class Array(T)

Overview

An Array is an ordered, integer-indexed collection of objects of type T.

Array indexing starts at 0. A negative index is assumed to be relative to the end of the array: -1 indicates the last element, -2 is the next to last element, and so on.

An Array can be created using the usual .new method (several are provided), or with an array literal:

Array(Int32).new  # => []
[1, 2, 3]         # Array(Int32)
[1, "hello", 'x'] # Array(Int32 | String | Char)

An Array can have mixed types, meaning T will be a union of types, but these are determined when the array is created, either by specifying T or by using an array literal. In the latter case, T will be set to the union of the array literal elements' types.

When creating an empty array you must always specify T:

[] of Int32 # same as Array(Int32)
[]          # syntax error

An Array is implemented using an internal buffer of some capacity and is reallocated when elements are pushed to it when more capacity is needed. This is normally known as a dynamic array.

You can use a special array literal syntax with other types too, as long as they define an argless .new method and a #<< method. Set is one such type:

set = Set{1, 2, 3} # => [1, 2, 3]
set.class          # => Set(Int32)

The above is the same as this:

set = Set(typeof(1, 2, 3)).new
set << 1
set << 2
set << 3

Included Modules

Defined in:

array.cr
json/to_json.cr
yaml/to_yaml.cr

Class Method Summary

Instance Method Summary

Instance methods inherited from module Comparable(T)

<(other : T) <, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) >, >=(other : T) >=

Instance methods inherited from module Iterable

cycle
cycle(n) cycle, each each, each_cons(count : Int) each_cons, each_slice(count : Int) each_slice, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object

Instance methods inherited from module Enumerable(T)

all?
all?(&block) all?, any?
any?(&block) any?, compact_map(&block) compact_map, count(item)
count(&block) count, cycle(&block)
cycle(n, &block) cycle, each(&block : T -> _) each, each_cons(count : Int, &block) each_cons, each_slice(count : Int, &block) each_slice, each_with_index(offset = 0, &block) each_with_index, each_with_object(obj, &block) each_with_object, find(if_none = nil, &block) find, first
first(count : Int) first, first? first?, flat_map(&block : T -> Array(U)) flat_map, grep(pattern) grep, group_by(&block : T -> U) group_by, in_groups_of(size : Int, filled_up_with : U = nil, &block)
in_groups_of(size : Int, filled_up_with : U = nil) in_groups_of, includes?(obj) includes?, index(obj)
index(&block) index, index_by(&block : T -> U) index_by, join(separator = "")
join(separator, io, &block)
join(separator = "", &block)
join(separator, io) join, map(&block : T -> U) map, map_with_index(&block : T, Int32 -> U) map_with_index, max max, max? max?, max_by(&block : T -> U) max_by, max_by?(&block : T -> U) max_by?, max_of(&block : T -> U) max_of, max_of?(&block : T -> U) max_of?, min min, min? min?, min_by(&block : T -> U) min_by, min_by?(&block : T -> U) min_by?, min_of(&block : T -> U) min_of, min_of?(&block : T -> U) min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : T -> U) minmax_by, minmax_by?(&block : T -> U) minmax_by?, minmax_of(&block : T -> U) minmax_of, minmax_of?(&block : T -> U) minmax_of?, none?(&block)
none? none?, one?(&block) one?, partition(&block) partition, product(initial : Number, &block)
product
product(initial : Number)
product(&block) product, reduce(memo, &block)
reduce(&block) reduce, reject(&block : T -> ) reject, select(&block : T -> ) select, size size, skip(count : Int) skip, skip_while(&block) skip_while, sum
sum(initial)
sum(&block)
sum(initial, &block) sum, take_while(&block) take_while, to_a to_a, to_h to_h, to_set to_set

