creating a generic sort method

Question

I am learning generic types and wanted to create a generic QuickSort method, the problem is classes are not co-variant and code cannot compile. the problem is making the Par

Answer 1

First step is to actually use generics:

void QuickSort<T>(T[] array, ...)

and

int Partition<T>(T[] array, ...)

In Partition remove the generic argument from Swap. It will be inferred by the compiler.

However, for this to work, you need to constrain T to IComparable<T>:

void QuickSort<T>(T[] array, ...) where T : IComparable<T>

and

int Partition<T>(T[] array, ...) where T : IComparable<T>

Finally, you need to replace the "less than" and "greater than" operators with calls to CompareTo:

if(array[midPoint].CompareTo(array[lowerBound]) < 0)

and

if(array[midPoint].CompareTo(array[lowerBound]) > 0)

Answer 2

What you're looking for is to constrain T to any type that implements IComparable<T>

This MSDN article nicely explains generic constrains in C#. Your method declaration will look like this:

public static T Partition<T>(T[] array, int mid)
    where T : IComparable<T>
{
    //code goes here
}

public static void QuickSort<T>(T[] array, int lower, int upper)
    where T : IComparable<T>
{
    //code goes here
}

It might also be helpful to link you to the MSDN article for IComparable<T>. Wherever you'd regularly compare two ints, you would instead call array[midPoint].CompareTo(array[upperBound]) > 0. All the comparison operators are the same if you check the result of CompareTo against 0.

And a small side note, when you call Swap<int>(..., the compiler can infer the type as int and you can simply call it as Swap(....