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PHP Iterator-based Sequences: Sequences that can be traversed with iterators

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sequence-php 1.0MIT/X Consortium ...7.4Algorithms, Tools, Libraries, Math, PSR
Description 

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This package can generate sequences that can be traversed with iterators.

It provides several classes that can generate sequence values that follow a specific pattern. Currently, it provides lessons that can generate sequences of types:

- Dynamic

- Exponential

- Sequences with configurable steps


The package also provides iterator classes to traverse the sequences and return the generated values. Currently, it gives iterators of types:

- Sequence

- Indexed array

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Documentation

PHP Iterator-based sequences

Packagist PHP Version Support Scrutinizer Code Quality Coverage Status Build and test License: MIT

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Python-like sequences with iterators for PHP.

How to install to your project

composer require smoren/sequence

Quick Reference

Loops

| Functionality | Description | Code Snippet | |---------------------------------------|------------------------------|---------------------------------------------------| | Range-based for | Python-like range-based loop | foreach(xrange($start, $size, $step) as $value) |

Sequences

| Class | Description | Code Snippet | |----------------------------------------|---------------------------------|-----------------------------------------------------------------------------| | Range | Iterable arithmetic progression | new Range($start, $size, $step) | | Exponential | Iterable geometric progression | new Exponential($start, $size, $step) | | DynamicSequence | Callback-configurable sequence | new DynamicSequence($start, $size, $nextValueGetter, $indexedValueGetter) |

Data containers

| Class | Description | Code Snippet | |----------------------------------|--------------------------|----------------------------| | IndexedArray | Python-like indexed list | new IndexedArray($array) |

Functions

| Function | Description | Code Snippet | |---------------------|--------------------------------------------------------------------------|------------------------------------------------| | xrange | Creates iterable range | xrange($start, $size, $step) | | map | Maps iterable collections and returns IndexedArray of mapped values | map($mapper, ...$collections) | | filter | Filters iterable collection and returning IndexedArray of filtered items | filter($collection, $filter) | | reduce | Reduces an iterable collection | reduce($collection, $reducer, $initialValue) |

Usage

Loops

Range-based for

Unlike the PHP built-in function range(), xrange() does not create an array, but a Traversable object that takes up a small amount of memory, regardless of the number of elements in the sequence.

use function Smoren\Sequence\Functions\xrange;

foreach(xrange(5) as $i) { // start: 0; count: 5; step: 1
    echo "{$i} ";
}
// 0 1 2 3 4

foreach(xrange(1, 5) as $i) { // start: 1; count: 5; step: 1
    echo "{$i} ";
}
// 1 2 3 4 5

foreach(xrange(1, 5, 2) as $i) { // start: 1; count: 5; step: 2
    echo "{$i} ";
}
// 1 3 5 7 9

Sequences

Range

Iterable arithmetic progression.


For infinite sequence use `$size = null`.

use Smoren\Sequence\Structs\Range; use Smoren\Sequence\Exceptions\OutOfRangeException;

/Simple int range/ $range = new Range(1, 3, 2); // (from, size, step) var_dump($range->isInfinite()); // false

foreach($range as $value) {

echo "{$value} ";

} // 1 3 5

var_dump($range[0]); // 1 var_dump($range[1]); // 3 var_dump($range[2]); // 5

try {

$range[3];

} catch(OutOfRangeException $e) {

echo "cannot get value from index out of range\n";

}

var_dump($range[-1]); // 5 var_dump($range[-2]); // 3 var_dump($range[-3]); // 1

try {

$range[-4];

} catch(OutOfRangeException $e) {

echo "cannot get value from index out of range\n";

}

/Infinite int range/ $range = new Range(1, null, 2); var_dump($range->isInfinite()); // true

foreach($range as $i => $value) {

echo "{$value} ";
if($i > 100) break;

} // 1 3 5 7 9 11 13...

/Float range/ $range = new Range(1.1, 3, 2.1); var_dump($range->isInfinite()); // false

foreach($range as $value) {

echo "{$value} ";

} // 1.1 3.2 5.3


#### Exponential

Iterable geometric progression.

