OILS
/
osh
/
tdop.py
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"""
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tdop.py - Library for expression parsing.
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"""
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from _devbuild.gen.id_kind_asdl import Id, Id_t
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from _devbuild.gen.syntax_asdl import (loc, arith_expr, arith_expr_e,
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arith_expr_t, word_t, CompoundWord,
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SimpleVarSub)
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from _devbuild.gen.types_asdl import lex_mode_e
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from core.error import p_die
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from core import ui
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from frontend import lexer
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from mycpp import mylib
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from mycpp.mylib import tagswitch
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from osh import word_
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from typing import (Callable, List, Dict, Tuple, Any, cast, TYPE_CHECKING)
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if TYPE_CHECKING: # break circular dep
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from osh.word_parse import WordParser
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from core import optview
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LeftFunc = Callable[['TdopParser', word_t, arith_expr_t, int], arith_expr_t]
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NullFunc = Callable[['TdopParser', word_t, int], arith_expr_t]
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def IsIndexable(node):
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# type: (arith_expr_t) -> bool
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"""In POSIX shell arith, a[1] is allowed but a[1][1] isn't.
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We also allow $a[i] and foo$x[i] (formerly parse_dynamic_arith)
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"""
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with tagswitch(node) as case:
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if case(arith_expr_e.VarSub, arith_expr_e.Word):
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return True
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return False
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def CheckLhsExpr(node, blame_word):
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# type: (arith_expr_t, word_t) -> None
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"""Determine if a node is a valid L-value by whitelisting tags.
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Valid:
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x = y
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a[1] = y
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Invalid:
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a[0][0] = y
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"""
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UP_node = node
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if node.tag() == arith_expr_e.Binary:
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node = cast(arith_expr.Binary, UP_node)
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if node.op_id == Id.Arith_LBracket and IsIndexable(node.left):
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return
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# But a[0][0] = 1 is NOT valid.
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if IsIndexable(node):
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return
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p_die("Left-hand side of this assignment is invalid", loc.Word(blame_word))
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#
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# Null Denotation
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#
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def NullError(p, t, bp):
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# type: (TdopParser, word_t, int) -> arith_expr_t
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# TODO: I need position information
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p_die("Token can't be used in prefix position", loc.Word(t))
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return None # never reached
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def NullConstant(p, w, bp):
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# type: (TdopParser, word_t, int) -> arith_expr_t
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name_tok = word_.LooksLikeArithVar(w)
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if name_tok:
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return SimpleVarSub(name_tok, lexer.TokenVal(name_tok))
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# Id.Word_Compound in the spec ensures this cast is valid
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return cast(CompoundWord, w)
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def NullParen(p, t, bp):
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# type: (TdopParser, word_t, int) -> arith_expr_t
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"""Arithmetic grouping."""
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r = p.ParseUntil(bp)
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p.Eat(Id.Arith_RParen)
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return r
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def NullPrefixOp(p, w, bp):
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# type: (TdopParser, word_t, int) -> arith_expr_t
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"""Prefix operator.
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Low precedence: return, raise, etc.
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return x+y is return (x+y), not (return x) + y
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High precedence: logical negation, bitwise complement, etc.
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!x && y is (!x) && y, not !(x && y)
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"""
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right = p.ParseUntil(bp)
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return arith_expr.Unary(word_.ArithId(w), right)
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#
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# Left Denotation
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#
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def LeftError(p, t, left, rbp):
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# type: (TdopParser, word_t, arith_expr_t, int) -> arith_expr_t
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# Hm is this not called because of binding power?
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p_die("Token can't be used in infix position", loc.Word(t))
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return None # never reached
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def LeftBinaryOp(p, w, left, rbp):
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# type: (TdopParser, word_t, arith_expr_t, int) -> arith_expr_t
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"""Normal binary operator like 1+2 or 2*3, etc."""
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# TODO: w should be a Token, and we should extract the token from it.
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return arith_expr.Binary(word_.ArithId(w), left, p.ParseUntil(rbp))
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def LeftAssign(p, w, left, rbp):
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# type: (TdopParser, word_t, arith_expr_t, int) -> arith_expr_t
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"""Normal binary operator like 1+2 or 2*3, etc."""
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# x += 1, or a[i] += 1
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CheckLhsExpr(left, w)
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return arith_expr.BinaryAssign(word_.ArithId(w), left, p.ParseUntil(rbp))
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#
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# Parser definition
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# TODO: To be consistent, move this to osh/tdop_def.py.
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#
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if mylib.PYTHON:
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def _ModuleAndFuncName(f):
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# type: (Any) -> Tuple[str, str]
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namespace = f.__module__.split('.')[-1]
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return namespace, f.__name__
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def _CppFuncName(f):
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# type: (Any) -> str
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return '%s::%s' % _ModuleAndFuncName(f)
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class LeftInfo(object):
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"""Row for operator.
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In C++ this should be a big array.
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"""
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def __init__(self, led=None, lbp=0, rbp=0):
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# type: (LeftFunc, int, int) -> None
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self.led = led or LeftError
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self.lbp = lbp
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self.rbp = rbp
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def __str__(self):
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# type: () -> str
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"""Used by C++ code generation."""
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return '{ %s, %d, %d },' % (_CppFuncName(
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self.led), self.lbp, self.rbp)
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def ModuleAndFuncName(self):
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# type: () -> Tuple[str, str]
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"""Used by C++ code generation."""
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return _ModuleAndFuncName(self.led)
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class NullInfo(object):
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"""Row for operator.
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In C++ this should be a big array.
