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1 from . import astnodes, lexer, semantics
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152
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2 from ppci import CompilerError
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3
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4 # binop precedence for expressions:
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5 binopPrecs = {'or': 5, 'and': 10, \
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6 '<': 20, '>': 20, '==': 20, '<=': 20, '>=': 20, '!=': 20, \
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7 '+': 30, '-': 30, '*': 40, '/': 40 }
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8
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9 class Parser:
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10 """ Parses sourcecode into an abstract syntax tree (AST) """
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11 def __init__(self, sema, diag):
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12 self.sema = sema
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13 self.diag = diag
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14 def parseSource(self, source):
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15 self.initLex(source)
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16 try:
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17 self.parsePackage()
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18 except CompilerError as e:
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19 self.diag.addDiag(e)
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20 def Error(self, msg):
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21 raise CompilerError(msg, self.token.loc)
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22 # Lexer helpers:
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23 def Consume(self, typ):
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24 if self.Peak == typ:
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25 return self.NextToken()
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26 else:
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27 self.Error('Excected: "{0}", got "{1}"'.format(typ, self.Peak))
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28 @property
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29 def Peak(self):
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30 return self.token.typ
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31 @property
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32 def PeakPrec(self):
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33 if self.Peak in binopPrecs:
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34 return binopPrecs[self.Peak]
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35 return -1
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36 def hasConsumed(self, typ):
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37 if self.Peak == typ:
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38 self.Consume(typ)
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39 return True
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40 return False
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41 def NextToken(self):
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42 t = self.token
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43 if t.typ != 'END': self.token = self.tokens.__next__()
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44 return t
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45 def initLex(self, source):
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46 self.tokens = lexer.tokenize(source) # Lexical stage
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47 self.token = self.tokens.__next__()
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48
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49 def parsePackage(self):
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50 self.Consume('package')
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51 name = self.Consume('ID')
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52 self.Consume(';')
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53 self.sema.handlePackage(name.val, name.loc)
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54 # TODO: parse uses
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55 while self.Peak != 'END':
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56 self.parseTopLevel()
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57 self.Consume('END')
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58
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59 def parseTopLevel(self):
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60 if self.Peak == 'function':
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61 self.parseFunctionDefinition()
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62 elif self.Peak == 'var':
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63 self.parseVarDef()
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64 self.Consume(';')
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65 else:
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66 self.Error('Expected function or variable')
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67
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68 def parseDesignator(self):
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69 """ A designator designates an object """
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70 name = self.Consume('ID')
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71 return self.sema.actOnDesignator(name.val, name.loc)
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72
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73 # Type system
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74 def parseType(self):
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75 d = self.parseDesignator()
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76 return d
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77
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78 # Variable declarations:
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79 def parseVarDef(self):
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80 self.Consume('var')
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81 t = self.parseType()
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82 def parseVar():
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83 name = self.Consume('ID')
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84 ival = None
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85 if self.hasConsumed('='):
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86 ival = self.parseExpression()
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87 self.sema.actOnVarDef(name.val, name.loc, t, ival)
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88 parseVar()
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89 while self.hasConsumed(','):
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90 parseVar()
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91
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92 # Procedures
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93 def parseFunctionDefinition(self):
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94 self.Consume('function')
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95 returntype = self.parseType()
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96 pname = self.Consume('ID')
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97 self.sema.actOnFuncDef1(pname.val, pname.loc)
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98 self.Consume('(')
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99 parameters = []
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100 if not self.hasConsumed(')'):
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101 def parseParameter():
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102 typ = self.parseType()
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103 name = self.Consume('ID')
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104 parameters.append(self.sema.actOnParameter(name.val, name.loc, typ))
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105 parseParameter()
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106 while self.hasConsumed(','):
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107 parseParameter()
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108 self.Consume(')')
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109 body = self.parseCompoundStatement()
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110 self.sema.actOnFuncDef2(parameters, returntype, body)
