<?php
namespace Smoren\Sequence\Functions;
use ArrayIterator;
use IteratorIterator;
use MultipleIterator;
use Smoren\Sequence\Structs\IndexedArray;
use Smoren\Sequence\Structs\Range;
/**
* Creates iterable range.
*
* @param int $start start value
* @param int<0, max>|null $size size of elements
* @param int $step range step
*
* @return Range<int> iterable range
*/
function xrange(int $start, ?int $size = null, int $step = 1): Range
{
if ($size === null) {
[$start, $size] = [0, $start];
}
return new Range($start, $size, $step);
}
/**
* Maps iterable collections and returns IndexedArray of mapped values.
*
* @template TInput
* @template TOutput
*
* @param callable(TInput $item): TOutput $mapper
* @param iterable<TInput> $collections
*
* @return IndexedArray<TOutput>
*/
function map(callable $mapper, iterable ...$collections): IndexedArray
{
$result = new IndexedArray();
if (count($collections) === 0) {
return $result;
}
$it = new MultipleIterator(MultipleIterator::MIT_NEED_ALL | MultipleIterator::MIT_KEYS_NUMERIC);
foreach ($collections as $collection) {
if (is_array($collection)) {
$collection = new ArrayIterator($collection);
}
$it->attachIterator(new IteratorIterator($collection));
}
foreach ($it as $values) {
$result[] = $mapper(...$values);
}
return $result;
}
/**
* Filters iterable collection and returns IndexedArray of filtered items.
*
* @template T
*
* @param iterable<T> $collection
* @param callable(T $item): bool $filter
*
* @return IndexedArray<T>
*/
function filter(iterable $collection, callable $filter): IndexedArray
{
$result = new IndexedArray();
foreach ($collection as $item) {
if ($filter($item)) {
$result[] = $item;
}
}
return $result;
}
/**
* Reduces iterable collection.
*
* @template TInput
* @template TOutput
*
* @param iterable<TInput> $collection
* @param callable(TOutput $carry, TInput $item): TOutput $reducer
* @param TOutput $initialValue
*
* @return TOutput
*/
function reduce(iterable $collection, callable $reducer, $initialValue = null)
{
$carry = $initialValue;
foreach ($collection as $item) {
$carry = $reducer($carry, $item);
}
return $carry;
}
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