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Scala example source code file (DeVirtualize.scala)

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

Java - Scala tags/keywords

compilationunit, defdef, int, list, list, listbuffer, polytype, symbol, symbol, synthetic, tree, tree, type, type

The Scala DeVirtualize.scala source code

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc
package typechecker

import symtab.Flags._
import transform.{ InfoTransform, TypingTransformers }
import scala.collection.mutable.ListBuffer

abstract class DeVirtualize /* extends InfoTransform with TypingTransformers {

  import global._
  import definitions._
  import typer.{typed, typedOperator, atOwner}

  /** the following two members override abstract members in Transform */
  val phaseName: String = "devirtualize"

  /** The phase might set the following new flags: */
  override def phaseNextFlags: Long = notDEFERRED | notOVERRIDE | notFINAL | lateABSTRACT

  def newTransformer(unit: CompilationUnit): DeVirtualizeTransformer =
    new DeVirtualizeTransformer(unit)
 
  /** The class does not change base-classes of existing classes */
  override def changesBaseClasses = false 

  def transformInfo(sym: Symbol, tp: Type): Type = 
    if (sym.isThisSym && sym.owner.isVirtualClass) {
      val clazz = sym.owner
      intersectionType(
        List(
          appliedType(abstractType(clazz).typeConstructor, clazz.typeParams map (_.tpe)),
          clazz.tpe))
    } else devirtualizeMap(tp)

  /* todo:
     handle constructor arguments
     check: overriding classes must have same type params
     virtual classes cannot have self types
   */

  /** Do the following transformations everywhere in a type:
   *
   * 1. Replace a virtual class
   *
   *  attrs mods class VC[Ts] <: Ps { decls }
   *  
   * by the following symbols
   *
   *  attrs mods1 type VC[Ts] <: dvm(Ps) with VC$trait[Ts]
   *  attrs mods2 trait VC$trait[Ts] extends AnyRef with ScalaObject { 
   *    this: VC[Ts] with VC$trait[Ts] => decls1
   *  }
   *  
   * The class symbol VC becomes the symbol of the workertrait.
   * 
   *  dvm    is the devirtalization mapping which converts refs to 
   *         virtual classes to refs to their abstract types (@see devirtualize)
   *  mods1  are the modifiers inherited to abstract types
   *  mods2  are the modifiers inherited to worker traits
   *  decls1 is decls but members that have an override modifier 
   *         lose it and any final modifier as well. 
   *
   * 2. For all virtual member classes VC which
   *    are not abstract and which are or inherit from a virtual class defined in current class
   *    add a factory (@see mkFactory)
   * 3. Convert TypeRef's to VC where VC is a virtual class to TypeRef's to AT, where AT
   *    is the abstract type corresponding to VC.
   *
   *  Note: If a class inherits vc's from two different paths, a vc in the 
   *  inheriting class has to be created beforehand. This is done in phase ??? (NOT YET DONE!)
   *
   *  Note: subclasses of virtual classes are treated as if they are virtual.
   *  isVirtualClass returns true for them also. 
   */
  object devirtualizeMap extends TypeMap {
    def apply(tp: Type): Type = mapOver(tp) match { 
      case tp1 @ ClassInfoType(parents, decls0, clazz) =>
        var decls = decls0
        def enter(sym: Symbol) = // at next phase because names of worker traits change
          atPhase(ownPhase.next) { decls.enter(sym) } 
        if (containsVirtuals(clazz)) {
          decls = new Scope
          for (m <- decls0.toList) {
            if (m.isVirtualClass) {
              m.setFlag(notDEFERRED | notFINAL | lateABSTRACT)
              enter(mkAbstractType(m))
            }
            enter(m)
          }
          for (m <- classesInNeedOfFactories(clazz))
            enter(mkFactory(m, clazz))
        }
        if (clazz.isVirtualClass) {
          println("virtual class: "+clazz+clazz.locationString)
          transformOwnerInfo(clazz) 
          decls = new Scope
          
          // add virtual fields for all primary constructor parameters
          for (row <- paramTypesAndIndices(clazz.primaryConstructor.tpe, 0))
            for ((pt, i) <- row) 
              enter(mkParamField(clazz, i, devirtualizeMap(pt)))

