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This is available as Vec\partition_async in the www repository.

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

namespace HH\Lib\Vec;

function partition_async<Tv>(
  Container<Tv> $container,
  (function(Tv): Awaitable<bool>) $value_predicate,
): Awaitable<(vec<Tv>, vec<Tv>)>;

For non-async predicates, see Vec\partition().

Time complexity: O(n * p), where p is the complexity of synchronous portions of $value_predicate Space complexity: O(n)

The IO operations for each of the calls to $value_predicate will happen in parallel.


  • Container<Tv>$container
  • (function(Tv): Awaitable<bool>) $value_predicate