Implement 6th assignment

a6-streams/src/main/scala/streams/GameDef.scala

@@ -84,7 +84,7 @@ trait GameDef {
    * This function returns the block at the start position of
    * the game.
    */
-  def startBlock: Block = ???
+  def startBlock: Block = Block(startPos, startPos)
 
   /**
    * A block is represented by the position of the two cubes that
@@ -134,23 +134,25 @@ trait GameDef {
      * Returns the list of blocks that can be obtained by moving
      * the current block, together with the corresponding move.
      */
-    def neighbors: List[(Block, Move)] = ???
+    def neighbors: List[(Block, Move)] =
+      List((left, Left), (right, Right), (up, Up), (down, Down))
 
     /**
      * Returns the list of positions reachable from the current block
      * which are inside the terrain.
      */
-    def legalNeighbors: List[(Block, Move)] = ???
+    def legalNeighbors: List[(Block, Move)] =
+      neighbors filter (_._1.isLegal)
 
     /**
      * Returns `true` if the block is standing.
      */
-    def isStanding: Boolean = ???
+    def isStanding: Boolean = b1 == b2
 
     /**
      * Returns `true` if the block is entirely inside the terrain.
      */
-    def isLegal: Boolean = ???
+    def isLegal: Boolean = terrain(b1) && terrain(b2)
 
   }
 }

a6-streams/src/main/scala/streams/Solver.scala

@@ -10,7 +10,8 @@ trait Solver extends GameDef {
   /**
    * Returns `true` if the block `b` is at the final position
    */
-  def done(b: Block): Boolean = ???
+  def done(b: Block): Boolean =
+    b.isStanding && b.b1 == goal
 
   /**
    * This function takes two arguments: the current block `b` and
@@ -28,15 +29,17 @@ trait Solver extends GameDef {
    * It should only return valid neighbors, i.e. block positions
    * that are inside the terrain.
    */
-  def neighborsWithHistory(b: Block, history: List[Move]): Stream[(Block, List[Move])] = ???
+  def neighborsWithHistory(b: Block, history: List[Move]): Stream[(Block, List[Move])] =
+    (b.legalNeighbors map (x => (x._1, x._2 :: history))).toStream
 
   /**
    * This function returns the list of neighbors without the block
    * positions that have already been explored. We will use it to
    * make sure that we don't explore circular paths.
    */
   def newNeighborsOnly(neighbors: Stream[(Block, List[Move])],
-                       explored: Set[Block]): Stream[(Block, List[Move])] = ???
+                       explored: Set[Block]): Stream[(Block, List[Move])] =
+    neighbors filter (b => !(explored contains b._1))
 
   /**
    * The function `from` returns the stream of all possible paths
@@ -62,18 +65,41 @@ trait Solver extends GameDef {
    * construct the correctly sorted stream.
    */
   def from(initial: Stream[(Block, List[Move])],
-           explored: Set[Block]): Stream[(Block, List[Move])] = ???
+           explored: Set[Block]): Stream[(Block, List[Move])] = {
+    if (initial.isEmpty) initial
+    else {
+      // Depth-first search
+//      val (currentBlock, history) = initial.head
+//      val newExplored = currentBlock.legalNeighbors.map(_._1)
+//      val newNeighbors = newNeighborsOnly(neighborsWithHistory(currentBlock, history), explored)
+//      initial #::: from(newNeighbors, explored ++ newExplored)
+
+      // Breadth-first search
+      val more: Stream[(Block, List[Move])] =
+        for {
+          (block, path) <- initial
+          (newBlock, newPath) <- newNeighborsOnly(neighborsWithHistory(block, path), explored)
+          if !(explored contains newBlock)
+        } yield (newBlock, newPath)
+      initial #::: from(more, explored ++ more.unzip._1)
+    }
+  }
 
   /**
    * The stream of all paths that begin at the starting block.
    */
-  lazy val pathsFromStart: Stream[(Block, List[Move])] = ???
+  lazy val pathsFromStart: Stream[(Block, List[Move])] = {
+    val initialStream = Stream((startBlock, List()))
+    val initialExplored: Set[Solver.this.type#Block] = Set(startBlock)
+    from(initialStream, initialExplored)
+  }
 
   /**
    * Returns a stream of all possible pairs of the goal block along
    * with the history how it was reached.
    */
-  lazy val pathsToGoal: Stream[(Block, List[Move])] = ???
+  lazy val pathsToGoal: Stream[(Block, List[Move])] =
+    pathsFromStart filter (x => done(x._1))
 
