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    module Codewars.GetClosestPoint where

type Point = (Float, Float)

dist :: Point -> Point -> Float
dist (x1, x2) (y1, y2)
  = sqrt (dx ^ 2 + dy ^ 2)
  where (dx, dy) = (y1 - x1, y2 - x2)

closestPoint :: Point -> [Point] -> Point
closestPoint point [p] = p
closestPoint point (p : ps)
  = closestBetweenTwo point p (dist point p) (closestPoint point ps)
  where
    closestBetweenTwo :: Point -> Point -> Float -> Point -> Point
    closestBetweenTwo p0 p1 initialDist p2
      | initialDist < dist point p2 = p1
      | otherwise                   = p2
      
closestPoint' :: Point -> [Point] -> Point
closestPoint' point [] = point
closestPoint' point (p : ps)
  = closestBetweenTwo point p (dist point p) ps
  where
    closestBetweenTwo :: Point -> Point -> Float -> [Point] -> Point
    closestBetweenTwo p0 p1 initialDist [] = p1
    closestBetweenTwo p0 p1 initialDist (p2 : ps)
      | initialDist < dis = closestBetweenTwo p0 p1 initialDist ps
      | otherwise         = closestBetweenTwo p0 p2 dis ps
      where dis = dist p0 p2
     Test Cases 
    module Codewars.GetClosestPointSpec where

import Codewars.GetClosestPoint (closestPoint, closestPoint')
import Test.Hspec
import Test.QuickCheck

spec :: Spec
spec = do
    describe "Points" $ do
      it "finds the closest Point" $ do
        let points = [(38, 19), (833, 938), (83, 49), (83, 83), (72, 15)]
        closestPoint (0, 0) points `shouldBe` (38, 19)
        closestPoint' (0, 0) points `shouldBe` (38, 19)

-- the following line is optional for 8.2
-- main = hspec spec
    View Run Output