Question

The passed by reference argument is a shared item between caller and callee.
Is this item in sharing for recursive calls of a function ?

Suppose this merge sort algorithm:

MergeSort(ref int[]S)
{
    .
    .
    .
    MergeSort(ref S1);
    MergeSort(ref S2);
    Merge(S1,S2,S);
}

By tracing algorithm for S={2,3,1,0} , we have :

                2,3,0,1
        2,3                 1,0
      2     3             1     0

At the end of algorithm ,compiler will do a merge into S in second level of tree, that merges(0,1) and (2,3) and creates (0,1,2,3).

We have just a one S array that is shared , How the compiler merge 2 of S arrays and merged them ?
So S is not sharing??

Thanks in advance

Answer 1

The object is passed by reference BUT in every recursive call, the variable S points [refers] to a different object. Thus, every merge() is actually preformed on a different object.