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Scala example source code file (TreeLoc.scala)

This example Scala source code file (TreeLoc.scala) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Scala by Example" TM.

Learn more about this Scala project at its project page.

Java - Scala tags/keywords

boolean, empty, none, option, parent, some, stream, traverse1, treeforest, treeloc

The TreeLoc.scala Scala example source code

package scalaz

import TreeLoc._
import annotation.tailrec

/**
 * A rose-tree zipper. Represents a [[scalaz.Tree]] together with a position in that tree.
 * Provides navigation, persistent update, insertion, and deletes.
 *
 * @param tree The currently selected node.
 * @param lefts The left siblings of the current node.
 * @param rights The right siblings of the current node.
 * @param parents The parent contexts of the current node.
 */
final case class TreeLoc[A](tree: Tree[A], lefts: TreeForest[A],
                            rights: TreeForest[A], parents: Parents[A]) {

  import Tree._

  /** Select the parent of the current node. */
  def parent: Option[TreeLoc[A]] = parents match {
    case (pls, v, prs) #:: ps => Some(loc(Node(v, combChildren(lefts, tree, rights)), pls, prs, ps))
    case Stream.Empty         => None
  }

  /** Select the root node of the tree. */
  @tailrec
  def root: TreeLoc[A] =
    parent match {
      case Some(z) => z.root
      case None    => this
    }

  /** Select the left sibling of the current node. */
  def left: Option[TreeLoc[A]] = lefts match {
    case t #:: ts     => Some(loc(t, ts, tree #:: rights, parents))
    case Stream.Empty => None
  }

  /** Select the right sibling of the current node. */
  def right: Option[TreeLoc[A]] = rights match {
    case t #:: ts     => Some(loc(t, tree #:: lefts, ts, parents))
    case Stream.Empty => None
  }

  /** Select the leftmost child of the current node. */
  def firstChild: Option[TreeLoc[A]] = tree.subForest match {
    case t #:: ts     => Some(loc(t, Stream.Empty, ts, downParents))
    case Stream.Empty => None
  }

  /** Select the rightmost child of the current node. */
  def lastChild: Option[TreeLoc[A]] = tree.subForest.reverse match {
    case t #:: ts     => Some(loc(t, ts, Stream.Empty, downParents))
    case Stream.Empty => None
  }

  /** Select the nth child of the current node. */
  def getChild(n: Int): Option[TreeLoc[A]] =
    for {lr <- splitChildren(Stream.Empty, tree.subForest, n)
         ls = lr._1
    } yield loc(ls.head, ls.tail, lr._2, downParents)

  /** Select the first immediate child of the current node that satisfies the given predicate. */
  def findChild(p: Tree[A] => Boolean): Option[TreeLoc[A]] = {
    @tailrec
    def split(acc: TreeForest[A], xs: TreeForest[A]): Option[(TreeForest[A], Tree[A], TreeForest[A])] =
      (acc, xs) match {
        case (acc, Stream.cons(x, xs)) => if (p(x)) Some((acc, x, xs)) else split(Stream.cons(x, acc), xs)
        case _                         => None
      }
    for (ltr <- split(Stream.Empty, tree.subForest)) yield loc(ltr._2, ltr._1, ltr._3, downParents)
  }

  /** Select the first descendant node of the current node that satisfies the given predicate. */
  def find(p: TreeLoc[A] => Boolean): Option[TreeLoc[A]] =
    Cobind[TreeLoc].cojoin(this).tree.flatten.find(p)

  /** Get the entire tree represented by this zipper. */
  def toTree: Tree[A] = root.tree

  /** Get the entire forest represented by this zipper. */
  def toForest: TreeForest[A] = combChildren(root.lefts, root.tree, root.rights)

  /** True if the current node is the root node. */
  def isRoot: Boolean = parents.isEmpty

  /** True if the current node has no left siblings. */
  def isFirst: Boolean = lefts.isEmpty

  /** True if the current node has no right siblings. */
  def isLast: Boolean = rights.isEmpty

  /** True if the current node has no children. */
  def isLeaf: Boolean = tree.subForest.isEmpty

