PPP Exercises: Type operators and genericity

Exercise:

1. Use a type operator to define a generic stack type 'GenStack'. The type operator takes the element type of the stack as parameter:
   

   Let GenStack(E <:Ok) <:Ok = ...
   

2. Write a generic stack implementation for 'GenStack' as polymorphic function 'genStack' using 'list'.

3. Use these definitions to define 'intStack :IntStack'.

4. Summarize and compare the different definitions and implementations of stacks in the exercises Generic abstract data types and implementations, Currying, and in this exercise.