// 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] = ...

}