HH\ImmSet::mapWithKey

Returns an ImmSet containing the values after an operation has been applied to each "key" and value in the current ImmSet

public function mapWithKey<Tu as arraykey>(
  (function(arraykey, Tv): Tu) $callback,
): ImmSet<Tu>;

Since ImmSets don't have keys, the callback uses the values as the keys as well.

Every value in the current ImmSet is affected by a call to mapWithKey(), unlike filterWithKey() where only values that meet a certain criteria are affected.

Parameters

• (function(arraykey, Tv): Tu) $callback

Returns

• ImmSet<Tu> - an ImmSet containing the values after a user-specified operation on the current ImmSet's values is applied.

Examples

See [Set::mapWithKey](</hack/reference/class/Set/mapWithKey/#examples>) for usage examples.