  /** True if the current node is not the root node. */
  def isChild: Boolean = !isRoot

  /** True if the current node has children. */
  def hasChildren: Boolean = !isLeaf

  /** Replace the current node with the given one. */
  def setTree(t: Tree[A]): TreeLoc[A] = loc(t, lefts, rights, parents)

  /** Modify the current node with the given function. */
  def modifyTree(f: Tree[A] => Tree[A]): TreeLoc[A] = setTree(f(tree))

  /** Modify the label at the current node with the given function. */
  def modifyLabel(f: A => A): TreeLoc[A] = setLabel(f(getLabel))

  /** Get the label of the current node. */
  def getLabel: A = tree.rootLabel

  /** Set the label of the current node. */
  def setLabel(a: A): TreeLoc[A] = modifyTree((t: Tree[A]) => Node(a, t.subForest))

  /** Insert the given node to the left of the current node and give it focus. */
  def insertLeft(t: Tree[A]): TreeLoc[A] = loc(t, lefts, Stream.cons(tree, rights), parents)

  /** Insert the given node to the right of the current node and give it focus. */
  def insertRight(t: Tree[A]): TreeLoc[A] = loc(t, Stream.cons(tree, lefts), rights, parents)

  /** Insert the given node as the first child of the current node and give it focus. */
  def insertDownFirst(t: Tree[A]): TreeLoc[A] = loc(t, Stream.Empty, tree.subForest, downParents)

  /** Insert the given node as the last child of the current node and give it focus. */
  def insertDownLast(t: Tree[A]): TreeLoc[A] = loc(t, tree.subForest.reverse, Stream.Empty, downParents)

  /** Insert the given node as the nth child of the current node and give it focus. */
  def insertDownAt(n: Int, t: Tree[A]): Option[TreeLoc[A]] =
    for (lr <- splitChildren(Stream.Empty, tree.subForest, n)) yield loc(t, lr._1, lr._2, downParents)

  /** Delete the current node and all its children. */
  def delete: Option[TreeLoc[A]] = rights match {
    case Stream.cons(t, ts) => Some(loc(t, lefts, ts, parents))
    case _                  => lefts match {
      case Stream.cons(t, ts) => Some(loc(t, ts, rights, parents))
      case _                  => for (loc1 <- parent) yield loc1.modifyTree((t: Tree[A]) => Node(t.rootLabel, Stream.Empty))
    }
  }

  /**
   * The path from the focus to the root.
   */
  def path: Stream[A] = getLabel #:: parents.map(_._2)

  /** Maps the given function over the elements. */
  def map[B](f: A => B): TreeLoc[B] = {
    val ff = (_: Tree[A]).map(f)
    TreeLoc.loc(tree map f, lefts map ff, rights map ff,
      parents.map {
        case (l, t, r) => (l map ff, f(t), r map ff)
      })
  }

  def cojoin: TreeLoc[TreeLoc[A]] = {

    val lft = (_: TreeLoc[A]).left
    val rgt = (_: TreeLoc[A]).right
    def dwn[A](tz: TreeLoc[A]): (TreeLoc[A], () => Stream[TreeLoc[A]]) = {
      val f = () => std.stream.unfold(tz.firstChild) {
        (o: Option[TreeLoc[A]]) => for (c <- o) yield (c, c.right)
      }
      (tz, f)
    }
    def uf[A](a: TreeLoc[A], f: TreeLoc[A] => Option[TreeLoc[A]]): Stream[Tree[TreeLoc[A]]] = {
      std.stream.unfold(f(a)) {
        (o: Option[TreeLoc[A]]) => for (c <- o) yield (Tree.unfoldTree(c)(dwn[A](_: TreeLoc[A])), f(c))
      }
    }

    val p = std.stream.unfold(parent) {
      (o: Option[TreeLoc[A]]) => for (z <- o) yield ((uf(z, lft), z, uf(z, rgt)), z.parent)
    }
    TreeLoc.loc(Tree.unfoldTree(this)(dwn[A](_: TreeLoc[A])), uf(this, lft), uf(this, rgt), p)
  }

  private def downParents = (lefts, tree.rootLabel, rights) #:: parents

  private def combChildren[A](ls: Stream[A], t: A, rs: Stream[A]) =
    ls.foldLeft(t #:: rs)((a, b) => b #:: a)

