CSC 123 Scary Test


A "scary test" tries to scare you into studying really hard for the real test.

Answer the following questions to the best of your ability:


1. Write a function in Scheme or Perl that returns 1 the first time
   it's called, -1 the second time, 1 the third time, etc ..., always
   alternating between -1 and +1.  Don't use global variables.


















2. Write a code fragement in Scheme, C or Perl that will behave differently
   depending on whether static or dynamic scoping is used.  If Perl is used,
   explain how to make the change from static to dynamic scoping.


















3. Assume that the C# classes B and C both extend superclass A, and that
   there is no further inheritance relationship between these classes.
   Assume also that:

   A a1 = new A();
   A a2 = new B();
   B b;
   C c = new C();
   
   Which of the following type casts are valid?  Which will fail at compile
   time, and which at runtime?

   b = (B)a1;

   b = (B)a2;

   b = (B)c;

   
4. Write the interface for observee objects of the Observer pattern