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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 dispatchTest.nice - Tree Walk
package openclassdispatch;

<T> void dispatchTest(Tree<T> t); 

dispatchTest(Tree this) { }

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

Size

// compilation unit size.nice
package openclassdispatch;

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

size(Tree t) = 1;

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

Pretty Print

/ compilation unit prettyPrint.nice
package openclassdispatch;

public <T> String prettyPrint(Tree<T> t);

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


public <T> String prettyPrint(Tree<T> t, String prefix);

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

prettyPrint(Interior t, 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.

-- IsaacGouy - 05 Sep 2003