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.

[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("\nError:\n");
	printf("------\n");
	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.

try
{
	...
	parser.Eval();
	...
}
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