {|p| ... } ⇒ Object #permutation ⇒ Enumerator #permutation(n) {|p| ... } ⇒ Object #permutation(n) ⇒ Enumerator

#pop ⇒ Object? #pop(n) ⇒ Object

#product(other_ary, ...) ⇒ Object #product(other_ary, ...) {|p| ... } ⇒ Object

#push(obj, ...) ⇒ Object

#rassoc(obj) ⇒ nil

#reject {|item| ... } ⇒ Object #reject ⇒ Enumerator

#reject! {|item| ... } ⇒ nil #reject! ⇒ Enumerator

#repeated_combination(n) {|c| ... } ⇒ Object #repeated_combination(n) ⇒ Enumerator

#new(size = 0, obj = nil) ⇒ `Object` #new(array) ⇒ `Object` #new(size) {|index| ... } ⇒ `Object`

.[] ⇒ `Object`

.try_convert(obj) ⇒ `Array`^?

#&(other_ary) ⇒ `Object`

#(int) ⇒ `Object` #(str) ⇒ `Object`

#+(other_ary) ⇒ `Object`

#-(other_ary) ⇒ `Object`

#<<(obj) ⇒ `Object`

#<=>(other_ary) ⇒ `-1`, ...

#==(other_ary) ⇒ `Boolean`

#[](index) ⇒ `Object`^? #[](start, length) ⇒ `nil` #[](range) ⇒ `nil` #slice(index) ⇒ `Object`^? #slice(start, length) ⇒ `nil` #slice(range) ⇒ `nil`

#[]=(index) ⇒ `Object` #[]=(start, length) ⇒ `Object`^? #[]=(range) ⇒ `Object`^?

#assoc(obj) ⇒ `nil`

#at(index) ⇒ `Object`^?

#bsearch {|x| ... } ⇒ `Object`

#clear ⇒ `Object`

#collect {|item| ... } ⇒ `Object` #map {|item| ... } ⇒ `Object` #collect ⇒ `Enumerator` #map ⇒ `Enumerator`

#collect! {|item| ... } ⇒ `Object` #map! {|item| ... } ⇒ `Object` #collect! ⇒ `Enumerator` #map! ⇒ `Enumerator`

#combination(n) {|c| ... } ⇒ `Object` #combination(n) ⇒ `Enumerator`

#compact ⇒ `Object`

#compact! ⇒ `nil`

#concat(other_ary) ⇒ `Object`

#count ⇒ `Integer` #count(obj) ⇒ `Integer` #count {|item| ... } ⇒ `Integer`

#cycle(n = nil) {|obj| ... } ⇒ `nil` #cycle(n = nil) ⇒ `Enumerator`

#delete(obj) ⇒ `nil` #delete(obj) { ... } ⇒ `Object`

#delete_at(index) ⇒ `Object`^?

#delete_if {|item| ... } ⇒ `Object` #delete_if ⇒ `Enumerator`

#drop(n) ⇒ `Object`

#drop_while {|arr| ... } ⇒ `Object` #drop_while ⇒ `Enumerator`

#each {|item| ... } ⇒ `Object` #each ⇒ `Enumerator`

#each_index {|index| ... } ⇒ `Object` #each_index ⇒ `Enumerator`

#empty? ⇒ `Boolean`

#eql?(other) ⇒ `Boolean`

#fetch(index) ⇒ `Object` #fetch(index, default) ⇒ `Object` #fetch(index) {|index| ... } ⇒ `Object`

#fill(obj) ⇒ `Object` #fill(obj, start[, length]) ⇒ `Object` #fill(obj, range) ⇒ `Object` #fill {|index| ... } ⇒ `Object` #fill(start[, length]) {|index| ... } ⇒ `Object` #fill(range) {|index| ... } ⇒ `Object`

#index(obj) ⇒ `Integer`^? #index {|item| ... } ⇒ `Integer`^? #index ⇒ `Enumerator`

