BaseTools/Source/Python/Common/Expression.py

   1 ## @file
   2 # This file is used to parse and evaluate expression in directive or PCD value.
   3 #
   4 # Copyright (c) 2011 - 2016, Intel Corporation. All rights reserved.<BR>
   5 # This program and the accompanying materials
   6 # are licensed and made available under the terms and conditions of the BSD License
   7 # which accompanies this distribution.    The full text of the license may be found at
   8 # http://opensource.org/licenses/bsd-license.php
   9 #
  10 # THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11 # WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 ## Import Modules
  14 #
  15 from Common.GlobalData import *
  16 from CommonDataClass.Exceptions import BadExpression
  17 from CommonDataClass.Exceptions import WrnExpression
  18 from Misc import GuidStringToGuidStructureString
  19
  20 ERR_STRING_EXPR         = 'This operator cannot be used in string expression: [%s].'
  21 ERR_SNYTAX              = 'Syntax error, the rest of expression cannot be evaluated: [%s].'
  22 ERR_MATCH               = 'No matching right parenthesis.'
  23 ERR_STRING_TOKEN        = 'Bad string token: [%s].'
  24 ERR_MACRO_TOKEN         = 'Bad macro token: [%s].'
  25 ERR_EMPTY_TOKEN         = 'Empty token is not allowed.'
  26 ERR_PCD_RESOLVE         = 'PCD token cannot be resolved: [%s].'
  27 ERR_VALID_TOKEN         = 'No more valid token found from rest of string: [%s].'
  28 ERR_EXPR_TYPE           = 'Different types found in expression.'
  29 ERR_OPERATOR_UNSUPPORT  = 'Unsupported operator: [%s]'
  30 ERR_REL_NOT_IN          = 'Expect "IN" after "not" operator.'
  31 WRN_BOOL_EXPR           = 'Operand of boolean type cannot be used in arithmetic expression.'
  32 WRN_EQCMP_STR_OTHERS    = '== Comparison between Operand of string type and Boolean/Number Type always return False.'
  33 WRN_NECMP_STR_OTHERS    = '!= Comparison between Operand of string type and Boolean/Number Type always return True.'
  34 ERR_RELCMP_STR_OTHERS   = 'Operator taking Operand of string type and Boolean/Number Type is not allowed: [%s].'
  35 ERR_STRING_CMP          = 'Unicode string and general string cannot be compared: [%s %s %s]'
  36 ERR_ARRAY_TOKEN         = 'Bad C array or C format GUID token: [%s].'
  37 ERR_ARRAY_ELE           = 'This must be HEX value for NList or Array: [%s].'
  38 ERR_EMPTY_EXPR          = 'Empty expression is not allowed.'
  39 ERR_IN_OPERAND          = 'Macro after IN operator can only be: $(FAMILY), $(ARCH), $(TOOL_CHAIN_TAG) and $(TARGET).'
  40
  41 ## SplitString
  42 #  Split string to list according double quote
  43 #  For example: abc"de\"f"ghi"jkl"mn will be: ['abc', '"de\"f"', 'ghi', '"jkl"', 'mn']
  44 #
  45 def SplitString(String):
  46     # There might be escaped quote: "abc\"def\\\"ghi"
  47     Str = String.replace('\\\\', '//').replace('\\\"', '\\\'')
  48     RetList = []
  49     InQuote = False
  50     Item = ''
  51     for i, ch in enumerate(Str):
  52         if ch == '"':
  53             InQuote = not InQuote
  54             if not InQuote:
  55                 Item += String[i]
  56                 RetList.append(Item)
  57                 Item = ''
  58                 continue
  59             if Item:
  60                 RetList.append(Item)
  61                 Item = ''
  62         Item += String[i]
  63     if InQuote:
  64         raise BadExpression(ERR_STRING_TOKEN % Item)
  65     if Item:
  66         RetList.append(Item)
  67     return RetList
  68
  69 ## ReplaceExprMacro
  70 #
  71 def ReplaceExprMacro(String, Macros, ExceptionList = None):
  72     StrList = SplitString(String)
  73     for i, String in enumerate(StrList):
  74         InQuote = False
  75         if String.startswith('"'):
