Name: Email:

Exercise 1: Consider the following procedure swap2.

  procedure swap2 (x, y : integer);
    procedure f() : integer;
      var z : integer;
    begin (* f *)
      z := x; x := y; return z;
    end;
    y := f();
  end;

Describe the effect of the procedure call swap2(i, A[i]) under each of the following parameter passing methods:

• call-by-value
• call-by-reference
• call-by-value-result
• macro expansion
  

Exercise 2: Consider the following program and describe the effect of running the program with both lexical scoping and dynamic scoping.

  program main;
    var x : integer;
    procedure sub1;
      begin
        writeln ('x=', x)
      end;
    procedure sub2;
      var x : integer;
      begin
        x := 10;
        sub1;
      end;
    begin
      x:= 5;
      sub2;
    end.

Exercise 3: Describe the stack contents (the activation records) for the following program at the point where f(1) is called.

program activations;
  function pred (m: integer) : integer;
    begin pred := m-l; end;
  function f (n: integer): integer;
  begin
    if n = 0 then 
        f := 1 
    else 
        f := n * f (pred(n))
  end;
begin
   f(3);
end.

Exercise 4: Write and compile the "hello world" program on your favorite C++ compiler. Submit the source code here.

Exercise 5: Modify the stack program that we described in class to implement a first-in/first out buffer, based on the following invariants:

• The buffer is empty when holds = 0
• The buffer is full when holds = stack_size
• The first_in element is in buffer[front]
• The last_in element is in buffer[rear]
• The elements wrap around the end of the array