getline() and reading data from text files - c++

Question

The program I code below should
List all payment made by each student, show amount paid and outstanding
I need some help with the following section:
void payment()
{
// Display message asking for the user input
std::cout << "List all payment made by each student, show amount paid and outstanding." << std::endl;
// Read from text file and Display list of payment
std::ifstream infile; // enable to open, read in and close a text file
float StudentCode; // to store the student enrolment number
float Amount; // to store the amount of money
float Type; // to store information on type of payment made
float Outstanding; // to store amount of money is due
infile.open("Payment.txt"); // open a text file called Payment
if (!infile)
{
std::cout << "Item list is empty" << std::endl; // if the file is empty it output the message
}
else
{
std::cout << "List of Payment: " << std::endl;
std::cout << "" << std::endl;
std::cout << "Enrolment No." << "Amount" << "Outstanding" << std::endl;
// If there is Student Code that has the same number, it need to combined the amount it paid
// For an example
// Student Code: 12 Amount: 25
// Student Code: 12 Amount: 50
// so it should display the following when the program runs:
// Student Code: 12 Amount: 75
while(!infile.eof()) // output the description of the text file onto the screen
{
getline(infile,StudentCode,Amount);
Outstanding = Amount - 100;
std::cout << StudentCode << Amount << "$" << Outstanding << std::endl;
//iter++;
}
std::cout << "End of list\n" << std::endl;
}
infile.close(); // close the text file
}
What is wrong with the getline part:
getline(infile,StudentCode, Amount);
Also the program should not display repeated Student Code but combine the amount it paid.
Where I explain in the comment section
// If there is Student Code that has the same number .....
How do I do this?

Answer 1

getline reads a line from a stream into a string. What you're trying to do, is more like this
while (infile >> StudentCode >> Amount) {
// process values
}
If you want to sum up all amounts, you must first accumulate and afterwards loop through the collected values and print them
std::map<int, float> amountsPaid;
int studentCode;
float amount;
// accumulate amounts
while (infile >> studentCode >> amount) {
amountsPaid[studentCode] += amount;
}
// loop through map and print all entries
for (auto i = amountsPaid.begin(); i != amountsPaid.end(); ++i) {
float outstanding = i->second - 100;
std::cout << i->first << ": " << i->second << "$, " << outstanding << '\n';
}

Answer 2

There are several problems here. One is that getline reads one line of text into a single std::string variable, not multiple float fields.
For that you might try
infile >> StudentCode >> Amount;
A second problem is that
while(!infile.eof())
will not check if the next input is going to work but if the previous input attempt failed beause it reached end-of-file.
The standard method is to combine these into
while (infile >> StudentCode >> Amount)
{
// do something with the code and amount
}

Answer 3

Your call to getline doesn't seem correct.
The documentation states
istream& getline ( istream& is, string& str, char delim );
But your giving it
getline(istream&, float, float);
You should be trying to read the line as a string and then parse out the 2 floats.
Since your using c++, if the file is well formatted you could just redirect cin and it'll be easier. You could just do something like
while (infile >> StudentCode) {
infile >> Amount;
}