-import java.lang.reflect.*;
-
-/** a parser which translates streams of Tokens of type T into a Forest<R> */
-public abstract class Parser<T extends Token, R> {
-
- private final Table pt;
-
- /**
- * create a parser to parse the grammar with start symbol <tt>u</tt>
- */
- protected Parser(Union u) { this.pt = new Table(u, top()); }
- protected Parser(Table pt) { this.pt = pt; }
-
- public abstract Forest<R> shiftedToken(T t, Token.Location loc);
- public abstract Topology<T> top();
-
-
- /** 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(); }
-
- /** parse <tt>input</tt>, using the table <tt>pt</tt> to drive the parser */
- public Forest<R> parse(Token.Stream<T> input) throws IOException, Failed {
- GSS gss = new GSS();
- Token.Location loc = input.getLocation();
- GSS.Phase current = gss.new Phase(null, input.next(), loc);
- current.newNode(null, null, pt.start, true, null);
- for(;;) {
- loc = input.getLocation();
- GSS.Phase next = gss.new Phase(current, input.next(), loc);
- current.reduce();
- Forest forest = current.token==null ? null : shiftedToken((T)current.token, loc);
- current.shift(next, forest);
- if (current.isDone()) return (Forest<R>)current.finalResult;
- current.checkFailure();
- current = next;
- }
- }
-