Thread: Stringstream runs into infinite loop

Originally Posted by manasij7479

but what do you mean about the enum?....would it be of any advantage over the bool?

At the moment, the bool just stores information about whether the token is or is not a double. You could do a little more and store information about whether the token, if it is not a number, is exactly what kind of operator.

Originally Posted by manasij7479

Now... how should the enum behave when it encounters the "sin"?

There could be an enumerator for a mathematical function that takes an argument.

Originally Posted by manasij7479

and what should be be the part of the constructor dealing with the enum be like?

Code that determines what the string value is, e.g., it could just be string comparison.

What will your calculator make of, say: 5 + 2 * 3? Is it 21?
Do you think about implementing brackets too? To be able to calculate: (5 + 2) * (2 - 5 * ( 4 + 12) ).

If you answer "yes" to both or at least the second of those questions, then... Well, it may seem as an overkill at first, but implementing Dijkstra's infix to postfix algorithm and then evaluating it as an expression in Reverse Polish Notation might be just what you want.
Adding new operators (and support for variables) is very easy once you get through those two algorithms.

Shunting-yard algorithm - Wikipedia, the free encyclopedia
Reverse Polish notation - Wikipedia, the free encyclopedia

Originally Posted by manasij7479

If possible I'd write a function to order the input into brackets according to operator priority..

It is possible, but don't do it. Your aim is ultimately to evaluate the expression, not format it. If you are able to format by placing parentheses in the correct places, then you are able to evaluate the expression with the correct operator precedence even without the formatting.

Originally Posted by manasij7479

Is it possible to call the right functions using their pointers without using a switch-case ....but only from their names..?

No, at least not in the way that you probably have in mind. I can think of a way to make this work, but I suspect that if you were to try to do so many things at once, you simply won't succeed at all. You can come back to this idea later.

Originally Posted by manasij7479

so that there will be a call only once in that place and the input can go into the correct place..//..

I suggest that you simply accept the input in reverse polish notation and get a working program up and running. With that working framework in place, you can then convert to use infix notation. In fact, this is the order in which I did it as a student.