          // remove OVERRIDE from all workertrait members, except if they override a member in Object
          for (m <- decls0.toList) {
            if (!m.isConstructor) {
              if ((m hasFlag OVERRIDE) && m.overriddenSymbol(ObjectClass) == NoSymbol)
                m setFlag (notOVERRIDE | notFINAL)
              enter(m)
            }
          }
          if (clazz.thisSym == clazz) clazz.typeOfThis = clazz.thisType
            // ... to give a hook on which we can hang selftype transformers
          ClassInfoType(List(ObjectClass.tpe, ScalaObjectClass.tpe), decls, clazz)
        } else {
          ClassInfoType(parents map this, decls, clazz)
        }
      case tp1 @ TypeRef(pre, clazz, args) if clazz.isVirtualClass =>
        TypeRef(pre, abstractType(clazz), args)
      case tp1 =>
        tp1
    }
  }

  /** Transform owner of given clazz symbol */
  protected def transformOwnerInfo(clazz: Symbol) { atPhase(ownPhase.next) { clazz.owner.info } }

  /** Names of derived classes and factories */
  protected def concreteClassName(clazz: Symbol) = 
    atPhase(ownPhase) { newTypeName(clazz.name+"$fix") }
  protected def factoryName(clazz: Symbol) = 
    atPhase(ownPhase) { newTermName("new$"+clazz.name) }

  /** Does `clazz' contain virtual classes? */
  protected def containsVirtuals(clazz: Symbol) = clazz.info.decls.toList exists (_.isVirtualClass)

  /** The inner classes that need factory methods in `clazz' 
   *  This is intended to catch situations like the following
   *
   *  abstract class C { 
   *    class V <: {...}
   *    class W extends V 
   *  }
   *  class D extends C {
   *    class V <: {...}
   *    // factories needed for V and W!
   *  }
   */
  protected def classesInNeedOfFactories(clazz: Symbol) = atPhase(ownPhase) {
    def isOverriddenVirtual(c: Symbol) = 
      c.isVirtualClass && clazz.info.decl(c.name).isVirtualClass
    val xs = clazz.info.members.toList filter (x => x.isVirtualClass && !x.hasFlag(ABSTRACT))
    for (m <- clazz.info.members.toList; 
         if (m.isVirtualClass && !(m hasFlag ABSTRACT) && 
             (m.info.baseClasses exists isOverriddenVirtual))) yield m
  }

  /** The abstract type corresponding to a virtual class. */  
  protected def abstractType(clazz: Symbol): Symbol =  atPhase(ownPhase.next) {
    val abstpe = clazz.owner.info.decl(atPhase(ownPhase) { clazz.name })
    assert(abstpe.isAbstractType)
    abstpe
  }

  /** The factory corresponding to a virtual class. */  
  protected def factory(clazz: Symbol, owner: Symbol) = atPhase(ownPhase.next) {
    val fsym = owner.info.member(factoryName(clazz))
    assert(fsym.isMethod, clazz)
    fsym
  }

  /** The name of the field representing a constructor parameter of a virtual class */
  protected def paramFieldName(clazz: Symbol, index: Int) = atPhase(ownPhase) {
    nme.expandedName(newTermName("param$"+index), clazz)
  }

  /** The name of the field representing a constructor parameter of a virtual class */
  protected def fixParamName(index: Int) = newTermName("fix$"+index)

  /** The field representing a constructor parameter of a virtual class */
  protected def paramField(clazz: Symbol, index: Int) = atPhase(ownPhase.next) {
    clazz.info.decl(paramFieldName(clazz, index))
  }

  /** The flags that an abstract type can inherit from its virtual class */
  protected val absTypeFlagMask = AccessFlags | DEFERRED

  /** The flags that a factory method can inherit from its virtual class */
  protected val factoryFlagMask = AccessFlags

  /** Create a polytype with given type parameters and given type, or return just the type
   *  if type params is empty. */
  protected def mkPolyType(tparams: List[Symbol], tp: Type) = 
    if (tparams.isEmpty) tp else PolyType(tparams, tp)

