scaloi.syntax.StrictTreeOps.scala Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of scaloi_2.13 Show documentation
Fyne thyngges from Learning Objects, an LO Venture
The newest version!
/*
 * Copyright 2007 Learning Objects
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package scaloi
package syntax

import scalaz.StrictTree
import scalaz.StrictTree.Node
import scalaz.std.vector._
import scalaz.syntax.std.boolean._
import scaloi.syntax.foldable._

import scala.annotation.nowarn

final class StrictTreeOps[A](private val self: StrictTree[A]) extends AnyVal {

  /** A catamorphism over a tree.
    *
    * `f` is invoked with the label of the root of `self` and with the result
    * of folding `self`'s children with `f`.
    *
    * @note this may stack-overflow on very large trees.
    */
  def foldTree[B](f: (A, Vector[B]) => B): B = {
    def loop(current: StrictTree[A]): B = {
      f(current.rootLabel, current.subForest.map(loop))
    }
    loop(self)
  }

  /** A top-down histomorphism over a tree.
    *
    * The tree is mapped with a function `f` that that can draw from
    * the root label of each node and the mapped values of ancestor
    * nodes.
    */
  def tdhisto[B](f: (List[B], A) => B): StrictTree[B] = {
    def loop(tree: StrictTree[A], ancestors: List[B]): StrictTree[B] = {
      val b = f(ancestors, tree.rootLabel)
      Node(b, tree.subForest.map(loop(_, b :: ancestors)))
    }
    loop(self, Nil)
  }

  /** Select the `ix`th subtree of this tree, if it exists. */
  def get(ix: Int): Option[StrictTree[A]] = self.subForest.lift.apply(ix)

  /** Finds a node matching the given predicate and returns the
    * path from the matching node to the root. */
  def findPath(f: A => Boolean): Option[List[StrictTree[A]]] = {
    def find(tree: StrictTree[A], parents: List[StrictTree[A]]): Option[List[StrictTree[A]]] = {
      val path = tree :: parents
      f(tree.rootLabel) option path orElse tree.subForest.findMap(find(_, path))
    }
    find(self, Nil)
  }

  /** Zip the tree's elements with their depth in the tree. */
  def zipWithDepth: StrictTree[(A, Int)] = {
    @nowarn("msg=exhaustive")
    def loop(node: StrictTree[A], depth: Int): StrictTree[(A, Int)] = node match {
      case Node(content, children) =>
        Node((content, depth), children.map(loop(_, 1 + depth)))
    }
    loop(self, 0)
  }
}

trait ToStrictTreeOps {
  import language.implicitConversions

  @inline implicit final def scaloiStrictTreeOps[A](self: StrictTree[A]): StrictTreeOps[A] =
    new StrictTreeOps[A](self)

}