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C++: while/if and return problem

Scorpia (25)
Hi,

I have a struct. User can decide do he want to print so there is 
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cout << endl << "Want to print? (1. yes, 2. no, 3. quit) ";
cin >> i.Print;


Problem is where I put that while loop. I have a main and sub program. In sub program I ask the info and main program prints it.

So I have this loop in sub program:

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	while (i.Print != 3)
		if (i.Print == 1)
		{
			return i;
		}
		else if (i.Print == 2)
		{
			cout << "Program has stoped."
		}
	cout << "You quit the program.";


But if user puts 2 (=no printing) it goes forever loop. I think this should be in main program but how can I move the value of i from sub to main?

I really hopes someone understands, sorry about bad english. I can show the whole code if it helps.
Handy Andy (5051)
Hello Scorpia,

while (i.Print != 3). What is the value of "i,Print"?

If you reach the else/if statement where does the value of "i,Print" change?

With out enough code to compile and test it is hard to say where the problem starts.

Andy
Scorpia (25)
User define the value of i.Print, it is either 1, 2 or 3. Its a pretty long code, maybe I can put it to pastebin or something? Its over 160 lines. :D
Handy Andy (5051)
Hello Scorpia,

Should fit here. I have seen 250+ lines posted here.

Andy
Scorpia (25)
Okey, here we go. :) And there is some finnish in.

And I like to hear some feedback about the code if somebody has a moment.

 
Last edited on
Handy Andy (5051)
Hello Scorpia,

First off you should use "<cmath>" not "<math.h>". "math.h" is a C header file and "cmath" is the C++ version. Also I have not seen any reason to need "<cmath>" in the program. Check http://www.cplusplus.com/reference/cmath/ to see what is available in "cmath". Then again I may have missed its need for now.

Prefer to use "double"s over "float"s.

I need a few minutes to go over the code.

Andy
Scorpia (25)
Oh right, I used that library when I have a few lines where it was needed but it's deleted already. So i delete that also. Thanks!
Handy Andy (5051)
Hello Scorpia,

Sorry about the delay. Between translating and testing this took longer than I thought.

Prefer to use the new line, ("\n"), over the "endl". "endl" is a function that takes time and the more you have the more time you will waste. At some point you may notice the program running slower.

In the beginning I changed these parts:
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#include <iostream>
#include <iomanip>
#include <limits>
#include <string>
//#include <cmath>  // <--- Proper file, but not needed.

void studentGrade(Student& student);  // <--- Changed.
. The function now makes better use of what you have.

In "main":
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for (int number = 0; number < count; number++)
{
    studentGrade(student[number]);
}

Here you are sending 1 element to the function to use.

This is the translated version, but it is to show more the concept of what I did.
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for (int number2 = 0; number2 < count; number2++)
{
    if (student[number2].Print == 1)
        cout << '\n'
            << "Student number: " << (number2 + 1) << ". information." << '\n'
            << "First name: " << student[number2].FirstName << '\n'
            << "Surname: " << student[number2].LastName << '\n'
            << "Rating of weekly exercises: " << student[number2].Grade << '\n'
            << "Grade assignment: " << student[number2].PracticeW << '\n' << '\n'
            << "Overall grade: " << student[number2].FirstName << ": " << student[number2].TotalGrade << ", rounded "
            << setprecision(1) << student[number2].TotalGrade << '\n';
}

The if statement is to allow something to display unless the functions choise was 2 or 3.

I put this after the above for loop because it works better:
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std::cout << "\n\n" << "Press enter to close the program. ";
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');  // <--- Requires header file <limits>.
std::cin.get();

return 0;  // <--- Not required, but makes a good break point.

Line 2 may not always be needed.

For the function, the parts I worked on:
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void studentGrade(Student& student)
{
    // Enter the data
    //Student student;  // <--- No longer needed.

    //cout << "1. Enter the student's first name: ";
    //cin >> student.FirstName;
    student.FirstName = "Stan"; // <--- Used for testing. Comment or remove when finished.
    cout << "1. Enter the student's first name: " << student.FirstName << '\n'; // <--- Used for testing. Comment or remove when finished.

cout << "\nThe total grade is as follows: weekly exercises " << student.Setting << "% and assignment " << 100 - student.Setting << "%." << '\n';

cout << "\nPrint data? (1. yes, 2. no, 3. interrupt): ";

Lines 6 - 9 is a little trick to not have to enter something each time the program runs, but it works best when int count{ 1 }; in "main". Once you know that the input is working it comes in very handy.

Line 11 was adding some spaces and using the "\n" instead of the "endl"s.

Line 13 I left where you originally had it, but did comment the following "cin". At least until I can get the while condition working better.

This is what I ended up with for the while loop:
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while (cin >> student.Print && !std::cin || (student.Print > 1 || student.Print < 4))
{
    if (!std::cin)
    {
        std::cerr << "\n Invalid Input! Must be a number.\n\n";

        std::cin.clear();
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');  // <--- Requires header file <limits>.
    }
    else if (student.Print == 1)
    {
        Grade1 = (student.Setting * Grade) / 100.0;
        Grade2 = ((100 - student.Setting) * student.PracticeW) / 100.0;

        TotalGrade = Grade1 + Grade2;

        student.TotalGrade = TotalGrade;

        return;
    }
    else if (student.Print == 2)
    {
        cout << "\n     Data will not be printed. The program will be aborted.\n\n";
        break;
    }
    else if (student.Print == 3)
    {
        std::cout << "\n   Program interrupted.\n\n";
        break;
    }
    else
    {
        std::cerr << "\n     Invalid Choice! try again.\n\nPrint data ? (1. yes, 2. no, 3. interrupt) : ";
    }
}


These changes appear to work for now, but there are some other things I want to try.

I would first get it working for 1 student then try for 2 or 3.

Andy
Handy Andy (5051)
Hello Scorpia,

After a little testing I came to this for the while loop:
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while (cout << "\nPrint data? (1. yes, 2. no, 3. interrupt): "  &&
           cin >> student.Print && !std::cin || (student.Print > 0 || student.Print < 4))


Andy
Scorpia (25)
Oh gosh what a angel we have here! :)
Thank you so much, this means a lot for me as a beginner. Good notes, clear and easy to understand. I try these and make my code even better. Thank you!

I have a another question about alphabetical order in printing but I think I should do new topic?
Last edited on
czerwonymoskit (9)
Missing {} in the while

If there are no parentheses the loop will do one line, or not at all if the condition is false. At other than 1 it spins endlessly.
You dont need { in if and if else.
Last edited on
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