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1 | package antlr; |
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2 | |
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3 | /* ANTLR Translator Generator |
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4 | * Project led by Terence Parr at http://www.cs.usfca.edu |
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5 | * Software rights: http://www.antlr.org/license.html |
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6 | */ |
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7 | |
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8 | import antlr.*; |
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9 | import antlr.collections.AST; |
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10 | |
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11 | public abstract class ParseTree extends BaseAST { |
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12 | |
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13 | /** Walk parse tree and return requested number of derivation steps. |
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14 | * If steps <= 0, return node text. If steps == 1, return derivation |
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15 | * string at step. |
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16 | */ |
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17 | public String getLeftmostDerivationStep(int step) { |
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18 | if ( step<=0 ) { |
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19 | return toString(); |
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20 | } |
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21 | StringBuffer buf = new StringBuffer(2000); |
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22 | getLeftmostDerivation(buf, step); |
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23 | return buf.toString(); |
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24 | } |
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25 | |
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26 | public String getLeftmostDerivation(int maxSteps) { |
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27 | StringBuffer buf = new StringBuffer(2000); |
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28 | buf.append(" "+this.toString()); |
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29 | buf.append("\n"); |
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30 | for (int d=1; d<maxSteps; d++) { |
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31 | buf.append(" =>"); |
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32 | buf.append(getLeftmostDerivationStep(d)); |
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33 | buf.append("\n"); |
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34 | } |
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35 | return buf.toString(); |
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36 | } |
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37 | |
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38 | /** Get derivation and return how many you did (less than requested for |
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39 | * subtree roots. |
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40 | */ |
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41 | protected abstract int getLeftmostDerivation(StringBuffer buf, int step); |
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42 | |
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43 | // just satisfy BaseAST interface; unused as we manually create nodes |
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44 | |
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45 | public void initialize(int i, String s) { |
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46 | } |
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47 | public void initialize(AST ast) { |
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48 | } |
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49 | public void initialize(Token token) { |
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50 | } |
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51 | } |
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