| /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * |
| * Copyright (C) 2001 Gerwin Klein <lsf@jflex.de> * |
| * Copyright (C) 2001 Bernhard Rumpe <rumpe@in.tum.de> * |
| * All rights reserved. * |
| * * |
| * This program is free software; you can redistribute it and/or modify * |
| * it under the terms of the GNU General Public License. See the file * |
| * COPYRIGHT for more information. * |
| * * |
| * This program is distributed in the hope that it will be useful, * |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of * |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * |
| * GNU General Public License for more details. * |
| * * |
| * You should have received a copy of the GNU General Public License along * |
| * with this program; if not, write to the Free Software Foundation, Inc., * |
| * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * |
| * * |
| * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ |
| |
| |
| import java.util.Enumeration; |
| import java.util.Hashtable; |
| |
| /** |
| * Symbol table for the interpreter, contains information about |
| * variables and functions. |
| * |
| * For every binding location of a name a symbol will be created. |
| * The symbol tables are connected hierarchically by pointers to |
| * the predecessor. Lookup takes predecessors into account. |
| */ |
| public class SymTab { |
| Hashtable h; // contains the liste of words |
| // key: String, value: SymtabEntry |
| |
| SymTab pred; // predecessor symbol table (if exists) |
| |
| public SymTab() { |
| this(null); |
| } |
| |
| public SymTab(SymTab p) { |
| h = new Hashtable(); |
| pred = p; |
| } |
| |
| public boolean enter(String s, SymtabEntry e) { |
| Object value = lookup(s); |
| h.put(s, e); |
| return(value==null); |
| } |
| |
| public SymtabEntry lookup(String s) { |
| Object value = h.get(s); |
| if (value==null && pred!=null) |
| value = pred.lookup(s); |
| return ((SymtabEntry)value); |
| } |
| |
| public String toString() { // for output with print |
| String res = "symbol table\n=============\n"; |
| Enumeration e = h.keys(); |
| String key; |
| |
| while(e.hasMoreElements()) { |
| key = (String)e.nextElement(); |
| res += key+" \t"+h.get(key)+"\n"; |
| } |
| |
| if (pred!=null) res+="++ predecessor!\n"; |
| return(res); |
| } |
| |
| public int size() { |
| return(h.size()); |
| } |
| } |
| |