Computer Science 3675
Summer 2000
Quiz 3

You have 25 minutes. Answer all of the questions.

1. What is the value of Scheme expression (car (cdr (cons 'horse (cons 'zebra ()))))?
2. Write a Scheme function called drop so that (drop n L) returns the result of removing the first n members from list L. If L has fewer than n members, then (drop n L) should return the empty list. For example, (drop 2 '(4 8 3 5 7)) = (3 5 7) and (drop 3 '(5 2)) = (). Be careful to use Scheme syntax correctly.
3. What part of a frame in the run-time stack allows a function to find its nonlocal variables? (There is one small part that gives a function access to the environment of its creator. What is it called?)
4. In the following C function definition, write an @ at each point where the compiler will insert an implicit fetch. (That is, make all @ operations explicit. Each variable stands for the variable, not the value of the variable.)

          int   test( int   x)
          {
            int   y,   a[  20];
            y =   x;
            a[  y] =   40;
            return   a[  y];
          }

5. In C++, a function is represented as the address of the machine-language code that performs that function. In languages that allow a function to be defined inside another function, that form of representation of a function, by itself, is not adequate. How is a function represented? What else is required in the representation? What is the representation of a function called?

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