anchor.diff:   * Returns the angle between the positive x-axis and the vector ([b],[a]).
    * The result, in radians, is in the range -PI..PI.
    *
  - * If [b] is positive, this is the same as [:atan(b/a):].
  + * If [b] is positive, this is the same as `atan(b/a)`.
    *
    * The result is negative when [a] is negative (including when [a] is the
    * double -0.0).
  
positive.code: /**
   * Converts [x] to a double and returns the arc cosine of the value.
   *
   * Returns a value in the range -PI..PI, or NaN if [x] is outside
   * the range -1..1.
   */
  external double acos(num x);
  
  /**
   * Converts [x] to a double and returns the arc sine of the value.
   * 
   * Returns a value in the range -PI..PI, or  NaN if [x] is outside
   * the range -1..1.
   */
  external double asin(num x);
  
  /**
   * Converts [x] to a dobule and returns the arc tangent of the value.
   * 
   * Returns a value in the range -PI/2..PI/2, or NaN if [x] is NaN.
   */
  external double atan(num x);
  
negative.code:   * Returns the larger of two numbers.
    *
    * Returns NaN if either argument is NaN.
    * The larger of `-0.0` and `0.0` is `0.0`. If the arguments are
    * otherwise equal (including int and doubles with the same mathematical value)
    * then it is unspecified which of the two arguments is returned.
    */
  