X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=assignment4.mdwn;h=9b7ec2c028622dc92e17dced54403aa6043b8896;hp=821b92e151d69c774494086d665a13429f9ab772;hb=27ce0d45d4ab28840605ec2130f6ba4ecd9d6213;hpb=a952192898d22300538716b640291d9943683a6a

diff --git a/assignment4.mdwn b/assignment4.mdwn
index 821b92e1..9b7ec2c0 100644
--- a/assignment4.mdwn
+++ b/assignment4.mdwn
@@ -64,19 +64,22 @@ return later in the term to the problem of determining when two trees have the
 same fringe. For now, one straightforward way to determine this would be:
 enumerate the fringe of the first tree. That gives you a list. Enumerate the
 fringe of the second tree. That also gives you a list. Then compare the two
-lists to see if they're equal. (You just programmed this above.)
+lists to see if they're equal.
 
-Write the fringe-enumeration function. It should work on the implementation of
-trees you designed in the previous step.
+Write the fringe-enumeration function. It should work on the
+implementation of trees you designed in the previous step.
 
-(See [[hints/Assignment 4 hint 3]] if you need some hints.)
+Then combine this with the list comparison function you wrote for question 2,
+to yield a same-fringe detector. (To use your list comparison function, you'll
+have to make sure you only use Church numerals as the labels of your leaves,
+though nothing enforces this self-discipline.)
 </OL>
 
 
 
 #Mutually-recursive functions#
 
-<OL start=4>
+<OL start=5>
 <LI>(Challenging.) One way to define the function `even` is to have it hand off
 part of the work to another function `odd`:
 
@@ -134,7 +137,7 @@ definitions of `even` and `odd`?
 notes](/week3/#index4h2) as a model, construct a pair `Y1` and `Y2` that behave
 in the way described.
 
-(See [[hints/Assignment 4 hint 4]] if you need some hints.)
+(See [[hints/Assignment 4 hint 3]] if you need some hints.)
 
 </OL>