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Treehugger.scala inspired by treehugger.js
package net.danieldietrich.scala.treehugger
sealed abstract class Tree
case class Node(id: Symbol)(children: Tree*) extends Tree
case class Leaf(id: Symbol)(value: String) extends Tree
object Example {
// 2 + 3 * 1
def syntax() = {
Node('Add)(
Leaf('Num)("2"),
Node('Mul)(
Leaf('Num)("3"),
Leaf('Num)("1")
)
)
}
def niceSyntax() = {
val Add = Node('Add)_
val Mul = Node('Mul)_
val Num = Leaf('Num)_
Add(Num("2"), Mul(Num("3"), Num("1")))
}
def openIssues() = {
// compilation error: value children is not a member of net.danieldietrich.scala.treehugger.Node
Node('Test)().children
// compilation error: value value is not a member of net.danieldietrich.scala.treehugger.Leaf
Leaf('Test)("test").value
}
}
package net.danieldietrich.scala.treehugger
// 1) removed curried constructors of case classes
// 2) added curried apply methods to companion objects
// 3) compilation workaround: changed case class constructors by adding implicit dummy args
sealed abstract class Tree
case class Node(id: Symbol, children: Seq[Tree])(implicit dummy: Manifest[Node]) extends Tree
object Node {
def apply(id: Symbol)(children: Tree*) = new Node(id, children.toSeq)
}
case class Leaf(id: Symbol, value: String)(implicit dummy: Manifest[Leaf]) extends Tree
object Leaf {
def apply(id: Symbol)(value: String) = new Leaf(id, value)
}
package net.danieldietrich.scala.treehugger
/*
* Added custom toString() implementation.
*
* Example:
*
* val Add = Node('Add)_
* val Mul = Node('Mul)_
* val Num = Leaf('Num)_
*
* // 2 + 3 * 1
* val ast = Add(Num("2"), Mul(Num("3"), Num("1")))
*
* println(ast)
*
* Output:
*
* Add(
* Num(2),
* Mul(
* Num(3),
* Num(1)
* )
* )
*
*/
sealed abstract class Tree {
protected val INDENT = " "
override def toString() = toString(0)
private[treehugger] def toString(depth: Int): String
}
case class Node(id: Symbol, children: Seq[Tree])(implicit dummy: Manifest[Node]) extends Tree {
private[treehugger] def toString(depth: Int) = {
val indent = INDENT * depth
indent + id.name +"(\n"+ children.map(_.toString(depth + 1)).reduce(_ +",\n"+ _ +"\n") + indent +")"
}
}
object Node {
def apply(id: Symbol)(children: Tree*) = new Node(id, children.toSeq)
}
case class Leaf(id: Symbol, value: String)(implicit dummy: Manifest[Leaf]) extends Tree {
private[treehugger] def toString(depth: Int) = {
val indent = INDENT * depth
indent + id.name +"("+ value +")"
}
}
object Leaf {
def apply(id: Symbol)(value: String) = new Leaf(id, value)
}
package net.danieldietrich.scala.treehugger
object Traverse {
// TODO(@@dd): implement collectTopDown, traverseTopDown, ...
// simple demo
def traverse(tree: Tree)(f: Tree => Unit) {
tree match {
case node: Node => f(node); node.children.foreach(traverse(_)(f))
case leaf: Leaf => f(leaf)
}
}
// example
def main(args: Array[String]) = {
val Add = Node('Add)_
val Mul = Node('Mul)_
val Num = Leaf('Num)_
// 2 + 3 * 1
val ast = Add(Num("2"), Mul(Num("3"), Num("1")))
val t = traverse(ast)_
t(_ match {
case Node(id, _) => println("Node("+ id.name +")")
case Leaf(id, value) => println("Leaf("+ id.name +") = "+ value)
})
}
}
package net.danieldietrich.scala.example.tree
import scala.collection.mutable.ListBuffer
sealed abstract class Tree
case class Node(id: Symbol, parent: Option[Node], children: ListBuffer[Tree] = ListBuffer()) extends Tree
case class Leaf(id: Symbol, parent: Option[Node], value: String) extends Tree
/*
* Constructing Trees with 'automatic' parent relation
*/
object Tree {
def Node(id: Symbol, initializer: (Node) => Unit)(implicit parent: Node = null) = {
val node = new Node(id, if (parent == null) None else Some(parent))
if (parent != null) parent.children += node
initializer.apply(node)
node
}
def Leaf(id: Symbol, value: String)(implicit parent: Node = null) = {
val leaf = new Leaf(id, (if (parent == null) None else Some(parent)), value)
if (parent != null) parent.children += leaf
leaf
}
// Example
def main(args: Array[String]) = {
// 2 + 3 * 1
val ast = Node('Add, implicit p => {
Leaf('Num, "1")
Node('Mul, implicit p => {
Leaf('Num, "3")
Leaf('Num, "2")
})
})
println(ast)
}
}
package net.danieldietrich.scala.mutable.treehugger
import scala.collection.mutable.ListBuffer
sealed abstract case class Tree(var parent: Option[Node]) {
def isLeaf() : Boolean
def isRoot() = parent match {
case Some(_) => false
case None => true
}
def root() : Tree = parent match {
case Some(p) => p.root()
case None => this
}
protected val INDENT = " "
override def toString() = toString(0)
private[treehugger] def toString(depth: Int): String
}
case class Node(id: Symbol, children: ListBuffer[Tree] = ListBuffer()) extends Tree(None) {
def isLeaf() = false
def add(child: Tree) = {
children += child
child.parent = Some(this)
this
}
private[treehugger] def toString(depth: Int) = {
val indent = INDENT * depth
indent + id.name +"(\n"+ children.map(_.toString(depth + 1)).reduce(_ +",\n"+ _ +"\n") + indent +")"
}
}
object Node {
def apply(id: Symbol)(children: Tree*) = {
val node = new Node(id)
children.foreach(node.add(_))
node
}
}
case class Leaf(id: Symbol, value: String)(implicit dummy: Manifest[Leaf]) extends Tree(None) {
def isLeaf() = true
private[treehugger] def toString(depth: Int) = {
val indent = INDENT * depth
indent + id.name +"("+ value +")"
}
}
object Leaf {
def apply(id: Symbol)(value: String) = new Leaf(id, value)
}
/*
* Mutable Trees with parent relation
*/
object Tree {
def main(args: Array[String]) = {
val Add = Node('Add)_
val Mul = Node('Mul)_
val Num = Leaf('Num)_
// 2 + 3 * 1
val ast = Add(Num("2"), Mul(Num("3"), Num("1")))
println(ast)
ast.add(Num("4"))
println(ast)
}
}
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