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213
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1 from . import astnodes, lexer
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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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213
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10 """ Parses sourcecode into an abstract syntax tree (AST) """
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11 def __init__(self, diag):
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12 self.diag = diag
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13
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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 return self.mod
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152
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19 except CompilerError as e:
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20 self.diag.addDiag(e)
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21 def Error(self, msg):
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22 raise CompilerError(msg, self.token.loc)
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213
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23 # Lexer helpers:
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24 def Consume(self, typ):
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148
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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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213
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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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213
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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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213
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37 def hasConsumed(self, typ):
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148
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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
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43 def NextToken(self):
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44 t = self.token
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45 if t.typ != 'END':
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46 self.token = self.tokens.__next__()
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47 return t
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48
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49 def initLex(self, source):
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50 self.tokens = lexer.tokenize(source) # Lexical stage
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51 self.token = self.tokens.__next__()
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215
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52 def addDeclaration(self, decl):
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53 self.currentPart.declarations.append(decl)
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54
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55 def parseUses(self):
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56 pass
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57
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58 def parsePackage(self):
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59 self.Consume('package')
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60 name = self.Consume('ID')
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61 self.Consume(';')
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62 self.mod = astnodes.Package(name.val, name.loc)
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63 self.currentPart = self.mod
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64 self.parseUses()
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65 # TODO: parse uses
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66 while self.Peak != 'END':
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67 self.parseTopLevel()
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68 self.Consume('END')
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69
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70 def parseTopLevel(self):
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71 if self.Peak == 'function':
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72 self.parseFunctionDef()
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73 elif self.Peak == 'var':
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74 self.parseVarDef()
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75 elif self.Peak == 'const':
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76 self.parseConstDef()
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77 elif self.Peak == 'type':
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78 self.parseTypeDef()
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79 else:
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80 self.Error('Expected function, var, const or type')
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81
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82 def parseDesignator(self):
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148
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83 """ A designator designates an object """
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84 name = self.Consume('ID')
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85 d = astnodes.Designator(name.val, name.loc)
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86 return d
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87
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88 # Type system
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89 def parseTypeSpec(self):
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90 # For now, do simple type spec, just parse an ID:
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91 return self.parseDesignator()
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92 if self.Peak == 'struct':
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93 self.Consume('struct')
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94 self.Consume('{')
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95 mems = []
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96 while self.Peak != '}':
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97 mem_t = self.parseTypeSpec()
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98 mem_n = self.Consume('ID')
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99 mems.append((mem_t, mem_n))
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100 while self.hasConsumed(','):
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101 mem_n = self.Consume('ID')
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102 mems.append((mem_t, mem_n))
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103 self.Consume(';')
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104 self.Consume('}')
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105 theT = astnodes.StructureType(mems)
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106 else:
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107 theT = self.parseDesignator()
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108 # Check for pointer suffix:
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109 while self.hasConsumed('*'):
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110 theT = astnodes.PointerType(theT)
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111 return theT
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112
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113 def parseTypeDef(self):
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114 self.Consume('type')
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115 newtype = self.parseTypeSpec()
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116 typename = self.Consume('ID')
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117 # TODO: action here :)
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118 self.Consume(';')
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119 return astnodes.DefinedType(typename, newtype)
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120
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121 # Variable declarations:
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122 def parseVarDef(self):
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123 self.Consume('var')
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124 t = self.parseTypeSpec()
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125 def parseVar():
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126 name = self.Consume('ID')
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127 v = astnodes.Variable(name.val, t)
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128 v.loc = name.loc
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129 if self.hasConsumed('='):
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130 v.ival = self.parseExpression()
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131 self.addDeclaration(v)
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132 parseVar()
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133 while self.hasConsumed(','):
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134 parseVar()
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135 self.Consume(';')
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136
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137 def parseConstDef(self):
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138 self.Consume('const')
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139 t = self.parseTypeSpec()
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140 def parseConst():
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141 name = self.Consume('ID')
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142 self.Consume('=')
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143 val = self.parseExpression()
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144 c = astnodes.Constant(name.val, t, val)
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145 c.loc = name.loc
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163
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146 parseConst()
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147 while self.hasConsumed(','):
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148 parseConst()
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149 self.Consume(';')
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150
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213
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151 # Procedures
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152 def parseFunctionDef(self):
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153 loc = self.Consume('function').loc
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154 returntype = self.parseTypeSpec()
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155 fname = self.Consume('ID').val
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156 f = astnodes.Function(fname, loc)
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157 self.addDeclaration(f)
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158 savePart = self.currentPart
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159 self.currentPart = f
