I am having issues in my main.cpp file where the program is telling me that Member reference base type 'int [11]' is not a structure or union for both my QuickSort line and my for loop too. Then in the cout line it says Adding 'int' to a string does not append to the string and "Use array indexing to silence this warning.

Below is my main.cpp file where I am having my issue.

#include <iostream>
#include "QuickSort.h"
using namespace std;

int main() 
 int F = 12, 2, 16, 30, 8, 28, 4, 10, 20, 6, 18;
 QuickSort(F, 0, F.length-1);
 for (int i = 0; i<F.length; i++)
 cout << F[i] + " ";
 
 return 0;

Just in case you need my other code to decipher.
Below is my QuickSort.h file:

using namespace std;
class QuickSortRecursion
 public:
 QuickSortRecursion();
 int Partition (int a, int low, int high);
 void QuickSort(int a, int low, int high);
private:
;

Below is my QuickSort.cpp file:

QuickSortRecursion::QuickSortRecursion()
 return;

int QuickSortRecursion::Partition(int a, int low, int high)
 int pivot = high;
 int i = low;
 int j = high;
 while (i<j)
 if (a[i] <= a[pivot])
 i++;
 if (a[i] > a[pivot])
 if ((a[i] > a[pivot]) && (a[j] <= a[pivot]))
 int temp = a[i];
 a[i] = a[j];
 a[j] = temp;
 i++;
 if (a[j] > a[pivot])
 j--;
 
 
 
 int temp = a[i];
 a[i] = a[pivot];
 a[pivot] = temp;
 return i;


 void QuickSortRecursion::QuickSort(int a, int low, int high)
 if (low >= high)
 return;
 
 int split = Partition (a, low, high);
 QuickSort(a, low, split-1);
 QuickSort(a, split+1, high);

In

int main() 
 int F = 12, 2, 16, 30, 8, 28, 4, 10, 20, 6, 18;
 QuickSort(F, 0, F.length-1);
 for (int i = 0; i<F.length; i++)
 cout << F[i] + " ";
 
 return 0;

F is an array and arrays do not have any members so there is no F.length.

Solutions (in order of personal preference)

Use std::size if it is available (New in C++17).

int main() 
 int F = 12, 2, 16, 30, 8, 28, 4, 10, 20, 6, 18;
 QuickSort(F, 0, std::size(F)-1); 
 for (int i = 0; i<std::size(F); i++)
 cout << F[i] + " ";
 
 return 0;

Use std::vector instead of a raw array. std::array is more fitting, but I don't have a good formula to make

std::array<int> F = 12, 2, 16, 30, 8, 28, 4, 10, 20, 6, 18;
 ^
 Need to specify array size here, and if you knew that you there 
 wouldn't be a problem.

Example with std::vector

int main() 
 std::vector<int> F = 12, 2, 16, 30, 8, 28, 4, 10, 20, 6, 18;
 QuickSort(F.data(), 0, F.size()-1); 
 for (int i = 0; i<F.size(); i++)
 cout << F[i] + " ";
 
 return 0;

Use sizeof to get the length in bytes and then divide it by the sizeof an element to get the number of elements in the array

int main() 
 int F = 12, 2, 16, 30, 8, 28, 4, 10, 20, 6, 18;
 const int length = sizeof(F) / sizeof(F[0]);
 QuickSort(F, 0, length -1); 
 for (int i = 0; i<length ; i++)
 cout << F[i] + " ";
 
 return 0;

Side Notes

If you have a constructor that does nothing, let the compiler generate it.

If you have a class with no state (member variables) consider making it a namespace instead.

The partitioning doesn't look right. It looks like you're trying for Lomuto Partitioning, but are a little bit off.