Class: Array

Inherits:
Object show all
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) #=> [true, true, true]

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}    #=> [{}, {}, {}, {}]
Array.new(4) {|i| i.to_s } #=> ["0", "1", "2", "3"]

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 tries to call #to_ary, then #to_a on its 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. Negative indices start counting from the end, with -1 being the last element.

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

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

arr.at(0) #=> 1

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

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

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

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

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

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

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

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

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

Obtaining Information about an Array

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

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

To check whether an array contains any elements at all

browsers.empty? #=> false

To check whether a particular item is included in the array

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

Adding Items to Arrays

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

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

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

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

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

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

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

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

Removing Items from an Array

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

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

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

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

To delete an element at a particular index:

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

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

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

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

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

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

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

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

Iterating over Arrays

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

Note that this operation leaves the array unchanged.

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

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

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

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

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

Selecting Items from an Array

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

Non-destructive Selection

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

Destructive Selection

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

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

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

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

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Enumerable

#chain, #chunk, #chunk_while, #collect_concat, #detect, #each_cons, #each_entry, #each_slice, #each_with_index, #each_with_object, #entries, #filter_map, #find, #find_all, #flat_map, #grep, #grep_v, #group_by, #inject, #lazy, #max_by, #member?, #min_by, #minmax_by, #partition, #reduce, #slice_after, #slice_before, #slice_when, #sort_by, #tally

Constructor Details

#new(size = 0, default = 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 default are sent, an array is created with size copies of default. Take notice that all elements will reference the same object default.

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:


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# File 'array.c', line 1012

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

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

Class Method Details

.[](*args) ⇒ 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/]

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# File 'array.c', line 1077

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

    return ary;
}

.try_convert(obj) ⇒ Array?

Tries to convert obj into an array, using the to_ary method. Returns the converted array or nil if obj cannot be converted. 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:


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# File 'array.c', line 950

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

Instance Method Details

#&(other_ary) ⇒ Array

Set Intersection — Returns a new array containing unique elements common to the two arrays. The order is preserved from the original array.

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

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

See also Array#uniq.

Returns:


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# File 'array.c', line 4649

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

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

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

    hash = ary_make_hash(ary2);

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

    return ary3;
}

#*(int) ⇒ Array #*(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"

Overloads:


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# File 'array.c', line 4112

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

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

    len = NUM2LONG(times);
    if (len == 0) {
	ary2 = ary_new(rb_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_CONST_PTR_TRANSIENT(ary);
    t = RARRAY_LEN(ary);
    if (0 < t) {
	ary_memcpy(ary2, 0, t, ptr);
	while (t <= len/2) {
            ary_memcpy(ary2, t, t, RARRAY_CONST_PTR_TRANSIENT(ary2));
            t *= 2;
        }
        if (t < len) {
            ary_memcpy(ary2, t, len-t, RARRAY_CONST_PTR_TRANSIENT(ary2));
        }
    }
  out:
    return ary2;
}

#+(other_ary) ⇒ Array

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" ]
c = a + [ "d", "e", "f" ]
c                         #=> [ "a", "b", "c", "d", "e", "f" ]
a                         #=> [ "a", "b", "c" ]

Note that

x += y

is the same as

x = x + y

This means that it produces a new array. As a consequence, repeated use of += on arrays can be quite inefficient.

See also Array#concat.

Returns:


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# File 'array.c', line 4020

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

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

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

#-(other_ary) ⇒ Array

Array Difference

Returns a new array that is a copy of the original array, removing all occurrences of any item that also appear in other_ary. The order is preserved from the original array.

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 ]

Note that while 1 and 2 were only present once in the array argument, and were present twice in the receiver array, all occurrences of each Integer are removed in the returned array.

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

See also Array#difference.

Returns:


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# File 'array.c', line 4539

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

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

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

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

#<<(obj) ⇒ Array

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.

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

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

Returns:


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# File 'array.c', line 1205

VALUE
rb_ary_push(VALUE ary, VALUE item)
{
    long idx = RARRAY_LEN((ary_verify(ary), ary));
    VALUE target_ary = ary_ensure_room_for_push(ary, 1);
    RARRAY_PTR_USE_TRANSIENT(ary, ptr, {
	RB_OBJ_WRITE(target_ary, &ptr[idx], item);
    });
    ARY_SET_LEN(ary, idx + 1);
    ary_verify(ary);
    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 element of ary is compared with the first one of other_ary using the <=> operator, then each of the second elements, etc… As soon as the result of any such comparison is non zero (i.e. the two corresponding elements are not equal), that result is returned for the whole array comparison.

If all the elements are equal, then the result 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.

nil is returned if the other_ary is not an array or if the comparison of two elements returned nil.

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

Returns:

  • (-1, 0, +1, nil)

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# File 'array.c', line 4440

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)

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# File 'array.c', line 4273

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

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

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:


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# File 'array.c', line 1584

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

#[]=(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.

See also Array#push, and Array#unshift.

a = Array.new
a[4] = "4";                 #=> [nil, nil, nil, nil, "4"]
a[0, 3] = [ 'a', 'b', 'c' ] #=> ["a", "b", "c", nil, "4"]
a[1..2] = [ 1, 2 ]          #=> ["a", 1, 2, nil, "4"]
a[0, 2] = "?"               #=> ["?", 2, nil, "4"]
a[0..2] = "A"               #=> ["A", "4"]
a[-1]   = "Z"               #=> ["A", "Z"]
a[1..-1] = nil              #=> ["A", nil]
a[1..-1] = []               #=> ["A"]
a[0, 0] = [ 1, 2 ]          #=> [1, 2, "A"]
a[3, 0] = "B"               #=> [1, 2, "A", "B"]

Overloads:


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# File 'array.c', line 2039

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

    if (argc == 3) {
	rb_ary_modify_check(ary);
	beg = NUM2LONG(argv[0]);
	len = NUM2LONG(argv[1]);
	goto range;
    }
    rb_check_arity(argc, 2, 2);
    rb_ary_modify_check(ary);
    if (FIXNUM_P(argv[0])) {
	offset = FIX2LONG(argv[0]);
	goto fixnum;
    }
    if (rb_range_beg_len(argv[0], &beg, &len, RARRAY_LEN(ary), 1)) {
	/* check if idx is Range */
      range:
	rpl = rb_ary_to_ary(argv[argc-1]);
        rb_ary_splice(ary, beg, len, RARRAY_CONST_PTR_TRANSIENT(rpl), RARRAY_LEN(rpl));
	RB_GC_GUARD(rpl);
	return argv[argc-1];
    }

    offset = NUM2LONG(argv[0]);
fixnum:
    rb_ary_store(ary, offset, argv[1]);
    return argv[1];
}

#all? {|obj| ... } ⇒ Boolean #all?(pattern) ⇒ Boolean

See also Enumerable#all?

