Issue with reading file into a vector (C++)

Question

So I'm currently a second year computer engineering student and I've run into a massive wall with this C++ data structures class I'm currently enrolled in. This program I have to create should read data from a file, input that data into a vector and display the minimum and maximum for that file. She also wants me to use a template, but I'm just trying to get this thing off the ground before I traverse that road. Now the issue I'm having is I can't get anything going besides this point in my code.

Now this code is obviously incomplete, but I can't seem to figure out how to read these values into a vector and then throw the values that are strings. To be honest with you, I'm lost in the sauce and am, for lack of a better metaphor, throwing brown stuff against a wall and seeing if it sticks. I understand these topics individually, but combining them and throwing in a data file has me lost. If someone could take the time to sit down and help me work this out because my professor hasn't been answering my emails for a week (online only course) and this project is due on Tuesday and I've been working for the last 2 days and have NOTHING completed.

I'd greatly appreciate the assistance and understand I'm on the verge of losing it. I have no issues in my Java, Diff Eq or HTML/CSS course but this C++ course is absolutely dominating me (Received a B in the intro to C++ course). Thanks again and I appreciate anyone who can help!

//Nicholas Stafford
//COP2535.0M1 
//Read in text file into multiple vectors and display maximum and minimum integers/strings.

#include <iostream> 
#include <string>
#include <vector>
#include <fstream>
#include <algorithm>


using namespace std;



int main() {

    ifstream inputFile; //File input object
    const int fSize = 6;
    int numCt = 0; //Counts number of integers
    vector<int> numInt(fSize);
    string numWd;


    //Open input file
    inputFile.open("minmax.txt");

    //Data validation for file
    if (inputFile)
    {
        //Try method to remove string values
        try
        {
            //Only pull the integer values into a vector
            while (inputFile >> numInt)
            {
                numCt++;
            }
        }
        catch (string noString)
        {
            cout << noString;
        }

    }
}

Answer 1

You mentioned that you have background in Java, and I regret to inform you that you're suffering from Java-itis:

    try
    {
        //Only pull the integer values into a vector
        while (inputFile >> numInt)
        {
            numCt++;
        }
    }
    catch (string noString)
    {
        cout << noString;
    }

This would be more or less how these kinds of things work in Java: if an error occurs, Java typically throws an exception. Here, you are attempting to read an int value, and you are assuming that an exception gets thrown if the next item read is not an integer.

That's how it typically works in Java, but that's not how C++ works.

If the >> operator fails, C++ sets the input stream to an error status, and return normally without performing the conversion, leaving the int value uninitialized. C++ does not throw an exception. C++ code, in general, throws far fewer exceptions than equivalent Java code.

Adding insult to injury, as I've said several times before, I think that beginners in C++ unfairly experience a lot of frustration, due to no fault of their own, with the >> operator on input streams. Their instructors teach them to use it all the time, but they really shouldn't. This is a textbook example why.

You are expecting that >> reads the next line of text. It doesn't. It reads the next whitespace-delimited glob from the input stream. If you have

2  3

then the >> operator will only read '2', and not '3'. Furthermore, the >> operator treats newlines just like any form of whitespace. And, as I mentioned, because of the way that >> handles error reporting, you explicitly have to check for it.

In conclusion, this how you should be handling each line of input, in C++:

std::string line;

std::getline(std::cin, line);

This reads a single line of text. That's it. Only after you've completed that step, you can start messing around with the >> operator, to figure out what's in there:

std::istringstream parse(line);

parse >> numInt;

if (parse.fail())
{
     // Conversion failed, to what you want with it.
}

Clean, and simple, and a parsing failure here won't affect the status of the std::cin input stream, which you'd otherwise be obligated to reset, upon a failure.