Partition

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Returns a 2-tuple containing dicts for which the given predicate returned true and false, respectively

namespace HH\Lib\Dict;

function partition<Tk as arraykey, Tv>(
  KeyedTraversable<Tk, Tv> $traversable,
  (function(Tv): bool) $predicate,
): (dict<Tk, Tv>, dict<Tk, Tv>);

Time complexity: O(n * p), where p is the complexity of $predicate. Space complexity: O(n)

Parameters

• KeyedTraversable<Tk,Tv> $traversable
• (function(Tv): bool) $predicate

Returns

• (dict<Tk, Tv>, dict<Tk, Tv>)