Overloads:

  • #all? {|obj| ... } ⇒ Boolean

    Yields:

    • (obj)

    Returns:

    • (Boolean)
  • #all?(pattern) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 'array.c', line 6387

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

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

#any? {|obj| ... } ⇒ Boolean #any?(pattern) ⇒ Boolean

See also Enumerable#any?

Overloads:

  • #any? {|obj| ... } ⇒ Boolean

    Yields:

    • (obj)

    Returns:

    • (Boolean)
  • #any?(pattern) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 'array.c', line 6351

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

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

#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.

See also Array#rassoc

s1 = [ "colors", "red", "blue", "green" ]
s2 = [ "letters", "a", "b", "c" ]
s3 = "foo"
a  = [ s1, s2, s3 ]
a.assoc("letters")  #=> [ "letters", "a", "b", "c" ]
a.assoc("foo")      #=> nil

Returns:

  • (nil)

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# File 'array.c', line 4176

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

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

#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:


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# File 'array.c', line 1639

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 modes: 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 cases), the block must always 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 always 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)

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# File 'array.c', line 2949

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

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

#bsearch_index {|x| ... } ⇒ Integer?

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

It supports two modes, depending on the nature of the block. They are exactly the same as in the case of the #bsearch method, with the only difference being that this method returns the index of the element instead of the element itself. For more details consult the documentation for #bsearch.

Yields:

  • (x)

Returns:


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# File 'array.c', line 2973

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

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

#clearArray

Removes all elements from self.

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

Returns:


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# File 'array.c', line 3882

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

#collect {|item| ... } ⇒ Array #map {|item| ... } ⇒ Array #collectEnumerator #mapEnumerator

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.collect {|x| x + "!"}           #=> ["a!", "b!", "c!", "d!"]
a.map.with_index {|x, i| x * i}   #=> ["", "b", "cc", "ddd"]
a                                 #=> ["a", "b", "c", "d"]

Overloads:


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# File 'array.c', line 3077

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

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

#collect! {|item| ... } ⇒ Array #map! {|item| ... } ⇒ Array #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!" ]
a.collect!.with_index {|x, i| x[0...i] }
a #=>  ["", "b", "c!", "d!"]

Overloads:


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# File 'array.c', line 3113

static VALUE
rb_ary_collect_bang(VALUE ary)
{
    long i;

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

#combination(n) {|c| ... } ⇒ Array #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:


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# File 'array.c', line 5886

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

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

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

#compactArray

Returns a copy of self with all nil elements removed.

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

Returns:


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# File 'array.c', line 5109

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

#compact!Array?

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:


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# File 'array.c', line 5076

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

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

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

    return ary;
}

#concat(other_ary1, other_ary2, ...) ⇒ Array

Appends the elements of other_arys to self.

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

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

a = [ 1, 2 ]
a.concat(a, a)                    #=> [1, 2, 1, 2, 1, 2]

See also Array#+.

Returns:


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# File 'array.c', line 4068

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

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

    ary_verify(ary);
    return ary;
}

#countInteger #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:


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# File 'array.c', line 5138

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

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

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

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

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

    return LONG2NUM(n);
}

#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:


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# File 'array.c', line 5622

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

    rb_check_arity(argc, 0, 1);

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

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

#deconstructObject


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# File 'array.c', line 6695

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

#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:


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# File 'array.c', line 3385

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

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

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

    ary_resize_smaller(ary, i2);

    ary_verify(ary);
    return v;
}

#delete_at(index) ⇒ Object?

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

See also Array#slice!

a = ["ant", "bat", "cat", "dog"]
a.delete_at(2)    #=> "cat"
a                 #=> ["ant", "bat", "dog"]
a.delete_at(99)   #=> nil

Returns:


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# File 'array.c', line 3476

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

#delete_if {|item| ... } ⇒ Array #delete_ifEnumerator

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.

See also Array#reject!

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

scores = [ 97, 42, 75 ]
scores.delete_if {|score| score < 80 }   #=> [97]

Overloads:


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# File 'array.c', line 3659

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

#difference(other_ary1, other_ary2, ...) ⇒ Array

Array Difference

Returns a new array that is a copy of the original array, removing all occurrences of any item that also appear in other_ary. The order is preserved from the original array.

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

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

Note that while 1 and 2 were only present once in the array argument, and were present twice in the receiver array, all occurrences of each Integer are removed in the returned array.

Multiple array arguments can be supplied and all occurrences of any element in those supplied arrays that match the receiver will be removed from the returned array.

[ 1, 'c', :s, 'yep' ].difference([ 1 ], [ 'a', 'c' ])  #=> [ :s, "yep" ]

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

See also Array#-.

Returns:


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# File 'array.c', line 4596

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

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

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

    ALLOCV_END(t0);

    return ary_diff;
}

#dig(idx, ...) ⇒ Object

Extracts the nested value specified by the sequence of idx objects by calling dig at each step, returning nil if any intermediate step is nil.

a = [[1, [2, 3]]]

a.dig(0, 1, 1)                    #=> 3
a.dig(1, 2, 3)                    #=> nil
a.dig(0, 0, 0)                    #=> TypeError: Integer does not have #dig method
[42, {foo: :bar}].dig(1, :foo)    #=> :bar

Returns:


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# File 'array.c', line 6513

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

#drop(n) ⇒ Array

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.

See also Array#take

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

Returns:


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# File 'array.c', line 6299

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

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

#drop_while {|obj| ... } ⇒ Array #drop_whileEnumerator

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.

See also Array#take_while

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

Overloads:


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# File 'array.c', line 6331

static VALUE
rb_ary_drop_while(VALUE ary)
{
    long i;

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

#each {|item| ... } ⇒ Array #eachEnumerator

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

If no block is given, an Enumerator is returned.

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

produces:

a -- b -- c --

Overloads:


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# File 'array.c', line 2139

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

#each_index {|index| ... } ⇒ Array #each_indexEnumerator

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:


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# File 'array.c', line 2169

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

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

#empty?Boolean

Returns true if self contains no elements.

[].empty?   #=> true

Returns:

  • (Boolean)

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# File 'array.c', line 2240

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 (according to Object#eql?).

Returns:

  • (Boolean)

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# File 'array.c', line 4309

static VALUE
rb_ary_eql(VALUE ary1, VALUE ary2)
{
    if (ary1 == ary2) return Qtrue;
    if (!RB_TYPE_P(ary2, T_ARRAY)) return Qfalse;
    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return Qfalse;
    if (RARRAY_CONST_PTR_TRANSIENT(ary1) == RARRAY_CONST_PTR_TRANSIENT(ary2)) return Qtrue;
    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:


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# File 'array.c', line 1724

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

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

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

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

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:


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# File 'array.c', line 3933

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

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

    if (item == Qundef) {
	VALUE v;
	long i;

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

#select {|item| ... } ⇒ Array #selectEnumerator #filter {|item| ... } ⇒ Array #filterEnumerator

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"]

See also Enumerable#select.

