1 | """
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2 | tdop.py - Library for expression parsing.
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3 | """
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4 |
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5 | from _devbuild.gen.id_kind_asdl import Id, Id_t
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6 | from _devbuild.gen.syntax_asdl import (loc, arith_expr, arith_expr_e,
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7 | arith_expr_t, word_e, word_t,
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8 | CompoundWord, Token)
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9 | from core.error import p_die
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10 | from core import ui
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11 | from mycpp import mylib
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12 | from mycpp.mylib import tagswitch
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13 | from osh import word_
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14 |
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15 | from typing import (Callable, List, Dict, Tuple, Any, cast, TYPE_CHECKING)
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16 |
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17 | if TYPE_CHECKING: # break circular dep
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18 | from osh.word_parse import WordParser
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19 | from core import optview
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20 | LeftFunc = Callable[['TdopParser', word_t, arith_expr_t, int],
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21 | arith_expr_t]
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22 | NullFunc = Callable[['TdopParser', word_t, int], arith_expr_t]
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23 |
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24 |
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25 | def IsIndexable(node):
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26 | # type: (arith_expr_t) -> bool
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27 | """In POSIX shell arith, a[1] is allowed but a[1][1] isn't.
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28 |
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29 | We also allow $a[i] and foo$x[i] (formerly parse_dynamic_arith)
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30 | """
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31 | with tagswitch(node) as case:
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32 | if case(arith_expr_e.VarSub, arith_expr_e.Word):
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33 | return True
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34 | return False
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35 |
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36 |
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37 | def CheckLhsExpr(node, blame_word):
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38 | # type: (arith_expr_t, word_t) -> None
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39 | """Determine if a node is a valid L-value by whitelisting tags.
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40 |
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41 | Valid:
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42 | x = y
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43 | a[1] = y
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44 | Invalid:
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45 | a[0][0] = y
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46 | """
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47 | UP_node = node
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48 | if node.tag() == arith_expr_e.Binary:
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49 | node = cast(arith_expr.Binary, UP_node)
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50 | if node.op.id == Id.Arith_LBracket and IsIndexable(node.left):
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51 | return
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52 | # But a[0][0] = 1 is NOT valid.
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53 |
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54 | if IsIndexable(node):
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55 | return
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56 |
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57 | p_die("Left-hand side of this assignment is invalid", loc.Word(blame_word))
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58 |
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59 |
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60 | #
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61 | # Null Denotation
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62 | #
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63 |
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64 |
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65 | def NullError(p, t, bp):
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66 | # type: (TdopParser, word_t, int) -> arith_expr_t
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67 | # TODO: I need position information
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68 | p_die("Token can't be used in prefix position", loc.Word(t))
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69 | return None # never reached
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70 |
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71 |
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72 | def NullConstant(p, w, bp):
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73 | # type: (TdopParser, word_t, int) -> arith_expr_t
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74 | name_tok = word_.LooksLikeArithVar(w)
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75 | if name_tok:
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76 | return name_tok
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77 |
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78 | # Id.Word_Compound in the spec ensures this cast is valid
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79 | return cast(CompoundWord, w)
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80 |
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81 |
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82 | def NullParen(p, t, bp):
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83 | # type: (TdopParser, word_t, int) -> arith_expr_t
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84 | """Arithmetic grouping."""
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85 | r = p.ParseUntil(bp)
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86 | p.Eat(Id.Arith_RParen)
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87 | return r
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88 |
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89 |
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90 | def NullPrefixOp(p, w, bp):
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91 | # type: (TdopParser, word_t, int) -> arith_expr_t
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92 | """Prefix operator.
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93 |
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94 | Low precedence: return, raise, etc.
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95 | return x+y is return (x+y), not (return x) + y
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96 |
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97 | High precedence: logical negation, bitwise complement, etc.
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98 | !x && y is (!x) && y, not !(x && y)
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99 | """
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100 | right = p.ParseUntil(bp)
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101 | return arith_expr.Unary(word_.ArithId(w), right)
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102 |
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103 |
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104 | #
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105 | # Left Denotation
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106 | #
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107 |
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108 |
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109 | def LeftError(p, t, left, rbp):
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110 | # type: (TdopParser, word_t, arith_expr_t, int) -> arith_expr_t
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111 | # Hm is this not called because of binding power?
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112 | p_die("Token can't be used in infix position", loc.Word(t))
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113 | return None # never reached
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114 |
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115 |
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116 | def LeftBinaryOp(p, w, left, rbp):
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117 | # type: (TdopParser, word_t, arith_expr_t, int) -> arith_expr_t
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118 | """Normal binary operator like 1+2 or 2*3, etc."""
