// helper method to support negative index into stack
public static StackValue SetValue(this HeapElement hs, int ix, StackValue sv)
{
if (ix >= hs.GetAllocatedSize())
{
throw new System.IndexOutOfRangeException();
}
int index = ix < 0 ? ix + hs.VisibleSize : ix;
StackValue svOld = hs.Stack[index];
hs.Stack[index] = sv;
return(svOld);
}
