MathPHP\SetTheory\Set::isProperSubset PHP Méthode

    public function isProperSubset(Set $B) : bool
    {
        $B_array = $B->asArray();
        $A∩B = array_intersect_key($this->A, $B_array);
        $A∖B = array_diff_key($this->A, $B_array);
        return count($A∩B) === count($this->A) && empty($A∖B) && count($this->A) === count($B);
    }

 /**
  * @dataProvider dataProviderForIsProperSet
  */
 public function testIsProperSubset(array $A, array $B)
 {
     $setA = new Set($A);
     $setB = new Set($B);
     $this->assertTrue($setA->isProperSubset($setB));
 }