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148
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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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148
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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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166
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11 def __init__(self, diag):
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12 self.sema = semantics.Semantics(diag)
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148
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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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152
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18 except CompilerError as e:
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19 self.diag.addDiag(e)
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20 return self.sema.mod
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148
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21 def Error(self, msg):
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152
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22 raise CompilerError(msg, self.token.loc)
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148
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23 # Lexer helpers:
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24 def Consume(self, typ):
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25 if self.Peak == typ:
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26 return self.NextToken()
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27 else:
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28 self.Error('Excected: "{0}", got "{1}"'.format(typ, self.Peak))
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29 @property
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30 def Peak(self):
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31 return self.token.typ
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32 @property
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33 def PeakPrec(self):
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34 if self.Peak in binopPrecs:
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35 return binopPrecs[self.Peak]
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36 return -1
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148
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37 def hasConsumed(self, typ):
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38 if self.Peak == typ:
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39 self.Consume(typ)
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40 return True
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41 return False
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42 def NextToken(self):
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43 t = self.token
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166
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44 if t.typ != 'END':
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45 self.token = self.tokens.__next__()
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46 return t
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47 def initLex(self, source):
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48 self.tokens = lexer.tokenize(source) # Lexical stage
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49 self.token = self.tokens.__next__()
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166
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50 def skipToSemi(self, tt):
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51 while self.Peak != tt and self.Peak != 'END':
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52 self.NextToken()
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53 if self.Peak == tt:
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54 self.Consume(tt)
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148
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55
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56 def parsePackage(self):
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57 self.Consume('package')
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58 name = self.Consume('ID')
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59 self.Consume(';')
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60 self.sema.handlePackage(name.val, name.loc)
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61 # TODO: parse uses
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62 while self.Peak != 'END':
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63 self.parseTopLevel()
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64 self.Consume('END')
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65
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66 def parseTopLevel(self):
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67 if self.Peak == 'function':
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68 self.parseFunctionDefinition()
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69 elif self.Peak == 'var':
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70 self.parseVarDef()
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163
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71 elif self.Peak == 'const':
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72 self.parseConstDef()
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73 else:
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74 self.Error('Expected function or variable')
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75
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76 def parseDesignator(self):
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77 """ A designator designates an object """
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78 name = self.Consume('ID')
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150
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79 return self.sema.actOnDesignator(name.val, name.loc)
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80
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81 # Type system
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82 def parseType(self):
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83 d = self.parseDesignator()
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84 return d
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85
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86 # Variable declarations:
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87 def parseVarDef(self):
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88 self.Consume('var')
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89 t = self.parseType()
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90 def parseVar():
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91 name = self.Consume('ID')
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92 ival = None
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93 if self.hasConsumed('='):
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94 ival = self.parseExpression()
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95 self.sema.actOnVarDef(name.val, name.loc, t, ival)
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96 parseVar()
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97 while self.hasConsumed(','):
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98 parseVar()
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99 self.Consume(';')
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100
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101 def parseConstDef(self):
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102 self.Consume('const')
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103 t = self.parseType()
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104 def parseConst():
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105 name = self.Consume('ID')
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106 self.Consume('=')
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107 val = self.parseExpression()
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108 self.sema.actOnConstDef(name.val, name.loc, t, val)
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109 parseConst()
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110 while self.hasConsumed(','):
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111 parseConst()
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112 self.Consume(';')
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113
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114 # Procedures
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115 def parseFunctionDefinition(self):
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116 self.Consume('function')
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117 returntype = self.parseType()
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118 pname = self.Consume('ID')
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119 self.sema.actOnFuncDef1(pname.val, pname.loc)
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120 self.Consume('(')
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121 parameters = []
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122 if not self.hasConsumed(')'):
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123 def parseParameter():
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124 typ = self.parseType()
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125 name = self.Consume('ID')
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126 parameters.append(self.sema.actOnParameter(name.val, name.loc, typ))
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127 parseParameter()
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128 while self.hasConsumed(','):
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129 parseParameter()
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130 self.Consume(')')
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131 body = self.parseCompoundStatement()
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132 self.sema.actOnFuncDef2(parameters, returntype, body)
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133