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111
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112 # Statements:
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113 def parseAssignment(self, lval):
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114 lval = astnodes.VariableUse(lval)
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115 self.Consume('=')
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116 rval = self.parseExpression()
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117 return astnodes.Assignment(lval, rval)
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118
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119 def parseProcedureCall(self, procedure):
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120 self.Consume('(')
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121 args = []
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122 if not self.hasConsumed(')'):
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123 args.append(self.parseExpression())
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124 while self.hasConsumed(','):
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125 args.append(self.parseExpression())
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126 self.Consume(')')
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127 return astnodes.ProcedureCall(procedure, args)
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128
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129 def parseIfStatement(self):
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130 self.Consume('if')
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131 self.Consume('(')
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132 condition = self.parseExpression()
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133 self.Consume(')')
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134 yes = self.parseCompoundStatement()
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135 if self.hasConsumed('else'):
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136 no = self.parseCompoundStatement()
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137 return astnodes.IfStatement(condition, yes, no)
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138 return astnodes.IfStatement(condition, yes)
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139
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140 def parseWhileStatement(self):
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141 self.Consume('while')
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142 self.Consume('(')
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143 condition = self.parseExpression()
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144 self.Consume(')')
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145 statements = self.parseCompoundStatement()
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146 return astnodes.WhileStatement(condition, statements)
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147
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148
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148 def parseReturnStatement(self):
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149 self.Consume('return')
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150 expr = self.parseExpression()
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151 return astnodes.ReturnStatement(expr)
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152
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153 def parseCompoundStatement(self):
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154 self.Consume('{')
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155 statements = [self.parseStatement()]
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156 while self.hasConsumed(';'):
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155
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157 if self.Peak == '}': break # Permit last ';'
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158 statements.append(self.parseStatement())
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159 self.Consume('}')
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160 return astnodes.CompoundStatement(statements)
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161
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162 def parseStatement(self):
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163 # Determine statement type based on the pending token:
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164 if self.Peak == 'if':
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165 return self.parseIfStatement()
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166 elif self.Peak == 'while':
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167 return self.parseWhileStatement()
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168 elif self.Peak == '{':
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169 return self.parseCompoundStatement()
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155
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170 elif self.Peak == ';':
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171 return astnodes.EmptyStatement()
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172 elif self.Peak == 'var':
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173 return self.parseVarDef()
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174 elif self.Peak == 'return':
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175 return self.parseReturnStatement()
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176 elif self.Peak == 'ID':
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177 designator = self.parseDesignator()
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178 if self.Peak == '(':
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179 return self.parseProcedureCall(designator)
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180 elif self.Peak == '=':
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181 return self.parseAssignment(designator)
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182 self.Error('Unable to determine statement')
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183
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184 # Parsing expressions:
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185 def parseExpression(self):
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186 return self.parseBinopRhs(self.parsePrimary(), 0)
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187 def parsePrimary(self):
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188 if self.hasConsumed('('):
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189 e = self.parseExpression()
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190 self.Consume(')')
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191 return e
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192 elif self.Peak == 'NUMBER':
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193 val = self.Consume('NUMBER')
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194 return self.sema.actOnNumber(val.val, val.loc)
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195 elif self.Peak == 'ID':
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196 d = self.parseDesignator()
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197 if self.Peak == '(':
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198 return self.parseProcedureCall(d)
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199 else:
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200 return self.sema.actOnVariableUse(d)
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201 self.Error('Expected NUM, ID or (expr), got {0}'.format(self.Peak))
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202
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203 def parseBinopRhs(self, lhs, min_prec):
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204 while self.PeakPrec >= min_prec:
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205 op_prec = self.PeakPrec
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206 op = self.Consume(self.Peak)
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207 rhs = self.parsePrimary()
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208 while self.PeakPrec > op_prec:
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209 rhs = self.parseBinopRhs(rhs, self.PeakPrec)
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210 lhs = self.sema.actOnBinop(lhs, op.typ, rhs, op.loc)
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211 return lhs
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212
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