isSquare.scala

import scala.math._

case class Point(x:Int, y:Int)

def isSquare(p1: Point, p2: Point, p3: Point, p4: Point): Boolean = {
  val points = Set(p2,p3,p4)
  (for{
    p1_x_Neighbor <- points.find(_.x == p1.x)
    p1_y_Neighbor <- points.find(_.y == p1.y)
    if abs(p1_y_Neighbor.x - p1.x) == abs(p1_x_Neighbor.y - p1.y)
  } yield{
    val lastPoint = (points -- Set(p1_x_Neighbor, p1_y_Neighbor)).head
    val sideLength = abs(p1_x_Neighbor.y - p1.y)
    (abs(lastPoint.x - p1.x) == sideLength) && (abs(lastPoint.y - p1.y) == sideLength)
  }).getOrElse(false)
}


assert(!isSquare(Point(1, 6), Point(6, 7), Point(2, 7), Point(9, 1)))
assert(!isSquare(Point(4, 1), Point(3, 4), Point(0, 5), Point(1, 2)))
assert(isSquare(Point(4, 6), Point(5, 5), Point(5, 6), Point(4, 5)))