dispatchTest(this@Tree) { }

dispatchTest(Tree this) { }

dispatchTest(this@Interior) {

dispatchTest(Interior this) {

size(t@Tree) = 1;

size(Tree t) = 1;

size(t@Interior) = 1 + t.getLeft().size() + t.getRight().size();

size(Interior t) = 1 + t.getLeft().size() + t.getRight().size();

prettyPrint(t@Tree) = t.prettyPrint( "" );

prettyPrint(Tree t) = t.prettyPrint( "" );

prettyPrint(t@Tree, prefix) = prefix + t.value() + "\n";

prettyPrint(Tree t, prefix) = prefix + t.value() + "\n";

prettyPrint(t@Interior, prefix) {

prettyPrint(Interior t, prefix) {

Tree and Interior represent a simple binary tree; which is extended with a subclass representing n-ary trees and 3 separate external methods ExtendedTreeVisitorIntermediateExample.

The original MultiJava code for this benchmark, and the Java comparison code, is available from this Technical Report: "MultiJava: Design, implementation, and evaluation of a Java-compatible language supporting modular open classes and symmetric multiple dispatch", Curtis Clifton, Iowa State University TR #01-10, November 2001.
ftp://ftp.cs.iastate.edu/pub/techreprts/TR01-10/TR.pdf

Curtis Clifton kindly gave permission for this use.

The benchmark results are similar to MultiJava. The Java Extensible Visitor pattern requires much more code, and more complex code, than Nice. The performance of the Java Extensible Visitor implementation degrades from the simple tree walk to the simple size calculation. For the slightly less-simple pretty print method the performance is worse than Nice.

Tree Walk

// compilation unit Tree.nice

// compilation unit dispatchTest.nice - Tree Walk

public class Tree { private !T value;

void dispatchTest(Tree t);

// internal implementation of prettyPrinting to // measure regular dispatch speed

dispatchTest(this@Tree) { }

// Unlike MultiJava?, in Nice there's no difference // to methods defined externally - like prettyPrint

dispatchTest(this@Interior) { this.getLeft().dispatchTest(); this.getRight().dispatchTest(); }

public String internalPrettyPrint(String prefix); internalPrettyPrint(prefix) = prefix + this.getValue().toString + "\n";

public String internalPrettyPrint(); internalPrettyPrint() = this.internalPrettyPrint("");

Size

public !T getValue() = value; }

// compilation unit size.nice
package openclassdispatch;

<T> int size(Tree<T> t);

size(t@Tree) = 1;

size(t@Interior) = 1 + t.getLeft().size() + t.getRight().size();

Pretty Print

// compilation unit Interior.nice

/ compilation unit prettyPrint.nice

public class Interior extends Tree { private Tree left; private Tree right;

public String prettyPrint(Tree t);

// internal implementation of prettyPrinting to // measure regular dispatch speed

prettyPrint(t@Tree) = t.prettyPrint( "" );

// Unlike MultiJava?, in Nice there's no difference // to methods defined externally - like prettyPrint

internalPrettyPrint(prefix) { let result = new StringBuffer?( prefix + this.getValue() + "\n" ); let newPrefix = prefix + "| "; result.append( this.getLeft().internalPrettyPrint( newPrefix ) ); result.append( this.getRight().internalPrettyPrint( newPrefix ) ); return result.toString; }

public String prettyPrint(Tree t, String prefix);

prettyPrint(t@Tree, prefix) = prefix + t.value() + "\n";

public Tree getLeft() = left; public Tree getRight() = right;

prettyPrint(t@Interior, prefix) { let result = new StringBuffer?( prefix + t.value() + "\n" ); let newPrefix = prefix + "| "; result.append( t.left().prettyPrint( newPrefix ) ); result.append( t.right().prettyPrint( newPrefix ) ); return result.toString();

Tree implementations

TreeVisitorClassesIntermediateExample gives implementations for the binary tree and n-ary tree.

%META:TOPICINFO{author="IsaacGouy" date="1062781980" format="1.0" version="1.1"}% %META:TOPICPARENT{name="CodeExamples"}% Tree and Interior represent a simple binary tree; which is extended with a subclass representing n-ary trees and 3 separate external methods ExtendedTreeVisitorIntermediateExample.

// compilation unit Tree.nice
package openclassdispatch;

public class Tree<T> {   
   private !T value;

// internal implementation of prettyPrinting to 
// measure regular dispatch speed

// Unlike MultiJava, in Nice there's no difference
// to methods defined externally -  like prettyPrint

   public String internalPrettyPrint(String prefix);
   internalPrettyPrint(prefix) = 
      prefix + this.getValue().toString + "\n";

   public String internalPrettyPrint();
   internalPrettyPrint() = this.internalPrettyPrint("");

   public !T getValue() = value;   
}

// compilation unit Interior.nice
package openclassdispatch;

public class Interior<T> extends Tree {
   private Tree<T> left;
   private Tree<T> right;

// internal implementation of prettyPrinting to 
// measure regular dispatch speed

// Unlike MultiJava, in Nice there's no difference
// to methods defined externally - like prettyPrint

   internalPrettyPrint(prefix) {
      let result = new StringBuffer( prefix + this.getValue() + "\n" );
      let newPrefix = prefix + "| ";
      result.append( this.getLeft().internalPrettyPrint( newPrefix ) );
      result.append( this.getRight().internalPrettyPrint( newPrefix ) );
      return result.toString;
   }

   public Tree<T> getLeft() = left;
   public Tree<T> getRight() = right;
}