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119 |
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120 | assert w.tag() == word_e.Operator, w
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121 | tok = cast(Token, w)
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122 |
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123 | return arith_expr.Binary(tok, left, p.ParseUntil(rbp))
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124 |
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125 |
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126 | def LeftAssign(p, w, left, rbp):
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127 | # type: (TdopParser, word_t, arith_expr_t, int) -> arith_expr_t
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128 | """Normal binary operator like 1+2 or 2*3, etc."""
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129 | # x += 1, or a[i] += 1
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130 |
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131 | CheckLhsExpr(left, w)
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132 | return arith_expr.BinaryAssign(word_.ArithId(w), left, p.ParseUntil(rbp))
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133 |
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134 |
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135 | #
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136 | # Parser definition
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137 | # TODO: To be consistent, move this to osh/tdop_def.py.
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138 | #
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139 |
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140 | if mylib.PYTHON:
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141 |
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142 | def _ModuleAndFuncName(f):
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143 | # type: (Any) -> Tuple[str, str]
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144 | namespace = f.__module__.split('.')[-1]
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145 | return namespace, f.__name__
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146 |
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147 | def _CppFuncName(f):
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148 | # type: (Any) -> str
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149 | return '%s::%s' % _ModuleAndFuncName(f)
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150 |
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151 | class LeftInfo(object):
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152 | """Row for operator.
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153 |
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154 | In C++ this should be a big array.
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155 | """
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156 |
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157 | def __init__(self, led=None, lbp=0, rbp=0):
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158 | # type: (LeftFunc, int, int) -> None
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159 | self.led = led or LeftError
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160 | self.lbp = lbp
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161 | self.rbp = rbp
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162 |
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163 | def __str__(self):
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164 | # type: () -> str
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165 | """Used by C++ code generation."""
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166 | return '{ %s, %d, %d },' % (_CppFuncName(
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167 | self.led), self.lbp, self.rbp)
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168 |
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169 | def ModuleAndFuncName(self):
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170 | # type: () -> Tuple[str, str]
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171 | """Used by C++ code generation."""
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172 | return _ModuleAndFuncName(self.led)
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173 |
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174 | class NullInfo(object):
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175 | """Row for operator.
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176 |
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177 | In C++ this should be a big array.
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178 | """
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179 |
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180 | def __init__(self, nud=None, bp=0):
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181 | # type: (NullFunc, int) -> None
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182 | self.nud = nud or LeftError
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183 | self.bp = bp
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184 |
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185 | def __str__(self):
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186 | # type: () -> str
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187 | """Used by C++ code generation."""
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188 | return '{ %s, %d },' % (_CppFuncName(self.nud), self.bp)
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189 |
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190 | def ModuleAndFuncName(self):
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191 | # type: () -> Tuple[str, str]
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192 | """Used by C++ code generation."""
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193 | return _ModuleAndFuncName(self.nud)
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194 |
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195 | class ParserSpec(object):
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196 | """Specification for a TDOP parser.
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197 |
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198 | This can be compiled to a table in C++.
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199 | """
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200 |
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201 | def __init__(self):
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202 | # type: () -> None
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203 | self.nud_lookup = {} # type: Dict[Id_t, NullInfo]
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204 | self.led_lookup = {} # type: Dict[Id_t, LeftInfo]
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205 |
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206 | def Null(self, bp, nud, tokens):
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207 | # type: (int, NullFunc, List[Id_t]) -> None
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208 | """Register a token that doesn't take anything on the left.
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209 |
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210 | Examples: constant, prefix operator, error.
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211 | """
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212 | for token in tokens:
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213 | self.nud_lookup[token] = NullInfo(nud=nud, bp=bp)
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214 | if token not in self.led_lookup:
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215 | self.led_lookup[token] = LeftInfo() # error
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216 |
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217 | def _RegisterLed(self, lbp, rbp, led, tokens):
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218 | # type: (int, int, LeftFunc, List[Id_t]) -> None
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219 | for token in tokens:
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220 | if token not in self.nud_lookup:
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221 | self.nud_lookup[token] = NullInfo(NullError)
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222 | self.led_lookup[token] = LeftInfo(lbp=lbp, rbp=rbp, led=led)
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223 |
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224 | def Left(self, bp, led, tokens):
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225 | # type: (int, LeftFunc, List[Id_t]) -> None
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226 | """Register a token that takes an expression on the left."""
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227 | self._RegisterLed(bp, bp, led, tokens)
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228 |
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229 | def LeftRightAssoc(self, bp, led, tokens):
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230 | # type: (int, LeftFunc, List[Id_t]) -> None
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231 | """Register a right associative operator."""