Instance methods inherited from class Reference

==(other)
==(other : self) ==, hash hash, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, same?(other : Reference)
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other)
===(other : YAML::Any)
===(other : JSON::Any) ===, =~(other) =~, class class, clone clone, crystal_type_id crystal_type_id, dup dup, hash hash, inspect
inspect(io : IO) inspect, itself itself, not_nil! not_nil!, tap(&block) tap, to_json to_json, to_pretty_json(io : IO)
to_pretty_json to_pretty_json, to_s
to_s(io : IO) to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&block) try

Class methods inherited from class Object

==(other : Class) ==, ===(other) ===, cast(other) : self cast, from_json(string_or_io) : self from_json, from_yaml(string : String) : self from_yaml, hash hash, inspect(io) inspect, name : String name, to_s(io) to_s, |(other : U.class) |

Class Method Detail

def self.build(capacity : Int, &block) #

Creates a new Array, allocating an internal buffer with the given capacity, and yielding that buffer. The given block must return the desired size of the array.

This method is unsafe, but is usually used to initialize the buffer by passing it to a C function.

Array.build(3) do |buffer|
  LibSome.fill_buffer_and_return_number_of_elements_filled(buffer)
end

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def self.each_product(arrays, &block) #

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def self.each_product(*arrays : Array, &block) #

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def self.from_json(string_or_io, &block) : Nil #

Parses a String or IO denoting a JSON array, yielding each of its elements to the given block. This is useful for decoding an array and processing its elements without creating an Array in memory, which might be expensive.

require "json"

Array(Int32).from_json("[1, 2, 3]") do |element|
  puts element
end

Output:

1
2
3

To parse and get an Array, use the block-less overload.


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def self.from_yaml(string : String, &block) #

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def self.new(pull : JSON::PullParser) #

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def self.new(size : Int, &block : Int32 -> T) #

Creates a new Array of the given size and invokes the given block once for each index of self, assigning the block's value in that index.

Array.new(3) { |i| (i + 1) ** 2 } # => [1, 4, 9]

ary = Array.new(3) { [1] }
puts ary # => [[1], [1], [1]]
ary[0][0] = 2
puts ary # => [[2], [1], [1]]

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def self.new(pull : YAML::PullParser) #

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def self.new(pull : YAML::PullParser, &block) #

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def self.new(pull : JSON::PullParser, &block) #

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def self.product(arrays) #

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def self.product(*arrays : Array) #

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def self.new(size : Int, value : T) #

Creates a new Array of the given size filled with the same value in each position.

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

ary = Array.new(3, [1])
puts ary # => [[1], [1], [1]]
ary[0][0] = 2
puts ary # => [[2], [2], [2]]

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def self.new(initial_capacity : Int) #

Creates a new empty Array backed by a buffer that is initially initial_capacity big.

The initial_capacity is useful to avoid unnecessary reallocations of the internal buffer in case of growth. If you have an estimate of the maximum number of elements an array will hold, the array should be initialized with that capacity for improved performance.

ary = Array(Int32).new(5)
ary.size # => 0

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def self.new #

Creates a new empty Array.


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Instance Method Detail

def &(other : Array(U)) #

Set intersection: returns a new Array containing elements common to self and other, excluding any duplicates. The order is preserved from self.

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

See also: #uniq.


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def *(times : Int) #

Repetition: Returns a new Array built by concatenating times copies of self.

["a", "b", "c"] * 2 # => [ "a", "b", "c", "a", "b", "c" ]

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def +(other : Array(U)) #

Concatenation. Returns a new Array built by concatenating self and other. The type of the new array is the union of the types of both the original arrays.

[1, 2] + ["a"]  # => [1,2,"a"] of (Int32 | String)
[1, 2] + [2, 3] # => [1,2,2,3]

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def -(other : Array(U)) #

Difference. Returns a new Array that is a copy of self, removing any items that appear in other. The order of self is preserved.

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

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def <<(value : T) #

Append. Alias for #push.

a = [1, 2]
a << 3 # => [1,2,3]

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def <=>(other : Array) #

Combined comparison operator. Returns 0 if self equals other, 1 if self is greater than other and -1 if self is smaller than other.

It compares the elements of both arrays in the same position using the #<=> operator. As soon as one of such comparisons returns a non-zero value, that result is the return value of the comparison.