  /** A lazy type to complete `sym', which is is generated for virtual class
   *  `clazz'. 
   *  The info of the symbol is computed by method `getInfo'.
   *  It is wrapped in copies of the type parameters of `clazz'.
   */
  abstract class PolyTypeCompleter(sym: Symbol, clazz: Symbol) extends LazyType {
    def getInfo: Type
    override val typeParams = cloneSymbols(clazz.typeParams, sym)
    override def complete(sym: Symbol) {
      sym.setInfo(
        mkPolyType(typeParams, getInfo.substSym(clazz.typeParams, typeParams)))
    }
  }

  protected def wasVirtualClass(sym: Symbol) = { 
    sym.isVirtualClass || {
      sym.info
      sym hasFlag notDEFERRED 
    }
  }

  protected def addOverriddenVirtuals(clazz: Symbol) = {
    (clazz.allOverriddenSymbols filter wasVirtualClass) ::: List(clazz)
  }

  protected def addOverriddenVirtuals(tpe: Type) = tpe match {
    case TypeRef(pre, sym, args) =>
      { for (vc <- sym.allOverriddenSymbols if wasVirtualClass(vc))
        yield typeRef(pre, vc, args) }.reverse ::: List(tpe)
  }

  protected def mkParamField(clazz: Symbol, index: Int, tpe: Type): Symbol = {
    val param = clazz.newMethod(clazz.pos, paramFieldName(clazz, index))
      .setFlag(PROTECTED | LOCAL | DEFERRED | EXPANDEDNAME | SYNTHETIC | STABLE)
    atPhase(ownPhase.next) {
      param.setInfo(NullaryMethodType(tpe))
    }
    param
  }

  protected def mkAbstractType(clazz: Symbol): Symbol = {
    val cabstype = clazz.owner.newAbstractType(clazz.pos, clazz.name)
      .setFlag(clazz.flags & absTypeFlagMask | SYNTHETIC)
      .setAnnotations(clazz.annotations)
    atPhase(ownPhase.next) {
      cabstype setInfo new PolyTypeCompleter(cabstype, clazz) {
        def getInfo = {
          val parents1 = clazz.info.parents map {
            p => devirtualizeMap(p.substSym(clazz.typeParams, typeParams))
          }
          val parents2 = addOverriddenVirtuals(clazz) map {
            c => typeRef(clazz.owner.thisType, c, typeParams map (_.tpe))
          }
          TypeBounds(NothingClass.tpe, intersectionType(parents1 ::: parents2))
        }
      }
    }
  }

  protected def paramTypesAndIndices(tpe: Type, start: Int): List[List[(Type, Int)]] = tpe match {
    case PolyType(_, restpe) => paramTypesAndIndices(restpe, start)
    case MethodType(params, restpe) =>
      val end = start + params.length
      (tpe.paramTypes zip List.range(start, end)) :: paramTypesAndIndices(restpe, end)
    case _ =>
      List()
  }
    
  /* Add a factory symbol for a virtual class  
   *
   *  attrs mods class VC[Ts] <: Ps { decls }
   *  with base classes BC[Us]'s
   *
   * which corresponds to the following definition :
   *
   *  attrs mods3 def new$VC[Ts](): VC[Ts] = {
   *    class VC$fix extends v2w(BC's[Ts]) with VC$trait[Ts] { ... }
   *    new VC$fix
   *  }
   *
   * where
   *  
   *  mods3  are the modifiers inherited to factories
   *  v2w maps every virtual class to its workertrait and leaves other types alone.
   *
   *  @param  clazz    The virtual class for which factory is added
   *  @param  owner    The owner for which factory is added as a member
   *  @param  scope    The scope into which factory is entered
   */
  def mkFactory(clazz: Symbol, owner: Symbol): Symbol = {
    val pos = if (clazz.owner == owner) clazz.pos else owner.pos
    val factory = owner.newMethod(pos, factoryName(clazz))
      .setFlag(clazz.flags & factoryFlagMask | SYNTHETIC)
      .setAnnotations(clazz.annotations)
    factory setInfo new PolyTypeCompleter(factory, clazz) {
      private def copyType(tpe: Type): Type = tpe match {
        case MethodType(formals, restpe) => MethodType(formals, copyType(restpe))
        case NullaryMethodType(restpe) => NullaryMethodType(copyType(restpe))
        case PolyType(_, _) => abort("bad case: "+tpe)
        case _ => owner.thisType.memberType(abstractType(clazz))
      }
      def getInfo = copyType(clazz.primaryConstructor.tpe)
    }
    factory
  }

  def distinct(ts: List[Type]): List[Type] = ts match {
    case List() => List()
    case t :: ts1 => t :: distinct(ts1 filter (_.typeSymbol != t.typeSymbol))
  }

