Possible use of Locatable to add source information to parsers

gistfile1.java

public class AnnotatedASTParserTest {

  //~ ----------------------------------------------------------------------------------------------------------------
  //~ Methods 
  //~ ----------------------------------------------------------------------------------------------------------------

  @Test
  public void canProduceAnASTWithSourceForEachNode() throws Exception {
    Parser<?> lparen = Scanners.isChar('(');
    Parser<?> rparen = Scanners.isChar(')');

    Parser<AnnotatedPair<String, String>> pairOfInts = Mapper.curry(AnnotatedPair.class).sequence(Scanners.INTEGER, //
        Mapper._(Scanners.isChar(',')), //
        Scanners.INTEGER).between(lparen, rparen).locate().cast();

    Parser<List<AnnotatedPair<String, String>>> listOfPairsOfIntegers = pairOfInts.sepBy(Scanners.WHITESPACES);

    List<AnnotatedPair<String, String>> result = listOfPairsOfIntegers.parse("(5,2)  (45,12)");

    assertThat(result.size(), is(2));
    assertThat(result.get(0).endIndex,is(5));    
  }

  public static class AnnotatedPair<A, B> implements Locatable {

    private final A a;
    private final B b;
    private String source;
    private int beginIndex;
    private int endIndex;

    public AnnotatedPair(A a, B b) {
      this.a = a;
      this.b = b;
    }

    @Override
    public void setSource(String source) {
      this.source = source;
    }

    @Override
    public void setLocation(int beginIndex, int endIndex) {
      this.beginIndex = beginIndex;
      this.endIndex = endIndex;
    }
  }
}