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"""
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def __init__(self, nud=None, bp=0):
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# type: (NullFunc, int) -> None
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self.nud = nud or LeftError
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self.bp = bp
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def __str__(self):
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# type: () -> str
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"""Used by C++ code generation."""
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return '{ %s, %d },' % (_CppFuncName(self.nud), self.bp)
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def ModuleAndFuncName(self):
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# type: () -> Tuple[str, str]
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"""Used by C++ code generation."""
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return _ModuleAndFuncName(self.nud)
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class ParserSpec(object):
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"""Specification for a TDOP parser.
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This can be compiled to a table in C++.
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"""
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def __init__(self):
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# type: () -> None
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self.nud_lookup = {} # type: Dict[Id_t, NullInfo]
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self.led_lookup = {} # type: Dict[Id_t, LeftInfo]
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def Null(self, bp, nud, tokens):
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# type: (int, NullFunc, List[Id_t]) -> None
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"""Register a token that doesn't take anything on the left.
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Examples: constant, prefix operator, error.
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"""
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for token in tokens:
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self.nud_lookup[token] = NullInfo(nud=nud, bp=bp)
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if token not in self.led_lookup:
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self.led_lookup[token] = LeftInfo() # error
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def _RegisterLed(self, lbp, rbp, led, tokens):
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# type: (int, int, LeftFunc, List[Id_t]) -> None
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for token in tokens:
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if token not in self.nud_lookup:
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self.nud_lookup[token] = NullInfo(NullError)
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self.led_lookup[token] = LeftInfo(lbp=lbp, rbp=rbp, led=led)
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def Left(self, bp, led, tokens):
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# type: (int, LeftFunc, List[Id_t]) -> None
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"""Register a token that takes an expression on the left."""
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self._RegisterLed(bp, bp, led, tokens)
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def LeftRightAssoc(self, bp, led, tokens):
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# type: (int, LeftFunc, List[Id_t]) -> None
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"""Register a right associative operator."""
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self._RegisterLed(bp, bp - 1, led, tokens)
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def LookupNud(self, token):
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# type: (Id_t) -> NullInfo
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# As long as the table is complete, this shouldn't fail
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return self.nud_lookup[token]
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def LookupLed(self, token):
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# type: (Id_t) -> LeftInfo
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"""Get a left_info for the token."""
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# As long as the table is complete, this shouldn't fail
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return self.led_lookup[token]
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class TdopParser(object):
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def __init__(self, spec, w_parser, parse_opts):
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# type: (ParserSpec, WordParser, optview.Parse) -> None
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self.spec = spec
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self.w_parser = w_parser
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self.parse_opts = parse_opts
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# NOTE: Next() overwrites this state, so we don't need a Reset() method in
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# between reuses of this TdopParser instance.
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self.cur_word = None # type: word_t # current token
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self.op_id = Id.Undefined_Tok
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def CurrentId(self):
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# type: () -> Id_t
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"""Glue used by the WordParser to check for extra tokens."""
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return word_.CommandId(self.cur_word)
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def AtToken(self, token_type):
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# type: (Id_t) -> bool
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return self.op_id == token_type
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def Eat(self, token_type):
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# type: (Id_t) -> None
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"""Assert that we're at the current token and advance."""
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if not self.AtToken(token_type):
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p_die(
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'Parser expected %s, got %s' %
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(ui.PrettyId(token_type), ui.PrettyId(self.op_id)),
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loc.Word(self.cur_word))
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self.Next()
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def Next(self):
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# type: () -> bool
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self.cur_word = self.w_parser.ReadWord(lex_mode_e.Arith)
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self.op_id = word_.ArithId(self.cur_word)
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return True
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def ParseUntil(self, rbp):
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# type: (int) -> arith_expr_t
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"""Parse to the right, eating tokens until we encounter a token with
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binding power LESS THAN OR EQUAL TO rbp."""
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# TODO: use Kind.Eof
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if self.op_id in (Id.Eof_Real, Id.Eof_RParen, Id.Eof_Backtick):
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p_die('Unexpected end of input', loc.Word(self.cur_word))
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t = self.cur_word
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null_info = self.spec.LookupNud(self.op_id)
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self.Next() # skip over the token, e.g. ! ~ + -
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node = null_info.nud(self, t, null_info.bp)
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while True:
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t = self.cur_word
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left_info = self.spec.LookupLed(self.op_id)
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# Examples:
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# If we see 1*2+ , rbp = 27 and lbp = 25, so stop.
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# If we see 1+2+ , rbp = 25 and lbp = 25, so stop.
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# If we see 1**2**, rbp = 26 and lbp = 27, so keep going.
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if rbp >= left_info.lbp:
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break
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self.Next() # skip over the token, e.g. / *
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node = left_info.led(self, t, node, left_info.rbp)
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return node
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def Parse(self):
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# type: () -> arith_expr_t
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self.Next() # may raise ParseError
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if not self.parse_opts.parse_sh_arith():
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# Affects:
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# echo $(( x ))
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# ${a[i]} which should be $[a[i]] -- could have better error
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#
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# Note: sh_expr_eval.UnsafeArith has a dynamic e_die() check
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#
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# Doesn't affect:
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# printf -v x # unsafe_arith.ParseLValue
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# unset x # unsafe_arith.ParseLValue
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# ${!ref} # unsafe_arith.ParseVarRef
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# declare -n # not fully implemented yet
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#
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# a[i+1]= # parse_sh_assign
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#
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# (( a = 1 )) # parse_dparen
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# for (( i = 0; ... # parse_dparen
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p_die("POSIX shell arithmetic isn't allowed (parse_sh_arith)",
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loc.Word(self.cur_word))
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return self.ParseUntil(0)
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