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134 # Statements:
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135 def parseAssignment(self, lval):
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136 lval = self.sema.actOnVariableUse(lval, lval.loc)
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137 loc = self.Consume('=').loc
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138 rval = self.parseExpression()
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139 self.Consume(';')
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140 return self.sema.actOnAssignment(lval, rval, loc)
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141
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142 def parseProcedureCall(self, procedure):
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143 self.Consume('(')
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144 args = []
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145 if not self.hasConsumed(')'):
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146 args.append(self.parseExpression())
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147 while self.hasConsumed(','):
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148 args.append(self.parseExpression())
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149 self.Consume(')')
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155
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150 return astnodes.ProcedureCall(procedure, args)
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151
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152 def parseIfStatement(self):
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153 loc = self.Consume('if').loc
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154 self.Consume('(')
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155 condition = self.parseExpression()
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156 self.Consume(')')
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157 yes = self.parseCompoundStatement()
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158 if self.hasConsumed('else'):
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159 no = self.parseCompoundStatement()
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160 else:
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161 no = astnodes.EmptyStatement()
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162 return self.sema.actOnIfStatement(condition, yes, no, loc)
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163
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164 def parseWhileStatement(self):
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165 self.Consume('while')
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166 self.Consume('(')
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167 condition = self.parseExpression()
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168 self.Consume(')')
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169 statements = self.parseCompoundStatement()
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170 return astnodes.WhileStatement(condition, statements)
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171
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172 def parseReturnStatement(self):
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173 self.Consume('return')
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174 expr = self.parseExpression()
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175 self.Consume(';')
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176 return astnodes.ReturnStatement(expr)
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177
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178 def parseCompoundStatement(self):
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179 self.Consume('{')
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180 statements = []
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181 while not self.hasConsumed('}'):
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182 s = self.parseStatement()
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183 if not type(s) is astnodes.EmptyStatement:
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184 statements.append(s)
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185 return astnodes.CompoundStatement(statements)
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186
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187 def parseStatement(self):
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188 # Determine statement type based on the pending token:
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189 if self.Peak == 'if':
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190 return self.parseIfStatement()
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191 elif self.Peak == 'while':
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192 return self.parseWhileStatement()
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193 elif self.Peak == '{':
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194 return self.parseCompoundStatement()
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158
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195 elif self.hasConsumed(';'):
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196 return astnodes.EmptyStatement()
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197 elif self.Peak == 'var':
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198 self.parseVarDef()
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199 return astnodes.EmptyStatement()
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200 elif self.Peak == 'return':
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201 return self.parseReturnStatement()
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202 elif self.Peak == 'ID':
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203 designator = self.parseDesignator()
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204 if self.Peak == '(':
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205 return self.parseProcedureCall(designator)
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206 elif self.Peak == '=':
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207 return self.parseAssignment(designator)
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208 self.Error('Unable to determine statement')
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209
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210 # Parsing expressions:
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211 def parseExpression(self):
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212 return self.parseBinopRhs(self.parsePrimary(), 0)
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213 # TODO: use this error handling:
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214 try:
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215 return self.parseBinopRhs(self.parsePrimary(), 0)
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216 except CompilerError as e:
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217 self.diag.addDiag(e)
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218 self.skipToSemi(';')
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219 return astnodes.Literal(0)
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220 def parsePrimary(self):
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221 if self.hasConsumed('('):
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222 e = self.parseExpression()
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223 self.Consume(')')
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224 return e
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225 elif self.Peak == 'NUMBER':
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226 val = self.Consume('NUMBER')
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227 return self.sema.actOnNumber(val.val, val.loc)
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228 elif self.Peak == 'REAL':
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229 val = self.Consume('REAL')
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230 return self.sema.actOnNumber(val.val, val.loc)
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166
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231 elif self.Peak == 'true':
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232 val = self.Consume('true')
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233 return self.sema.actOnNumber(True, val.loc)
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234 elif self.Peak == 'false':
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235 val = self.Consume('false')
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236 return self.sema.actOnNumber(False, val.loc)
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237 elif self.Peak == 'ID':
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238 d = self.parseDesignator()
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155
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239 if self.Peak == '(':
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240 return self.parseProcedureCall(d)
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241 else:
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242 return self.sema.actOnVariableUse(d, d.loc)
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243 self.Error('Expected NUM, ID or (expr), got {0}'.format(self.Peak))
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244
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245 def parseBinopRhs(self, lhs, min_prec):
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246 while self.PeakPrec >= min_prec:
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247 op_prec = self.PeakPrec
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248 op = self.Consume(self.Peak)
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249 rhs = self.parsePrimary()
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250 while self.PeakPrec > op_prec:
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251 rhs = self.parseBinopRhs(rhs, self.PeakPrec)
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252 lhs = self.sema.actOnBinop(lhs, op.typ, rhs, op.loc)
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253 return lhs
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254
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