News for UCLA Computer Science 131, winter 2019

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Here are news items that affect the core assignments and class material.

2019-02-24

• The last test case in Homework 5 has been corrected as follows, where deleted text is marked like this and inserted text is marked like this:

  (expr-compare '((lambda (a) (eq? a ((λ (a b) (let ((a b) (b a)) (a b)))
                                      a (lambda (a) a))))
                  (λlambda (b a) (b a)))
                '((λ (a) (eqv? a ((lambda (b a) (let ((a b) (b a)) (a b)))
                                  a (λ (b) a))))
                  (lambda (a b) (a b))))
    ⇒ ((λ (a)
        ((if % eq? eqv?)
         a
         ((λ (a!b b!a) (let ((a (if % b!a a!b)) (b (if % a!b b!a))) (a b)))
          a (λ (a!b) (if % a!b a)))))
       (lambda (b!a a!b) (b!a a!b)))
  

  (Thanks to Micah Kim for spotting the problems.)

2019-02-05

• Homework 3 is available and is due a week from today.

2019-01-25

• Homework 2's test6 has been corrected by replacing Node (Term, [Node (Num, [Leaf "2"])]) with Node (Expr, [Node (Term, [Node (Num, [Leaf "2"])])]). (Thanks to Micah Kim.)

2019-01-22

• Homework 2 now has three more little test cases test5, test6 and test7.

2019-01-19

• A typo Nuam has been corrected to Num in Homework 2.

2019-01-18

• As a result of today's discussions, Homework 2 has been corrected as follows.
  1. In the sample session just before the user types '#use "hw2sample.ml";;', the type that make_parser eventually returns has been corrected from ('a, 'b) parse_tree to ('a, 'b) parse_tree option.
  2. For correctness some text was inserted in the following: "This test should check that parse_tree_leaves is in some sense the inverse function of make_parser gram, in that when make_parser gram frag returns Some tree, then parse_tree_leaves tree equals frag."
  3. For clarity some text was inserted and some deleted in the following: "When applied to an acceptor accept and a fragment frag, the matcher must return the first acceptable match of a prefix of frag, by trying the grammar rules in order; try the grammar rules in order and return the result of calling accept on the suffix corresponding to the first acceptable matching prefix of frag; this is not necessarily the shortest nor the longest acceptable match."
• Homework 2 is available.

2019-01-08

• Homework 1 is available.
• Create your SEASnet account and then check that it works as soon as you can, as there are occasionally delays before your account is activated.
• Here are suggestions if you're interested in the course but are neither enrolled nor on the waiting list.
  • Read Enrollment in Undergraduate Computer Science Classes and follow its advice.
  • Any PTEs are not typically given out until the end of the second week, to make sure that enough resources are available. You can try coming to classes before then. Sign up on any attendance sheet that is being passed around.