Haversine Distance

Calculates the distance on a sphere between two points given in latitude and longitude using the haversine formula.

The haversine formula can be found on Wikipedia

The Haversine Distance is implemented as a function as a class would be kind of overkill.

haversineDinstance(la1: Double, lo1: Double, la2: Double, lo2: Double, radius: Double = 6367444.7) -> Double

la1 is the latitude of point 1 in degrees.
lo1 is the longitude of point 1 in degrees.
la2 is the latitude of point 2 in degrees.
lo2 is the longitude of point 2 in degrees.
radius is the radius of the sphere considered in meters, which defaults to the mean radius of the earth (from WolframAlpha).

The function contains 3 closures in order to make the code more readable and comparable to the Haversine formula given by the Wikipedia page mentioned above.

haversine implements the haversine, a trigonometric function.
ahaversine the inverse function of the haversine.
dToR a closure converting degrees to radians.

The result of haversineDistance is returned in meters.

Written for Swift Algorithm Club by Jaap Wijnen.