Array#filter is an alias for Array#select.

Overloads:


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# File 'array.c', line 3233

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

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

#select! {|item| ... } ⇒ Array? #select!Enumerator #filter! {|item| ... } ⇒ Array? #filter!Enumerator

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

The array may not be changed instantly every time the block is called.

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

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

See also Array#keep_if.

Array#filter! is an alias for Array#select!.

Overloads:


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# File 'array.c', line 3314

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

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

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

#find_index(obj) ⇒ Integer? #find_index {|item| ... } ⇒ Integer? #find_indexEnumerator #index(obj) ⇒ Integer? #index {|item| ... } ⇒ Integer? #indexEnumerator

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.

See also Array#rindex.

An Enumerator is returned if neither a block nor argument is given.

a = [ "a", "b", "c" ]
a.index("b")              #=> 1
a.index("z")              #=> nil
a.index {|x| x == "b"}    #=> 1

Overloads:


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# File 'array.c', line 1778

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

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

#firstObject? #first(n) ⇒ Array

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:


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# File 'array.c', line 1660

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

#flattenArray #flatten(level) ⇒ Array

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]]

Overloads:


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# File 'array.c', line 5316

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

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

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

    return result;
}

#flatten!Array? #flatten!(level) ⇒ Array?

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:


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# File 'array.c', line 5272

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

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

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

    return ary;
}

#hashInteger

Compute a hash-code for this array.

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

See also Object#hash.

Returns:


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# File 'array.c', line 4331

static VALUE
rb_ary_hash(VALUE ary)
{
    long i;
    st_index_t h;
    VALUE n;

    h = rb_hash_start(RARRAY_LEN(ary));
    h = rb_hash_uint(h, (st_index_t)rb_ary_hash);
    for (i=0; i<RARRAY_LEN(ary); i++) {
	n = rb_hash(RARRAY_AREF(ary, i));
	h = rb_hash_uint(h, NUM2LONG(n));
    }
    h = rb_hash_end(h);
    return ST2FIX(h);
}

#include?(object) ⇒ Boolean

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

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

Returns:

  • (Boolean)

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# File 'array.c', line 4360

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

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

#find_index(obj) ⇒ Integer? #find_index {|item| ... } ⇒ Integer? #find_indexEnumerator #index(obj) ⇒ Integer? #index {|item| ... } ⇒ Integer? #indexEnumerator

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.

See also Array#rindex.

An Enumerator is returned if neither a block nor argument is given.

a = [ "a", "b", "c" ]
a.index("b")              #=> 1
a.index("z")              #=> nil
a.index {|x| x == "b"}    #=> 1

Overloads:


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# File 'array.c', line 1778

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

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

#replace(other_ary) ⇒ Array #initialize_copy(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"]

Overloads:


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# File 'array.c', line 3831

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 shared_root = 0;

        if (ARY_OWNS_HEAP_P(copy)) {
            ary_heap_free(copy);
	}
        else if (ARY_SHARED_P(copy)) {
            shared_root = ARY_SHARED_ROOT(copy);
            FL_UNSET_SHARED(copy);
        }
        FL_SET_EMBED(copy);
        ary_memcpy(copy, 0, RARRAY_LEN(orig), RARRAY_CONST_PTR_TRANSIENT(orig));
        if (shared_root) {
            rb_ary_decrement_share(shared_root);
        }
        ARY_SET_LEN(copy, RARRAY_LEN(orig));
    }
    else {
        VALUE shared_root = ary_make_shared(orig);
        if (ARY_OWNS_HEAP_P(copy)) {
            ary_heap_free(copy);
        }
        else {
            rb_ary_unshare_safe(copy);
        }
        FL_UNSET_EMBED(copy);
        ARY_SET_PTR(copy, ARY_HEAP_PTR(orig));
        ARY_SET_LEN(copy, ARY_HEAP_LEN(orig));
        rb_ary_set_shared(copy, shared_root);
    }
    ary_verify(copy);
    return copy;
}

#insert(index, obj...) ⇒ Array

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. If a negative index is used, the given values will be inserted after that element, so using an index of -1 will insert the values at the end of the array.

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"]

Returns:


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# File 'array.c', line 2088

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

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

#inspectString #to_sString Also known as: to_s

Creates a string representation of self, by calling #inspect on each element.

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

Overloads:


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# File 'array.c', line 2456

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);
}

#intersection(other_ary1, other_ary2, ...) ⇒ Array

Set Intersection — Returns a new array containing unique elements common to self and other_arys. Order is preserved from the original array.

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

[ 1, 1, 3, 5 ].intersection([ 3, 2, 1 ])                    # => [ 1, 3 ]
[ "a", "b", "z" ].intersection([ "a", "b", "c" ], [ "b" ])  # => [ "b" ]
[ "a" ].intersection #=> [ "a" ]

See also Array#&.

Returns:


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# File 'array.c', line 4701

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

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

    return result;
}

#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 an empty string.

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

For nested arrays, join is applied recursively:

[ "a", [1, 2, [:x, :y]], "b" ].join("-")   #=> "a-1-2-x-y-b"

Returns:


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# File 'array.c', line 2412

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

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

    return rb_ary_join(ary, sep);
}

#keep_if {|item| ... } ⇒ Array #keep_ifEnumerator

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

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

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

See also Array#select!.

Overloads:


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# File 'array.c', line 3344

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

#lastObject? #last(n) ⇒ Array

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:


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# File 'array.c', line 1687

VALUE
rb_ary_last(int argc, const VALUE *argv, VALUE ary)
{
    if (argc == 0) {
	long len = RARRAY_LEN(ary);
	if (len == 0) return Qnil;
	return RARRAY_AREF(ary, len-1);
    }
    else {
	return ary_take_first_or_last(argc, argv, ary, ARY_TAKE_LAST);
    }
}

#lengthInteger Also known as: size

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

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

Returns:


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# File 'array.c', line 2224

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

#collect {|item| ... } ⇒ Array #map {|item| ... } ⇒ Array #collectEnumerator #mapEnumerator

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.collect {|x| x + "!"}           #=> ["a!", "b!", "c!", "d!"]
a.map.with_index {|x, i| x * i}   #=> ["", "b", "cc", "ddd"]
a                                 #=> ["a", "b", "c", "d"]

Overloads:


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# File 'array.c', line 3077

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

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

#collect! {|item| ... } ⇒ Array #map! {|item| ... } ⇒ Array #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!" ]
a.collect!.with_index {|x, i| x[0...i] }
a #=>  ["", "b", "c!", "d!"]

