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

Returns a new vec containing only the values for which the given async predicate returns true

namespace HH\Lib\Vec;

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

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

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