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 LanguageCheckTest {

     // BEGIN: visitor.language.check.exception

     private static class Valid10Language extends Visitor/*version1.0*/ {

         public void visitPlus(Plus s) {

             s.getFirst().visit(this);

             s.getSecond().visit(this);

         }

         public void visitNumber(Number n) { 

         }

     }

     public static boolean isValid10Language(Expression expression) {

         Valid10Language valid = new Valid10Language();

         try {

             expression.visit(valid);

             return true; // yes, no unknown elements

         } catch (IllegalStateException ex) {

             return false; // no, probably from visitMinus of Visitor/*2.0*/

         }

     }

     // END: visitor.language.check.exception

     @Test public void printOnePlusOne() {

         Number one = new Number(1);

         Expression expression = new Plus(one, one);

         assertTrue("Valid language", isValid10Language(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));

         assertTrue("Valid language", isValid10Language(plus));

     }

 }