Overloads:


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# File 'array.c', line 3113

static VALUE
rb_ary_collect_bang(VALUE ary)
{
    long i;

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

#maxObject #max {|a, b| ... } ⇒ Object #max(n) ⇒ Array #max(n) {|a, b| ... } ⇒ Array

Returns the object in ary with the maximum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

ary = %w(albatross dog horse)
ary.max                                   #=> "horse"
ary.max {|a, b| a.length <=> b.length}    #=> "albatross"

If the n argument is given, maximum n elements are returned as an array.

ary = %w[albatross dog horse]
ary.max(2)                                  #=> ["horse", "dog"]
ary.max(2) {|a, b| a.length <=> b.length }  #=> ["albatross", "horse"]

Overloads:


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# File 'array.c', line 4849

static VALUE
rb_ary_max(int argc, VALUE *argv, VALUE ary)
{
    struct cmp_opt_data cmp_opt = { 0, 0 };
    VALUE result = Qundef, v;
    VALUE num;
    long i;

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

    if (rb_block_given_p()) {
	for (i = 0; i < RARRAY_LEN(ary); i++) {
	   v = RARRAY_AREF(ary, i);
	   if (result == Qundef || rb_cmpint(rb_yield_values(2, v, result), v, result) > 0) {
	       result = v;
	   }
	}
    }
    else {
	for (i = 0; i < RARRAY_LEN(ary); i++) {
	   v = RARRAY_AREF(ary, i);
	   if (result == Qundef || OPTIMIZED_CMP(v, result, cmp_opt) > 0) {
	       result = v;
	   }
	}
    }
    if (result == Qundef) return Qnil;
    return result;
}

#minObject #min {|a, b| ... } ⇒ Object #min(n) ⇒ Array #min(n) {|a, b| ... } ⇒ Array

Returns the object in ary with the minimum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

ary = %w(albatross dog horse)
ary.min                                   #=> "albatross"
ary.min {|a, b| a.length <=> b.length}    #=> "dog"

If the n argument is given, minimum n elements are returned as an array.

ary = %w[albatross dog horse]
ary.min(2)                                  #=> ["albatross", "dog"]
ary.min(2) {|a, b| a.length <=> b.length }  #=> ["dog", "horse"]

Overloads:


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# File 'array.c', line 4902

static VALUE
rb_ary_min(int argc, VALUE *argv, VALUE ary)
{
    struct cmp_opt_data cmp_opt = { 0, 0 };
    VALUE result = Qundef, v;
    VALUE num;
    long i;

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

    if (rb_block_given_p()) {
	for (i = 0; i < RARRAY_LEN(ary); i++) {
	   v = RARRAY_AREF(ary, i);
	   if (result == Qundef || rb_cmpint(rb_yield_values(2, v, result), v, result) < 0) {
	       result = v;
	   }
	}
    }
    else {
	for (i = 0; i < RARRAY_LEN(ary); i++) {
	   v = RARRAY_AREF(ary, i);
	   if (result == Qundef || OPTIMIZED_CMP(v, result, cmp_opt) < 0) {
	       result = v;
	   }
	}
    }
    if (result == Qundef) return Qnil;
    return result;
}

#minmaxArray #minmax {|a, b| ... } ⇒ Array

Returns a two element array which contains the minimum and the maximum value in the array.

Can be given an optional block to override the default comparison method a <=> b.

Overloads:

  • #minmaxArray

    Returns:

  • #minmax {|a, b| ... } ⇒ Array

    Yields:

    • (a, b)

    Returns:


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# File 'array.c', line 4944

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

#none? {|obj| ... } ⇒ Boolean #none?(pattern) ⇒ Boolean

See also Enumerable#none?

Overloads:

  • #none? {|obj| ... } ⇒ Boolean

    Yields:

    • (obj)

    Returns:

    • (Boolean)
  • #none?(pattern) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 'array.c', line 6423

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

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

#one? {|obj| ... } ⇒ Boolean #one?(pattern) ⇒ Boolean

See also Enumerable#one?

Overloads:

  • #one? {|obj| ... } ⇒ Boolean

    Yields:

    • (obj)

    Returns:

    • (Boolean)
  • #one?(pattern) ⇒ Boolean

    Returns:

    • (Boolean)

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# File 'array.c', line 6459

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

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

#permutation {|p| ... } ⇒ Array #permutationEnumerator #permutation(n) {|p| ... } ⇒ Array #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:


5793
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# File 'array.c', line 5793

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

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

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

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

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

#popObject? #pop(n) ⇒ Array

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:


1288
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# File 'array.c', line 1288

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

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

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

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

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, ...) ⇒ Array

    Returns:

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

    Yields:

    • (p)

    Returns:


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# File 'array.c', line 6141

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 = Qundef;
    VALUE *arrays = RARRAY_PTR(t0); /* The arrays we're computing the product of */
    int *counters = ALLOCV_N(int, t1, n); /* The current position in each one */
    VALUE result = Qnil;      /* The array we'll be returning, when no block given */
    long i,j;
    long resultlen = 1;

    RBASIC_CLEAR_CLASS(t0);

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

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

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

	/* put it on the result array */
	if (NIL_P(result)) {
	    FL_SET(t0, 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);
    ALLOCV_END(t1);

    return NIL_P(result) ? ary : result;
}

#push(obj, ...) ⇒ Array #append(obj, ...) ⇒ Array Also known as: append

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]

Overloads:


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# File 'array.c', line 1245

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.

See also Array#assoc.

a = [ [ 1, "one"], [2, "two"], [3, "three"], ["ii", "two"] ]
a.rassoc("two")    #=> [2, "two"]
a.rassoc("four")   #=> nil

Returns:

  • (nil)

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# File 'array.c', line 4209

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

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

#reject {|item| ... } ⇒ Array #rejectEnumerator

Returns a new array containing the items in self for which the given block is not true. The ordering of non-rejected elements is maintained.

See also Array#delete_if

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

Overloads:


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# File 'array.c', line 3630

static VALUE
rb_ary_reject(VALUE ary)
{
    VALUE rejected_ary;

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

#reject! {|item| ... } ⇒ Array? #reject!Enumerator

Deletes every element of self for which the block evaluates to true, if no changes were made returns nil.

The array may not be changed instantly every time the block is called.

See also Enumerable#reject and Array#delete_if.

