Question

I’m referencing a templated quicksort method in my cpp function like this:

Main.cpp

QuickSort<vector<int>>(testData);

Where testData is:

int arr[] = {0, 5, 3, 4, 2, 1, 4};
vector<int> testData (arr, arr + sizeof(arr) / sizeof(arr[0]));

The declaration of quicksort in the .h file is:

Sorting.h

template <typename T>
void QuickSort(std::vector<T>& Unsorted);

And the function definition is:

Sorting.cpp

template <typename T>
void QuickSort(std::vector<T>& Unsorted) 
{
         //implementation here
}

Am I losing my mind? I’m just trying to pass a vector of ints by reference. Could someone tell me where I’m going wrong?

Answer 1

templates cannot have separate definition and declaration

also

QuickSort<int>(vec);

in case of functions declaration and definition must be in the saem place, ie:

#include <vector>

template <typename T>
void qs(std::vector<T>&v );

int main() {
  std::vector<int> v;
  qs(v);
}


void qs(std::vector<T>&v ) { 
}

wont compile, when

#include <vector>

template <typename T>
void qs(std::vector<T>&v ) {}

int main() {
  std::vector<int> v;
  qs(v);
}

compiles just fine, check in stl how template functions are made.
The thing is, that compiler must know entire function before its usage, and he doesnt in your case