HH\Lib\Vec\diff_by
Returns a new vec containing only the elements of the first Traversable that do not appear in the second one, where an element's identity is determined by the scalar function
namespace HH\Lib\Vec;
function diff_by<Tv, Ts as arraykey>(
Traversable<Tv> $first,
Traversable<Tv> $second,
(function(Tv): Ts) $scalar_func,
): vec<Tv>;
For vecs that contain arraykey elements, see Vec\diff().
Time complexity: O((n + m) * s), where n is the size of $first, m is the
size of $second, and s is the complexity of $scalar_func
Space complexity: O(n + m), where n is the size of $first and m is the size
of $second -- note that this is bigger than O(n)
Parameters
Traversable<Tv>$firstTraversable<Tv>$second(function(Tv): Ts) $scalar_func
Returns
vec<Tv>