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318
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1 #!/usr/bin/python
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2
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319
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3 """
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321
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4 Bottom up rewrite generator.
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319
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5
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6 This script takes as input a description of patterns and outputs a
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7 matcher class that can match trees given the patterns.
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8
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9 Patterns are specified as follows:
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10 reg -> ADDI32(reg, reg) 2 (. add NT0 NT1 .)
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319
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11 reg -> MULI32(reg, reg) 3 (. .)
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12 or a multiply add:
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13 reg -> ADDI32(MULI32(reg, reg), reg) 4 (. muladd $1, $2, $3 .)
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14 The general specification pattern is:
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15 [result] -> [tree] [cost] [template code]
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16
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321
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17 Trees
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18 -----
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19
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20 A tree is described using parenthesis notation. For example a node X with
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21 three child nodes is described as:
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22 X(a, b, b)
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23 Trees can be nested:
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24 X(Y(a, a), a)
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25 The 'a' in the example above indicates an open connection to a next tree
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26 pattern.
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27
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28
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29 In the example above 'reg' is a non-terminal. ADDI32 is a terminal. non-terminals
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30 cannot have child nodes. A special case occurs in this case:
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31 reg -> rc
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32 where 'rc' is a non-terminal. This is an example of a chain rule. Chain rules
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33 can be used to allow several variants of non-terminals.
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34
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35 The generated matcher uses dynamic programming to find the best match of the
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36 tree. This strategy consists of two steps:
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37 - label: During this phase the given tree is traversed in a bottom up way.
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38 each node is labelled with a possible matching rule and the corresponding cost.
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39 - select: In this step, the tree is traversed again, selecting at each point
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40 the cheapest way to get to the goal.
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41
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42 """
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43
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318
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44 import sys
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321
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45 import os
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318
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46 import argparse
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47 from ppci import Token
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319
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48 from pyyacc import ParserException, EOF
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321
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49 import yacc
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319
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50 import baselex
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51 from tree import Tree
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52
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321
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53 # Generate parser on the fly:
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54 spec_file = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'burg.x')
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55 burg_parser = yacc.load_as_module(spec_file)
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56
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318
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57
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58 class BurgLexer:
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59 def feed(self, txt):
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60 tok_spec = [
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319
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61 ('id', r'[A-Za-z][A-Za-z\d_]*', lambda typ, val: (typ, val)),
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62 ('kw', r'%[A-Za-z][A-Za-z\d_]*', lambda typ, val: (val, val)),
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63 ('number', r'\d+', lambda typ, val: (typ, int(val))),
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64 ('STRING', r"'[^']*'", lambda typ, val: ('id', val[1:-1])),
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65 ('template', r"\(\..*\.\)", lambda typ, val: (typ, val)),
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66 ('OTHER', r'[:;\|\(\),]', lambda typ, val: (val, val)),
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67 ('SKIP', r'[ ]', None)
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68 ]
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69
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70 lines = txt.split('\n')
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71
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72 def tokenize():
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73 for line in lines:
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74 line = line.strip()
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75 if not line:
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76 continue # Skip empty lines
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77 elif line == '%%':
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78 yield Token('%%', '%%')
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79 else:
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80 yield from baselex.tokenize(tok_spec, line)
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81 yield Token(EOF, EOF)
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82 self.tokens = tokenize()
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83 self.token = self.tokens.__next__()
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84
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85 def next_token(self):
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86 t = self.token
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87 if t.typ != EOF:
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88 self.token = self.tokens.__next__()
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89 return t
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90
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91
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319
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92 class Rule:
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320
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93 """ A rewrite rule. Specifies a tree that can be rewritten into a result
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94 at a specific cost """
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95 def __init__(self, non_term, tree, cost, template):
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96 self.non_term = non_term
