Nrthugu

I'm trying to create a member method on my array class for sorting. I typedef'd two function pointers in my class one for a generic sorting method, and the other for the comparator. I'm having trouble navigating through the errors to determine exactly what is wrong with the way I'm calling it. I hope I've provided enough information, but here's what I got.

The error I'm getting:

main.cpp: In function ‘int main(int, char**)’:

main.cpp:222:67: error: no matching function for call to ‘array<int>::sort(<unresolved overloaded function type>, <unresolved overloaded function type>)’

 sort(wrap_insertion_sort_recursive<int>, custom_comparator<int>);

                                                                ^

main.cpp:55:6: note: candidate: void array<T>::sort(array<T>::p_sort_func, array<T>::p_comparator_func) [with T = int; array<T>::p_sort_func = void (*)(array<int>&, bool (*)(int, int)); array<T>::p_comparator_func = bool (*)(int, int)]

 void array<T>::sort(array<T>::p_sort_func sort_func,

      ^~~~~~~~

main.cpp:55:6: note:   no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘array<int>::p_sort_func {aka void (*)(array<int>&, bool (*)(int, int))}’

I'm defining my typedefs here:

template <typename T>

class array {

 public:

  typedef bool (*p_comparator_func)(T a, T b); 

  typedef void (*p_sort_func)(class array<T> &array, p_comparator_func);

  ...

  void sort(array::p_sort_func sort_func,

      array::p_comparator_func comparator_func);



  ...

}

My implementation of sort:

template <typename T>

void array<T>::sort(array<T>::p_sort_func sort_func,

                    array<T>::p_comparator_func comparator_func)

{

  if(comparator_func == nullptr) {

    comparator_func = this->default_comparator;

  }



  if(sort_func == nullptr) {

    sort_func = this->default_sort;

  }



  sort_func(*this, comparator_func);

}

The sort function I am passing:

template <typename T>

void wrap_insertion_sort_recursive(class array<T> &array,

  class array<T>::p_comparator_func comparator)

{

  insertion_sort_recursive(array, array.get_capacity(), comparator);

}

My custom comparator:

template <typename T>

bool custom_comparator(T a, T b)

{ 

  return a < b;

}

And where I'm calling it in main:

class array<int> a(5);

a[0] = 8;

a[1] = 6;

a[2] = 7;

a[3] = 1;

a[4] = 3;



std::cout << "attempting sort" << std::endl;

a.sort(wrap_insertion_sort_recursive<int>, custom_comparator<int>);

The problem specifically was with:

template <typename T>

void wrap_insertion_sort_recursive(class array<T> &array,

  class array<T>::p_comparator_func comparator)

{

  insertion_sort_recursive(array, array.get_capacity(), comparator);

}

Instead of class I should have used typename as described in this nice article all about typename here.

So the fixed version would be:

template <typename T>

void wrap_insertion_sort_recursive(class array<T> &array,

  typename array<T>::p_comparator_func comparator)

{

  insertion_sort_recursive(array, array.get_capacity(), comparator);

}