For infinite sequence use $size = null.

use Smoren\Sequence\Structs\Exponential;
use Smoren\Sequence\Exceptions\OutOfRangeException;

/Simple int exponential sequence/
$sequence = new Exponential(1, 4, 2); // (from, size, step)
var_dump($sequence->isInfinite()); // false

foreach($sequence as $value) {
    echo "{$value} ";
}
// 1 2 4 8

var_dump($sequence[0]); // 1
var_dump($sequence[1]); // 2
var_dump($sequence[2]); // 4
var_dump($sequence[3]); // 8

try {
    $sequence[4];
} catch(OutOfRangeException $e) {
    echo "cannot get value from index out of range\n";
}

var_dump($sequence[-1]); // 8
var_dump($sequence[-2]); // 4
var_dump($sequence[-3]); // 2
var_dump($sequence[-4]); // 1

try {
    $sequence[-5];
} catch(OutOfRangeException $e) {
    echo "cannot get value from index out of range\n";
}

/Infinite int exponential sequence/
$sequence = new Exponential(1, null, 2);
var_dump($sequence->isInfinite()); // true

foreach($sequence as $i => $value) {
    echo "{$value} ";
    if($i > 100) break;
}
// 1 2 4 8 16 32 64...

/Infinite float exponential sequence/
$sequence = new Exponential(0.5, null, 2);
var_dump($sequence->isInfinite()); // true

foreach($sequence as $value) {
    echo "{$value} ";
}
// 0.5 0.25 0.125...

Dynamic Sequence

Implementation of sequence configured with callables.


For infinite sequence use `$size = null`.

use Smoren\Sequence\Structs\DynamicSequence;

// (from, size, nextValueGetter, indexValueGetter) $sequence = new DynamicSequence(1, 5, static function($previousValue) {

return $previousValue + 1;

}, static function($index, $startValue) {

return $startValue + $index;

});

var_dump(iterator_to_array($sequence)); // [1, 2, 3, 4, 5]


### Data containers

#### Indexed Array

Python-like indexed list.

Its keys are always an unbroken sequence of natural numbers starting from zero.

It is also allowed to access array elements from the end with negative indices.

OutOfRangeException will be thrown when trying to access a non-existent index.

use Smoren\Sequence\Structs\IndexedArray; use Smoren\Sequence\Exceptions\OutOfRangeException;

$array = new IndexedArray([10, 20, 30]);

$array[0] = 11; $array[-1] = 33; $array[1] = 22; var_dump(count($array)); // 3 print_r($array->toArray()); // [11, 22, 33]

unset($array[1]); print_r($array->toArray()); // [11, 33]

$array[] = 111; print_r($array->toArray()); // [11, 33, 111]

try {

$array[3];

} catch(OutOfRangeException $e) {

echo "cannot get value from index out of range\n";

}

try {

$array[3] = 1;

} catch(OutOfRangeException $e) {

echo "cannot set value from index out of range\n";

}

try {

unset($array[3]);

} catch(OutOfRangeException $e) {

echo "cannot unset value from index out of range\n";

}


### Functions

#### xrange

Creates iterable range.

Works like `xrange()` function in python2 or `range()` function in python3.

use function Smoren\Sequence\Functions\xrange;

$range = xrange(5);
print_r(iterator_to_array($range));
// [0, 1, 2, 3, 4]

$range = xrange(1, 5);
print_r(iterator_to_array($range));
// [1, 2, 3, 4, 5]

$range = xrange(1, 5, 2);
print_r(iterator_to_array($range));
// [1, 3, 5, 7, 9]

map

Maps iterable collection and creating IndexedArray of mapped values as a result.


use function Smoren\Sequence\Functions\map;

$ids = [1, 2, 3]; $names = ['Mary', 'Jane', 'Alice']; $result = map(static function(int $id, string $name) {

return "{$id}. {$name}";

}, $ids, $names); print_r($result->toArray()); // ['1. Mary', '2. Jane', '3. Alice']


#### filter

Filters iterable collection and returning IndexedArray of filtered items.

use function Smoren\Sequence\Functions\filter;

$input = [1, 2, 3, 4, 5];
$result = filter($input, static function($item) {
    return $item > 2;
});
print_r($result->toArray());
// [3, 4, 5]

reduce

Reduces an iterable collection.


use function Smoren\Sequence\Functions\reduce;

$input = [1, 2, 3, 4, 5]; $result = reduce($input, static function($carry, $item) {

return $carry + $item;

}, 0); var_dump($result); // 15


## Unit testing

composer install composer test-init composer test


## Standards

PHP Sequence conforms to the following standards:

* PSR-1 ? Basic coding standard
* PSR-4 ? Autoloader
* PSR-12 ? Extended coding style guide


## License

PHP Sequence is licensed under the MIT License.

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