class Deque(T)

Overview

A Deque ("double-ended queue") is a collection of objects of type T that behaves much like an Array.

Deque has a subset of Array's API. It performs better than an Array when there are frequent insertions or deletions of items near the beginning or the end.

The most typical use case of a Deque is a queue: use #push to add items to the end of the queue and #shift to get and remove the item at the beginning of the queue.

This Deque is implemented with a dynamic array used as a circular buffer.

Included Modules

Defined in:

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from module Indexable(T)

[](index : Int) [], []?(index : Int) []?, bsearch(&block : T -> Bool) bsearch, bsearch_index(&block : T, Int32 -> Bool) bsearch_index, dig(index : Int, *subindexes) dig, dig?(index : Int, *subindexes) dig?, each(*, start : Int, count : Int, &)
each(*, within range : Range, &)
each(&)
each
each
, each_index(*, start : Int, count : Int, &)
each_index(&) : Nil
each_index
each_index
, empty? empty?, equals?(other : Indexable, &)
equals?(other, &)
equals?
, fetch(index, default)
fetch(index : Int, &)
fetch
, first
first(&)
first
, first? first?, hash(hasher) hash, index(object, offset : Int = 0)
index(offset : Int = 0, &)
index
, join(separator = "") join, last
last(&)
last
, last? last?, reverse_each(&) : Nil
reverse_each
reverse_each
, rindex(offset = size - 1, &)
rindex(value, offset = size - 1)
rindex
, sample(random = Random::DEFAULT) sample, size size, to_a to_a, unsafe_fetch(index : Int) unsafe_fetch, values_at(*indexes : Int) values_at

Instance methods inherited from module Enumerable(T)

all?(&)
all?(pattern)
all?
all?
, any?(&)
any?(pattern)
any?
any?
, chunks(&block : T -> U) forall U chunks, compact_map(&) compact_map, count(&)
count(item)
count
, cycle(n, &)
cycle(&)
cycle
, each(&block : T -> _) each, each_cons(count : Int, reuse = false, &) each_cons, each_cons_pair(& : T, T -> _) : Nil each_cons_pair, each_slice(count : Int, reuse = false, &) each_slice, each_with_index(offset = 0, &) each_with_index, each_with_object(obj, &) each_with_object, empty? empty?, find(if_none = nil, &) find, first(count : Int)
first
first
, first? first?, flat_map(&block : T -> Array(U) | Iterator(U) | U) forall U flat_map, grep(pattern) grep, group_by(&block : T -> U) forall U group_by, in_groups_of(size : Int, filled_up_with : U = nil) forall U
in_groups_of(size : Int, filled_up_with : U = nil, reuse = false, &) forall U
in_groups_of
, includes?(obj) includes?, index(&)
index(obj)
index
, index_by(&block : T -> U) forall U index_by, join(separator = "", &)
join(separator, io, &)
join(separator = "")
join(separator, io)
join
, map(&block : T -> U) forall U map, map_with_index(offset = 0, &block : T, Int32 -> U) forall U map_with_index, max max, max? max?, max_by(&block : T -> U) forall U max_by, max_by?(&block : T -> U) forall U max_by?, max_of(&block : T -> U) forall U max_of, max_of?(&block : T -> U) forall U max_of?, min min, min? min?, min_by(&block : T -> U) forall U min_by, min_by?(&block : T -> U) forall U min_by?, min_of(&block : T -> U) forall U min_of, min_of?(&block : T -> U) forall U min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : T -> U) forall U minmax_by, minmax_by?(&block : T -> U) forall U minmax_by?, minmax_of(&block : T -> U) forall U minmax_of, minmax_of?(&block : T -> U) forall U minmax_of?, none?
none?(&)
none?(pattern)
none?
, one?(&)
one?(pattern)
one?
one?
, partition(&) partition, product
product(initial : Number)
product(initial : Number, &)
product(&)
product
, reduce(memo, &)
reduce(&)
reduce
, reduce?(&) reduce?, reject(pattern)
reject(type : U.class) forall U
reject(&block : T -> )
reject
, select(pattern)
select(type : U.class) forall U
select(&block : T -> )
select
, size size, skip(count : Int) skip, skip_while(&) skip_while, sum(initial)
sum
sum(initial, &)
sum(&)
sum
, take_while(&) take_while, tally : Hash(T, Int32) tally, to_a to_a, to_h
to_h(&block : T -> Tuple(K, V)) forall K, V
to_h
, to_set to_set, zip(*others : Indexable | Iterable | Iterator, &)
zip(*others : Indexable | Iterable | Iterator)
zip
, zip?(*others : Indexable | Iterable | Iterator, &)
zip?(*others : Indexable | Iterable | Iterator)
zip?

Instance methods inherited from module Iterable(T)

chunk(reuse = false, &block : T -> U) forall U chunk, chunk_while(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B chunk_while, cycle(n)
cycle
cycle
, each each, each_cons(count : Int, reuse = false) each_cons, each_slice(count : Int, reuse = false) each_slice, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object, slice_after(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_after(pattern, reuse : Bool | Array(T) = false)
slice_after
, slice_before(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_before(pattern, reuse : Bool | Array(T) = false)
slice_before
, slice_when(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B slice_when

Instance methods inherited from class Reference

==(other : self)
==(other : JSON::Any)
==(other : YAML::Any)
==(other)
==
, dup dup, hash(hasher) hash, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference)
same?(other : Nil)
same?
, to_s(io : IO) : Nil to_s

