From: Jim Pryor <profjim@jimpryor.net>
Date: Mon, 4 Oct 2010 01:14:50 +0000 (-0400)
Subject: Merge branch 'pryor'
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=0a79dd27b99169648a1f03ec0b8847a1c5b822fc;hp=93875f124b3af0b7e114373588fa110d79f9abc0

Merge branch 'pryor'
---

diff --git a/assignment4.mdwn b/assignment4.mdwn
index 7073dc6b..12c1ef2a 100644
--- a/assignment4.mdwn
+++ b/assignment4.mdwn
@@ -68,8 +68,6 @@ lists to see if they're equal. (You just programmed this above.)
 
 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.)
 </OL>
 
 
@@ -134,7 +132,7 @@ 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>
 
diff --git a/hints/assignment_4_hint_3.mdwn b/hints/assignment_4_hint_3.mdwn
index 48063d3a..9cfef8ad 100644
--- a/hints/assignment_4_hint_3.mdwn
+++ b/hints/assignment_4_hint_3.mdwn
@@ -1,2 +1,26 @@
-Hints for enumerating a tree's fringe.
+Hints for Y1,Y2. 
+
+*	Begin by trying to define `X1` and `X2` directly, then once they're working, you can abstract back to a pair of combinators `Y1` and `Y2` that generate `X1` and `X2` for a given pair of arguments `T1` and `T2`.
+
+	You want:
+
+		X1 <~~> T1 X1 X2 and
+		X2 <~~> T2 X1 X2
+
+*	X1 is presumably going to have some form like:
+
+		(\elem1 elem2 ... (T1
+							(do-something-with-the-elems-to-make-X1)
+							(do-something-with-the-elems-to-make-X2)
+						  ))
+		some-elem1 some-elem2 ...
+	
+	Right? What will the form of X2 be?
+
+*	Can you see how to go on?
+
+*	Call the displayed abstract above `(\elem1 elem2 ... (...))` "elem0". What's the relation between `X1`, `elem0`, `elem1`, `elem2`...?
+
+*	Go on, now you can do it.
+
 
diff --git a/hints/assignment_4_hint_4.mdwn b/hints/assignment_4_hint_4.mdwn
deleted file mode 100644
index 9cfef8ad..00000000
--- a/hints/assignment_4_hint_4.mdwn
+++ /dev/null
@@ -1,26 +0,0 @@
-Hints for Y1,Y2. 
-
-*	Begin by trying to define `X1` and `X2` directly, then once they're working, you can abstract back to a pair of combinators `Y1` and `Y2` that generate `X1` and `X2` for a given pair of arguments `T1` and `T2`.
-
-	You want:
-
-		X1 <~~> T1 X1 X2 and
-		X2 <~~> T2 X1 X2
-
-*	X1 is presumably going to have some form like:
-
-		(\elem1 elem2 ... (T1
-							(do-something-with-the-elems-to-make-X1)
-							(do-something-with-the-elems-to-make-X2)
-						  ))
-		some-elem1 some-elem2 ...
-	
-	Right? What will the form of X2 be?
-
-*	Can you see how to go on?
-
-*	Call the displayed abstract above `(\elem1 elem2 ... (...))` "elem0". What's the relation between `X1`, `elem0`, `elem1`, `elem2`...?
-
-*	Go on, now you can do it.
-
-