If all elements are equal, the comparison is based on the size of the arrays.

[8] <=> [1, 2, 3] # => 1
[2] <=> [4, 2, 3] # => -1
[1, 2] <=> [1, 2] # => 0

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def ==(other : Array) #

Equality. Returns true if each element in self is equal to each corresponding element in other.

ary = [1, 2, 3]
ary == [1, 2, 3] # => true
ary == [2, 3]    # => false

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def [](index : Int) #

Returns the element at the given index.

Negative indices can be used to start counting from the end of the array. Raises IndexError if trying to access an element outside the array's range.

ary = ['a', 'b', 'c']
ary[0]  # => 'a'
ary[2]  # => 'c'
ary[-1] # => 'c'
ary[-2] # => 'b'

ary[3]  # raises IndexError
ary[-4] # raises IndexError

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def [](range : Range(Int, Int)) #

Returns all elements that are within the given range.

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

Raises IndexError if the starting index is out of range.

a = ["a", "b", "c", "d", "e"]
a[1..3]    # => ["b", "c", "d"]
a[4..7]    # => ["e"]
a[6..10]   # => Index Error
a[5..10]   # => []
a[-2...-1] # => ["d"]

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def [](start : Int, count : Int) #

Returns count or less (if there aren't enough) elements starting at the given start index.

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

Raises IndexError if the starting index is out of range.

a = ["a", "b", "c", "d", "e"]
a[-3, 3] # => ["c", "d", "e"]
a[6, 1]  # => Index Error
a[1, 2]  # => ["b", "c"]
a[5, 1]  # => []

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def []=(index : Int, value : T) #

Sets the given value at the given index.

Negative indices can be used to start counting from the end of the array. Raises IndexError if trying to set an element outside the array's range.

ary = [1, 2, 3]
ary[0] = 5
p ary # => [5,2,3]

ary[3] = 5 # => IndexError

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def []=(index : Int, count : Int, values : Array(T)) #

Replaces a subrange with the elements of the given array.

a = [1, 2, 3, 4, 5]
a[1, 3] = [6, 7, 8]
a # => [1, 6, 7, 8, 5]

a = [1, 2, 3, 4, 5]
a[1, 3] = [6, 7]
a # => [1, 6, 7, 5]

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

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def []=(range : Range(Int, Int), values : Array(T)) #

Replaces a subrange with the elements of the given array.

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

a = [1, 2, 3, 4, 5]
a[1..3] = [6, 7]
a # => [1, 6, 7, 5]

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

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def []=(range : Range(Int, Int), value : T) #

Replaces a subrange with a single value.

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

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

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def []=(index : Int, count : Int, value : T) #

Replaces a subrange with a single value. All elements in the range index...index+count are removed and replaced by a single element value.

If count is zero, value is inserted at index.

Negative values of index count from the end of the array.

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

a = [1, 2, 3, 4, 5]
a[1, 0] = 6
a # => [1, 6, 2, 3, 4, 5]

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def []?(index : Int) #

Returns the element at the given index.

Negative indices can be used to start counting from the end of the array. Returns nil if trying to access an element outside the array's range.

ary = ['a', 'b', 'c']
ary[0]?  # => 'a'
ary[2]?  # => 'c'
ary[-1]? # => 'c'
ary[-2]? # => 'b'

ary[3]?  # nil
ary[-4]? # nil

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def at(index : Int, &block) #

Returns the element at the given index, if in bounds, otherwise executes the given block and returns its value.

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

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def at(index : Int) #

Returns the element at the given index, if in bounds, otherwise raises IndexError.

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

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def bsearch(&block) #

By using binary search, returns the first element for which the passed block returns true.

If the block returns false, the finding element exists behind. If the block returns true, the finding element is itself or exists infront.

Binary search needs sorted array, so self has to be sorted.

Returns nil if the block didn't return true for any element.

