The Deque class

Introduction

(PECL ds >= 1.0.0)

A Deque (pronounced “deck”) is a sequence of values in a contiguous buffer that grows and shrinks automatically. The name is a common abbreviation of “double-ended queue” and is used internally by Ds\Queue.

Two pointers are used to keep track of a head and a tail. The pointers can “wrap around” the end of the buffer, which avoids the need to move other values around to make room. This makes shift and unshift very fast — something a Ds\Vector can’t compete with.

Accessing a value by index requires a translation between the index and its corresponding position in the buffer: ((head + position) % capacity).

Strengths

• Supports array syntax (square brackets).
• Uses less overall memory than an array for the same number of values.
• Automatically frees allocated memory when its size drops low enough.
• get(), set(), push(), pop(), shift(), and unshift() are all O(1).

Weaknesses

• Capacity must be a power of 2.
• insert() and remove() are O(n).

Class synopsis

public allocate(int $capacity): void

public apply(callable $callback): void

public capacity(): int

public clear(): void

public contains(mixed ...$values): bool

public copy(): Ds\Deque

public filter(callable $callback = ?): Ds\Deque

public find(mixed $value): mixed

public first(): mixed

public get(int $index): mixed

public insert(int $index, mixed ...$values): void

public isEmpty(): bool

public join(string $glue = ?): string

public last(): mixed

public map(callable $callback): Ds\Deque

public merge(mixed $values): Ds\Deque

public pop(): mixed

public push(mixed ...$values): void

public reduce(callable $callback, mixed $initial = ?): mixed

public remove(int $index): mixed

public reverse(): void

public reversed(): Ds\Deque

public rotate(int $rotations): void

public set(int $index, mixed $value): void

public shift(): mixed

public slice(int $index, int $length = ?): Ds\Deque

public sort(callable $comparator = ?): void

public sorted(callable $comparator = ?): Ds\Deque

public sum(): int|float

public toArray(): array

public unshift(mixed $values = ?): void

Predefined Constants

Ds\Deque::MIN_CAPACITY

Changelog

Table of Contents

• Ds\Deque::allocate — Allocates enough memory for a required capacity
• Ds\Deque::apply — Updates all values by applying a callback function to each value
• Ds\Deque::capacity — Returns the current capacity
• Ds\Deque::clear — Removes all values from the deque
• Ds\Deque::__construct — Creates a new instance
• Ds\Deque::contains — Determines if the deque contains given values
• Ds\Deque::copy — Returns a shallow copy of the deque
• Ds\Deque::count — Returns the number of values in the collection
• Ds\Deque::filter — Creates a new deque using a callable to determine which values to include
• Ds\Deque::find — Attempts to find a value's index
• Ds\Deque::first — Returns the first value in the deque
• Ds\Deque::get — Returns the value at a given index
• Ds\Deque::insert — Inserts values at a given index
• Ds\Deque::isEmpty — Returns whether the deque is empty
• Ds\Deque::join — Joins all values together as a string
• Ds\Deque::jsonSerialize — Returns a representation that can be converted to JSON
• Ds\Deque::last — Returns the last value
• Ds\Deque::map — Returns the result of applying a callback to each value
• Ds\Deque::merge — Returns the result of adding all given values to the deque
• Ds\Deque::pop — Removes and returns the last value
• Ds\Deque::push — Adds values to the end of the deque
• Ds\Deque::reduce — Reduces the deque to a single value using a callback function
• Ds\Deque::remove — Removes and returns a value by index
• Ds\Deque::reverse — Reverses the deque in-place
• Ds\Deque::reversed — Returns a reversed copy
• Ds\Deque::rotate — Rotates the deque by a given number of rotations
• Ds\Deque::set — Updates a value at a given index
• Ds\Deque::shift — Removes and returns the first value
• Ds\Deque::slice — Returns a sub-deque of a given range
• Ds\Deque::sort — Sorts the deque in-place
• Ds\Deque::sorted — Returns a sorted copy
• Ds\Deque::sum — Returns the sum of all values in the deque
• Ds\Deque::toArray — Converts the deque to an array
• Ds\Deque::unshift — Adds values to the front of the deque