HH\Lib\C\first_key
Returns the first key of the given KeyedTraversable, or null if the KeyedTraversable is empty
namespace HH\Lib\C;
function first_key<Tk, Tv>(
KeyedTraversable<Tk, Tv> $traversable,
): ?Tk;
For non-empty Traversables, see C\first_keyx
.
Time complexity: O(1) Space complexity: O(1)
Parameters
KeyedTraversable<Tk,
Tv> $traversable
Returns
?Tk