Error Handling

In case of an error both parser class and the parser DLL provide similar methods for querying the information associated with the error. In the parser class they are member functions of the exception class mu::Parser::exception_type and in the DLL version they are normal functions. These functions are:

  • exception.GetMsg() / mupGetErrorMsg() - returns the error message.
  • exception.GetExpr() / mupGetExpr() - returns the current formula (if a formula is set)
  • exception.GetToken() / mupGetErrorToken() - returns the token associated with the error (if applicable)
  • exception.GetPos() / mupGetErrorPos() - returns the current formula position (if applicable)
  • exception.GetCode() / mupGetErrorCode() - returns the error code.

The following table lists the parser error codes. The first column contains the enumeration values as defined in the enumeration mu::EErrorCodes located in the file muParserError.h. Since they are only accessible from C++ the second column lists their numeric code and the third column contains the error description.

Enumeration name Value Description
ecUNEXPECTED_OPERATOR 0 Unexpected binary operator found
ecUNASSIGNABLE_TOKEN 1 Token cant be identified
ecUNEXPECTED_EOF 2 Unexpected end of formula. (Example: "2+sin(")
ecUNEXPECTED_ARG_SEP 3 An unexpected argument separator has been found. (Example: "1,23")
ecUNEXPECTED_ARG 4 An unexpected argument has been found
ecUNEXPECTED_VAL 5 An unexpected value token has been found
ecUNEXPECTED_VAR 6 An unexpected variable token has been found
ecUNEXPECTED_PARENS 7 Unexpected parenthesis, opening or closing
ecUNEXPECTED_STR 8 A string has been found at an inapropriate position
ecSTRING_EXPECTED 9 A string function has been called with a different type of argument
ecVAL_EXPECTED 10 A numerical function has been called with a non value type of argument
ecMISSING_PARENS 11 Missing parens. (Example: "3*sin(3")
ecUNEXPECTED_FUN 12 Unexpected function found. (Example: "sin(8)cos(9)")
ecUNTERMINATED_STRING 13 unterminated string constant. (Example: "3*valueof("hello)")
ecTOO_MANY_PARAMS 14 Too many function parameters
ecTOO_FEW_PARAMS 15 Too few function parameters. (Example: "ite(1<2,2)")
ecOPRT_TYPE_CONFLICT 16 binary operators may only be applied to value items of the same type
ecSTR_RESULT 17 result is a string
ecINVALID_NAME 18 Invalid function, variable or constant name.
ecINVALID_BINOP_IDENT 19 Invalid binary operator identifier.
ecINVALID_INFIX_IDENT 20 Invalid infix operator identifier.
ecINVALID_POSTFIX_IDENT 21 Invalid postfix operator identifier.
ecBUILTIN_OVERLOAD 22 Trying to overload builtin operator
ecINVALID_FUN_PTR 23 Invalid callback function pointer
ecINVALID_VAR_PTR 24 Invalid variable pointer
ecEMPTY_EXPRESSION 25 The expression string is empty
ecNAME_CONFLICT 26 Name conflict
ecOPT_PRI 27 Invalid operator priority
ecDOMAIN_ERROR 28 catch division by zero, sqrt(-1), log(0) (currently unused)
ecDIV_BY_ZERO 29 Division by zero (currently unused)
ecGENERIC 30 Error that does not fit any other code but is not an internal error
ecLOCALE 31 Conflict with current locale
ecUNEXPECTED_CONDITIONAL 32 Unexpected if then else operator
ecMISSING_ELSE_CLAUSE 33 Missing else clause
ecMISPLACED_COLON 34 Misplaced colon
ecUNREASONABLE_NUMBER_OF_COMPUTATIONS 35 The vectors submitted to bulk mode computations are too short.
ecIDENTIFIER_TOO_LONG 36 A submitted identifier longer than 100 characters.
ecEXPRESSION_TOO_LONG 37 The submitted expression is longer than 5000 characters.
ecINVALID_CHARACTERS_FOUND 38 Internal error of any kind.
ecINTERNAL_ERROR 39 Internal error of any kind.

[DLL interface]

Since dynamic libraries with functions exported in C-style can't throw exceptions the DLL version provides the user with a callback mechanism to raise errors. Simply add a callback function that does the handling of errors. Additionally you can query the error flag with mupError(). Please note that by calling this function you will automatically reset the error flag!

// Callback function for errors
void OnError(muParserHandle_t hParser)
	printf("Message:  \"%s\"\n", mupGetErrorMsg(hParser));
	printf("Token:    \"%s\"\n", mupGetErrorToken(hParser));
	printf("Position: %d\n", mupGetErrorPos(hParser));
	printf("Errc:     %d\n", mupGetErrorCode(hParser));


// Set a callback for error handling
mupSetErrorHandler(hParser, OnError);

// The next function could raise an error
fVal = mupEval(hParser);

// Test for the error flag
if (!mupError()) 
	printf("%f\n", fVal);

See also: example2/example2.c

[Parser class interface]

In case of an error the parser class raises an exception of type Parser::exception_type. This class provides you with several member functions that allow querying the exact cause as well as additional information for the error.

catch(mu::Parser::exception_type &e)
	cout << "Message:  " << e.GetMsg() << "\n";
	cout << "Formula:  " << e.GetExpr() << "\n";
	cout << "Token:    " << e.GetToken() << "\n";
	cout << "Position: " << e.GetPos() << "\n";
	cout << "Errc:     " << e.GetCode() << "\n";

See also: example1/example1.cpp