  @tailrec
  private def splitChildren[A](acc: Stream[A], xs: Stream[A], n: Int): Option[(Stream[A], Stream[A])] =
    (acc, xs, n) match {
      case (acc, xs, 0)                 => Some((acc, xs))
      case (acc, Stream.cons(x, xs), n) => splitChildren(Stream.cons(x, acc), xs, n - 1)
      case _                            => None
    }
}

sealed abstract class TreeLocInstances {
  implicit val treeLocInstance: Comonad[TreeLoc] with Traverse1[TreeLoc] = new Comonad[TreeLoc] with Traverse1[TreeLoc] {
    import Stream.Empty
    import scalaz.std.stream._

    def copoint[A](p: TreeLoc[A]): A = p.tree.rootLabel

    override def map[A, B](fa: TreeLoc[A])(f: A => B): TreeLoc[B] = fa map f

    def cobind[A, B](fa: TreeLoc[A])(f: TreeLoc[A] => B): TreeLoc[B] = map(cojoin(fa))(f)

    override def cojoin[A](a: TreeLoc[A]): TreeLoc[TreeLoc[A]] = a.cojoin

    override def all[A](fa: TreeLoc[A])(f: A => Boolean) =
      Foldable[Tree].all(fa.tree)(f) && ForestT.all(fa.lefts)(f) && ForestT.all(fa.rights)(f) && ParentsT.all(fa.parents)(f)

    override def any[A](fa: TreeLoc[A])(f: A => Boolean) =
      Foldable[Tree].any(fa.tree)(f) || ForestT.any(fa.lefts)(f) || ForestT.any(fa.rights)(f) || ParentsT.any(fa.parents)(f)

    override def foldMap1[A, B](fa: TreeLoc[A])(f: A => B)(implicit B: Semigroup[B]) =
      foldMapLeft1(fa)(f)((b, a) => B.append(b, f(a)))

    override def foldMap[A, B](fa: TreeLoc[A])(f: A => B)(implicit B: Monoid[B]) =
      B.append(
        B.append(
          Foldable[Tree].foldMap(fa.tree)(f),
          ForestT.foldMap(fa.lefts)(f)
        ),
        B.append(
          ForestT.foldMap(fa.rights)(f),
          ParentsT.foldMap(fa.parents)(f)
        )
      )

    override def foldLeft[A, B](fa: TreeLoc[A], z: B)(f: (B, A) => B) =
      ParentsT.foldLeft(
        fa.parents, ForestT.foldLeft(
          fa.rights, ForestT.foldLeft(
            fa.lefts, Foldable[Tree].foldLeft(fa.tree, z)(f))(f))(f))(f)

    override def foldMapLeft1[A, B](fa: TreeLoc[A])(z: A => B)(f: (B, A) => B) =
      ParentsT.foldLeft(
        fa.parents, ForestT.foldLeft(
          fa.rights, ForestT.foldLeft(
            fa.lefts, Foldable1[Tree].foldMapLeft1(fa.tree)(z)(f))(f))(f))(f)