  /** The concrete class symbol VC$fix in the factory symbol (@see mkFactory)
   *  @param clazz    the virtual class
   *  @param factory  the factory which returns an instance of this class
   */
  protected def mkConcreteClass(clazz: Symbol, factory: Symbol) = {
    val cclazz = factory.newClass(clazz.pos, concreteClassName(clazz))
      .setFlag(FINAL | SYNTHETIC)
      .setAnnotations(clazz.annotations)
      
    cclazz setInfo new LazyType {
      override def complete(sym: Symbol) {
        val parents1 = atPhase(ownPhase) {
          var superclazz = clazz
          do {
            superclazz = superclazz.info.parents.head.typeSymbol
          } while (wasVirtualClass(superclazz)) 
          val bcs = superclazz :: (clazz.info.baseClasses takeWhile (superclazz != )).reverse
          println("MKConcrete1 "+cclazz+factory.locationString+" "+bcs+" from "+clazz+clazz.locationString)
          println("MKConcrete2 "+cclazz+factory.locationString+" "+(bcs map factory.owner.thisType.memberType))
          bcs map factory.owner.thisType.memberType
        }
        atPhase(ownPhase.next) {
          val parents2 = 
            distinct(parents1.flatMap(addOverriddenVirtuals))
            .map(_.substSym(clazz.typeParams, factory.typeParams))
          sym setInfo ClassInfoType(parents2, new Scope, cclazz)
        }
      }
    }

    cclazz
  }

  /** Perform the following tree transformations:
   *  
   *  1. Add trees for abstract types (@see devirtualize),
   *     worker traits (@see devirtualize)
   *     and factories (@see mkFactory)
   *  
   *  2. Replace a new VC().init(...) where VC is a virtual class with new$VC(...)
   *  
   *  3. Replace references to VC.this and VC.super where VC is a virtual class
   *     with VC$trait.this and VC$trait.super
   *
   *  4. Transform type references to virtual classes to type references of corresponding
   *     abstract types.
   */
  class DeVirtualizeTransformer(unit: CompilationUnit) extends TypingTransformer(unit) { 
    // all code is executed at phase ownPhase.next
    
    /** Add trees for abstract types, worker traits, and factories (@see mkFactory)
     *  to template body `stats'
     */  
    override def transformStats(stats: List[Tree], exprOwner: Symbol): List[Tree] = {
      val stats1 = stats flatMap transformStat
      val fclasses = atPhase(ownPhase) {
        if (currentOwner.isClass && containsVirtuals(currentOwner)) classesInNeedOfFactories(currentOwner)  
        else List()
      }
      val newDefs = fclasses map factoryDef
      if (newDefs.isEmpty) stats1 else stats1 ::: newDefs
    }

    def fixClassDef(clazz: Symbol, factory: Symbol): Tree = {
      val cclazz = mkConcreteClass(clazz, factory) 
      val overrideBridges = 
        for (m <- clazz.info.decls.toList if m hasFlag notOVERRIDE) 
        yield overrideBridge(m, cclazz)
      
      val vparamss: List[List[ValDef]] = atPhase(ownPhase) {
        paramTypesAndIndices(clazz.primaryConstructor.tpe, 0) map {
          _ map {
          case (pt, i) =>
            atPos(factory.pos) {
              ValDef(Modifiers(PARAMACCESSOR | PRIVATE | LOCAL), fixParamName(i), 
                     TypeTree(devirtualizeMap(pt)), EmptyTree)
            }
          }
        }
      }
      val pfields: List[DefDef] = atPhase(ownPhase) {
        paramTypesAndIndices(clazz.primaryConstructor.tpe, 0) flatMap {
          _ map {
          case (pt, i) =>
            val pfield = cclazz.newMethod(cclazz.pos, paramFieldName(clazz, i))
              .setFlag(PROTECTED | LOCAL | EXPANDEDNAME | SYNTHETIC | STABLE)
              .setInfo(NullaryMethodType(pt))
            cclazz.info.decls enter pfield
            atPos(factory.pos) {
              DefDef(pfield, Ident(fixParamName(i)))
            }
          }
        }
      }
      atPos(clazz.pos) {
        ClassDef(cclazz, Modifiers(0), vparamss, List(List()), pfields ::: overrideBridges, clazz.pos.focus)
      }
    }
      

