1. Read section 5.1 of [Harper](http://www.cs.cmu.edu/~rwh/isml/book.pdf) 
    about tuple types and tuple patterns.  Also look at the list
    examples in sections 9.1 and 9.2 of Harper.

    Now consider the pattern `(x::y::zs, w)`. For each of the following
    expressions, tell whether the pattern matches the value denoted. If
    the pattern matches, say what values are bound to the four variables
    `x`, `y`, `zs`, and `w`. If it does not match, explain why not.

    (a) `([1, 2, 3], ("COMP", 105))`
    (b) `(("COMP", 105), [1, 2, 3])`
    (c) `([("COMP", 105)], (1, 2, 3))`
    (d) `(["COMP", "105"], true)`
    (e) `([true, false], 2.718281828)`

    Answers here:

    (a)

    (b)

    (c)

    (d)

    (e)


    You are now starting to be ready to use pattern matching.





 2. Look at the clausal function definition of `outranks` on page 83
    of [Harper](http://www.cs.cmu.edu/~rwh/isml/book.pdf).  Using the
    clausal definition enables us to avoid nested `case` expressions
    such as we might find in Standard ML or μML, and it enables us to
    avoid nested `if` expressions such as we might find in μScheme.
    This particular example also collapses multiple cases by using the
    "wildcard pattern" `_`.

    A wildcard by itself can match anything, but a wildcard in a
    clausal definition can match only things that are not matched by
    preceding clauses.  Answer these questions about the wildcards in
    `outranks`:

    (a) In the second clause, what three suits can the `_` match?

        →

    (b) In the fifth clause, what suits can the `_` match?

        →

    (c) In the eighth and final clause, what suits can the `_` match?

        →


    You are now ready to match patterns that combine tuples with
    algebraic data types.


 3. In Ramsey's chapter 5, the `eval` code for applying a function
    appears in code chunk 365c.  In evaluating `APPLY (f, args)`, if
    expression `f` does not evaluate to either a primitive function or
    a closure, the code raises the `RuntimeError` exception.

    (a) Show a piece of μScheme code that would, when evaluated, cause
        chunk 365c to raise the `RuntimeError` exception.

        →

    (b) When exception `RuntimeError` is raised, what happens from the
        user's point of view?





    You are now ready for problems G, L, and M.


 4. "Free" variables are those that are not bound to a value in the current scope. You can find a
    longer discussion and precise definition in section 5.11
    of Ramsey's book, which starts on page 375. Read the section 
    and identify the free variables of the following expressions:

     (a) Free variables of `(lambda (x) (lambda (y) (equal? x y)))`

         →

     (b) Free variables of `(lambda (y) (equal? x y))`

         →


    You are now ready to improve the μScheme interpreter in problem 2.