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

Overloads:


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# File 'array.c', line 3609

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

#repeated_combination(n) {|c| ... } ⇒ Array #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:


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# File 'array.c', line 6085

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

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

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

#repeated_permutation(n) {|p| ... } ⇒ Array #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:


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# File 'array.c', line 5991

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

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

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

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

#replace(other_ary) ⇒ Array #initialize_copy(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"]

Overloads:


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# File 'array.c', line 3831

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 shared_root = 0;

        if (ARY_OWNS_HEAP_P(copy)) {
            ary_heap_free(copy);
	}
        else if (ARY_SHARED_P(copy)) {
            shared_root = ARY_SHARED_ROOT(copy);
            FL_UNSET_SHARED(copy);
        }
        FL_SET_EMBED(copy);
        ary_memcpy(copy, 0, RARRAY_LEN(orig), RARRAY_CONST_PTR_TRANSIENT(orig));
        if (shared_root) {
            rb_ary_decrement_share(shared_root);
        }
        ARY_SET_LEN(copy, RARRAY_LEN(orig));
    }
    else {
        VALUE shared_root = ary_make_shared(orig);
        if (ARY_OWNS_HEAP_P(copy)) {
            ary_heap_free(copy);
        }
        else {
            rb_ary_unshare_safe(copy);
        }
        FL_UNSET_EMBED(copy);
        ARY_SET_PTR(copy, ARY_HEAP_PTR(orig));
        ARY_SET_LEN(copy, ARY_HEAP_LEN(orig));
        rb_ary_set_shared(copy, shared_root);
    }
    ary_verify(copy);
    return copy;
}

#reverseArray

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

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

Returns:


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# File 'array.c', line 2597

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

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

#reverse!Array

Reverses self in place.

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

Returns:


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# File 'array.c', line 2581

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

#reverse_each {|item| ... } ⇒ Array #reverse_eachEnumerator

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:


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# File 'array.c', line 2196

static VALUE
rb_ary_reverse_each(VALUE ary)
{
    long len;

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

#rindex(obj) ⇒ Integer? #rindex {|item| ... } ⇒ Integer? #rindexEnumerator

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.

See also Array#index.

If neither block nor argument is given, an Enumerator is returned instead.

a = [ "a", "b", "b", "b", "c" ]
a.rindex("b")             #=> 3
a.rindex("z")             #=> nil
a.rindex {|x| x == "b"}   #=> 3

Overloads:


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# File 'array.c', line 1830

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

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

#rotate(count = 1) ⇒ Array

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"]

Returns:


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# File 'array.c', line 2694

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

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

#rotate!(count = 1) ⇒ Array

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"]

Returns:


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# File 'array.c', line 2669

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

#sampleObject #sample(random: rng) ⇒ Object #sample(n) ⇒ Array #sample(n, random: rng) ⇒ Array

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.

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

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

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

Overloads:


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# File 'array.c', line 5444

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

    if (OPTHASH_GIVEN_P(opts)) {
	VALUE rnd;
	ID keyword_ids[1];

	keyword_ids[0] = id_random;
	rb_get_kwargs(opts, keyword_ids, 0, 1, &rnd);
	if (rnd != Qundef) {
	    randgen = rnd;
	}
    }
    len = RARRAY_LEN(ary);
    if (rb_check_arity(argc, 0, 1) == 0) {
	if (len < 2)
	    i = 0;
	else
	    i = RAND_UPTO(len);

	return rb_ary_elt(ary, i);
    }
    nv = argv[0];
    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);
    if (len < k && n <= numberof(idx)) {
	for (i = 0; i < n; ++i) {
	    if (rnds[i] >= len) return rb_ary_new_capa(0);
	}
    }
    if (n > len) n = len;
    switch (n) {
      case 0:
	return rb_ary_new_capa(0);
      case 1:
	i = rnds[0];
	return rb_ary_new_from_values(1, &RARRAY_AREF(ary, i));
      case 2:
	i = rnds[0];
	j = rnds[1];
	if (j >= i) j++;
	return rb_ary_new_from_args(2, RARRAY_AREF(ary, i), RARRAY_AREF(ary, 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_new_from_args(3, RARRAY_AREF(ary, i), RARRAY_AREF(ary, j), RARRAY_AREF(ary, k));
    }
    memo_threshold =
	len < 2560 ? len / 128 :
	len < 5120 ? len / 64 :
	len < 10240 ? len / 32 :
	len / 16;
    if (n <= numberof(idx)) {
	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_new_capa(n);
        RARRAY_PTR_USE_TRANSIENT(result, ptr_result, {
	    for (i=0; i<n; i++) {
		ptr_result[i] = RARRAY_AREF(ary, idx[i]);
	    }
	});
    }
    else if (n <= memo_threshold / 2) {
	long max_idx = 0;
#undef RUBY_UNTYPED_DATA_WARNING
#define RUBY_UNTYPED_DATA_WARNING 0
	VALUE vmemo = Data_Wrap_Struct(0, 0, st_free_table, 0);
	st_table *memo = st_init_numtable_with_size(n);
	DATA_PTR(vmemo) = memo;
	result = rb_ary_new_capa(n);
	RARRAY_PTR_USE(result, ptr_result, {
	    for (i=0; i<n; i++) {
		long r = RAND_UPTO(len-i) + i;
		ptr_result[i] = r;
		if (r > max_idx) max_idx = r;
	    }
	    len = RARRAY_LEN(ary);
	    if (len <= max_idx) n = 0;
	    else if (n > len) n = len;
            RARRAY_PTR_USE_TRANSIENT(ary, ptr_ary, {
		for (i=0; i<n; i++) {
		    long j2 = j = ptr_result[i];
		    long i2 = i;
		    st_data_t value;
		    if (st_lookup(memo, (st_data_t)i, &value)) i2 = (long)value;
		    if (st_lookup(memo, (st_data_t)j, &value)) j2 = (long)value;
		    st_insert(memo, (st_data_t)j, (st_data_t)i2);
		    ptr_result[i] = ptr_ary[j2];
		}
	    });
	});
	DATA_PTR(vmemo) = 0;
	st_free_table(memo);
    }
    else {
	result = rb_ary_dup(ary);
	RBASIC_CLEAR_CLASS(result);
	RB_GC_GUARD(ary);
	RARRAY_PTR_USE(result, ptr_result, {
	    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_SET_CLASS_RAW(result, rb_cArray);
    }
    ARY_SET_LEN(result, n);

    return result;
}

#select {|item| ... } ⇒ Array #selectEnumerator #filter {|item| ... } ⇒ Array #filterEnumerator

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"]

See also Enumerable#select.

Array#filter is an alias for Array#select.

Overloads:


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# File 'array.c', line 3233

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

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

#select! {|item| ... } ⇒ Array? #select!Enumerator #filter! {|item| ... } ⇒ Array? #filter!Enumerator

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

The array may not be changed instantly every time the block is called.

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

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

See also Array#keep_if.

Array#filter! is an alias for Array#select!.

Overloads:


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# File 'array.c', line 3314

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

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

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

#shiftObject? #shift(n) ⇒ Array

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:


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# File 'array.c', line 1361

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

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

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

    return result;
}

#shuffleArray #shuffle(random: rng) ⇒ Array

Returns a new array with elements of self shuffled.

