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