  76             InQuote = True
  77         MacroStartPos = String.find('$(')
  78         if MacroStartPos < 0:
  79             for Pcd in gPlatformPcds.keys():
  80                 if Pcd in String:
  81                     if Pcd not in gConditionalPcds:
  82                         gConditionalPcds.append(Pcd)
  83             continue
  84         RetStr = ''
  85         while MacroStartPos >= 0:
  86             RetStr = String[0:MacroStartPos]
  87             MacroEndPos = String.find(')', MacroStartPos)
  88             if MacroEndPos < 0:
  89                 raise BadExpression(ERR_MACRO_TOKEN % String[MacroStartPos:])
  90             Macro = String[MacroStartPos+2:MacroEndPos]
  91             if Macro not in Macros:
  92                 # From C reference manual:
  93                 # If an undefined macro name appears in the constant-expression of
  94                 # !if or !elif, it is replaced by the integer constant 0.
  95                 RetStr += '0'
  96             elif not InQuote:
  97                 Tklst = RetStr.split()
  98                 if Tklst and Tklst[-1] in ['IN', 'in'] and ExceptionList and Macro not in ExceptionList:
  99                     raise BadExpression(ERR_IN_OPERAND)
 100                 # Make sure the macro in exception list is encapsulated by double quote
 101                 # For example: DEFINE ARCH = IA32 X64
 102                 # $(ARCH) is replaced with "IA32 X64"
 103                 if ExceptionList and Macro in ExceptionList:
 104                     RetStr += '"' + Macros[Macro] + '"'
 105                 elif Macros[Macro].strip():
 106                     RetStr += Macros[Macro]
 107                 else:
 108                     RetStr += '""'
 109             else:
 110                 RetStr += Macros[Macro]
 111             RetStr += String[MacroEndPos+1:]
 112             String = RetStr
 113             MacroStartPos = String.find('$(')
 114         StrList[i] = RetStr
 115     return ''.join(StrList)
 116
 117 SupportedInMacroList = ['TARGET', 'TOOL_CHAIN_TAG', 'ARCH', 'FAMILY']
 118
 119 class ValueExpression(object):
 120     # Logical operator mapping
 121     LogicalOperators = {
 122         '&&' : 'and', '||' : 'or',
 123         '!'  : 'not', 'AND': 'and',
 124         'OR' : 'or' , 'NOT': 'not',
 125         'XOR': '^'  , 'xor': '^',
 126         'EQ' : '==' , 'NE' : '!=',
 127         'GT' : '>'  , 'LT' : '<',
 128         'GE' : '>=' , 'LE' : '<=',
 129         'IN' : 'in'
 130     }
 131
 132     NonLetterOpLst = ['+', '-', '&', '|', '^', '!', '=', '>', '<']
 133
 134     PcdPattern = re.compile(r'[_a-zA-Z][0-9A-Za-z_]*\.[_a-zA-Z][0-9A-Za-z_]*$')
 135     HexPattern = re.compile(r'0[xX][0-9a-fA-F]+$')
 136     RegGuidPattern = re.compile(r'[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}')
 137
 138     SymbolPattern = re.compile("("
 139                                  "\$\([A-Z][A-Z0-9_]*\)|\$\(\w+\.\w+\)|\w+\.\w+|"
 140                                  "&&|\|\||!(?!=)|"
 141                                  "(?<=\W)AND(?=\W)|(?<=\W)OR(?=\W)|(?<=\W)NOT(?=\W)|(?<=\W)XOR(?=\W)|"
 142                                  "(?<=\W)EQ(?=\W)|(?<=\W)NE(?=\W)|(?<=\W)GT(?=\W)|(?<=\W)LT(?=\W)|(?<=\W)GE(?=\W)|(?<=\W)LE(?=\W)"
 143                                ")")
 144
 145     @staticmethod
 146     def Eval(Operator, Oprand1, Oprand2 = None):
 147         WrnExp = None
 148
 149         if Operator not in ["==", "!=", ">=", "<=", ">", "<", "in", "not in"] and \
 150             (type(Oprand1) == type('') or type(Oprand2) == type('')):
 151             raise BadExpression(ERR_STRING_EXPR % Operator)
 152
 153         TypeDict = {
 154             type(0)  : 0,
 155             type(0L) : 0,
 156             type('') : 1,