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

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

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

Overloads:


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# File 'array.c', line 5408

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!Array #shuffle!(random: rng) ⇒ Array

Shuffles elements in self in place.

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

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

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

Overloads:


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# File 'array.c', line 5357

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

    if (OPTHASH_GIVEN_P(opts)) {
	VALUE rnd;
	ID keyword_ids[1];

	keyword_ids[0] = id_random;
	rb_get_kwargs(opts, keyword_ids, 0, 1, &rnd);
	if (rnd != Qundef) {
	    randgen = rnd;
	}
    }
    rb_check_arity(argc, 0, 0);
    rb_ary_modify(ary);
    i = len = RARRAY_LEN(ary);
    RARRAY_PTR_USE(ary, ptr, {
	while (i) {
	    long j = RAND_UPTO(i);
	    VALUE tmp;
            if (len != RARRAY_LEN(ary) || ptr != RARRAY_CONST_PTR_TRANSIENT(ary)) {
                rb_raise(rb_eRuntimeError, "modified during shuffle");
	    }
	    tmp = ptr[--i];
	    ptr[i] = ptr[j];
	    ptr[j] = tmp;
	}
    }); /* WB: no new reference */
    return ary;
}

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

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:


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# File 'array.c', line 1584

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

#slice!(index) ⇒ Object? #slice!(start, length) ⇒ Array? #slice!(range) ⇒ Array?

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:


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# File 'array.c', line 3503

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_CONST_PTR_TRANSIENT(ary)+pos);
	RBASIC_SET_CLASS(arg2, rb_obj_class(ary));
	rb_ary_splice(ary, pos, len, 0, 0);
	return arg2;
    }

    rb_check_arity(argc, 1, 2);
    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));
}

#sortArray #sort {|a, b| ... } ⇒ Array

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 an integer less than 0 when b follows a, 0 when a and b are equivalent, or an integer greater than 0 when a follows b.

The result is not guaranteed to be stable. When the comparison of two elements returns 0, the order of the elements is unpredictable.

ary = [ "d", "a", "e", "c", "b" ]
ary.sort                     #=> ["a", "b", "c", "d", "e"]
ary.sort {|a, b| b <=> a}    #=> ["e", "d", "c", "b", "a"]

To produce the reverse order, the following can also be used (and may be faster):

ary.sort.reverse!             #=> ["e", "d", "c", "b", "a"]

See also Enumerable#sort_by.

Overloads:


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# File 'array.c', line 2886

VALUE
rb_ary_sort(VALUE ary)
{
    ary = rb_ary_dup(ary);
    rb_ary_sort_bang(ary);
    return ary;
}

#sort!Array #sort! {|a, b| ... } ⇒ Array

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 an integer less than 0 when b follows a, 0 when a and b are equivalent, or an integer greater than 0 when a follows b.

The result is not guaranteed to be stable. When the comparison of two elements returns 0, the order of the elements is unpredictable.

ary = [ "d", "a", "e", "c", "b" ]
ary.sort!                     #=> ["a", "b", "c", "d", "e"]
ary.sort! {|a, b| b <=> a}    #=> ["e", "d", "c", "b", "a"]

See also Enumerable#sort_by.

Overloads:


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# File 'array.c', line 2797

VALUE
rb_ary_sort_bang(VALUE ary)
{
    rb_ary_modify(ary);
    assert(!ARY_SHARED_P(ary));
    if (RARRAY_LEN(ary) > 1) {
	VALUE tmp = ary_make_substitution(ary); /* only ary refers tmp */
	struct ary_sort_data data;
	long len = RARRAY_LEN(ary);
	RBASIC_CLEAR_CLASS(tmp);
	data.ary = tmp;
	data.cmp_opt.opt_methods = 0;
	data.cmp_opt.opt_inited = 0;
	RARRAY_PTR_USE(tmp, ptr, {
            ruby_qsort(ptr, len, sizeof(VALUE),
                       rb_block_given_p()?sort_1:sort_2, &data);
	}); /* WB: no new reference */
	rb_ary_modify(ary);
        if (ARY_EMBED_P(tmp)) {
            if (ARY_SHARED_P(ary)) { /* ary might be destructively operated in the given block */
                rb_ary_unshare(ary);
		FL_SET_EMBED(ary);
            }
	    ary_memcpy(ary, 0, ARY_EMBED_LEN(tmp), ARY_EMBED_PTR(tmp));
            ARY_SET_LEN(ary, ARY_EMBED_LEN(tmp));
        }
        else {
            if (!ARY_EMBED_P(ary) && ARY_HEAP_PTR(ary) == ARY_HEAP_PTR(tmp)) {
                FL_UNSET_SHARED(ary);
                ARY_SET_CAPA(ary, RARRAY_LEN(tmp));
            }
            else {
                assert(!ARY_SHARED_P(tmp));
                if (ARY_EMBED_P(ary)) {
                    FL_UNSET_EMBED(ary);
                }
                else if (ARY_SHARED_P(ary)) {
                    /* ary might be destructively operated in the given block */
                    rb_ary_unshare(ary);
                }
                else {
                    ary_heap_free(ary);
                }
                ARY_SET_PTR(ary, ARY_HEAP_PTR(tmp));
                ARY_SET_HEAP_LEN(ary, len);
                ARY_SET_CAPA(ary, ARY_HEAP_LEN(tmp));
            }
            /* tmp was lost ownership for the ptr */
            FL_UNSET(tmp, FL_FREEZE);
            FL_SET_EMBED(tmp);
            ARY_SET_EMBED_LEN(tmp, 0);
            FL_SET(tmp, FL_FREEZE);
        }
        /* tmp will be GC'ed. */
        RBASIC_SET_CLASS_RAW(tmp, rb_cArray); /* rb_cArray must be marked */
    }
    ary_verify(ary);
    return ary;
}

#sort_by! {|obj| ... } ⇒ Array #sort_by!Enumerator

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

The result is not guaranteed to be stable. When two keys are equal, the order of the corresponding elements is unpredictable.

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

See also Enumerable#sort_by.

Overloads:


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# File 'array.c', line 3043

static VALUE
rb_ary_sort_by_bang(VALUE ary)
{
    VALUE sorted;

    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
    rb_ary_modify(ary);
    sorted = rb_block_call(ary, rb_intern("sort_by"), 0, 0, sort_by_i, 0);
    rb_ary_replace(ary, sorted);
    return ary;
}

#sum(init = 0) ⇒ Numeric #sum(init = 0) {|e| ... } ⇒ Numeric

Returns the sum of elements. For example, [e1, e2, e3].sum returns init + e1 + e2 + e3.

