"no matching function call" with templated functions project - c++

Question

I am writing a program to generate and sort an array of random numbers.
The compiler gives me the following error:
select.cxx: In function ‘void selectionsort(Item*, SizeType)
[withItem = int, SizeType = long unsigned int]’:
select.cxx:95: instantiated from here
select.cxx:16: error: no matching function for call to ‘swap(int*&, long unsigned int&, long unsigned int&)’
Here is my code:
#include <cassert>
#include <cstdlib>
#include <iostream>
#include <time.h>
using namespace std;
template <class Item, class SizeType>
void selectionsort(Item data[], SizeType n)
{
for (SizeType i = 0; i = n - 2; i++)
{
SizeType j = index_of_minimal(data, i, n);
swap(data, i, j); //data[i] swapped with data[j](minimum)
}
}
template <class Item, class SizeType>
std::size_t index_of_minimal(const Item data[], SizeType i, SizeType n)
{
size_t min = i; //holds index of minimum (initialized to i)
Item t1 = data[i]; //temporary holder for comparing values, initialized as i (starting value)
Item t2; //second holder
for (SizeType j = i++; j = n - 1; j++)
{
t2 = data[j];
if (t2 < t1)
{
t1 = data[j];
min = j;
}
}
return min;
}
template <class Item, class SizeType>
void swap(Item data[], SizeType i, SizeType j) //data[i] swapped with data[j](minimum)
{
Item temp; //holds value to be swapped
temp = data[i];
data[i] = data[j];
data[j] = temp;
}
template <class Item, class SizeType>
void listPrint(Item data[ ], SizeType n)
{
cout << "array:";
for (SizeType i = 0; i = n - 1; i++)
{
cout << " " << data[i];
}
cout << endl;
}
int myrand(int lower, int upper)
{
return (lower + rand() % ( upper - lower + 1 ) );
}
int main()
{
size_t n; //user input
//For random number generator//
srand(time(NULL));
cout << "Please enter a number:" << endl;
cin >> n;
while (n < 1)
{
cout << "Error: please enter a number 1 or larger" << endl;
cin >> n;
}
int rNumbers[n]; //declares int array of size n
int randomN; //to hold randomly generated number
for (size_t i = 0; i < n; i++)
{
randomN = myrand(1, 1000); //generates a random number as randomN
rNumbers[i] = randomN;
}
cout << "Unsorted ";
listPrint(rNumbers, n);
selectionsort(rNumbers, n);
cout << "Sorted ";
listPrint(rNumbers, n);
}
I have a feeling that the problem has to do with the data types passed to the swap function. I am also confused as to why the first line of the error states that SizeType = long unsigned int, when the data type of n as declared in main() is size_t.

Answer 1

Make sure that the other functions you call inside your template function are visible. So, define selection_sort() after swap() and index_of_minimal().
Side remark:
int rNumbers[n]; //declares int array of size n
declares a variable sized array, which is not standard C++ (some compilers support it though, but you shouldn't rely on this). If you want a run-time sized array, use std::vector instead.
Regarding your confusion at the end, size_t is a type alias, which in your implementation it happens to be for unsigned long int, so that's why the error mentions it.