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160 self.Consume('(')
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161 parameters = []
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162 if not self.hasConsumed(')'):
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163 def parseParameter():
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164 typ = self.parseTypeSpec()
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165 name = self.Consume('ID')
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166 param = astnodes.Variable(name.val, typ)
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167 param.loc = name.loc
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168 self.addDeclaration(param)
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169 parameters.append(param)
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170 parseParameter()
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171 while self.hasConsumed(','):
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172 parseParameter()
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173 self.Consume(')')
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174 paramtypes = [p.typ for p in parameters]
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175 f.typ = astnodes.FunctionType(paramtypes, returntype)
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176 f.body = self.parseCompoundStatement()
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177 self.currentPart = savePart
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178
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179 # Statements:
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180 def parseAssignment(self, lval):
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181 lval = astnodes.VariableUse(lval, lval.loc)
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182 loc = self.Consume('=').loc
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183 rval = self.parseExpression()
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184 self.Consume(';')
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185 return astnodes.Assignment(lval, rval, loc)
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186
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187 def parseCall(self, func):
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188 self.Consume('(')
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189 args = []
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190 if not self.hasConsumed(')'):
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191 args.append(self.parseExpression())
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192 while self.hasConsumed(','):
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193 args.append(self.parseExpression())
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194 self.Consume(')')
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195 return astnodes.FunctionCall(func, args, func.loc)
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196
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197 def parseIfStatement(self):
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198 loc = self.Consume('if').loc
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199 self.Consume('(')
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200 condition = self.parseExpression()
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201 self.Consume(')')
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202 yes = self.parseCompoundStatement()
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203 if self.hasConsumed('else'):
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204 no = self.parseCompoundStatement()
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205 else:
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206 no = astnodes.EmptyStatement()
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207 return astnodes.IfStatement(condition, yes, no, loc)
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208
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209 def parseWhileStatement(self):
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210 loc = self.Consume('while').loc
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211 self.Consume('(')
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212 condition = self.parseExpression()
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213 self.Consume(')')
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214 statements = self.parseCompoundStatement()
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215 return astnodes.WhileStatement(condition, statements, loc)
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216
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217 def parseReturnStatement(self):
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218 self.Consume('return')
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219 expr = self.parseExpression()
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220 self.Consume(';')
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221 return astnodes.ReturnStatement(expr)
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222
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223 def parseCompoundStatement(self):
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224 self.Consume('{')
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225 statements = []
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226 while not self.hasConsumed('}'):
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227 s = self.parseStatement()
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228 if not type(s) is astnodes.EmptyStatement:
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229 statements.append(s)
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230 return astnodes.CompoundStatement(statements)
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231
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232 def parseStatement(self):
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233 # Determine statement type based on the pending token:
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234 if self.Peak == 'if':
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235 return self.parseIfStatement()
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236 elif self.Peak == 'while':
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237 return self.parseWhileStatement()
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238 elif self.Peak == '{':
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239 return self.parseCompoundStatement()
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158
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240 elif self.hasConsumed(';'):
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241 return astnodes.EmptyStatement()
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242 elif self.Peak == 'var':
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243 self.parseVarDef()
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244 return astnodes.EmptyStatement()
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245 elif self.Peak == 'return':
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246 return self.parseReturnStatement()
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247 else:
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248 designator = self.parseDesignator()
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249 if self.Peak == '(':
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250 return self.parseCall(designator)
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251 elif self.Peak == '=':
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252 return self.parseAssignment(designator)
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253 else:
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254 self.Error('Unable to determine statement')
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255
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256 # Parsing expressions:
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257 def parseExpression(self):
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258 return self.parseBinopRhs(self.parsePrimary(), 0)
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259
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260 def parsePrimary(self):
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261 if self.hasConsumed('('):
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262 e = self.parseExpression()
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263 self.Consume(')')
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264 return e
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265 elif self.Peak == 'NUMBER':
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266 val = self.Consume('NUMBER')
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267 return astnodes.Literal(val.val, val.loc)
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163
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268 elif self.Peak == 'REAL':
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269 val = self.Consume('REAL')
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270 return astnodes.Literal(val.val, val.loc)
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166
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271 elif self.Peak == 'true':
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272 val = self.Consume('true')
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273 return astnodes.Literal(True, val.loc)
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166
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274 elif self.Peak == 'false':
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275 val = self.Consume('false')
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276 return astnodes.Literal(False, val.loc)
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277 elif self.Peak == 'ID':
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278 d = self.parseDesignator()
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279 if self.Peak == '(':
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280 return self.parseCall(d)
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281 else:
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282 return astnodes.VariableUse(d, d.loc)
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283 self.Error('Expected NUM, ID or (expr), got {0}'.format(self.Peak))
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284
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285 def parseBinopRhs(self, lhs, min_prec):
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286 while self.PeakPrec >= min_prec:
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287 op_prec = self.PeakPrec
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288 op = self.Consume(self.Peak)
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289 rhs = self.parsePrimary()
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290 while self.PeakPrec > op_prec:
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291 rhs = self.parseBinopRhs(rhs, self.PeakPrec)
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292 lhs = astnodes.Binop(lhs, op.typ, rhs, op.loc)
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293 return lhs
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294
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