PHP Ds\Sequence Functions

A Sequence arranges values in a single, linear order. In some programming languages, a sequence is called a list. It works like an array but uses incremental integer keys. Here's how it works:

• The index values of a sequence are [0, 1, 2, …, size – 1], where "size" is the number of items in the array.
• You can access sequence elements using these index values, so you can get any value by its index within the range [0, size – 1].

In PHP 7, the DS\Sequence is an efficient data structure, serving as an alternative to arrays.

Requirements:

PHP 7 is needed for both the extension and compatibility polyfill.

Installation:

The easiest way to install this data structure is using the PECL extension:

pecl install ds

Syntax:

abstract public Ds\Sequence::Function()

Example:

Below is an example showing the Ds\Sequence::capacity() function in PHP:

<?php
// Declare a sequence
$seq = new \Ds\Vector();

// Use capacity() function
var_dump($seq->capacity());

// Push elements into sequence
$seq->push(...range(1, 100));

// Use capacity() function
var_dump($seq->capacity());

// Pop element from sequence
$seq->pop();

// Use capacity() function
var_dump($seq->capacity());
?>

Output:

int(8)
int(100)
int(100)

This example shows how to declare a sequence, use the capacity() function, add elements, and remove elements.

The complete list of data structure DS\SequenceFunctuon is given below:

Sequence Functions	Description
allocate()	Allocate enough memory to hold the specified capacity of elements in the sequence. This may be useful when you know the expected size of the sequence beforehand to avoid unnecessary reallocations.
apply()	Applies a callback function to each element of the sequence, modifying the original sequence in place.
capacity()	Get the current capacity of the sequence, which is the maximum number of elements it can hold without needing to be resized.
contains()	Check whether a specified value exists in the sequence.
filter()	Create a new sequence containing only elements that pass a certain test defined by a callback function.
find()	Searches for the first element in the sequence that satisfies a specific condition defined by a callback function.
first()	Return the first element from the sequence. If the sequence is empty, it may return an error or null value.
get()	Get the value at the specified index in the sequence.
insert()	Insert a new value at a specified index in the sequence.
join()	Join all elements in the sequence into a single string using a specified delimiter (optional).
last()	Return the last element from the sequence. If the sequence is empty, it may return an error or null value.
map()	Applies a callback function to each element of the sequence and returns a new sequence containing the results.
merge()	Create a new sequence by merging the current sequence with one or more additional sequences or values.
pop()	Remove and return the last element from the sequence.
push()	Add one or more elements to the end of the sequence.
reduce()	Apply a function against an accumulator and each element in the sequence to reduce it to a single value.
remove()	Remove and return an element from the sequence by its index.
reverse()	Reverse the order of elements in the sequence in place.
reversed()	Return a new sequence with the elements of the current sequence in reversed order.
rotate()	Rotate the elements of the sequence by a specified number of positions.
set()	Update the value at a specific index in the sequence.
shift()	Remove and return the first element from the sequence.
slice()	Extract a section of the sequence as a new sequence.
sort()	Sort the elements of the sequence in place according to a comparison function.
sorted()	Return a new sequence containing the elements of the current sequence sorted according to a comparison function.
sum()	Calculate the sum of all elements in the sequence.
unshift()	Add one or more elements to the beginning of the sequence.