1 | /**************************************************************************
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2 | *
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3 | * QueryParser.cpp -- Query parser for a simple query language
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4 | * Copyright (C) 2000 Rodger McNab
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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 as published by
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8 | * the Free Software Foundation; either version 2 of the License, or
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9 | * (at your option) any later version.
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10 | *
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11 | * This program is distributed in the hope that it will be useful,
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | * GNU General Public License for more details.
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15 | *
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16 | * You should have received a copy of the GNU General Public License
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17 | * along with this program; if not, write to the Free Software
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18 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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19 | *
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20 | **************************************************************************/
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21 |
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22 | #include "QueryParser.h"
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23 | #include "QueryLex.h"
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24 |
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25 |
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26 | static QueryNode *ParseExpression (UCArray::const_iterator &here,
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27 | UCArray::const_iterator end);
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28 |
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29 | static QueryNode *AndAdd (QueryNode *t1, QueryNode *t2) {
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30 | if (t1 == NULL) return t2;
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31 | if (t2 == NULL) return t1;
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32 |
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33 | AndQueryNode *andNode = new AndQueryNode;
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34 | andNode->leftNode = t1;
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35 | andNode->rightNode = t2;
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36 | return andNode;
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37 | }
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38 |
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39 | static QueryNode *OrAdd (QueryNode *t1, QueryNode *t2) {
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40 | if (t1 == NULL) return t2;
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41 | if (t2 == NULL) return t1;
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42 |
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43 | OrQueryNode *orNode = new OrQueryNode;
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44 | orNode->leftNode = t1;
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45 | orNode->rightNode = t2;
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46 | return orNode;
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47 | }
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48 |
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49 | static QueryNode *NotAdd (QueryNode *t1, QueryNode *t2) {
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50 | if (t1 == NULL) return t2;
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51 | if (t2 == NULL) return t1;
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52 |
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53 | NotQueryNode *notNode = new NotQueryNode;
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54 | notNode->queryNode = t1;
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55 | notNode->notNode = t2;
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56 | return notNode;
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57 | }
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58 |
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59 | // expects the opening bracket to have already been parsed
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60 | // and discarded
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61 | static QueryNode *ParseBracketExpression (UCArray::const_iterator &here,
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62 | UCArray::const_iterator end) {
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63 | // get everything in the expression
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64 | QueryNode *curTree = ParseExpression (here, end);
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65 |
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66 | // gobble up tokens until a closing bracket is found
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67 | // or the end of the string
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68 | LexEl el;
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69 | while (ParseLexEl (here, end, el)) {
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70 | if (el.lexType == CloseBracketE) break;
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71 | }
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72 |
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73 | return curTree;
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74 | }
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75 |
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76 | static int ParseInt (UCArray::const_iterator &here,
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77 | UCArray::const_iterator end) {
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78 | LexEl el;
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79 | UCArray::const_iterator oldHere = here;
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80 | if (ParseLexEl (here, end, el) && el.lexType == IntegerE)
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81 | return el.num;
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82 |
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83 | here = oldHere; // not an integer
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84 | return 0;
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85 | }
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86 |
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87 |
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88 | static void ParseTermModifiers (UCArray::const_iterator &here,
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89 | UCArray::const_iterator end,
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90 | TermNode &termNode) {
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91 | LexEl el;
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92 | UCArray::const_iterator oldHere = here;
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93 | while (ParseLexEl (here, end, el)) {
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94 | if (el.lexType == TermWeightE) {
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95 | termNode.termWeight = ParseInt (here, end);
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96 |
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97 | } else if (el.lexType == StemMethodE) {
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98 | termNode.stemMethod = ParseInt (here, end);
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99 |
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100 | } else if (el.lexType == RangeE) {
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101 | termNode.startRange = ParseInt (here, end);
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102 | termNode.endRange = ParseInt (here, end);
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103 |
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104 | } else if (el.lexType == AtE) {
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105 | termNode.startRange = termNode.endRange = ParseInt (here, end);
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106 |
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107 | } else {
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108 | // no term modifiers
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109 | here = oldHere;
