X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=exercises%2Fassignment3.mdwn;h=7121faee69e9b388627e33f971b4f0d2b8ee299d;hp=57b6d4d82e668da5ebe1f4889cbdae910adbfc23;hb=a68ef218fe101b9d4e7aec684d93bc8391b971a9;hpb=57be0c4918eef2e0441645bb32464bedc94c6477

diff --git a/exercises/assignment3.mdwn b/exercises/assignment3.mdwn
index 57b6d4d8..7121faee 100644
--- a/exercises/assignment3.mdwn
+++ b/exercises/assignment3.mdwn
@@ -1,5 +1,3 @@
-** *Work In Progress* **
-
 ## Lists and List Comprehensions
 
 1.  In Kapulet, what does `[ [x, 2*x] | x from [1, 2, 3] ]` evaluate to?
@@ -18,6 +16,7 @@
 
 8.  Suppose you have two lists of integers, `left` and `right`. You want to determine whether those lists are equal, that is, whether they have all the same members in the same order. How would you implement such a list comparison? You can write it in Scheme or Kapulet using `letrec`, or if you want more of a challenge, in the Lambda Calculus using your preferred encoding for lists. If you write it in Scheme, don't rely on applying the built-in comparison operator `equal?` to the lists themselves. (Nor on the operator `eqv?`, which might not do what you expect.) You can however rely on the comparison operator `=` which accepts only number arguments. If you write it in the Lambda Calculus, you can use your implementation of `leq`, requested below, to write an equality operator for Church-encoded numbers. [[Here is a hint|assignment3 hint3]], if you need it.
 
+    (The function you're trying to define here is like `eqlist?` in Chapter 5 of *The Little Schemer*, though you are only concerned with lists of numbers, whereas the function from *The Little Schemer* also works on lists containing symbolic atoms --- and in the final version from that Chapter, also on lists that contain other, embedded lists.)
 
 
 ## Numbers
@@ -78,6 +77,11 @@ Using the mapping specified in this week's notes, translate the following lambda
 
 25. For each of the above translations, how many `I`s are there? Give a rule for describing what each `I` corresponds to in the original lambda term.
 
+    This generalization depends on you omitting the translation rule:
+
+        6. @a(Xa)       =   X            if a is not in X
+
+
 Evaluation strategies in Combinatory Logic
 ------------------------------------------