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97 self.tree = tree
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98 self.cost = cost
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99 self.template = template
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100 self.nr = 0
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101
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102 def __repr__(self):
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103 return '{} -> {} ${}'.format(self.non_term, self.tree, self.cost)
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104
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105
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106 class Symbol:
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107 def __init__(self, name):
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108 self.name = name
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109
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110
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111 class Term(Symbol):
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112 pass
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113
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114
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115 class Nonterm(Symbol):
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116 def __init__(self, name):
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117 super().__init__(name)
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320
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118 self.chain_rules = []
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319
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119
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120
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121 class BurgSystem:
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122 def __init__(self):
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123 self.rules = []
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124 self.symbols = {}
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125 self.goal = None
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126
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127 def symType(self, t):
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128 return (s.name for s in self.symbols.values() if type(s) is t)
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129
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130 terminals = property(lambda s: s.symType(Term))
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131
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132 non_terminals = property(lambda s: s.symType(Nonterm))
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133
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134 def add_rule(self, non_term, tree, cost, template):
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135 template = template[2:-2].strip()
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136 if not template:
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137 template = 'pass'
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138 rule = Rule(non_term, tree, cost, template)
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320
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139 if len(tree.children) == 0 and tree.name not in self.terminals:
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140 self.non_term(tree.name).chain_rules.append(rule)
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319
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141 self.non_term(rule.non_term)
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142 self.rules.append(rule)
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143 rule.nr = len(self.rules)
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144
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145 def non_term(self, name):
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146 if name in self.terminals:
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147 raise BurgError('Cannot redefine terminal')
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148 if not self.goal:
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149 self.goal = name
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320
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150 return self.install(name, Nonterm)
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319
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151
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152 def tree(self, name, *args):
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153 return Tree(name, *args)
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154
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155 def install(self, name, t):
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156 assert type(name) is str
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157 if name in self.symbols:
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158 assert type(self.symbols[name]) is t
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159 else:
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160 self.symbols[name] = t(name)
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161 return self.symbols[name]
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162
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163 def add_terminal(self, terminal):
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164 self.install(terminal, Term)
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165
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166
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167 class BurgError(Exception):
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168 pass
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169
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170
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171 class BurgParser(burg_parser.Parser):
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319
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172 """ Derived from automatically generated parser """
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173 def parse(self, l):
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174 self.system = BurgSystem()
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175 super().parse(l)
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176 return self.system
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177
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178
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179 class BurgGenerator:
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180 def print(self, *args):
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181 """ Print helper function that prints to output file """
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182 print(*args, file=self.output_file)
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183
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184 def generate(self, system, output_file):
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185 """ Generate script that implements the burg spec """
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186 self.output_file = output_file
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187 self.system = system
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188
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189 self.print('#!/usr/bin/python')
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190 self.print('from tree import Tree, BaseMatcher, State')
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191 self.print()
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192 self.print('class Matcher(BaseMatcher):')
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320
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193 self.print(' def __init__(self):')
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194 self.print(' self.kid_functions = {}')
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195 self.print(' self.nts_map = {}')
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196 self.print(' self.pat_f = {}')
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197 for rule in self.system.rules:
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198 kids, dummy = self.compute_kids(rule.tree, 't')
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199 rule.num_nts = len(dummy)
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200 lf = 'lambda t: [{}]'.format(', '.join(kids), rule)
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201 pf = 'self.P{}'.format(rule.nr)
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202 self.print(' # {}: {}'.format(rule.nr, rule))
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203 self.print(' self.kid_functions[{}] = {}'.format(rule.nr, lf))
