DocumentationHSLReferenceFunctionHH\Lib\Dict\filter_keys

HH\Lib\Dict\filter_keys

Requires the Hack Standard Library to be installed.

Facebook Engineer?

This function is available as Dict\filter_keys() in Facebook's www repository.

Returns a new dict containing only the keys for which the given predicate returns true

namespace HH\Lib\Dict;

function filter_keys<Tk as arraykey, Tv>(
  KeyedTraversable<Tk, Tv> $traversable,
  ?(function(Tk): bool) $key_predicate = NULL,
): dict<Tk, Tv>;

The default predicate is casting the key to boolean.

Time complexity: O(n * p), where p is the complexity of $value_predicate (which is O(1) if not provided explicitly) Space complexity: O(n)

Parameters

KeyedTraversable<Tk, Tv> $traversable
?(function(Tk): bool) $key_predicate = NULL

Returns

dict<Tk, Tv>