scalaz.TreeLoc.scala Maven / Gradle / Ivy
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package scalaz
import Scalaz._
/** A rose-tree zipper. Represents a scalaz.Tree together with a position in that tree. Provides navigation, persistent update, insertion, and deletes. */
sealed trait TreeLoc[+A] {
/** The currently selected node. */
val tree: Tree[A]
/** The left siblings of the current node. */
val lefts: Stream[Tree[A]]
/** The right siblings of the current node. */
val rights: Stream[Tree[A]]
/** The parent contexts of the current node. */
val parents: Stream[(Stream[Tree[A]], A, Stream[Tree[A]])]
/** 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. */
def root: TreeLoc[A] = parent.some(_.root).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]] = {
def split(acc: Stream[Tree[A]], xs: Stream[Tree[A]]): Option[(Stream[Tree[A]], Tree[A], Stream[Tree[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]] =
this.cojoin.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: Stream[Tree[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[AA >: A](t: Tree[AA]): TreeLoc[AA] = loc(t, lefts, rights, parents)
/** Modify the current node with the given function. */
def modifyTree[AA >: A](f: Tree[AA] => Tree[AA]): TreeLoc[AA] = setTree(f(tree))
/** Modify the label at the current node with the given function. */
def modifyLabel[AA >: A](f: AA => AA): TreeLoc[AA] = setLabel(f(getLabel))
/** Get the label of the current node. */
def getLabel: A = tree.rootLabel
/** Set the label of the current node. */
def setLabel[AA >: A](a: AA): TreeLoc[AA] = modifyTree((t: Tree[AA]) => node(a, t.subForest))
/** Insert the given node to the left of the current node and give it focus. */
def insertLeft[AA >: A](t: Tree[AA]): TreeLoc[AA] = 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[AA >: A](t: Tree[AA]): TreeLoc[AA] = 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[AA >: A](t: Tree[AA]): TreeLoc[AA] = 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[AA >: A](t: Tree[AA]): TreeLoc[AA] = 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[AA >: A](n: Int, t: Tree[AA]): Option[TreeLoc[AA]] =
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)
private def downParents = (lefts, tree.rootLabel, rights) #:: parents
private def combChildren[A](ls: Stream[A], t: A, rs: Stream[A]) =
ls.foldl(t #:: rs)((a, b) => b #:: a)
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
}
}
trait TreeLocs {
def loc[A](t: Tree[A], l: Stream[Tree[A]], r: Stream[Tree[A]], p: Stream[(Stream[Tree[A]], A, Stream[Tree[A]])]): TreeLoc[A] =
new TreeLoc[A] {
val tree = t
val lefts = l
val rights = r
val parents = p
override def toString = ""
}
def fromForest[A](ts: Stream[Tree[A]]) = ts match {
case (Stream.cons(t, ts)) => Some(loc(t, Stream.Empty, ts, Stream.Empty))
}
}
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