1 | namespace HeuristicLab.Algorithms.PushGP.Parser {
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2 | using System.Collections.Generic;
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3 | using System.Globalization;
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4 |
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5 | using HeuristicLab.Algorithms.PushGP.Expressions;
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6 |
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7 | public static class PushGPParser {
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8 | private const string openBrace = "(";
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9 |
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10 | private const string closeBrace = ")";
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11 |
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12 | private const char delimiter = ' ';
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13 |
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14 | private static readonly CultureInfo cultureInfo = CultureInfo.CreateSpecificCulture("en-US");
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15 |
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16 | private static readonly char[] symbolTrim = { '\r', '\n' };
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17 |
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18 | public static Expression Parse(string source, int startIndex = 0) {
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19 | var symbols = source.Split(delimiter);
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20 |
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21 | int endIndex;
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22 | return Parse(symbols, 0, out endIndex);
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23 | }
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24 |
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25 | private static Expression Parse(string[] symbols, int startIndex, out int endIndex) {
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26 | var expressions = new List<Expression>();
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27 |
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28 | for (var i = startIndex; i < symbols.Length; i++) {
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29 | var symbol = symbols[i].TrimEnd(symbolTrim);
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30 |
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31 | if (string.IsNullOrWhiteSpace(symbol)) continue;
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32 |
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33 | switch (symbol) {
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34 | case openBrace:
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35 | var subExpression = Parse(symbols, i + 1, out endIndex);
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36 | expressions.Insert(0, subExpression);
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37 | i = endIndex;
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38 | continue;
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39 | case closeBrace:
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40 | endIndex = i;
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41 | return new ExecExpandExpression(expressions.ToArray());
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42 | }
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43 |
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44 | // literal
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45 | Expression expression;
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46 | if (TryParseLiteral(symbol, out expression)) {
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47 | expressions.Insert(0, expression);
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48 | continue;
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49 | }
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50 |
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51 | // expression
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52 | if (ExpressionTable.TryGetStatelessExpression(symbol, out expression)
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53 | || ExpressionTable.TryGetStatefullExpression(symbol, out expression)) {
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54 | expressions.Insert(0, expression);
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55 | continue;
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56 | }
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57 |
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58 | // identifier - custom expression or named literals
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59 | expressions.Insert(0, new NameDefineXExecExpression(symbol));
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60 | }
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61 |
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62 | endIndex = symbols.Length - 1;
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63 |
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64 | return expressions.Count == 1
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65 | ? expressions[0]
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66 | : new ExecExpandExpression(expressions.ToArray());
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67 | }
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68 |
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69 | private static bool TryParseLiteral(string word, out Expression expression) {
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70 | long longValue;
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71 | if (long.TryParse(word, out longValue)) {
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72 | expression = new IntegerPushExpression(longValue);
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73 | return true;
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74 | }
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75 |
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76 | double floatValue;
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77 | if (double.TryParse(word, NumberStyles.Float, cultureInfo, out floatValue)) {
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78 | expression = new FloatPushExpression(floatValue);
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79 | return true;
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80 | }
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81 |
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82 | bool booleanValue;
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83 | if (bool.TryParse(word, out booleanValue)) {
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84 | expression = new BooleanPushExpression(booleanValue);
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85 | return true;
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86 | }
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87 |
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88 | expression = null;
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89 | return false;
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90 | }
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91 | }
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92 | } |
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