<?php
namespace Encase\Functional;
/**
* Get the value of the first element in `$iterable`.
*
* @param \Traversable|iterable|string|stdClass|null
* @return mixed|null The first element in `$iterable` or null if empty.
*/
function first($iterable)
{
$type = assertType($iterable, ['\Traversable', 'iterable', 'string', 'stdClass', 'null'], 'iterable');
if (empty($iterable)) {
return null;
}
if ($type === 'string') {
return \mb_substr($iterable, 0, 1);
}
// Account for external iterators.
if ($iterable instanceof \IteratorAggregate) {
$iterable = $iterable->getIterator();
}
// Ensure iterators are valid so we return null rather than false like
// end() does. If it's an \ArrayIterator, we can treat it as an array, for
// whatever reason...
if ($iterable instanceof \Iterator) {
if (!$iterable->valid()) {
return null;
}
$iterable->rewind();
return $iterable->current();
}
return \reset($iterable);
}
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