[2, 5, 7, 10].bsearch { |x| x >= 4 } # => 5
[2, 5, 7, 10].bsearch { |x| x > 10 } # => nil

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def bsearch_index(&block) #

By using binary search, returns the index of the first element for which the passed block returns true.

If the block returns false, the finding element exists behind. If the block returns true, the finding element is itself or exists infront.

Binary search needs sorted array, so self has to be sorted.

Returns nil if the block didn't return true for any element.

[2, 5, 7, 10].bsearch_index { |x, i| x >= 4 } # => 1
[2, 5, 7, 10].bsearch_index { |x, i| x > 10 } # => nil

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def clear #

Removes all elements from self.

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

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def clone #

Returns a new Array that has self's elements cloned. That is, it returns a deep copy of self.

Use #dup if you want a shallow copy.

ary = [[1, 2], [3, 4]]
ary2 = ary.clone
ary[0][0] = 5
puts ary  # => [[5, 2], [3, 4]]
puts ary2 # => [[1, 2], [3, 4]]

ary2 << [7, 8]
puts ary  # => [[5, 2], [3, 4]]
puts ary2 # => [[1, 2], [3, 4], [7, 8]]

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def combinations(size : Int = self.size) #

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def compact #

Returns a copy of self with all nil elements removed.

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

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def compact! #

Removes all nil elements from self.

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

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def concat(other : Array) #

Appends the elements of other to self, and returns self.

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

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def concat(other : Enumerable) #

Appends the elements of other to self, and returns self.

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

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def delete(obj) #

Removes all items from self that are equal to obj.

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

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def delete_at(index : Int, count : Int) #

Removes count elements from self starting at index. If the size of self is less than count, removes values to the end of the array without error. Returns an array of the removed elements with the original order of self preserved. Raises IndexError if index is out of range.

a = ["ant", "bat", "cat", "dog"]
a.delete_at(1, 2)  # => ["bat", "cat"]
a                  # => ["ant", "dog"]
a.delete_at(99, 1) # => IndexError

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def delete_at(index : Int) #

Removes the element at index, returning that element. Raises IndexError if index is out of range.

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

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def delete_at(range : Range(Int, Int)) #

Removes all elements within the given range. Returns an array of the removed elements with the original order of self preserved. Raises IndexError if the index is out of range.

a = ["ant", "bat", "cat", "dog"]
a.delete_at(1..2)    # => ["bat", "cat"]
a                    # => ["ant", "dog"]
a.delete_at(99..100) # => IndexError

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def dup #

Returns a new Array that has exactly self's elements. That is, it returns a shallow copy of self.

Use #clone if you want a deep copy.

ary = [[1, 2], [3, 4]]
ary2 = ary.dup
ary[0][0] = 5
puts ary  # => [[5, 2], [3, 4]]
puts ary2 # => [[5, 2], [3, 4]]

ary2 << [7, 8]
puts ary  # => [[5, 2], [3, 4]]
puts ary2 # => [[5, 2], [3, 4], [7, 8]]

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def each(&block) #

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

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

produces:

a -- b -- c --

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def each #

Returns an Iterator for the elements of self.

a = ["a", "b", "c"]
iter = a.each
iter.next # => "a"
iter.next # => "b"

The returned iterator keeps a reference to self: if the array changes, the returned values of the iterator change as well.


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def each_combination(size : Int = self.size, &block) #

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def each_combination(size : Int = self.size) #

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def each_index #

Returns an Iterator for each index in self.

a = ["a", "b", "c"]
iter = a.each_index
iter.next # => 0
iter.next # => 1

The returned iterator keeps a reference to self. If the array changes, the returned values of the iterator will change as well.


