disjoint function

@useResult bool disjoint(Iterable<Object?> a, Iterable<Object?> b)

Returns true if a and b have no common elements.

Example

disjoint([1, 2], [3, 4]); // true
disjoint([1, 2], []); // true

disjoint([1, 2], [2, 3]); // false

Implementation details

This function assumes that the iterables have efficient length computations, i.e. the length is cached. This is true for most standard library collections.

Implementation

@useResult bool disjoint(Iterable<Object?> a, Iterable<Object?> b) {
  if (a.isEmpty || b.isEmpty) {
    return true;
  }

  final (iterable, contains) = switch ((a, b)) {
    (_, _) when a is Set<Object?> || (b is! Set<Object?> && a.length > b.length) => (b, a),
    _ => (a, b),
  };

  for (final element in iterable) {
    if (contains.contains(element)) {
      return false;
    }
  }

  return true;
}