package org.apidesign.test.visitor;

 import static junit.framework.Assert.*;

 import org.apidesign.visitor.Language.Expression;

 import org.apidesign.visitor.Language.Number;

 import org.apidesign.visitor.Language.Plus;

 import org.apidesign.visitor.Language.Visitor;

 import org.junit.Test;

 public class CountNumbersTest {

     // BEGIN: visitor.count.numbers.traversal

     private static class CountNumbers extends Visitor/*version1.0*/ {

         int cnt;

         @Override

         public boolean visitUnknown(Expression exp) {

             return true;

         }

         @Override

         public void visitNumber(Number n) {

             cnt++;

         }

     }

     public static int countNumbers(Expression expression) {

         CountNumbers counter = new CountNumbers();

         expression.visit(counter);

         return counter.cnt;

     }

     // END: visitor.count.numbers.traversal

     @Test public void printOnePlusOne() {

         Number one = new Number(1);

         Expression expression = new Plus(one, one);

         assertEquals("Two 1's", 2, countNumbers(expression));

     }

     @Test public void printOnePlusTwoPlusThree() {

         Number one = new Number(1);

         Number two = new Number(2);

         Number three = new Number(3);

         Expression plus = new Plus(one, new Plus(two, three));

         assertEquals("Three", 3, countNumbers(plus));

     }

 }