HH\Set::retain
Alters the current Set so that it only contains the values that meet a
supplied condition on each value
public function retain(
(function(Tv): bool) $callback,
): Set<Tv>;
This method is like filter(), but mutates the current Set too in
addition to returning the current Set.
Future changes made to the current Set ARE reflected in the returned
Set, and vice-versa.
Parameters
(function(Tv): bool) $callback
Returns
Set<Tv>- Returns itself.
Examples
$s = Set {'red', 'green', 'blue', 'yellow'};
// Only keep values beginning with 'r' or 'b'
$s->retain($color ==> $color[0] === 'r' || $color[0] === 'b');
\var_dump($s);