    /** The factory definition for virtual class `clazz' (@see mkFactory)
     *  For a virtual class  
     *
     *  attrs mods class VC[Ts] <: Ps { decls }
     *  with overridden classes _VC[Us]'s
     *
     * we need the following factory:
     *
     *  attrs mods3 def new$VC[Ts](): VC[Ts] = {
     *    class VC$fix extends _VC$trait's[Ts] with VC$trait[Ts] {
     *      override-bridges
     *    }
     *    new VC$fix.asInstanceOf[VC[Ts]]
     *  }
     *
     * where
     *  
     *  mods3  are the modifiers inherited to factories
     *  override-bridges are definitions that link every symbol in a worker trait
     *                   that was overriding something to the overridden symbol
     *                   //todo: not sure what happens with abstract override?
     */
    def factoryDef(clazz: Symbol): Tree = {
      val factorySym = factory(clazz, currentOwner)
      val cclazzDef = fixClassDef(clazz, factorySym)
      println("Concrete: "+cclazzDef)
      val abstpeSym = abstractType(clazz)
      localTyper.typed {
        atPos(factorySym.pos) {
          DefDef(factorySym,
            Block(
              List(cclazzDef), 
              TypeApply(
                Select(
                  gen.mkForwarder(
                    Select(New(TypeTree(cclazzDef.symbol.tpe)), nme.CONSTRUCTOR),
                    factorySym.paramss),
                  Any_asInstanceOf),
             List(
               TypeTree(
                 currentOwner.thisType.memberType(abstpeSym)
                 .substSym(abstpeSym.typeParams, factorySym.typeParams))))))
        }
      }
    }

    /** Create an override bridge for method `meth' in concrete class `cclazz'.
     *  An override bridge has the form
     *
     *   override f(xs1)...(xsN) = super.f(xs)...(xsN)
     */
    def overrideBridge(meth: Symbol, cclazz: Symbol) = atPos(meth.pos) {
      val bridge = meth.cloneSymbol(cclazz)
        .resetFlag(notOVERRIDE | notFINAL)
      cclazz.info.decls.enter(bridge)
      val superRef: Tree = Select(Super(cclazz, tpnme.EMPTY), meth)
      DefDef(bridge, gen.mkForwarder(superRef, bridge.paramss))
    }

    /** Replace definitions of virtual classes by definitions of corresponding
     *  abstract type and worker traits.
     *  Eliminate constructors of former virtual classes because these are now traits.
     */
    protected def transformStat(tree: Tree): List[Tree] = {
      val sym = tree.symbol
      tree match {
        case ClassDef(mods, name, tparams, templ) 
        if (wasVirtualClass(sym)) =>
          val clazz = sym
          val absTypeSym = abstractType(clazz)
          val abstypeDef = TypeDef(absTypeSym)
          List(localTyper.typed(abstypeDef), transform(tree))
        case DefDef(_, nme.CONSTRUCTOR, _, _, _, _) 
        if (wasVirtualClass(sym.owner)) =>
          if (atPhase(ownPhase)(sym != sym.owner.primaryConstructor))
            unit.error(tree.pos, "virtual classes cannot have auxiliary constructors")
          List()
        case _ =>
          List(transform(tree))
      }
    }

    override def transform(tree0: Tree): Tree = {
      val tree = super.transform(tree0)
      val sym = tree.symbol
      tree match {
        // Replace a new VC().init() where VC is a virtual class with new$VC
        case Apply(Select(New(tpt), name), args) if (sym.isConstructor && wasVirtualClass(sym.owner)) =>
          val clazz = sym.owner
          val fn = 
            Select(
              gen.mkAttributedQualifier(tpt.tpe.prefix),
              factory(clazz, clazz.owner).name)
          println("fac "+factory(clazz, clazz.owner).tpe)
          val targs = tpt.tpe.typeArgs
          atPos(tree.pos) {
            localTyper.typed {
              val res = 
                Apply(if (targs.isEmpty) fn else TypeApply(fn, targs map TypeTree), args)
                println("typing "+res+" from "+args)
                res
              }
            }
        
