/**
* Create a lambda-style function representing the secant line through two points
*
* @see create_function(), Math_PolynomialOp::createFunction()
*
* @access public
*
* @param object $p
* @param float $x1
* @param float $x2
* @return string
*/
function createSecantFunction($p, $x1, $x2)
{
$m = Math_PolynomialOp::getSecantSlopeAt($p, $x1, $x2);
$y1 = Math_PolynomialOp::evaluate($p, $x1);
$b = -1 * $m * $x1 + $y1;
return create_function('$x', 'return (' . $m . ' * $x) + ' . $b . ';');
}
