hphp/hack/manual/apis/Interfaces/ConstSet/takeWhile.md
:::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 ConstSet containing the values of the current ConstSet up to
but not including the first value that produces false when passed to the
specified callback
public function takeWhile(
(function(Tv): bool) $fn,
): ConstSet<Tv>;
The returned ConstSet will always be a proper subset of the current
ConstSet.
(function(Tv): bool) $fn - The callback that is used to determine the stopping condition.ConstSet<Tv> - A ConstSet that is a proper subset of the current ConstSet
up until the callback returns false.