If a block is given, the block is applied to each element before addition.

If ary is empty, it returns init.

[].sum                             #=> 0
[].sum(0.0)                        #=> 0.0
[1, 2, 3].sum                      #=> 6
[3, 5.5].sum                       #=> 8.5
[2.5, 3.0].sum(0.0) {|e| e * e }   #=> 15.25
[Object.new].sum                   #=> TypeError

The (arithmetic) mean value of an array can be obtained as follows.

mean = ary.sum(0.0) / ary.length

This method can be used for non-numeric objects by explicit init argument.

["a", "b", "c"].sum("")            #=> "abc"
[[1], [[2]], [3]].sum([])          #=> [1, [2], 3]

However, Array#join and Array#flatten is faster than Array#sum for array of strings and array of arrays.

["a", "b", "c"].join               #=> "abc"
[[1], [[2]], [3]].flatten(1)       #=> [1, [2], 3]

Array#sum method may not respect method redefinition of “+” methods such as Integer#+.

Overloads:


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# File 'array.c', line 6585

static VALUE
rb_ary_sum(int argc, VALUE *argv, VALUE ary)
{
    VALUE e, v, r;
    long i, n;
    int block_given;

    v = (rb_check_arity(argc, 0, 1) ? argv[0] : LONG2FIX(0));

    block_given = rb_block_given_p();

    if (RARRAY_LEN(ary) == 0)
        return v;

    n = 0;
    r = Qundef;
    for (i = 0; i < RARRAY_LEN(ary); i++) {
        e = RARRAY_AREF(ary, i);
        if (block_given)
            e = rb_yield(e);
        if (FIXNUM_P(e)) {
            n += FIX2LONG(e); /* should not overflow long type */
            if (!FIXABLE(n)) {
                v = rb_big_plus(LONG2NUM(n), v);
                n = 0;
            }
        }
        else if (RB_TYPE_P(e, T_BIGNUM))
            v = rb_big_plus(e, v);
        else if (RB_TYPE_P(e, T_RATIONAL)) {
            if (r == Qundef)
                r = e;
            else
                r = rb_rational_plus(r, e);
        }
        else
            goto not_exact;
    }
    v = finish_exact_sum(n, r, v, argc!=0);
    return v;

  not_exact:
    v = finish_exact_sum(n, r, v, i!=0);

    if (RB_FLOAT_TYPE_P(e)) {
        /*
         * Kahan-Babuska balancing compensated summation algorithm
         * See http://link.springer.com/article/10.1007/s00607-005-0139-x
         */
        double f, c;
        double x, t;

        f = NUM2DBL(v);
        c = 0.0;
        goto has_float_value;
        for (; i < RARRAY_LEN(ary); i++) {
            e = RARRAY_AREF(ary, i);
            if (block_given)
                e = rb_yield(e);
            if (RB_FLOAT_TYPE_P(e))
              has_float_value:
                x = RFLOAT_VALUE(e);
            else if (FIXNUM_P(e))
                x = FIX2LONG(e);
            else if (RB_TYPE_P(e, T_BIGNUM))
                x = rb_big2dbl(e);
            else if (RB_TYPE_P(e, T_RATIONAL))
                x = rb_num2dbl(e);
            else
                goto not_float;

            if (isnan(f)) continue;
            if (isnan(x)) {
                f = x;
                continue;
            }
            if (isinf(x)) {
                if (isinf(f) && signbit(x) != signbit(f))
                    f = NAN;
                else
                    f = x;
                continue;
            }
            if (isinf(f)) continue;

            t = f + x;
            if (fabs(f) >= fabs(x))
                c += ((f - t) + x);
            else
                c += ((x - t) + f);
            f = t;
        }
        f += c;
        return DBL2NUM(f);

      not_float:
        v = DBL2NUM(f);
    }

    goto has_some_value;
    for (; i < RARRAY_LEN(ary); i++) {
        e = RARRAY_AREF(ary, i);
        if (block_given)
            e = rb_yield(e);
      has_some_value:
        v = rb_funcall(v, idPLUS, 1, e);
    }
    return v;
}

#take(n) ⇒ Array

Returns first n elements from the array.

If a negative number is given, raises an ArgumentError.

See also Array#drop

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

Returns:


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# File 'array.c', line 6244

static VALUE
rb_ary_take(VALUE obj, VALUE n)
{
    long len = NUM2LONG(n);
    if (len < 0) {
	rb_raise(rb_eArgError, "attempt to take negative size");
    }
    return rb_ary_subseq(obj, 0, len);
}

#take_while {|obj| ... } ⇒ Array #take_whileEnumerator

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.

See also Array#drop_while

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

Overloads:


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# File 'array.c', line 6271

static VALUE
rb_ary_take_while(VALUE ary)
{
    long i;

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

#to_aArray

Returns self.

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

Returns:


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# File 'array.c', line 2478

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_aryArray

Returns self.

Returns:


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# File 'array.c', line 2538

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

#to_hHash #to_h {|item| ... } ⇒ Hash

Returns the result of interpreting ary as an array of [key, value] pairs.

[[:foo, :bar], [1, 2]].to_h  # => {:foo => :bar, 1 => 2}

If a block is given, the results of the block on each element of the array will be used as pairs.

["foo", "bar"].to_h {|s| [s.ord, s]}  # => {102=>"foo", 98=>"bar"}

Overloads:

  • #to_hHash

    Returns:

  • #to_h {|item| ... } ⇒ Hash

    Yields:

    • (item)

    Returns:


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# File 'array.c', line 2507

static VALUE
rb_ary_to_h(VALUE ary)
{
    long i;
    VALUE hash = rb_hash_new_with_size(RARRAY_LEN(ary));
    int block_given = rb_block_given_p();

    for (i=0; i<RARRAY_LEN(ary); i++) {
	const VALUE e = rb_ary_elt(ary, i);
	const VALUE elt = block_given ? rb_yield_force_blockarg(e) : e;
	const VALUE key_value_pair = rb_check_array_type(elt);
	if (NIL_P(key_value_pair)) {
	    rb_raise(rb_eTypeError, "wrong element type %"PRIsVALUE" at %ld (expected array)",
		     rb_obj_class(elt), i);
	}
	if (RARRAY_LEN(key_value_pair) != 2) {
	    rb_raise(rb_eArgError, "wrong array length at %ld (expected 2, was %ld)",
		i, RARRAY_LEN(key_value_pair));
	}
	rb_hash_aset(hash, RARRAY_AREF(key_value_pair, 0), RARRAY_AREF(key_value_pair, 1));
    }
    return hash;
}

#transposeArray

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.

Returns:


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# File 'array.c', line 3790

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;
}

#union(other_ary1, other_ary2, ...) ⇒ Array

Set Union — Returns a new array by joining other_arys with self, excluding any duplicates and preserving the order from the given arrays.