   /**
    * The (or one of the) shortest sequence(s) of moves to reach the
@@ -83,5 +109,7 @@ trait Solver extends GameDef {
    * the first move that the player should perform from the starting
    * position.
    */
-  lazy val solution: List[Move] = ???
+  lazy val solution: List[Move] =
+    if (pathsToGoal.isEmpty) Nil
+    else pathsToGoal.head._2
 }

a6-streams/src/main/scala/streams/StringParserTerrain.scala

@@ -52,7 +52,11 @@ trait StringParserTerrain extends GameDef {
    * a valid position (not a '-' character) inside the terrain described
    * by `levelVector`.
    */
-  def terrainFunction(levelVector: Vector[Vector[Char]]): Pos => Boolean = ???
+  def terrainFunction(levelVector: Vector[Vector[Char]]): Pos => Boolean = { case pos =>
+      pos.y >= 0 && pos.x >= 0 &&
+      pos.x < levelVector.size && pos.y < levelVector(pos.x).size &&
+      levelVector(pos.x)(pos.y) != '-'
+    }
 
   /**
    * This function should return the position of character `c` in the
@@ -62,7 +66,11 @@ trait StringParserTerrain extends GameDef {
    * Hint: you can use the functions `indexWhere` and / or `indexOf` of the
    * `Vector` class
    */
-  def findChar(c: Char, levelVector: Vector[Vector[Char]]): Pos = ???
+  def findChar(c: Char, levelVector: Vector[Vector[Char]]): Pos = {
+    val x = levelVector indexWhere (_.contains(c))
+    val y = levelVector(x).indexOf(c)
+    Pos(x, y)
+  }
 
   private lazy val vector: Vector[Vector[Char]] =
     Vector(level.split("\n").map(str => Vector(str: _*)): _*)

a6-streams/src/test/scala/streams/BloxorzSuite.scala

@@ -17,13 +17,14 @@ class BloxorzSuite extends FunSuite {
      * is a valid solution, i.e. leads to the goal.
      */
     def solve(ls: List[Move]): Block =
-      ls.foldLeft(startBlock) { case (block, move) => move match {
-        case Left => block.left
-        case Right => block.right
-        case Up => block.up
-        case Down => block.down
+      ls.foldLeft(startBlock) {
+        case (block, move) => move match {
+          case Left => block.left
+          case Right => block.right
+          case Up => block.up
+          case Down => block.down
+        }
       }
-    }
   }
 
   trait Level1 extends SolutionChecker {
@@ -42,14 +43,53 @@ class BloxorzSuite extends FunSuite {
 
   test("terrain function level 1") {
     new Level1 {
-      assert(terrain(Pos(0,0)), "0,0")
-      assert(!terrain(Pos(4,11)), "4,11")
+      assert(terrain(Pos(0, 0)), "0,0")
+      assert(!terrain(Pos(4, 11)), "4,11")
     }
   }
 
   test("findChar level 1") {
     new Level1 {
-      assert(startPos == Pos(1,1))
+      assert(startPos == Pos(1, 1))
+    }
+  }
+
+  test("neighborsWithHistory") {
+    new Level1 {
+      val actual = neighborsWithHistory(Block(Pos(1, 1), Pos(1, 1)), List(Left, Up)).toSet
+      val expected = Set(
+        (Block(Pos(1, 2), Pos(1, 3)), List(Right, Left, Up)),
+        (Block(Pos(2, 1), Pos(3, 1)), List(Down, Left, Up)))
+      assert(actual == expected)
+    }
+  }
+
+  test("newNeighborsOnly") {
+    new Level1 {
+      val actual: Stream[(Block, List[Move])] = newNeighborsOnly(
+        Set(
+          (Block(Pos(1, 2), Pos(1, 3)), List(Right, Left, Up)),
+          (Block(Pos(2, 1), Pos(3, 1)), List(Down, Left, Up))).toStream,
+        Set(Block(Pos(1, 2), Pos(1, 3)), Block(Pos(1, 1), Pos(1, 1))))
+
+      val expected: Set[(Block, List[Move])] = Set(
+        (Block(Pos(2, 1), Pos(3, 1)), List(Down, Left, Up)))
+
+      assert(actual.toSet == expected)
+    }
+  }
+
+  test("`pathsFromStart` are legal") {
+    new Level1 {
+      assert(pathsFromStart.take(30).toList.forall(_._1.isLegal))
+    }
+  }
+
+  test("`pathsFromStart` path lengths are increasing") {
+    new Level1 {
+      val lengthStream: Stream[Int] = pathsFromStart map (x => x._2.length)
+      val ascendingPairs: Stream[(Int, Int)] = lengthStream zip lengthStream.drop(1)
+      assert(ascendingPairs.take(30).toList.forall(x => x._1 <= x._2))
     }
   }
 
@@ -64,4 +104,15 @@ class BloxorzSuite extends FunSuite {
       assert(solution.length == optsolution.length)
     }
   }
+
+  test("no solution") {
+    new SolutionChecker {
+      val level =
+        """----------
+          |oSoTooo---
+          |----------""".stripMargin
+
+      assert(solution.isEmpty)
+    }
+  }
 }