diff -r 0587ef444547 -r 48de09728447 progs/sudoku_test.scala
--- a/progs/sudoku_test.scala	Sat Mar 11 23:22:05 2023 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,88 +0,0 @@
-// Sudoku
-//========
-
-// call parallel version with
-//
-// scala -cp scala-parallel-collections_2.13-0.2.0.jar sudoku_test.scala 
-//
-// or
-//
-// scalac -cp scala-parallel-collections_2.13-0.2.0.jar sudoku_test.scala
-// java -cp .:scala-library-2.13.0.jar:scala-parallel-collections_2.13-0.2.0.jar Sudoku
-
-object Sudoku extends App { 
-
-import scala.collection.parallel.CollectionConverters._
-
-type Pos = (Int, Int)
-val emptyValue = '.'
-val maxValue = 9
-
-val allValues = "123456789".toList
-val indexes = (0 to 8).toList
-
-
-def empty(game: String) = game.indexOf(emptyValue)
-def isDone(game: String) = empty(game) == -1 
-def emptyPosition(game: String) = {
-  val e = empty(game)
-  (e % maxValue, e / maxValue)
-}
-
-
-def get_row(game: String, y: Int) = indexes.map(col => game(y * maxValue + col))
-def get_col(game: String, x: Int) = indexes.map(row => game(x + row * maxValue))
-
-def get_box(game: String, pos: Pos): List[Char] = {
-    def base(p: Int): Int = (p / 3) * 3
-    val x0 = base(pos._1)
-    val y0 = base(pos._2)
-    for (x <- (x0 until x0 + 3).toList;
-         y <- (y0 until y0 + 3).toList) yield game(x + y * maxValue)
-}         
-
-
-def update(game: String, pos: Int, value: Char): String = 
-  game.updated(pos, value)
-
-def toAvoid(game: String, pos: Pos): List[Char] = 
-  (get_col(game, pos._1) ++ get_row(game, pos._2) ++ get_box(game, pos))
-
-def candidates(game: String, pos: Pos): List[Char] = 
-  allValues.diff(toAvoid(game, pos))
-
-def search(game: String): List[String] = {
-  if (isDone(game)) List(game)
-  else {
-    val cs = candidates(game, emptyPosition(game))
-    cs.par.map(c => search(update(game, empty(game), c))).toList.flatten
-  }
-}
-
-
-def pretty(game: String): String = 
-  "\n" + (game.grouped(maxValue).mkString(",\n"))
-
-
-val game2 = """8........
-              |..36.....
-              |.7..9.2..
-              |.5...7...
-              |....457..
-              |...1...3.
-              |..1....68
-              |..85...1.
-              |.9....4..""".stripMargin.replaceAll("\\n", "")
-
-// for measuring time
-def time_needed[T](i: Int, code: => T) = {
-  val start = System.nanoTime()
-  for (j <- 1 to i) code
-  val end = System.nanoTime()
-  s"${(end - start) / 1.0e9} secs"
-}
-
-
-println(time_needed(10, search(game2)))
-
-}