Getting stuck with repeat statement - swift

Question

I am trying to delete all old coordinates from an array from the condition that the coordinates are too far away from my current location. However the repeat statement gets stuck on repeat, deleting all the coordinates.
var locationArray = [Double]()
var distArray = [CLLocationDistance]()
let maxDis: CLLocationDistance = CLLocationDistance(exactly: 2000)!
let LAT = Double(location.coordinate.latitude)
let LONG = Double(location.coordinate.longitude)
repeat{
locationArray.insert(contentsOf: [LAT, LONG], at: 0)
} while locationArray.count <= 4
let oldCo = CLLocation(latitude: LAT, longitude: LONG)
let newlat = locationArray[2]
let newlong = locationArray[3]
let newCo = CLLocation(latitude: newlat, longitude: newlong)
let dist = newCo.distance(from: oldCo)
distArray.append(dist)
let distArraySum = (distArray.reduce(0) { $0 + $1 })
print(distArraySum)
repeat{
if distArraySum >= maxDis {
locationArray.remove(at: locationArray.count-2)
locationArray.remove(at: locationArray.count-1)
distArray.remove(at: 0)
print("deleted Coordinates")
}
} while distArraySum >= maxDis
The app terminates because I am getting stuck on my repeat statement, and every element in the distArray gets removed until there are no more elements. So when it repeats again and I try to remove an element from an empty array, I get a fatal error.

Answer 1

Once you calculate disArraySum you never recalculate it within the repeat loop. The result of distArraySum >= maxDis will never change and so your loop will either always execute or never execute, but it will never dynamically change state.
Additionally, you might want to consider changing locationArray to an array of tuples; it looks like you're interleaving lat and lon, it would be easier conceptually e.g.:
var locationArray:[(lat: Double, lon: Double)] = []
This will let you avoid having to do
locationArray.remove(at: locationArray.count-2)
locationArray.remove(at: locationArray.count-1)
And while we're at it, if I can make a suggestion to use for each instead, then the final loop might look like the following untested code:
for (i, coordinates) in locationArray.enumerate().reverse() {
if (some condition using coordinates.lat and coordinates.lon) {
locationArray.removeAtIndex(i)
}
}