public static Func <double, double> GetFunction(string stringExpr)
{
if (!stringExpr.Contains("x"))
{
throw new ArgumentException("Expression must contains variable x");
}
var expression = new Expression(stringExpr);
expression.addArguments(new Argument("x"));
if (!expression.checkSyntax())
{
throw new ArgumentException("Invalid expression");
}
return(x =>
{
expression.setArgumentValue("x", x);
return expression.calculate();
});
}