/* An expression to return the square root of a number without using the $sqrt function */
/* Pointless, but demonstrates capability */

(
  /**
   * Implements the square root function
   * Uses the Newton-Raphson method
   */
  $my_sqrt := function($n) {(

    $good_enough := function($guess) {
      $abs($guess * $guess - $n) < 0.000000000001
    };
    $improve_guess := function($guess) {
      ($guess + $n / $guess) / 2
    };

    /* Iterate using a tail-recursive function until convergence */
    $sqrt_iter := function($guess) {
      $good_enough($guess) ? $guess : $sqrt_iter($improve_guess($guess))
    };
    $n >= 0 ? $sqrt_iter(1) : "no complex numbers today"
  )};
  $my_sqrt($$)
)