#first ⇒ `Object`^? #first(n) ⇒ `Object`

#flatten ⇒ `Object` #flatten(level) ⇒ `Object`

#flatten! ⇒ `nil` #flatten!(level) ⇒ `nil`

#frozen? ⇒ `Boolean`

#hash ⇒ `Fixnum`

#include?(object) ⇒ `Boolean`

#index(obj) ⇒ `Integer`^? #index {|item| ... } ⇒ `Integer`^? #index ⇒ `Enumerator`

#replace(other_ary) ⇒ `Object`

#insert(index, obj...) ⇒ `Object`

#inspect ⇒ `String` #to_s ⇒ `String` Also known as: to_s

#join(separator = $,) ⇒ `String`

#keep_if {|item| ... } ⇒ `Object` #keep_if ⇒ `Enumerator`

#last ⇒ `Object`^? #last(n) ⇒ `Object`

#length ⇒ `Integer` Also known as: size

#collect {|item| ... } ⇒ `Object` #map {|item| ... } ⇒ `Object` #collect ⇒ `Enumerator` #map ⇒ `Enumerator`

#collect! {|item| ... } ⇒ `Object` #map! {|item| ... } ⇒ `Object` #collect! ⇒ `Enumerator` #map! ⇒ `Enumerator`

#pack ⇒ `Object`

#permutation {|p| ... } ⇒ `Object` #permutation ⇒ `Enumerator` #permutation(n) {|p| ... } ⇒ `Object` #permutation(n) ⇒ `Enumerator`

#pop ⇒ `Object`^? #pop(n) ⇒ `Object`

#product(other_ary, ...) ⇒ `Object` #product(other_ary, ...) {|p| ... } ⇒ `Object`

#push(obj, ...) ⇒ `Object`

#rassoc(obj) ⇒ `nil`

#reject {|item| ... } ⇒ `Object` #reject ⇒ `Enumerator`

#reject! {|item| ... } ⇒ `nil` #reject! ⇒ `Enumerator`

#repeated_combination(n) {|c| ... } ⇒ `Object` #repeated_combination(n) ⇒ `Enumerator`

#repeated_permutation(n) {|p| ... } ⇒ `Object` #repeated_permutation(n) ⇒ `Enumerator`

#replace(other_ary) ⇒ `Object`

#reverse ⇒ `Object`

#reverse! ⇒ `Object`

#reverse_each {|item| ... } ⇒ `Object` #reverse_each ⇒ `Enumerator`

#rindex(obj) ⇒ `Integer`^? #rindex {|item| ... } ⇒ `Integer`^? #rindex ⇒ `Enumerator`

#rotate(count = 1) ⇒ `Object`

#rotate!(count = 1) ⇒ `Object`

#sample ⇒ `Object` #sample(random:rng) ⇒ `Object` #sample(n) ⇒ `Object` #sample(n, random:rng) ⇒ `Object`

#select {|item| ... } ⇒ `Object` #select ⇒ `Enumerator`

#select! {|item| ... } ⇒ `nil` #select! ⇒ `Enumerator`

#shift ⇒ `Object`^? #shift(n) ⇒ `Object`

#shuffle ⇒ `Object` #shuffle(random:rng) ⇒ `Object`

#shuffle! ⇒ `Object` #shuffle!(random:rng) ⇒ `Object`

#[](index) ⇒ `Object`^? #[](start, length) ⇒ `nil` #[](range) ⇒ `nil` #slice(index) ⇒ `Object`^? #slice(start, length) ⇒ `nil` #slice(range) ⇒ `nil`

#slice!(index) ⇒ `Object`^? #slice!(start, length) ⇒ `nil` #slice!(range) ⇒ `nil`

#sort ⇒ `Object` #sort {|a, b| ... } ⇒ `Object`

#sort! ⇒ `Object` #sort! {|a, b| ... } ⇒ `Object`

#sort_by! {|obj| ... } ⇒ `Object` #sort_by! ⇒ `Enumerator`