function testAntiDerivative()
{
$p = new Math_Polynomial('12x^3 + 6x^2 + 2x + 4');
$first_der = Math_PolynomialOp::getDerivative($p);
$anti_der = Math_PolynomialOp::getAntiDerivative($first_der, 1, 4);
$this->assertTrue($anti_der->toString() == $p->toString());
}
/**
* Get the nth anti-derivative of a Math_Polynomial
*
* Returns the nth anti-derivative of the Polynomial. An optional constant can
* be passed in to have that appended as the x^0 term.
*
* @see PolynomialOp::getDerivative()
*
* @access public
* @static
*
* @param object $p
* @param integer $n
* @param integer $c
*/
function &getAntiDerivative($p, $n = 1, $c = 0)
{
if (!is_a($p, 'Math_Polynomial')) {
$p = new Math_Polynomial($p);
}
$result = new Math_Polynomial();
// This will store the Polynomial's derivative
$count = $p->numTerms();
for ($i = 0; $i < $count; $i++) {
// For each term, divide coefficient by exponent + 1, add one to exponent
$term = $p->getTerm($i);
$der_term = new Math_PolynomialTerm($term->getCoefficient() / ($term->getExponent() + 1), $term->getExponent() + 1);
$result->addTerm($der_term);
}
for ($i = 0; $i < $n - 1; $i++) {
// If we want other than the 1st derivative, keep going...
$result = Math_PolynomialOp::getAntiDerivative($result);
}
if ($c) {
$result->addTerm(new Math_PolynomialTerm($c, 0));
}
return $result;
}
