In-Program Evaluation

In my projects I often need to evaluate expressions. So I created a class that provides evaluation of expressions with the posibility to declare variables and easy functions. For this article I include the XEvaluate-class in a 'calculator'-dialog, but normaly, I use the class in my application like this: XString erg = Evaluate("1+2*sqr(3)").

!!! The XString-class that XEvaluate uses, was also contributed at codeguru.

You can use external variables in a XDoubleMap. This typedef is allready defined in XEvaluate.h (typedef CMap<CString, LPCTSTR, double, double> XDoubleMap;):

	XDoubleMap var;
	var["alpha"] = 10;
	var["beta"] = 20;
	var["test"] = 1.234;

	double erg = dtoa(Evaluate("alpha+beta", var));

It's possible to use userdefined functions with one argument (this argument has to be 'x')

	Evaluate("f:=sin(x)+cos(x)");
	double erg = dtoa(Evaluate("f(pi/2)"));

You can also call Evaluate with more than one expression, if you divide the expressions by a semikolon:

	double erg = dtoa(Evaluate("a=10;b=20;c=a+b");

The following functions and operations are included in XEvaluate:

Use the sample program to find out what's possible with this class.

Download demo project - 47KB

Download source - 8KB