How to write nested generic function

Question

I am trying to write a generic Heap Sort algorithm. I get the following error. What could be the reason?

The type T cannot be used as type parameter T in the generic type or method Heap.MainClass.MaxHeapify<T>(T[], int, int). There is no boxing or type parameter conversion from T to System.IComparable<T> (CS0314) (HeapSort)

Answer 1

You need to specify the same generic constraint that T must implement IComparable<T> on the HeapSort function as well:

private static void HeapSort<T>(T[] items) where T : IComparable<T>

You specified this constraint on the MaxHeapify method and in order to call it, T must satisfy this condition.

Answer 2

The MaxHeapify<T>() method has a generic constraint of where T : IComparable but your HeapSort<T>() method doesn't have it, and so the compiler is not able to resolve the call to MaxHeapify from HeapSort method. You should add a generic constraint of where : IComparable to your HeapSort<T>() method also.

private static void HeapSort<T>(T[] items) where T : IComparable<T>