 157             type(True) : 2
 158         }
 159
 160         EvalStr = ''
 161         if Operator in ["!", "NOT", "not"]:
 162             if type(Oprand1) == type(''):
 163                 raise BadExpression(ERR_STRING_EXPR % Operator)
 164             EvalStr = 'not Oprand1'
 165         else:
 166             if Operator in ["+", "-"] and (type(True) in [type(Oprand1), type(Oprand2)]):
 167                 # Boolean in '+'/'-' will be evaluated but raise warning
 168                 WrnExp = WrnExpression(WRN_BOOL_EXPR)
 169             elif type('') in [type(Oprand1), type(Oprand2)] and type(Oprand1)!= type(Oprand2):
 170                 # == between string and number/boolean will always return False, != return True
 171                 if Operator == "==":
 172                     WrnExp = WrnExpression(WRN_EQCMP_STR_OTHERS)
 173                     WrnExp.result = False
 174                     raise WrnExp
 175                 elif Operator == "!=":
 176                     WrnExp = WrnExpression(WRN_NECMP_STR_OTHERS)
 177                     WrnExp.result = True
 178                     raise WrnExp
 179                 else:
 180                     raise BadExpression(ERR_RELCMP_STR_OTHERS % Operator)
 181             elif TypeDict[type(Oprand1)] != TypeDict[type(Oprand2)]:
 182                 if Operator in ["==", "!=", ">=", "<=", ">", "<"] and set((TypeDict[type(Oprand1)], TypeDict[type(Oprand2)])) == set((TypeDict[type(True)], TypeDict[type(0)])):
 183                     # comparison between number and boolean is allowed
 184                     pass
 185                 elif Operator in ['&', '|', '^', "and", "or"] and set((TypeDict[type(Oprand1)], TypeDict[type(Oprand2)])) == set((TypeDict[type(True)], TypeDict[type(0)])):
 186                     # bitwise and logical operation between number and boolean is allowed
 187                     pass
 188                 else:
 189                     raise BadExpression(ERR_EXPR_TYPE)
 190             if type(Oprand1) == type('') and type(Oprand2) == type(''):
 191                 if (Oprand1.startswith('L"') and not Oprand2.startswith('L"')) or \
 192                     (not Oprand1.startswith('L"') and Oprand2.startswith('L"')):
 193                     raise BadExpression(ERR_STRING_CMP % (Oprand1, Operator, Oprand2))
 194             if 'in' in Operator and type(Oprand2) == type(''):
 195                 Oprand2 = Oprand2.split()
 196             EvalStr = 'Oprand1 ' + Operator + ' Oprand2'
 197
 198         # Local symbols used by built in eval function
 199         Dict = {
 200             'Oprand1' : Oprand1,
 201             'Oprand2' : Oprand2
 202         }
 203         try:
 204             Val = eval(EvalStr, {}, Dict)
 205         except Exception, Excpt:
 206             raise BadExpression(str(Excpt))
 207
 208         if Operator in ['and', 'or']:
 209             if Val:
 210                 Val = True
 211             else:
 212                 Val = False
 213
 214         if WrnExp:
 215             WrnExp.result = Val
 216             raise WrnExp
 217         return Val
 218
 219     def __init__(self, Expression, SymbolTable={}):
 220         self._NoProcess = False
 221         if type(Expression) != type(''):
 222             self._Expr = Expression
 223             self._NoProcess = True
 224             return
 225
 226         self._Expr = ReplaceExprMacro(Expression.strip(),
 227                                   SymbolTable,
 228                                   SupportedInMacroList)
 229
 230         if not self._Expr.strip():
 231             raise BadExpression(ERR_EMPTY_EXPR)
 232
 233         #
 234         # The symbol table including PCD and macro mapping
 235         #