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232 | self._RegisterLed(bp, bp - 1, led, tokens)
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233 |
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234 | def LookupNud(self, token):
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235 | # type: (Id_t) -> NullInfo
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236 |
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237 | # As long as the table is complete, this shouldn't fail
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238 | return self.nud_lookup[token]
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239 |
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240 | def LookupLed(self, token):
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241 | # type: (Id_t) -> LeftInfo
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242 | """Get a left_info for the token."""
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243 |
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244 | # As long as the table is complete, this shouldn't fail
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245 | return self.led_lookup[token]
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246 |
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247 |
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248 | class TdopParser(object):
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249 |
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250 | def __init__(self, spec, w_parser, parse_opts):
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251 | # type: (ParserSpec, WordParser, optview.Parse) -> None
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252 | self.spec = spec
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253 | self.w_parser = w_parser
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254 | self.parse_opts = parse_opts
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255 |
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256 | # NOTE: Next() overwrites this state, so we don't need a Reset() method in
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257 | # between reuses of this TdopParser instance.
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258 | self.cur_word = None # type: word_t # current token
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259 | self.op_id = Id.Undefined_Tok
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260 |
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261 | def CurrentId(self):
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262 | # type: () -> Id_t
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263 | """Glue used by the WordParser to check for extra tokens."""
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264 | return word_.ArithId(self.cur_word)
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265 |
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266 | def AtToken(self, token_type):
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267 | # type: (Id_t) -> bool
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268 | return self.op_id == token_type
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269 |
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270 | def Eat(self, token_type):
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271 | # type: (Id_t) -> None
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272 | """Assert that we're at the current token and advance."""
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273 | if not self.AtToken(token_type):
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274 | p_die(
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275 | 'Parser expected %s, got %s' %
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276 | (ui.PrettyId(token_type), ui.PrettyId(self.op_id)),
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277 | loc.Word(self.cur_word))
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278 | self.Next()
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279 |
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280 | def Next(self):
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281 | # type: () -> bool
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282 | self.cur_word = self.w_parser.ReadArithWord()
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283 | self.op_id = word_.ArithId(self.cur_word)
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284 | return True
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285 |
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286 | def ParseUntil(self, rbp):
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287 | # type: (int) -> arith_expr_t
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288 | """Parse to the right, eating tokens until we encounter a token with
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289 | binding power LESS THAN OR EQUAL TO rbp."""
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290 | # TODO: use Kind.Eof
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291 | if self.op_id in (Id.Eof_Real, Id.Eof_RParen, Id.Eof_Backtick):
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292 | p_die('Unexpected end of input', loc.Word(self.cur_word))
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293 |
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294 | t = self.cur_word
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295 | null_info = self.spec.LookupNud(self.op_id)
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296 |
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297 | self.Next() # skip over the token, e.g. ! ~ + -
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298 | node = null_info.nud(self, t, null_info.bp)
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299 |
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300 | while True:
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301 | t = self.cur_word
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302 | left_info = self.spec.LookupLed(self.op_id)
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303 |
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304 | # Examples:
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305 | # If we see 1*2+ , rbp = 27 and lbp = 25, so stop.
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306 | # If we see 1+2+ , rbp = 25 and lbp = 25, so stop.
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307 | # If we see 1**2**, rbp = 26 and lbp = 27, so keep going.
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308 | if rbp >= left_info.lbp:
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309 | break
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310 | self.Next() # skip over the token, e.g. / *
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311 |
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312 | node = left_info.led(self, t, node, left_info.rbp)
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313 |
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314 | return node
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315 |
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316 | def Parse(self):
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317 | # type: () -> arith_expr_t
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318 |
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319 | self.Next() # may raise ParseError
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320 |
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321 | if not self.parse_opts.parse_sh_arith():
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322 | # Affects:
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323 | # echo $(( x ))
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324 | # ${a[i]} which should be $[a[i]] -- could have better error
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325 | #
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326 | # Note: sh_expr_eval.UnsafeArith has a dynamic e_die() check
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327 | #
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328 | # Doesn't affect:
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329 | # printf -v x # unsafe_arith.ParseLValue
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330 | # unset x # unsafe_arith.ParseLValue
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331 | # ${!ref} # unsafe_arith.ParseVarRef
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332 | # declare -n # not fully implemented yet
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333 | #
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334 | # a[i+1]= # parse_sh_assign
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335 | #
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336 | # (( a = 1 )) # parse_dparen
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337 | # for (( i = 0; ... # parse_dparen
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338 |
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339 | p_die("POSIX shell arithmetic isn't allowed (parse_sh_arith)",
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340 | loc.Word(self.cur_word))
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341 |
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342 | return self.ParseUntil(0)
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