function

atan2

Source

/**
 * A variant of [atan].
 *
 * Converts both arguments to doubles.
 *
 * 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):].
 *
 * The result is negative when [a] is negative (including when [a] is the
 * double -0.0).
 *
 * If [a] is equal to zero, the vector ([b],[a]) is considered parallel to
 * the x-axis, even if [b] is also equal to zero. The sign of [b] determines
 * the direction of the vector along the x-axis.
 *
 * Returns NaN if either argument is NaN.
 */
external double atan2(num a, num b);