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