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def each_index(&block) #

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

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

produces:

0 -- 1 -- 2 --

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def each_permutation(size : Int = self.size) #

Returns an Iterator over each possible permutation of size of self.

iter = [1, 2, 3].each_permutation
iter.next # => [1, 2, 3]
iter.next # => [1, 3, 2]
iter.next # => [2, 1, 3]
iter.next # => [2, 3, 1]
iter.next # => [3, 1, 2]
iter.next # => [3, 2, 1]
iter.next # => Iterator::Stop

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def each_permutation(size : Int = self.size, &block) #

Yields each possible permutation of size of self.

a = [1, 2, 3]
sums = [] of Int32
a.each_permutation(2) { |p| sums << p.sum } #=> [1, 2, 3]
sums #=> [3, 4, 3, 5, 4, 5]

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def each_repeated_combination(size : Int = self.size, &block) #

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def each_repeated_combination(size : Int = self.size) #

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def each_repeated_permutation(size : Int = self.size, &block) #

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def empty? #

Returns true if self is empty, false otherwise.

([] of Int32).empty? # => true
([1]).empty?         # => false

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def equals?(other : Array, &block) #

Determines if self equals other according to a comparison done by the given block.

If self's size is the same as other's size, this method yields elements from self and other in tandem: if the block returns true for all of them, this method returns true. Otherwise it returns false.

a = [1, 2, 3]
b = ["a", "ab", "abc"]
a.equals?(b) { |x, y| x == y.size } # => true
a.equals?(b) { |x, y| x == y }      # => false

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def fill(value : T) #

Replaces every element in self with the given value. Returns self.

a = [1, 2, 3]
a.fill(9) # => [9, 9, 9]

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def fill(value : T, range : Range(Int, Int)) #

Replaces every element in range with value. Returns self.

Negative values of from count from the end of the array.

a = [1, 2, 3, 4, 5]
a.fill(9, 2..3) # => [1, 2, 9, 9, 5]

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def fill(range : Range(Int, Int), &block) #

Yields each index of self, in the given range, to the given block and then assigns the block's value in that position. Returns self.

a = [1, 2, 3, 4, 5, 6]
a.fill(2..3) { |i| i * i } # => [1, 2, 4, 9, 5, 6]

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def fill(from : Int, &block) #

Yields each index of self, starting at from, to the given block and then assigns the block's value in that position. Returns self.

Negative values of from count from the end of the array.

a = [1, 2, 3, 4]
a.fill(2) { |i| i * i } # => [1, 2, 4, 9]

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def fill(from : Int, count : Int, &block) #

Yields each index of self, starting at from and just count times, to the given block and then assigns the block's value in that position. Returns self.

Negative values of from count from the end of the array.

a = [1, 2, 3, 4, 5, 6]
a.fill(2, 2) { |i| i * i } # => [1, 2, 4, 9, 5, 6]

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def fill(value : T, from : Int) #

Replaces every element in self, starting at from, with the given value. Returns self.

Negative values of from count from the end of the array.

a = [1, 2, 3, 4, 5]
a.fill(9, 2) # => [1, 2, 9, 9, 9]

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def fill(value : T, from : Int, count : Int) #

Replaces every element in self, starting at from and only count times, with the given value. Returns self.

Negative values of from count from the end of the array.

a = [1, 2, 3, 4, 5]
a.fill(9, 2, 2) # => [1, 2, 9, 9, 5]

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def fill(&block) #

Yields each index of self to the given block and then assigns the block's value in that position. Returns self.

a = [1, 2, 3, 4]
a.fill { |i| i * i } # => [0, 1, 4, 9]

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def first(n : Int) #

Returns the first n elements of the array.

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

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def first(&block) #

Returns the first element of self if it's not empty, or the given block's value.

([1, 2, 3]).first { 4 }   # => 1
([] of Int32).first { 4 } # => 4

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def first #

Returns the first element of self if it's not empty, or raises IndexError.

([1, 2, 3]).first   # => 1
([] of Int32).first # => raises IndexError

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def first? #

Returns the first element of self if it's not empty, or nil.

([1, 2, 3]).first?   # => 1
([] of Int32).first? # => nil

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def flatten #

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.

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]

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def hash #

Returns a hash code based on self's size and elements.

See Object#hash.


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def insert(index : Int, object : T) #

Insert object before the element at index and shifting successive elements, if any. Returns self.