 236         self._Symb = SymbolTable
 237         self._Symb.update(self.LogicalOperators)
 238         self._Idx = 0
 239         self._Len = len(self._Expr)
 240         self._Token = ''
 241         self._WarnExcept = None
 242
 243         # Literal token without any conversion
 244         self._LiteralToken = ''
 245
 246     # Public entry for this class
 247     #   @param RealValue: False: only evaluate if the expression is true or false, used for conditional expression
 248     #                     True : return the evaluated str(value), used for PCD value
 249     #
 250     #   @return: True or False if RealValue is False
 251     #            Evaluated value of string format if RealValue is True
 252     #
 253     def __call__(self, RealValue=False, Depth=0):
 254         if self._NoProcess:
 255             return self._Expr
 256
 257         self._Depth = Depth
 258
 259         self._Expr = self._Expr.strip()
 260         if RealValue and Depth == 0:
 261             self._Token = self._Expr
 262             if self.__IsNumberToken():
 263                 return self._Expr
 264
 265             try:
 266                 Token = self._GetToken()
 267                 if type(Token) == type('') and Token.startswith('{') and Token.endswith('}') and self._Idx >= self._Len:
 268                     return self._Expr
 269             except BadExpression:
 270                 pass
 271
 272             self._Idx = 0
 273             self._Token = ''
 274
 275         Val = self._OrExpr()
 276         RealVal = Val
 277         if type(Val) == type(''):
 278             if Val == 'L""':
 279                 Val = False
 280             elif not Val:
 281                 Val = False
 282                 RealVal = '""'
 283             elif not Val.startswith('L"') and not Val.startswith('{'):
 284                 Val = True
 285                 RealVal = '"' + RealVal + '"'
 286
 287         # The expression has been parsed, but the end of expression is not reached
 288         # It means the rest does not comply EBNF of <Expression>
 289         if self._Idx != self._Len:
 290             raise BadExpression(ERR_SNYTAX % self._Expr[self._Idx:])
 291
 292         if RealValue:
 293             RetVal = str(RealVal)
 294         elif Val:
 295             RetVal = True
 296         else:
 297             RetVal = False
 298
 299         if self._WarnExcept:
 300             self._WarnExcept.result = RetVal
 301             raise self._WarnExcept
 302         else:
 303             return RetVal
 304
 305     # Template function to parse binary operators which have same precedence
 306     # Expr [Operator Expr]*
 307     def _ExprFuncTemplate(self, EvalFunc, OpLst):
 308         Val = EvalFunc()
 309         while self._IsOperator(OpLst):
 310             Op = self._Token
 311             try:
 312                 Val = self.Eval(Op, Val, EvalFunc())
 313             except WrnExpression, Warn:
 314                 self._WarnExcept = Warn
 315                 Val = Warn.result
 316         return Val
 317
 318     # A [|| B]*
 319     def _OrExpr(self):
 320         return self._ExprFuncTemplate(self._AndExpr, ["OR", "or", "||"])
 321
 322     # A [&& B]*
 323     def _AndExpr(self):
 324         return self._ExprFuncTemplate(self._BitOr, ["AND", "and", "&&"])
 325
 326     # A [ | B]*
 327     def _BitOr(self):
 328         return self._ExprFuncTemplate(self._BitXor, ["|"])
 329
 330     # A [ ^ B]*
 331     def _BitXor(self):
 332         return self._ExprFuncTemplate(self._BitAnd, ["XOR", "xor", "^"])
 333
 334     # A [ & B]*
 335     def _BitAnd(self):
 336         return self._ExprFuncTemplate(self._EqExpr, ["&"])
 337
 338     # A [ == B]*
 339     def _EqExpr(self):
 340         Val = self._RelExpr()
