Haversine Distance calculator

main.go

package main

import (
    "fmt"
    "math"
)

const earthRadiusKM = 6371.0

type Location struct {
    Latitude  float64
    Longitude float64
}

func degreeToRadians(angle float64) float64 {
    return angle * (math.Pi / 180.0)
}

func NewLocation(lat_degree float64, long_degree float64) Location {
    return Location{
        Latitude:  degreeToRadians(lat_degree),
        Longitude: degreeToRadians(long_degree),
    }
}

func hav_function(angle_rad float64) float64 {
    return (1 - math.Cos(angle_rad)) / 2.0
}

func hav_formula(first_city Location, second_city Location) float64 {
    // first, find the difference between latitudes and longitudes
    var latitude_diff float64 = first_city.Latitude - second_city.Latitude
    var longitude_diff float64 = first_city.Longitude - second_city.Longitude

    // then, compute the haversine of those variables
    var hav_latitude float64 = hav_function(latitude_diff)
    var hav_longitude float64 = hav_function(longitude_diff)

    // last, put the results into formula
    return hav_latitude + math.Cos(first_city.Latitude)*math.Cos(second_city.Latitude)*hav_longitude
}

func archaversine(hav_angle float64) float64 {
    var sqrt_hav_angle float64 = math.Sqrt(hav_angle)
    return 2.0 * math.Asin(sqrt_hav_angle)
}

func haversine_distance(first_city Location, second_city Location) float64 {
    var hav_central_angle float64 = hav_formula(first_city, second_city)
    var central_angle_rad float64 = archaversine(hav_central_angle)
    return earthRadiusKM * central_angle_rad
}

func main() {
    var lat float64
    var long float64
    fmt.Scanf("%f %f", &lat, &long)
    var first_city = NewLocation(lat, long)

    fmt.Scanf("%f %f", &lat, &long)
    var second_city = NewLocation(lat, long)

    fmt.Printf("distance between 2 cities = %f km\n", haversine_distance(first_city, second_city))
}