// Part 2 about finding a single tour for a board
//================================================
// copy any function you need from file knight1.scala
object CW7b {
type Pos = (Int, Int) // a position on a chessboard
type Path = List[Pos] // a path...a list of positions
//(2a) Implement a first-function that finds the first
// element, say x, in the list xs where f is not None.
// In that case Return f(x), otherwise None. If possible,
// calculate f(x) only once.
//def first(xs: List[Pos], f: Pos => Option[Path]) : Option[Path] = ...
//(2b) Implement a function that uses the first-function for
// trying out onward moves, and searches recursively for a
// knight tour on a dim * dim-board.
//def first_tour(dim: Int, path: Path) : Option[Path] = ...
}