diff -r 9b5165b8a762 -r 0587ef444547 progs/knight6.scala
--- a/progs/knight6.scala	Sat Mar 11 23:12:49 2023 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,72 +0,0 @@
-import scala.util._
-
-type Pos = (Int, Int)
-
-
-def print_board(n: Int)(steps: List[Pos]): Unit = {
-  for (i <- 0 until n) {
-    for (j <- 0 until n) {
-      print(f"${steps.reverse.indexOf((i, j))}%3.0f ")
-    }
-    println
-  } 
-}
-
-def add_pair(x: Pos)(y: Pos) = 
-  (x._1 + y._1, x._2 + y._2)
-
-def dist(n: Int)(y: Pos) = 
-  (n / 2 - y._1).abs + (n / 2 - y._2).abs
-
-def is_legal(n: Int)(x: Pos) = 
-  0 <= x._1 && 0 <= x._2 && x._1 < n && x._2 < n
-
-def moves(n: Int)(x: Pos): List[Pos] = {
-  List(( 1,  2),( 2,  1),( 2, -1),( 1, -2),
-       (-1, -2),(-2, -1),(-2,  1),(-1,  2)).map(add_pair(x)).filter(is_legal(n))
-}
-
-def moves_filtered(n: Int)(steps: List[Pos])(x: Pos): List[Pos] = {
-  moves(n)(x).filterNot(steps.contains(_))
-}
-
-def ordered_moves(n: Int)(steps: List[Pos])(x: Pos): List[Pos] = 
-  moves_filtered(n)(steps)(x).sortBy((x: Pos) => (moves_filtered(n)(steps)(x).length, dist(n)(x)))
-
-/*def first[A, B](xs: List[A], f: A => Option[B]): Option[B] = xs match {
-  case Nil => None
-  case x::xs => {
-    val result = f(x)
-    if (result.isDefined) result else first(xs, f)
-  }
-}*/
-
-def first[A, B](xs: List[A], f: A => Option[B]): Option[B] =
-  xs.par.flatMap(f(_)).headOption
-
-// non-circle tours, including distance
-def tour(n: Int)(steps: List[Pos]): Option[List[Pos]] = {
-  if (steps.length ==  n * n) //&& moves(n)(steps.head).contains(steps.last)) 
-    Some(steps)
-  else first(ordered_moves(n)(steps)(steps.head), (x: Pos) => tour(n)(x::steps))
-}
-
-//val n = 8
-val n = 6
-println(s"number simple tours: n = $n")
-
-println(print_board(n)((tour(n)(List((0, 0)))).get))
-//println((for (i <- 0 until n; j <- 0 until n) yield tour(n)(List((i, j)))).flatten.distinct.size) 
-
-
-
-
-
-/*
-def first[A, B](xs: List[A], f: A => Option[B]): Option[B] =
-  xs.view.flatMap(f(_)).headOption
-*/
-
-/*
-
-*/