Invalid Operand for the Type?

[BleaS]

||In function `int main()':| C:\Documents and Settings\bleas\My Documents\Backup\Projects\Accelerated C++ Projects\Chapter 2\Quartiles_1.0.cpp|32|error: invalid operands of types `double' and `double' to binary `operator%'|

This error specifically refers to:

    if(quarter_d % 2 == 0)
    {
        quarter = size/4;
    }
    {
        quarter = size/4 + 1;
    }

I'm trying to write a program that shows a group of numbers in quartiles, depending on the size. Since some numbers are not evenly divided by 4, and I can't show half a number, I decided I would try to round any such number up by one. So something like 75 numbers (divided by four is 18 and some change) would instead show 75-19, 17-19*2, etc... however, the error above is what I get for trying the module. Looking for a bit of help please.

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

using namespace std;

int main()
{
    cout << "Welcome to Quartiles 1.0!"
         << endl
         << "Please enter your numbers...";

    vector<int> numbers;
    int run = 1, current_number;

    while(cin >> current_number)
    {
        numbers.push_back(current_number);
    }

    sort(numbers.begin(), numbers.end());

    typedef vector<int>::size_type vec_sz;
    vec_sz size = numbers.size();

    int quarter;
    double quarter_d = size/4;

    if(quarter_d % 2 == 0)
    {
        quarter = size/4;
    }
    {
        quarter = size/4 + 1;
    }

    int counter = 0, current_quarter = 1;

    while(counter != quarter)
    {
        if(current_quarter == 1)
        {
            cout << numbers[quarter*3+counter] << endl;
        }
        else if(current_number == 2)
        {
            cout << numbers[quarter*2+counter] << endl;
        }
        else if(current_number == 3)
        {
            cout << numbers[quarter+counter] << endl;
        }
        else if(current_number == 4)
        {
            cout << numbers[counter] << endl;
        }

        ++counter;
        if(counter == quarter && current_number < 4)
        {
            cout << endl << "Next Set" << endl << endl;
            ++current_number;
            counter = 0;
        }
    }

    return 0;
}

[laserlight]

The problem is that operator&#37; is not defined for double. You could use std::fmod() from <cmath>, but in this case you probably should just stick to using int instead of double.

[BleaS]

The problem with using int is that it will not retain the decimals. I need the decimals to determine whether or not it needs to go up one number. As you can see, it eventually becomes an int, but it has to be a double to determine the true value I need to sort with.

Edit:

Oops, I did change it to

    int quarter = size/4 == 0 ? quarter = size/4
                              : quarter = size/4 + 1;

Seems to work, but my end output is not what I expected, so I have some more looking to do.

[laserlight]

The problem with using int is that it will not retain the decimals. I need the decimals to determine whether or not it needs to go up one number.

Notice that 75 &#37; 18 == 3. Basically, you can use operator% on int to decide if your range is perfectly divisible by 4, and based on that you can adjust the sub-ranges.