1 import M4c._

     2 

     3 //type Pos = (Int, Int)

     4 //type Path = List[Pos]

     5 

     6 def add_pair_urban(x: Pos)(y: Pos): Pos = 

     7   (x._1 + y._1, x._2 + y._2)

     8 

     9 def is_legal_urban(dim: Int, path: Path)(x: Pos): Boolean = 

    10   0 <= x._1 && 0 <= x._2 && x._1 < dim && x._2 < dim && !path.contains(x)

    11 

    12 def moves_urban(x: Pos): List[Pos] = 

    13   List(( 1,  2),( 2,  1),( 2, -1),( 1, -2),

    14        (-1, -2),(-2, -1),(-2,  1),(-1,  2)).map(add_pair_urban(x))

    15 

    16 def legal_moves_urban(dim: Int, path: Path, x: Pos): List[Pos] = 

    17   moves_urban(x).filter(is_legal_urban(dim, path))

    18 

    19 def correct_urban(dim: Int)(p: Path): Boolean = p match {

    20   case Nil => true

    21   case x::Nil => true

    22   case x::y::p => 

    23     if (legal_moves_urban(dim, p, y).contains(x)) correct_urban(dim)(y::p) else false

    24 }

    25 

    26 

    27 val ts70 = tour_on_mega_board(70, List((0,0))).get

    28 assert(correct_urban(70)(ts70) == true)

    29