Haversine formula

editable example

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ghul

use IO.Std.write_line

use System.Math.sin

use System.Math.cos

use System.Math.asin

use System.Math.sqrt

use System.Math.pi

let earth_radius_km = 6372.8D

radians(degrees: double) -> double => degrees * pi / 180.0D

haversine(theta: double) -> double => sin(theta / 2.0D) * sin(theta / 2.0D)

great_circle_distance(

(latitude_1, longitude_1): (double, double),

(latitude_2, longitude_2): (double, double),

radius: double

) -> double =>

let chord =

haversine(radians(latitude_2 - latitude_1)) +

cos(radians(latitude_1)) * cos(radians(latitude_2)) *

haversine(radians(longitude_2 - longitude_1))

in

2.0D * radius * asin(sqrt(chord))

let nashville = (36.12D, -86.67D)

let los_angeles = (33.94D, -118.40D)

let distance =

great_circle_distance(nashville, los_angeles, earth_radius_km)

write_line("BNA to LAX: {distance:F6} km")

BNA to LAX: 2887.259951 km