// here I try to utilize the Stack class
public void UseStack(Stack stack)
{
// what type should I use for the variable to hold the result of the Stack.Pop method?
type ??? item = stack.Pop();
// if I use IEquatable
IEquatable item1 = stack.Pop();
IEquatable item2 = stack.Pop();
item1.Equals(item2); // then I can do this
Type itemType = item1.GetType(); // but I can't do this
string s = item1.ToString(); // nor can I do this
// Ok, this calls for another interface that composes all of these other interfaces into one
}