import java.lang.reflect.*;
/** a parser which translates streams of Tokens of type T into a Forest<R> */
-public class Parser<T extends Token, R> {
+public abstract class Parser<T extends Token, R> {
private final Table pt;
if (p.element() != null) reachable(p.element(), h);
}
- //public Parser( Topology top) { this(new Table( top)); }
- //public Parser(String s, Topology top) { this(new Table(s, top)); }
-
/**
* create a parser to parse the grammar with start symbol <tt>u</tt>
- * @param top a "sample" Topology<T> that can be cloned (FIXME, demanding this is lame)
*/
- public Parser(Union u, Topology<T> top) { this(new Table(u, top)); }
+ protected Parser(Union u) { this.pt = new Table(u, top()); }
+ protected Parser(Table pt) { this.pt = pt; }
+
+ public abstract Forest<R> shiftedToken(T t);
+ public abstract Topology<T> top();
- Parser(Table pt) { this.pt = pt; }
/** parse <tt>input</tt> for a exactly one unique result, throwing <tt>Ambiguous</tt> if not unique or <tt>Failed</tt> if none */
public Tree<R> parse1(Token.Stream<T> input) throws IOException, Failed, Ambiguous { return parse(input).expand1(); }
for(;;) {
GSS.Phase next = gss.new Phase(current, input.next());
current.reduce();
- current.shift(next);
+ Forest forest = current.token==null ? null : shiftedToken((T)current.token);
+ current.shift(next, forest);
if (current.isDone()) return (Forest<R>)current.finalResult;
current.checkFailure();
current = next;
// Table //////////////////////////////////////////////////////////////////////////////
+ static class Top extends Union { public Top() { super("0"); } }
+
/** an SLR(1) parse table which may contain conflicts */
static class Table {
private final Union start0 = new Top();
private final Sequence start0seq;
- static class Top extends Union { public Top() { super("0"); } }
public final Walk.Cache cache = new Walk.Cache();