1 | /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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2 | * Copyright (C) 2001 Gerwin Klein <[email protected]> *
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3 | * Copyright (C) 2001 Bernhard Rumpe <[email protected]> *
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4 | * All rights reserved. *
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5 | * *
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6 | * This program is free software; you can redistribute it and/or modify *
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7 | * it under the terms of the GNU General Public License. See the file *
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8 | * COPYRIGHT for more information. *
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9 | * *
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10 | * This program is distributed in the hope that it will be useful, *
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11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of *
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12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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13 | * GNU General Public License for more details. *
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14 | * *
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15 | * You should have received a copy of the GNU General Public License along *
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16 | * with this program; if not, write to the Free Software Foundation, Inc., *
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17 | * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA *
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18 | * *
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19 | * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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20 |
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21 |
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22 | import java.util.*;
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23 |
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24 | /**
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25 | * Symbol table for the interpreter, contains information about
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26 | * variables and functions.
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27 | *
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28 | * For every binding location of a name a symbol will be created.
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29 | * The symbol tables are connected hierarchically by pointers to
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30 | * the predecessor. Lookup takes predecessors into account.
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31 | */
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32 | public class SymTab {
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33 | Hashtable h; // contains the liste of words
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34 | // key: String, value: SymtabEntry
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35 |
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36 | SymTab pred; // predecessor symbol table (if exists)
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37 |
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38 | public SymTab() {
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39 | this(null);
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40 | }
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41 |
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42 | public SymTab(SymTab p) {
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43 | h = new Hashtable();
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44 | pred = p;
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45 | }
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46 |
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47 | public boolean enter(String s, SymtabEntry e) {
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48 | Object value = lookup(s);
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49 | h.put(s, e);
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50 | return(value==null);
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51 | }
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52 |
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53 | public SymtabEntry lookup(String s) {
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54 | Object value = h.get(s);
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55 | if (value==null && pred!=null)
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56 | value = pred.lookup(s);
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57 | return ((SymtabEntry)value);
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58 | }
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59 |
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60 | public String toString() { // for output with print
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61 | String res = "symbol table\n=============\n";
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62 | Enumeration e = h.keys();
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63 | String key;
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64 |
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65 | while(e.hasMoreElements()) {
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66 | key = (String)e.nextElement();
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67 | res += key+" \t"+h.get(key)+"\n";
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68 | }
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69 |
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70 | if (pred!=null) res+="++ predecessor!\n";
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71 | return(res);
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72 | }
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73 |
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74 | public int size() {
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75 | return(h.size());
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76 | }
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77 | }
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78 |
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