How to check if input is an operand?

[Zoo]

I am trying to find a way to check if an input is an operand.
Is it okay if I go:

  fstream file;
  file.open("sample.txt", ios::in);
  if (file==int) // not seems right. Intend to check if the input is operand or not 

Anyone helps me out?

[Chervil]

Perhaps something like this, though really it depends on what is supposed to be in the file and what you intend to do with it.

    ifstream file("sample.txt");
    int number;
    
    if (file >> number)
    {
        cout << "number is an integer " << number << endl;
    }
    else
    {
        cout << "not an integer" << endl;
        file.clear(); // reset error flags
    } 

[Zoo]

Yeah. I am trying to create a program which converts infix notation to postfix notation. In the text file it contains infix notation, and thus I have to convert file input to postfix notation.
Contents of textfile:
A + B * (C - D * E) / F
AB * CDE + (RST - UV / XX) * 3 - X5

[Chervil]

A + B * (C - D * E) / F
AB * CDE + (RST - UV / XX) * 3 - X5

A looks like an operand, but it isn't an integer (rather it is just a symbol)
RST could be a single operand, or three variables R, S AND T multiplied together?
3 is an integer
X5 - I assume is a single variable

It might be necessary to go through the text a single character at a time, following some rules which you have to devise, in order to determine what each character or group of characters represents.

[Zoo]

I actually have two text files, which in the second one, has mostly integers.


23 * (8 - 3 * 2) - 5 * (30 - 18)
12.53 + 21.2 * (33.2-15.4/2) - 8.5 * (2.6 + 12/2)


I will try it man, and I would ask for help again if I encountered any problems later.

[Chervil]

Small comment, there are floating-point numbers such as 12.53 here.
Rather than trying to distinguish between integer and floating, point, I'd just use type double for all the numbers.