Negative values of index count from the end of the array.

a = ["a", "b", "c"]
a.insert(0, "x")  # => ["x", "a", "b", "c"]
a.insert(2, "y")  # => ["x", "a", "y", "b", "c"]
a.insert(-1, "z") # => ["x", "a", "y", "b", "c", "z"]

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def last(&block) #

Returns the last element of self if it's not empty, or the given block's value.

([1, 2, 3]).last { 4 }   # => 3
([] of Int32).last { 4 } # => 4

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def last(n : Int) #

Returns the last n elements of the array.

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

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def last #

Returns the last element of self if it's not empty, or raises IndexError.

([1, 2, 3]).last   # => 3
([] of Int32).last # => raises IndexError

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def last? #

Returns the last element of self if it's not empty, or nil.

([1, 2, 3]).last?   # => 1
([] of Int32).last? # => nil

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def map(&block : T -> U) #

Optimized version of Enumerable#map.


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def map!(&block) #

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

a = [1, 2, 3]
a.map! { |x| x * x }
a # => [1, 4, 9]

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def map_with_index(&block : T, Int32 -> U) #

Optimized version of Enumerable#map_with_index.


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def permutations(size : Int = self.size) #

Returns an Array with all possible permutations of size.

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

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def pop(&block) #

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def pop #

Removes the last value from self, at index size - 1. This method returns the removed value. Raises IndexError if array is of 0 size.

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

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def pop(n : Int) #

Removes the last n values from self, at index size - 1. This method returns an array of the removed values, with the original order preserved.

If n is greater than the size of self, all values will be removed from self without raising an error.

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

a = ["a", "b", "c"]
a.pop(4) # => ["a", "b", "c"]
a        # => []

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def pop? #

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def product(enumerable : Enumerable(U), &block) #

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def product(ary : Array(U)) #

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def push(*values : T) #

Append multiple values. The same as #push, but takes an arbitrary number of values to push into self. Returns self.

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

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def push(value : T) #

Append. Pushes one value to the end of self, given that the type of the value is T (which might be a single type or a union of types). This method returns self, so several calls can be chained. See #pop for the opposite effect.

a = ["a", "b"]
a.push("c") # => ["a", "b", "c"]
a.push(1)   # => Errors, because the array only accepts String.

a = ["a", "b"] of (Int32 | String)
a.push("c") # => ["a", "b", "c"]
a.push(1)   # => ["a", "b", "c", 1]

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def reject!(&block) #

Modifies self, deleting the elements in the collection for which the passed block returns true. Returns nil if no changes were made.

See also Array#reject


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def repeated_combinations(size : Int = self.size) #

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def repeated_permutations(size : Int = self.size) #

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def replace(other : Array) #

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def reverse #

Returns an array with all the elements in the collection reversed.

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

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def reverse! #

Reverses in-place all the elements of self.


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def reverse_each(&block) #

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

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

produces:

c -- b -- a --

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def reverse_each #

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def rindex(value) #

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def rindex(&block) #

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def rotate(n = 1) #

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def rotate!(n = 1) #

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def sample(n : Int, random = Random::DEFAULT) #

Returns n number of random elements from self, using the given random number generator. Raises IndexError if self is empty.

a = [1, 2, 3]
a.sample(2)                # => [2, 1]
a.sample(2, Random.new(1)) # => [1, 3]

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def sample(random = Random::DEFAULT) #

Returns a random element from self, using the given random number generator. Raises IndexError if self is empty.

a = [1, 2, 3]
a.sample                # => 2
a.sample                # => 1
a.sample(Random.new(1)) # => 3

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def select!(&block) #

Modifies self, keeping only the elements in the collection for which the passed block returns true. Returns nil if no changes were made.

See also Array#select


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def shift(&block) #

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def shift #

Removes the first value of self, at index 0. This method returns the removed value. Raises IndexError if array is of 0 size.

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

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def shift(n : Int) #

Removes the first n values of self, starting at index 0. This method returns an array of the removed values.