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204 self.print(' self.nts_map[{}] = {}'.format(rule.nr, dummy))
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205 self.print(' self.pat_f[{}] = {}'.format(rule.nr, pf))
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206 self.print()
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207 for rule in self.system.rules:
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208 if rule.num_nts > 0:
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209 args = ', ' + ', '.join('nt{}'.format(x) for x in range(rule.num_nts))
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210 else:
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211 args = ''
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212 self.print(' def P{}(self{}):'.format(rule.nr, args))
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213 self.print(' {}'.format(rule.template))
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214 self.emit_state()
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215 self.print(' def gen(self, tree):')
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216 self.print(' self.burm_label(tree)')
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217 self.print(' if not tree.state.has_goal("{}"):'.format(self.system.goal))
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218 self.print(' raise Exception("Tree not covered")')
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219 self.print(' self.apply_rules(tree, "{}")'.format(self.system.goal))
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220
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221 def emit_record(self, rule, state_var):
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222 # TODO: check for rules fullfilled (by not using 999999)
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223 self.print(' nts = self.nts({})'.format(rule.nr))
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224 self.print(' kids = self.kids(tree, {})'.format(rule.nr))
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225 self.print(' c = sum(x.state.get_cost(y) for x, y in zip(kids, nts)) + {}'.format(rule.cost))
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226 self.print(' tree.state.set_cost("{}", c, {})'.format(rule.non_term, rule.nr))
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227 for cr in self.system.symbols[rule.non_term].chain_rules:
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228 self.print(' # Chain rule: {}'.format(cr))
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229 self.print(' tree.state.set_cost("{}", c + {}, {})'.format(cr.non_term, cr.cost, cr.nr))
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230
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231 def emit_state(self):
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232 """ Emit a function that assigns a new state to a node """
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233 self.print(' def burm_state(self, tree):')
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234 self.print(' tree.state = State()')
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235 for term in self.system.terminals:
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236 self.emitcase(term)
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237 self.print()
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238
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239 def emitcase(self, term):
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240 rules = [rule for rule in self.system.rules if rule.tree.name == term]
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241 for rule in rules:
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242 condition = self.emittest(rule.tree, 'tree')
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243 self.print(' if {}:'.format(condition))
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244 self.emit_record(rule, 'state')
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245
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246 def compute_kids(self, t, root_name):
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247 """ Compute of a pattern the blanks that must be provided from below in the tree """
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248 if t.name in self.system.non_terminals:
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249 return [root_name], [t.name]
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250 else:
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251 k = []
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252 nts = []
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253 for i, c in enumerate(t.children):
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254 pfx = root_name + '.children[{}]'.format(i)
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255 kf, dummy = self.compute_kids(c, pfx)
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256 nts.extend(dummy)
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257 k.extend(kf)
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258 return k, nts
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259
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260
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261 def emittest(self, tree, prefix):
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262 """ Generate condition for a tree pattern """
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263 ct = (c for c in tree.children if c.name not in self.system.non_terminals)
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264 child_tests = (self.emittest(c, prefix + '.children[{}]'.format(i)) for i, c in enumerate(ct))
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265 child_tests = ('({})'.format(ct) for ct in child_tests)
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266 child_tests = ' and '.join(child_tests)
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267 child_tests = ' and ' + child_tests if child_tests else ''
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268 tst = '{}.name == "{}"'.format(prefix, tree.name)
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269 return tst + child_tests
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318
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270
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271
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321
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272 def make_argument_parser():
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273 """ Constructs an argument parser """
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318
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274 parser = argparse.ArgumentParser(description='pyburg bottom up rewrite system generator compiler compiler')
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275 parser.add_argument('source', type=argparse.FileType('r'), \
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276 help='the parser specification')
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277 parser.add_argument('-o', '--output', type=argparse.FileType('w'), \
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278 default=sys.stdout)
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279 return parser
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280
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281
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282 def main(args):
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283 src = args.source.read()
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284 args.source.close()
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285
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286 # Parse specification into burgsystem:
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287 l = BurgLexer()
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288 p = BurgParser()
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289 l.feed(src)
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290 burg_system = p.parse(l)
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291
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292 # Generate matcher:
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293 generator = BurgGenerator()
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294 generator.generate(burg_system, args.output)
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295
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296
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297 if __name__ == '__main__':
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321
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298 # Parse arguments:
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299 args = make_argument_parser().parse_args()
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300 main(args)
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