 341         while self._IsOperator(["==", "!=", "EQ", "NE", "IN", "in", "!", "NOT", "not"]):
 342             Op = self._Token
 343             if Op in ["!", "NOT", "not"]:
 344                 if not self._IsOperator(["IN", "in"]):
 345                     raise BadExpression(ERR_REL_NOT_IN)
 346                 Op += ' ' + self._Token
 347             try:
 348                 Val = self.Eval(Op, Val, self._RelExpr())
 349             except WrnExpression, Warn:
 350                 self._WarnExcept = Warn
 351                 Val = Warn.result
 352         return Val
 353
 354     # A [ > B]*
 355     def _RelExpr(self):
 356         return self._ExprFuncTemplate(self._AddExpr, ["<=", ">=", "<", ">", "LE", "GE", "LT", "GT"])
 357
 358     # A [ + B]*
 359     def _AddExpr(self):
 360         return self._ExprFuncTemplate(self._UnaryExpr, ["+", "-"])
 361
 362     # [!]*A
 363     def _UnaryExpr(self):
 364         if self._IsOperator(["!", "NOT", "not"]):
 365             Val = self._UnaryExpr()
 366             try:
 367                 return self.Eval('not', Val)
 368             except WrnExpression, Warn:
 369                 self._WarnExcept = Warn
 370                 return Warn.result
 371         return self._IdenExpr()
 372
 373     # Parse identifier or encapsulated expression
 374     def _IdenExpr(self):
 375         Tk = self._GetToken()
 376         if Tk == '(':
 377             Val = self._OrExpr()
 378             try:
 379                 # _GetToken may also raise BadExpression
 380                 if self._GetToken() != ')':
 381                     raise BadExpression(ERR_MATCH)
 382             except BadExpression:
 383                 raise BadExpression(ERR_MATCH)
 384             return Val
 385         return Tk
 386
 387     # Skip whitespace or tab
 388     def __SkipWS(self):
 389         for Char in self._Expr[self._Idx:]:
 390             if Char not in ' \t':
 391                 break
 392             self._Idx += 1
 393
 394     # Try to convert string to number
 395     def __IsNumberToken(self):
 396         Radix = 10
 397         if self._Token.lower()[0:2] == '0x' and len(self._Token) > 2:
 398             Radix = 16
 399         try:
 400             self._Token = int(self._Token, Radix)
 401             return True
 402         except ValueError:
 403             return False
 404         except TypeError:
 405             return False
 406
 407     # Parse array: {...}
 408     def __GetArray(self):
 409         Token = '{'
 410         self._Idx += 1
 411         self.__GetNList(True)
 412         Token += self._LiteralToken
 413         if self._Idx >= self._Len or self._Expr[self._Idx] != '}':
 414             raise BadExpression(ERR_ARRAY_TOKEN % Token)
 415         Token += '}'
 416
 417         # All whitespace and tabs in array are already stripped.
 418         IsArray = IsGuid = False
 419         if len(Token.split(',')) == 11 and len(Token.split(',{')) == 2 \
 420             and len(Token.split('},')) == 1:
 421             HexLen = [11,6,6,5,4,4,4,4,4,4,6]
 422             HexList= Token.split(',')
 423             if HexList[3].startswith('{') and \
 424                 not [Index for Index, Hex in enumerate(HexList) if len(Hex) > HexLen[Index]]:
 425                 IsGuid = True
 426         if Token.lstrip('{').rstrip('}').find('{') == -1:
 427             if not [Hex for Hex in Token.lstrip('{').rstrip('}').split(',') if len(Hex) > 4]:
 428                 IsArray = True
 429         if not IsArray and not IsGuid:
 430             raise BadExpression(ERR_ARRAY_TOKEN % Token)
 431         self._Idx += 1
 432         self._Token = self._LiteralToken = Token
 433         return self._Token
 434
 435     # Parse string, the format must be: "..."