If n is greater than the size of self, all values will be removed from self without raising an error.

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

a = ["a", "b", "c"]
a.shift(4) # => ["a", "b", "c"]
a          # => []

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def shift? #

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def shuffle(random = Random::DEFAULT) #

Returns an array with all the elements in the collection randomized using the given random number generator.


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def shuffle!(random = Random::DEFAULT) #

Modifies self by randomizing the order of elements in the collection using the given random number generator. Returns self.


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def size #

Returns the number of elements in the array.

[:foo, :bar].size # => 2

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def sort(&block : T, T -> Int32) #

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def sort #

Returns an array with all elements in the collection sorted.

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

Optionally, a block may be given that must implement a comparison, either with the comparison operator #<=> or a comparison between a and b, where a < b yields -1, a == b yields 0, and a > b yields 1.


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def sort! #

Modifies self by sorting the elements in the collection.

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

Optionally, a block may be given that must implement a comparison, either with the comparison operator #<=> or a comparison between a and b, where a < b yields -1, a == b yields 0, and a > b yields 1.


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def sort!(&block : T, T -> Int32) #

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def sort_by(&block : T -> _) #

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def sort_by!(&block : T -> _) #

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def swap(index0, index1) #

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def to_a #

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def to_json(io) #

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def to_s(io : IO) #

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def to_unsafe : Pointer(T) #

Returns a pointer to the internal buffer where self's elements are stored.

This method is unsafe because it returns a pointer, and the pointed might eventually not be that of self if the array grows and its internal buffer is reallocated.

ary = [1, 2, 3]
ary.to_unsafe[0] # => 1

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def to_yaml(yaml : YAML::Generator) #

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def transpose #

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

a = [[:a, :b], [:c, :d], [:e, :f]]
a.transpose # => [[:a, :c, :e], [:b, :d, :f]]
a           # => [[:a, :b], [:c, :d], [:e, :f]]

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def uniq(&block : T -> _) #

Returns a new Array by removing duplicate values in self, using the block's value for comparison.

a = [{"student", "sam"}, {"student", "george"}, {"teacher", "matz"}]
a.uniq { |s| s[0] } # => [{"student", "sam"}, {"teacher", "matz"}]
a                   # => [{"student", "sam"}, {"student", "george"}, {"teacher", "matz"}]

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def uniq #

Returns a new Array by removing duplicate values in self.

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

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def uniq!(&block) #

Removes duplicate elements from self, using the block's value for comparison. Returns self.

a = [{"student", "sam"}, {"student", "george"}, {"teacher", "matz"}]
a.uniq! { |s| s[0] } # => [{"student", "sam"}, {"teacher", "matz"}]
a                    # => [{"student", "sam"}, {"teacher", "matz"}]

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def uniq! #

Removes duplicate elements from self. Returns self.

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

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def unshift(*values : T) #

Prepend multiple values. The same as #unshift, but takes an arbitrary number of values to add to the array. Returns self.


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def unshift(obj : T) #

Prepend. Adds obj to the beginning of self, given that the type of the value is T (which might be a single type or a union of types). This method returns self, so several calls can be chained. See #shift for the opposite effect.

a = ["a", "b"]
a.unshift("c") # => ["c", a", "b"]
a.unshift(1)   # => Errors, because the array only accepts String.

a = ["a", "b"] of (Int32 | String)
a.unshift("c") # => ["c", "a", "b"]
a.unshift(1)   # => [1, "a", "b", "c"]

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def update(index : Int, &block) #

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def values_at(*indexes : Int) #

Returns a tuple populated with the elements at the given indexes. Raises IndexError if any index is invalid.

["a", "b", "c", "d"].values_at(0, 2) # => {"a", "c"}

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def zip(other : Array(U)) #

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def zip(other : Array, &block) #

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def zip?(other : Array(U)) #

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def zip?(other : Array, &block) #

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def |(other : Array(U)) #

Set union: returns a new Array by joining self with other, excluding any duplicates, and preserving the order from self.

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

See also: #uniq.


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