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

[ "a", "b", "c" ].union( [ "c", "d", "a" ] )    #=> [ "a", "b", "c", "d" ]
[ "a" ].union( ["e", "b"], ["a", "c", "b"] )    #=> [ "a", "e", "b", "c" ]
[ "a" ].union #=> [ "a" ]

See also Array#|.

Returns:


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# File 'array.c', line 4797

static VALUE
rb_ary_union_multi(int argc, VALUE *argv, VALUE ary)
{
    int i;
    long sum;
    VALUE hash, ary_union;

    sum = RARRAY_LEN(ary);
    for (i = 0; i < argc; i++) {
        argv[i] = to_ary(argv[i]);
        sum += RARRAY_LEN(argv[i]);
    }

    if (sum <= SMALL_ARRAY_LEN) {
        ary_union = rb_ary_new();

        rb_ary_union(ary_union, ary);
        for (i = 0; i < argc; i++) rb_ary_union(ary_union, argv[i]);

        return ary_union;
    }

    hash = ary_make_hash(ary);
    for (i = 0; i < argc; i++) rb_ary_union_hash(hash, argv[i]);

    ary_union = rb_hash_values(hash);
    ary_recycle_hash(hash);
    return ary_union;
}

#uniqArray #uniq {|item| ... } ⇒ Array

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.

self is traversed in order, and the first occurrence is kept.

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:


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# File 'array.c', line 5039

static VALUE
rb_ary_uniq(VALUE ary)
{
    VALUE hash, uniq;

    if (RARRAY_LEN(ary) <= 1) {
        hash = 0;
        uniq = rb_ary_dup(ary);
    }
    else if (rb_block_given_p()) {
	hash = ary_make_hash_by(ary);
	uniq = rb_hash_values(hash);
    }
    else {
	hash = ary_make_hash(ary);
	uniq = rb_hash_values(hash);
    }
    RBASIC_SET_CLASS(uniq, rb_obj_class(ary));
    if (hash) {
        ary_recycle_hash(hash);
    }

    return uniq;
}

#uniq!Array? #uniq! {|item| ... } ⇒ Array?

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.

self is traversed in order, and the first occurrence is kept.

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!Array?

    Returns:

  • #uniq! {|item| ... } ⇒ Array?

    Yields:

    • (item)

    Returns:


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# File 'array.c', line 4987

static VALUE
rb_ary_uniq_bang(VALUE ary)
{
    VALUE hash;
    long hash_size;

    rb_ary_modify_check(ary);
    if (RARRAY_LEN(ary) <= 1)
        return Qnil;
    if (rb_block_given_p())
	hash = ary_make_hash_by(ary);
    else
	hash = ary_make_hash(ary);

    hash_size = RHASH_SIZE(hash);
    if (RARRAY_LEN(ary) == hash_size) {
	return Qnil;
    }
    rb_ary_modify_check(ary);
    ARY_SET_LEN(ary, 0);
    if (ARY_SHARED_P(ary) && !ARY_EMBED_P(ary)) {
	rb_ary_unshare(ary);
	FL_SET_EMBED(ary);
    }
    ary_resize_capa(ary, hash_size);
    rb_hash_foreach(hash, push_value, ary);
    ary_recycle_hash(hash);

    return ary;
}

#unshift(obj, ...) ⇒ Array #prepend(obj, ...) ⇒ Array Also known as: prepend

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"]

Overloads:


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# File 'array.c', line 1487

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

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

    target_ary = ary_ensure_room_for_unshift(ary, argc);
    ary_memcpy0(ary, 0, argc, argv, target_ary);
    ARY_SET_LEN(ary, len + argc);
    return ary;
}

#values_at(selector, ...) ⇒ Array

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

The selectors may be either integer indices or ranges.

See also Array#select.

a = %w{ a b c d e f }
a.values_at(1, 3, 5)          # => ["b", "d", "f"]
a.values_at(1, 3, 5, 7)       # => ["b", "d", "f", nil]
a.values_at(-1, -2, -2, -7)   # => ["f", "e", "e", nil]
a.values_at(4..6, 3...6)      # => ["e", "f", nil, "d", "e", "f"]

Returns:


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# File 'array.c', line 3198

static VALUE
rb_ary_values_at(int argc, VALUE *argv, VALUE ary)
{
    long i, olen = RARRAY_LEN(ary);
    VALUE result = rb_ary_new_capa(argc);
    for (i = 0; i < argc; ++i) {
	append_values_at_single(result, ary, olen, argv[i]);
    }
    RB_GC_GUARD(ary);
    return result;
}

#zip(arg, ...) ⇒ Array #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 than 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, ...) ⇒ Array

    Returns:

  • #zip(arg, ...) {|arr| ... } ⇒ nil

    Yields:

    • (arr)

    Returns:

    • (nil)

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# File 'array.c', line 3719

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

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

    if (rb_block_given_p()) {
	int arity = rb_block_arity();

	if (arity > 1) {
	    VALUE work, *tmp;

	    tmp = ALLOCV_N(VALUE, work, argc+1);

	    for (i=0; i<RARRAY_LEN(ary); i++) {
		tmp[0] = RARRAY_AREF(ary, i);
		for (j=0; j<argc; j++) {
		    tmp[j+1] = rb_ary_elt(argv[j], i);
		}
		rb_yield_values2(argc+1, tmp);
	    }

	    if (work) ALLOCV_END(work);
	}
	else {
	    for (i=0; i<RARRAY_LEN(ary); i++) {
		VALUE tmp = rb_ary_new2(argc+1);

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

	for (i=0; i<len; i++) {
	    VALUE tmp = rb_ary_new_capa(argc+1);

	    rb_ary_push(tmp, RARRAY_AREF(ary, i));
	    for (j=0; j<argc; j++) {
		rb_ary_push(tmp, rb_ary_elt(argv[j], i));
	    }
	    rb_ary_push(result, tmp);
	}
    }

    return result;
}

#|(other_ary) ⇒ Array

Set Union — Returns a new array by joining ary with other_ary, excluding any duplicates and preserving the order from the given arrays.

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

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

See also Array#union.

Returns:


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# File 'array.c', line 4760

static VALUE
rb_ary_or(VALUE ary1, VALUE ary2)
{
    VALUE hash, ary3;

    ary2 = to_ary(ary2);
    if (RARRAY_LEN(ary1) + RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
	ary3 = rb_ary_new();
        rb_ary_union(ary3, ary1);
        rb_ary_union(ary3, ary2);
	return ary3;
    }

    hash = ary_make_hash(ary1);
    rb_ary_union_hash(hash, ary2);

    ary3 = rb_hash_values(hash);
    ary_recycle_hash(hash);
    return ary3;
}