haversine.swift

// The fixed formula 
struct Global {
    static var schoolID: Int? // Work around for passing the selected location ID
    static var userCoord: CLLocationCoordinate2D?
    
    func computeDistance() -> Double {
        // User coordinate
        let uLat: Double = 35.6603676639829
        let uLng: Double = -80.4443005566303
        // School coordinate
        let sLat: Double = 35.523075
        let sLon: Double = -80.54142
        
        let radius: Double = 3959.0 // Miles
        
        let deltaP = (sLat.degreesToRadians - uLat.degreesToRadians)
        let deltaL = (sLon.degreesToRadians - uLng.degreesToRadians)
        let a = sin(deltaP/2) * sin(deltaP/2) + cos(uLat.degreesToRadians) * cos(sLat.degreesToRadians) * sin(deltaL/2) * sin(deltaL/2)
        let c = 2 * atan2(sqrt(a), sqrt(1-a))
        let d = radius * c
        
        return d.roundToPlaces(2) // distance in miles rounded to 2 decimal places
    }
}