    override def traverse1Impl[G[_], A, B](fa: TreeLoc[A])(f: A => G[B])(implicit G: Apply[G]) = fa.lefts match {
      case l #:: ls =>
        val lefts1 = ForestT1.traverse1(OneAnd(l, ls))(f)
        fa.rights match {
          case r #:: rs =>
            val rights1 = ForestT1.traverse1(OneAnd(r, rs))(f)
            fa.parents match {
              case p #:: ps =>
                G.apply4(fa.tree.traverse1(f), lefts1, rights1, ParentsT1.traverse1(OneAnd(p, ps))(f))(
                  (tree, lefts, rights, parents) =>
                    TreeLoc(
                      tree = tree,
                      lefts = lefts.head #:: lefts.tail,
                      rights = rights.head #:: rights.tail,
                      parents = parents.head #:: parents.tail
                    )
                )
              case Empty =>
                G.apply3(fa.tree.traverse1(f), lefts1, rights1)(
                  (tree, lefts, rights) =>
                    TreeLoc(
                      tree = tree,
                      lefts = lefts.head #:: lefts.tail,
                      rights = rights.head #:: rights.tail,
                      parents = Empty
                    )
                )
            }
          case Empty =>
            fa.parents match {
              case p #:: ps =>
                G.apply3(fa.tree.traverse1(f), lefts1, ParentsT1.traverse1(OneAnd(p, ps))(f))(
                  (tree, lefts, parents) =>
                    TreeLoc(
                      tree = tree,
                      lefts = lefts.head #:: lefts.tail,
                      rights = Empty,
                      parents = parents.head #:: parents.tail
                    )
                )
              case Empty =>
                G.apply2(fa.tree.traverse1(f), lefts1)(
                  (tree, lefts) =>
                    TreeLoc(
                      tree = tree,
                      lefts = lefts.head #:: lefts.tail,
                      rights = Empty,
                      parents = Empty
                    )
                )
            }
        }
      case Empty =>
        fa.rights match {
          case r #:: rs =>
            val rights1 = ForestT1.traverse1(OneAnd(r, rs))(f)
            fa.parents match {
              case p #:: ps =>
                G.apply3(fa.tree.traverse1(f), rights1, ParentsT1.traverse1(OneAnd(p, ps))(f))(
                  (tree, rights, parents) =>
                    TreeLoc(
                      tree = tree,
                      lefts = Empty,
                      rights = rights.head #:: rights.tail,
                      parents = parents.head #:: parents.tail
                    )
                )
              case Empty =>
                G.apply2(fa.tree.traverse1(f), rights1)(
                  (tree, rights) =>
                    TreeLoc(
                      tree = tree,
                      lefts = Empty,
                      rights = rights.head #:: rights.tail,
                      parents = Empty
                    )
                )
            }
          case Empty =>
            fa.parents match {
              case p #:: ps =>
                G.apply2(fa.tree.traverse1(f), ParentsT1.traverse1(OneAnd(p, ps))(f))(
                  (tree, parents) =>
                    TreeLoc(
                      tree = tree,
                      lefts = Empty,
                      rights = Empty,
                      parents = parents.head #:: parents.tail
                    )
                )
              case Empty =>
                G.map(fa.tree.traverse1(f))(t =>
                  TreeLoc(t, Empty, Empty, Empty)
                )
            }
        }
    }

    override def foldMapRight1[A, B](fa: TreeLoc[A])(z: A => B)(f: (A, => B) => B) =
      ParentsT.foldMapRight1Opt(fa.parents)(z)(f) match {
        case Some(p) =>
          fa.tree.foldRight(
            ForestT.foldRight(fa.lefts, ForestT.foldRight(fa.rights, p)(f))(f)
          )(f)
        case None =>
          ForestT.foldMapRight1Opt(fa.rights)(z)(f) match {
            case Some(r) =>
              fa.tree.foldRight(ForestT.foldRight(fa.lefts, r)(f))(f)
            case None =>
              ForestT.foldMapRight1Opt(fa.lefts)(z)(f) match {
                case Some(l) =>
                  fa.tree.foldRight(l)(f)
                case None =>
                  Foldable1[Tree].foldMapRight1(fa.tree)(z)(f)
              }
          }
      }

    private[this] val ForestT: Traverse[TreeForest] =
      Traverse[Stream].compose[Tree]

    private[this] val ForestT1: Traverse1[Lambda[a => OneAnd[Stream, Tree[a]]]] =
      Traverse1[Lambda[a => OneAnd[Stream, a]]].compose[Tree]

    private[this] implicit val ParentT: Traverse1[Parent] = new Traverse1[Parent] {

      override def all[A](fa: Parent[A])(f: A => Boolean) =
        ForestT.all(fa._1)(f) && f(fa._2) && ForestT.all(fa._3)(f)

      override def any[A](fa: Parent[A])(f: A => Boolean) =
        ForestT.any(fa._1)(f) || f(fa._2) || ForestT.any(fa._3)(f)

