HH\Lib\Keyset\filter
Returns a new keyset containing only the values for which the given predicate
returns true
namespace HH\Lib\Keyset;
function filter<Tv as arraykey>(
Traversable<Tv> $traversable,
?(function(Tv): bool) $value_predicate = NULL,
): keyset<Tv>;
The default predicate is casting the value to boolean.
To remove null values in a typechecker-visible way, see Keyset\filter_nulls()
.
Time complexity: O(n * p), where p is the complexity of $value_predicate
Space complexity: O(n)
Parameters
Traversable<Tv>
$traversable
?(function(Tv): bool) $value_predicate = NULL
Returns
keyset<Tv>
Examples
$result = Keyset\filter(keyset[1,2,3,4], $val ==> $val%2==0);
print_r($result);
//result: keyset[2,4]
$result = Keyset\filter(keyset[1,2,3,4], $val ==> $val==0);
print_r($result);
//result: keyset[]
$result = Keyset\filter(keyset[1,2,3,4], $val ==> $val == $val);
print_r($result);
//result: keyset[1,2,3,4]