Constructor methods inherited from class Reference

new new

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other)
===
, =~(other) =~, __crystal_pseudo_! : Bool __crystal_pseudo_!, __crystal_pseudo_as(type : Class) __crystal_pseudo_as, __crystal_pseudo_as?(type : Class) __crystal_pseudo_as?, __crystal_pseudo_is_a?(type : Class) : Bool __crystal_pseudo_is_a?, __crystal_pseudo_nil? : Bool __crystal_pseudo_nil?, __crystal_pseudo_responds_to?(name : Symbol) : Bool __crystal_pseudo_responds_to?, class class, dup dup, hash(hasher)
hash
hash
, in?(*values : Object) : Bool
in?(collection) : Bool
in?
, inspect : String
inspect(io : IO) : Nil
inspect
, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&) tap, to_json
to_json(io : IO)
to_json
, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ")
to_pretty_json
, to_s : String
to_s(io : IO) : Nil
to_s
, to_yaml(io : IO)
to_yaml
to_yaml
, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

Class methods inherited from class Object

from_json(string_or_io, root : String)
from_json(string_or_io)
from_json
, from_yaml(string_or_io : String | IO) from_yaml

Constructor Detail

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

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

Deque.new(3, 'a') # => Deque{'a', 'a', 'a'}

def self.new(array : Array(T)) #

Creates a new Deque that copies its items from an Array.

Deque.new([1, 2, 3]) # => Deque{1, 2, 3}

def self.new(initial_capacity : Int) #

Creates a new empty Deque 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 a deque will hold, you should initialize it with that capacity for improved execution performance.

deq = Deque(Int32).new(5)
deq.size # => 0

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

def self.new #

Creates a new empty Deque


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

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

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

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

Class Method Detail

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

Instance Method Detail

def +(other : Deque(U)) forall U #

Concatenation. Returns a new Deque built by concatenating two deques together to create a third. The type of the new deque is the union of the types of both the other deques.


def <<(value : T) #

Alias for #push.


def ==(other : Deque) #

Returns true if it is passed a Deque and equals? returns true for both deques, the caller and the argument.

deq = Deque{2, 3}
deq.unshift 1
deq == Deque{1, 2, 3} # => true
deq == Deque{2, 3}    # => false

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

Sets the given value at the given index.

Raises IndexError if the deque had no previous value at the given index.


def clear #

Removes all elements from self.


def clone #

Returns a new Deque that has this deque's elements cloned. That is, it returns a deep copy of this deque.

Use #dup if you want a shallow copy.


def concat(other : Enumerable(T)) #

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


def delete(obj) #

Removes all items from self that are equal to obj.

a = Deque{"a", "b", "b", "b", "c"}
a.delete("b") # => true
a             # => Deque{"a", "c"}

def delete_at(index : Int) #

Deletes the item that is present at the index. Items to the right of this one will have their indices decremented. Raises IndexError if trying to delete an element outside the deque's range.

a = Deque{1, 2, 3}
a.delete_at(1) # => 2
a              # => Deque{1, 3}

def delete_if(&) #

def dup #

Returns a new Deque that has exactly this deque's elements. That is, it returns a shallow copy of this deque.


def each(&) : Nil #

Yields each item in this deque, from first to last.

Do not modify the deque while using this variant of #each!


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

Insert a new item before the item at index. Items to the right of this one will have their indices incremented.

a = Deque{0, 1, 2}
a.insert(1, 7) # => Deque{0, 7, 1, 2}

def inspect(io : IO) : Nil #
Description copied from class Reference

Appends a String representation of this object which includes its class name, its object address and the values of all instance variables.

class Person
  def initialize(@name : String, @age : Int32)
  end
end

Person.new("John", 32).inspect # => #<Person:0x10fd31f20 @name="John", @age=32>

def pop(&) #

Removes and returns the last item, if not empty, otherwise executes the given block and returns its value.


def pop #

Removes and returns the last item. Raises IndexError if empty.

a = Deque{1, 2, 3}
a.pop # => 3
a     # => Deque{1, 2}

def pop(n : Int) #

Removes the last n (at most) items in the deque.


def pop? #

Removes and returns the last item, if not empty, otherwise nil.


def pretty_print(pp) #

def push(value : T) #

Adds an item to the end of the deque.

a = Deque{1, 2}
a.push 3 # => Deque{1, 2, 3}

def rotate!(n : Int = 1) #

Rotates this deque in place so that the element at n becomes first.

  • For positive n, equivalent to n.times { push(shift) }.
  • For negative n, equivalent to (-n).times { unshift(pop) }.

def shift(n : Int) #

Removes the first n (at most) items in the deque.


def shift #

Removes and returns the first item. Raises IndexError if empty.

a = Deque{1, 2, 3}
a.shift # => 1
a       # => Deque{2, 3}

def shift(&) #

Removes and returns the first item, if not empty, otherwise executes the given block and returns its value.


def shift? #

Removes and returns the first item, if not empty, otherwise nil.


def size #

Returns the number of elements in the deque.

Deque{:foo, :bar}.size # => 2

def swap(i, j) #

Swaps the items at the indices i and j.


def to_json(json : JSON::Builder) #

def to_s(io : IO) : Nil #
Description copied from class Reference

Appends a short String representation of this object which includes its class name and its object address.

class Person
  def initialize(@name : String, @age : Int32)
  end
end

Person.new("John", 32).to_s # => #<Person:0x10a199f20>

def unsafe_fetch(index : Int) #
Description copied from module Indexable(T)

Returns the element at the given index, without doing any bounds check.

Indexable makes sure to invoke this method with index in 0...size, so converting negative indices to positive ones is not needed here.

Clients never invoke this method directly. Instead, they access elements with #[](index) and #[]?(index).

This method should only be directly invoked if you are absolutely sure the index is in bounds, to avoid a bounds check for a small boost of performance.


def unshift(value : T) #

Adds an item to the beginning of the deque.

a = Deque{1, 2}
a.unshift 0 # => Deque{0, 1, 2}