 436     def __GetString(self):
 437         Idx = self._Idx
 438
 439         # Skip left quote
 440         self._Idx += 1
 441
 442         # Replace escape \\\", \"
 443         Expr = self._Expr[self._Idx:].replace('\\\\', '//').replace('\\\"', '\\\'')
 444         for Ch in Expr:
 445             self._Idx += 1
 446             if Ch == '"':
 447                 break
 448         self._Token = self._LiteralToken = self._Expr[Idx:self._Idx]
 449         if not self._Token.endswith('"'):
 450             raise BadExpression(ERR_STRING_TOKEN % self._Token)
 451         self._Token = self._Token[1:-1]
 452         return self._Token
 453
 454     # Get token that is comprised by alphanumeric, underscore or dot(used by PCD)
 455     # @param IsAlphaOp: Indicate if parsing general token or script operator(EQ, NE...)
 456     def __GetIdToken(self, IsAlphaOp = False):
 457         IdToken = ''
 458         for Ch in self._Expr[self._Idx:]:
 459             if not self.__IsIdChar(Ch):
 460                 break
 461             self._Idx += 1
 462             IdToken += Ch
 463
 464         self._Token = self._LiteralToken = IdToken
 465         if not IsAlphaOp:
 466             self.__ResolveToken()
 467         return self._Token
 468
 469     # Try to resolve token
 470     def __ResolveToken(self):
 471         if not self._Token:
 472             raise BadExpression(ERR_EMPTY_TOKEN)
 473
 474         # PCD token
 475         if self.PcdPattern.match(self._Token):
 476             if self._Token not in self._Symb:
 477                 Ex = BadExpression(ERR_PCD_RESOLVE % self._Token)
 478                 Ex.Pcd = self._Token
 479                 raise Ex
 480             self._Token = ValueExpression(self._Symb[self._Token], self._Symb)(True, self._Depth+1)
 481             if type(self._Token) != type(''):
 482                 self._LiteralToken = hex(self._Token)
 483                 return
 484
 485         if self._Token.startswith('"'):
 486             self._Token = self._Token[1:-1]
 487         elif self._Token in ["FALSE", "false", "False"]:
 488             self._Token = False
 489         elif self._Token in ["TRUE", "true", "True"]:
 490             self._Token = True
 491         else:
 492             self.__IsNumberToken()
 493
 494     def __GetNList(self, InArray=False):
 495         self._GetSingleToken()
 496         if not self.__IsHexLiteral():
 497             if InArray:
 498                 raise BadExpression(ERR_ARRAY_ELE % self._Token)
 499             return self._Token
 500
 501         self.__SkipWS()
 502         Expr = self._Expr[self._Idx:]
 503         if not Expr.startswith(','):
 504             return self._Token
 505
 506         NList = self._LiteralToken
 507         while Expr.startswith(','):
 508             NList += ','
 509             self._Idx += 1
 510             self.__SkipWS()
 511             self._GetSingleToken()
 512             if not self.__IsHexLiteral():
 513                 raise BadExpression(ERR_ARRAY_ELE % self._Token)
 514             NList += self._LiteralToken
 515             self.__SkipWS()
 516             Expr = self._Expr[self._Idx:]
 517         self._Token = self._LiteralToken = NList
 518         return self._Token
 519
 520     def __IsHexLiteral(self):
 521         if self._LiteralToken.startswith('{') and \
 522             self._LiteralToken.endswith('}'):
 523             return True
 524
 525         if self.HexPattern.match(self._LiteralToken):
 526             Token = self._LiteralToken[2:]
 527             Token = Token.lstrip('0')
 528             if not Token:
 529                 self._LiteralToken = '0x0'
 530             else:
 531                 self._LiteralToken = '0x' + Token.lower()
 532             return True
 533         return False
 534
 535     def _GetToken(self):
 536         return self.__GetNList()
 537
 538     @staticmethod
 539     def __IsIdChar(Ch):
 540         return Ch in '._/:' or Ch.isalnum()
 541
 542     # Parse operand
 543     def _GetSingleToken(self):
 544         self.__SkipWS()
 545         Expr = self._Expr[self._Idx:]
 546         if Expr.startswith('L"'):
 547             # Skip L
 548             self._Idx += 1
 549             UStr = self.__GetString()
 550             self._Token = 'L"' + UStr + '"'
 551             return self._Token
 552
 553         self._Token = ''
 554         if Expr:
 555             Ch = Expr[0]
 556             Match = self.RegGuidPattern.match(Expr)
 557             if Match and not Expr[Match.end():Match.end()+1].isalnum() \
 558                 and Expr[Match.end():Match.end()+1] != '_':
 559                 self._Idx += Match.end()
 560                 self._Token = ValueExpression(GuidStringToGuidStructureString(Expr[0:Match.end()]))(True, self._Depth+1)
 561                 return self._Token
 562             elif self.__IsIdChar(Ch):
 563                 return self.__GetIdToken()
 564             elif Ch == '"':
 565                 return self.__GetString()
 566             elif Ch == '{':
 567                 return self.__GetArray()
 568             elif Ch == '(' or Ch == ')':
 569                 self._Idx += 1
 570                 self._Token = Ch
 571                 return self._Token
 572
 573         raise BadExpression(ERR_VALID_TOKEN % Expr)
 574
 575     # Parse operator
 576     def _GetOperator(self):
 577         self.__SkipWS()
 578         LegalOpLst = ['&&', '||', '!=', '==', '>=', '<='] + self.NonLetterOpLst
 579
 580         self._Token = ''
 581         Expr = self._Expr[self._Idx:]
 582
 583         # Reach end of expression
 584         if not Expr:
 585             return ''
 586
 587         # Script operator: LT, GT, LE, GE, EQ, NE, and, or, xor, not
 588         if Expr[0].isalpha():
 589             return self.__GetIdToken(True)
 590
 591         # Start to get regular operator: +, -, <, > ...
 592         if Expr[0] not in self.NonLetterOpLst:
 593             return ''
 594
 595         OpToken = ''
 596         for Ch in Expr:
 597             if Ch in self.NonLetterOpLst:
 598                 if '!' == Ch and OpToken:
 599                     break
 600                 self._Idx += 1
 601                 OpToken += Ch
 602             else:
 603                 break
 604
 605         if OpToken not in LegalOpLst:
 606             raise BadExpression(ERR_OPERATOR_UNSUPPORT % OpToken)
 607         self._Token = OpToken
 608         return OpToken
 609
 610     # Check if current token matches the operators given from OpList
 611     def _IsOperator(self, OpList):
 612         Idx = self._Idx
 613         self._GetOperator()
 614         if self._Token in OpList:
 615             if self._Token in self.LogicalOperators:
 616                 self._Token = self.LogicalOperators[self._Token]
 617             return True
 618         self._Idx = Idx
 619         return False
 620
 621 if __name__ == '__main__':
 622     pass
 623     while True:
 624         input = raw_input('Input expr: ')
 625         if input in 'qQ':
 626             break
 627         try:
 628             print ValueExpression(input)(True)
 629             print ValueExpression(input)(False)
 630         except WrnExpression, Ex:
 631             print Ex.result
 632             print str(Ex)
 633         except Exception, Ex:
 634             print str(Ex)