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110 | break;
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111 | }
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112 |
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113 | oldHere = here;
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114 | }
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115 | }
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116 |
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117 | // expects the starting quote to have been parsed
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118 | // and discarded
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119 | static void ParsePhrase (UCArray::const_iterator &here,
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120 | UCArray::const_iterator end,
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121 | ProxMatchQueryNode &proxNode) {
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122 | LexEl el;
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123 | while (ParseLexEl (here, end, el)) {
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124 | if (el.lexType == TermE || el.lexType == IntegerE) {
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125 | TermNode termNode;
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126 | termNode.term = el.text;
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127 | ParseTermModifiers (here, end, termNode);
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128 | proxNode.terms.push_back (termNode);
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129 |
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130 | } else if (el.lexType == QuoteE) {
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131 | break;
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132 |
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133 | } else {
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134 | // error
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135 | break;
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136 | }
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137 | }
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138 | }
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139 |
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140 | static QueryNode *ParseTerm (UCArray::const_iterator &here,
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141 | UCArray::const_iterator end) {
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142 | LexEl el;
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143 |
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144 | UCArray::const_iterator oldHere = here;
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145 | if (!ParseLexEl (here, end, el)) return NULL;
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146 |
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147 | if (el.lexType == OpenBracketE)
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148 | return ParseBracketExpression (here, end);
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149 |
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150 | ProxMatchQueryNode *proxNode = new ProxMatchQueryNode;
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151 |
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152 | // check for a tag
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153 | if (el.lexType == TagE) {
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154 | oldHere = here; // don't backtrack past here
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155 | if (!ParseLexEl (here, end, el)) return NULL;
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156 | if (el.lexType == TermE) {
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157 | proxNode->tagNodePtr = new TagNode;
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158 | proxNode->tagNodePtr->tagName = el.text;
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159 | if (!ParseLexEl (here, end, el)) return NULL;
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160 | }
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161 | }
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162 |
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163 | if (el.lexType == TermE || el.lexType == IntegerE) {
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164 | TermNode termNode;
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165 | termNode.term = el.text;
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166 | ParseTermModifiers (here, end, termNode);
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167 | proxNode->terms.push_back (termNode);
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168 | return proxNode;
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169 |
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170 | } else if (el.lexType == QuoteE) {
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171 | ParsePhrase (here, end, *proxNode);
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172 | return proxNode;
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173 | }
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174 |
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175 | // not a term
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176 | here = oldHere;
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177 | delete proxNode;
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178 | return NULL;
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179 | }
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180 |
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181 |
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182 | static QueryNode *ParseExpression (UCArray::const_iterator &here,
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183 | UCArray::const_iterator end) {
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184 | LexEl el;
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185 | QueryNode *curTree = NULL;
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186 |
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187 | UCArray::const_iterator oldHere = here;
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188 | while (ParseLexEl (here, end, el)) {
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189 | if (el.lexType == OpenBracketE ||
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190 | el.lexType == TermE ||
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191 | el.lexType == QuoteE ||
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192 | el.lexType == IntegerE ||
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193 | el.lexType == TagE) {
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194 | // some type of term, back track and parse it
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195 | here = oldHere;
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196 | curTree = OrAdd (curTree, ParseTerm (here, end));
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197 |
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198 | } else if (el.lexType == AndOpE) {
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199 | curTree = AndAdd (curTree, ParseTerm (here, end));
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200 |
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201 | } else if (el.lexType == OrOpE) {
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202 | curTree = OrAdd (curTree, ParseTerm (here, end));
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203 |
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204 | } else if (el.lexType == NotOpE) {
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205 | curTree = NotAdd (curTree, ParseTerm (here, end));
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206 |
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207 | } else break;
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208 |
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209 | oldHere = here;
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210 | }
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211 |
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212 | return curTree;
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213 | }
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214 |
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215 | QueryNode *ParseQuery (const UCArray &queryStr) {
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216 | UCArray::const_iterator here = queryStr.begin();
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217 | UCArray::const_iterator end = queryStr.end();
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218 | return ParseExpression (here, end);
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219 | }
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