C++ Trouble doing simple addition in while() loop

Question

Hopefully someone can tell me what I'm doing wrong. I'm reading up to a specific point on each line within a text file and then trying to add that value to the value on the next line and continue doing so until the end of the file/loop. But at the moment, it will only add the values from the first two lines and not...

123 + 456 + 789 = totalPayroll.

My code is as follows:

inStream.open("staffMembers.txt");

while(getline(inStream.ignore(256, '$'), line))
{
    totalPayroll = stoi(line) + stoi(line);
}

inStream.close();

cout << "$" << totalPayroll << endl;

My text file is formatted as follows:

1 | Person One | $123
2 | Person Two | $456
3 | Person Three | $789

That it exactly what I wanted. Thank you! Would you mind explaining what += means exactly in an answer and I'll mark it as correct. — cvandal
– cvandal, Commented May 6, 2013 at 3:37

Qaz · Accepted Answer · 2013-05-06 03:40:32Z

5

In your loop, you're reassigning totalPayroll the value of stoi(line) + stoi(line) for every line, so it ends up finally being 2*789.

You need to keep a continuous sum:

totalPayroll = totalPayroll + stoi(line);

This also has a short form using a compound assignment operator, which does the same thing:

totalPayroll += stoi(line);

answered May 6, 2013 at 3:40

Qaz

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Comments

j883376 · Accepted Answer · 2013-05-06 03:40:59Z

2

As chris mentioned in his comment, totalPayroll += stoi(line); should solve your problem.

The C++ operator += is a shorthand way of writing totalPayroll = totalPayroll + stoi(line);. It adds the value given on the righthand side of the operator to the current value of the variable.

answered May 6, 2013 at 3:40

j883376

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3 Comments

Bill Over a year ago

why do you post an answer when someone has already pointed it out in the comments?? just for points? :)

Qaz Over a year ago

@Bill, I should have figured that would be it from the beginning and went straight for an answer. As it is, I posted one just before j883376. It's entirely possible mine wasn't even noticed.

j883376 Over a year ago

I was elaborating on what chris pointed out in his comment, since cvandal was unsure what += meant. Since chris made an answer himself a couple seconds before I hit submit, he got upvoted accordingly

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