      override def foldLeft[A, B](fa: Parent[A], z: B)(f: (B, A) => B) =
        ForestT.foldLeft(fa._3, f(ForestT.foldLeft(fa._1, z)(f), fa._2))(f)

      override def foldMap[A, B](fa: Parent[A])(f: A => B)(implicit B: Monoid[B]) =
        B.append(B.append(ForestT.foldMap(fa._1)(f), f(fa._2)), ForestT.foldMap(fa._3)(f))

      override def traverse1Impl[G[_], A, B](fa: Parent[A])(f: A => G[B])(implicit G: Apply[G]): G[Parent[B]] = {
        (fa._1, fa._3) match {
          case (x #:: xs, y #:: ys) =>
            G.apply3(ForestT1.traverse1(OneAnd(x, xs))(f), f(fa._2), ForestT1.traverse1(OneAnd(y, ys))(f)) {
              case (l, c, r) =>
                (l.head #:: l.tail, c, r.head #:: r.tail)
            }
          case (x #:: xs, _) =>
            G.apply2(ForestT1.traverse1(OneAnd(x, xs))(f), f(fa._2)) {
              case (l, c) =>
                (l.head #:: l.tail, c, Empty)
            }
          case (_, x #:: xs) =>
            G.apply2(f(fa._2), ForestT1.traverse1(OneAnd(x, xs))(f)) {
              case (c, r) =>
                (Empty, c, r.head #:: r.tail)
            }
          case (Empty, Empty) =>
            G.map(f(fa._2))(c => (Empty, c, Empty))
        }
      }

      override def foldMapRight1[A, B](fa: Parent[A])(z: A => B)(f: (A, => B) => B): B =
        ForestT.foldMapRight1Opt(fa._3)(z)(f) match {
          case Some(r) =>
            ForestT.foldRight(fa._1, f(fa._2, r))(f)
          case None =>
            ForestT.foldRight(fa._1, z(fa._2))(f)
        }
    }

    private[this] val ParentsT: Traverse[Parents] =
      Traverse[Stream].compose[Parent]

    private[this] val ParentsT1: Traverse1[Lambda[a => OneAnd[Stream, Parent[a]]]] =
      Traverse1[Lambda[a => OneAnd[Stream, a]]].compose[Parent]
  }


  implicit def treeLocEqual[A](implicit A: Equal[A]): Equal[TreeLoc[A]] =
    new TreeLocEqual[A] { def E = A }

  implicit def treeLocOrder[A](implicit A: Order[A]): Order[TreeLoc[A]] =
    new Order[TreeLoc[A]] with TreeLocEqual[A] {
      def E = A
      import std.stream._, std.tuple._

      override def order(a: TreeLoc[A], b: TreeLoc[A]) =
        Divide[Order].deriving4(Function.unlift(TreeLoc.unapply[A])).order(a, b)
    }
}

object TreeLoc extends TreeLocInstances {
  type TreeForest[A] =
  Stream[Tree[A]]

  type Parent[A] =
  (TreeForest[A], A, TreeForest[A])

  type Parents[A] =
  Stream[Parent[A]]

  def loc[A](t: Tree[A], l: TreeForest[A], r: TreeForest[A], p: Parents[A]): TreeLoc[A] =
    TreeLoc(t, l, r, p)

  def fromForest[A](ts: TreeForest[A]): Option[TreeLoc[A]] = ts match {
    case (Stream.cons(t, ts)) => Some(loc(t, Stream.Empty, ts, Stream.Empty))
    case _ => None
  }
}

private trait TreeLocEqual[A] extends Equal[TreeLoc[A]] {
  implicit def E: Equal[A]
  import std.stream._, std.tuple._

  override final def equal(a: TreeLoc[A], b: TreeLoc[A]) = {
    Equal[Tree[A]].equal(a.tree, b.tree) &&
    Equal[TreeForest[A]].equal(a.lefts, b.lefts) &&
    Equal[TreeForest[A]].equal(a.rights, b.rights) &&
    Equal[Parents[A]].equal(a.parents, b.parents)
  }
}

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