        case Template(parents, self, body) if (wasVirtualClass(sym.owner)) =>
          // add param field accessors
          val paramFieldAccessors = new ListBuffer[Tree]
          val paramFields = new ListBuffer[Tree]
          val presupers = new ListBuffer[Tree]
          val others = new ListBuffer[Tree]
          var paramFieldCount = 0
          for (stat <- body) {
            if (stat.symbol != null && (stat.symbol hasFlag PARAMACCESSOR))
              stat match {
                case pacc @ ValDef(mods, name, tpt, rhs) =>
                  pacc.symbol resetFlag PARAMACCESSOR setFlag PRESUPER
                  val pfield = paramField(sym.owner, paramFieldCount)
                  paramFieldCount += 1
                  pfield setPos pacc.pos
                  paramFields += localTyper.typed(DefDef(pfield, EmptyTree))
                  val pfieldRef = localTyper.typed { 
                    atPos(pacc.pos) { 
                      Select(This(sym.owner), pfield) 
                    } 
                  }
                  paramFieldAccessors += treeCopy.ValDef(pacc, mods, name, tpt, pfieldRef)
                case _ =>
                  stat.symbol resetFlag PARAMACCESSOR // ??? can we do this                  
                  others += stat
              }
            else 
              (if (stat.symbol != null && (stat.symbol hasFlag PRESUPER)) presupers else others) += stat
          }
          treeCopy.Template(tree, parents, self, 
                            paramFieldAccessors.toList ::: 
                            presupers.toList ::: 
                            paramFields.toList :::
                            others.toList)
        case _ =>
          tree setType atPhase(ownPhase)(devirtualizeMap(tree.tpe))
      }
    }
    override def transformUnit(unit: CompilationUnit) = atPhase(ownPhase.next) { 
      super.transformUnit(unit)
    }
  }
}

    

/*
    class A {
      trait C[X, Y] <: { 
        var x: X
        def f(y: Y): X = { println("A.T"); x } 
      }
      class D[X](xp: X) extends C[X, Int] { 
        var x: X = xp
        override def f(y: Int) = { println(y); super.f(y) } 
      }
    }
    class B extends A {
      override trait C[X, Y] <: { 
        override def f(y: Y): X = { println("B.T"); super.f(y) } 
        def g: X = x
      }
    }
    object Test extends B {
      val c = new D[String]("OK")
      println(c.g)
      println(c.f(42))
    }

maps to:

  class A {
    type C[X, Y] <: C$trait[X, Y]

    trait C$trait[X, Y] { this: C with C$trait => 
      var x: X
      def f(y: Y): X = { println("A.T"); x }
    } 

    class D[X](xp: X) extends C[X, Int] { 
      var x: X = xp
      override def f(y: Int) = { println(y); super.f(y) } 
    }

      protected[this] val x: Int; val y = x; def f(z:Int) = z + 1 }

    type D <: C with DT

    trait DT extends { self: D => def f(z:Int) = z + 2 }

    trait preDT extends { self: D => val z: Int; val x = f(z) }

    def newC(x: Int): C
    def newD(x: Int): D

    //type C = CT
    //type D = C with DT

    class CC(_x:Int) extends { val x = _x } with CT

    def newC[X, Y](x:Int): C = 
      new CC(x).asInstanceOf[C]

    class DC(_z:Int) extends { val z = _z } with preDT with CT with DT {
      override def f(z:Int) = super.f(z)
    }

    def newD(z:Int):D = new DC(z).asInstanceOf[D]
  }

  class B extends A {
    type C <: CT with CT2

    trait CT2 { self : C => def g = 2 }

    //type C = CT with CT2
    //type D = C with DT

    class CC2(_x:Int) extends { val x = _x } with CT with CT2

    def newC(x:Int): C = new CC2(x).asInstanceOf[C]

    class DC2(_z:Int) extends { val z = _z } with preDT with CT with CT2
      with DT { override def f(z:Int) = super.f(z) }

    def newD(z:Int): D = new DC2(z).asInstanceOf[D]
  }

*/

*/

Other Scala examples (source code examples)

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my book on functional programming

 

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