PHP Ds\Deque Functions

A deque (short for "double-ended queue") is a data structure that stores a sequence of values in a memory buffer that automatically grows and shrinks. 

Requirements: You need PHP 7 to use this extension and its compatibility polyfill.

Installation: The easiest way to install the deque data structure is with the PECL extension. Run the following command:

pecl install ds

Syntax:

public Ds\Deque:: function()

Example:

Here’s an example of how to use the `Ds\Deque::get()` function in PHP:

<?php

// Declare a deque
$deck = new \Ds\Deque([10, 20, 3, 40, 50, 6]);

echo "Elements in the Deque\n";

// Display the deque elements
print_r($deck);

echo "\nElement at index 2 in the deque: ";

// Use the get() function to find the value at index 2
var_dump($deck->get(2));

?>

Output:

Elements in the Deque
Ds\Deque Object
(
    [0] => 10
    [1] => 20
    [2] => 3
    [3] => 40
    [4] => 50
    [5] => 6
)

Element at index 2 in the deque: int(3)

This example shows how to declare a deque, display its elements, and get a specific element by its index.

The complete list of Ds\Deque functions are given below:

Deque Functions	Description
allocate(size)	Allocate memory for the deque to hold a specific number of elements (`size`). This pre-allocates space to potentially avoid performance overhead during insertions or removals.
apply(callback)	Apply a callback function to each element in the deque. The callback function takes the current element value and index as arguments and can modify the element in-place.
capacity()	Return the current maximum number of elements the deque can hold without needing reallocation.
clear()	Remove all elements from the deque.
__construct([initial_size])	**Optional:** Create a new deque instance. In some implementations, a deque can be created without an explicit constructor call. You can optionally provide an initial size for the deque.
copy()	Create a new deque that is a shallow copy of the original deque. Changes to the original deque will not be reflected in the copy, and vice versa.
count()	Return the number of elements currently in the deque.
filter(callback)	Create a new deque containing only the elements that pass a test defined by the callback function.
find(value)	Return the index of the first occurrence of a specific value in the deque, or -1 if not found.
first()	Return the first element in the deque (same as get(0)). If the deque is empty, it may return an error or null value.
get(index)	Return the element at the specified index in the deque.
insert(index, value)	Insert a new element at a specific index in the deque.
isEmpty()	Check whether the deque is empty (contains no elements).
join(separator)	Join all elements of the deque into a string, separated by the provided delimiter (separator).
last()	Return the last element in the deque (same as get(count() - 1)). If the deque is empty, it may return an error or null value.
map(callback)	Create a new deque by applying a callback function to each element of the original deque. The callback function's return value becomes the element in the new deque.
merge(...values)	Add all the provided values to the end of the deque.
pop()	Remove and return the last element from the deque. If the deque is empty, it may return an error or null value.
push(value)	Add a new element to the end of the deque.
remove(index)	Remove and return the element at the specified index from the deque.
reverse()	Reverse the order of elements in the deque in-place.
reversed()	Create a new deque containing a reversed copy of the elements from the original deque.
rotate(offset)	Rotate the elements in the deque by a specified number of positions. Positive offsets shift elements to the right, negative offsets to the left.
set(index, value)	Set the value at the specified index in the deque.
shift()	Remove and return the first element from the deque. If the deque is empty, it may return an error or null value.
slice(start, length)	Extract a sub-deque containing a range of elements from the original deque.
sort(comparison_function)	Sort the elements of the deque in-place. You can optionally provide a comparison function to define the sorting order.
sorted(comparison_function)	Create a new deque containing a sorted copy of the elements from the original deque. You can optionally provide a comparison function to define the sorting order.
sum()	Return the sum of all the elements in the deque.
toArray()	Convert the deque to a regular PHP array.
unshift(value)	Add one or more elements to the beginning of the deque.