X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=hints%2Fassignment_4_answer_4.mdwn;h=c2cd1fd7a937c678f7936d6527f1a304713b434d;hp=17c8490f3dfef97fdcca21e3f2f0d09d137e046a;hb=eb911b5d944e52796284fc88109e8e171f7bd81d;hpb=880952bd8862bde3c8e71238097fc2726c244e57

diff --git a/hints/assignment_4_answer_4.mdwn b/hints/assignment_4_answer_4.mdwn
index 17c8490f..c2cd1fd7 100644
--- a/hints/assignment_4_answer_4.mdwn
+++ b/hints/assignment_4_answer_4.mdwn
@@ -13,15 +13,17 @@
 			in
 
 
-	Y1 t1 t2 ~~> elem1 elem1 elem2
+	X1 === Y1 t1 t2 ~~> elem1 elem1 elem2
 			 === (\elem1 elem2. t1 (elem1 elem1 elem2) (elem2 elem1 elems2)) elem1 elem2
 			 ~~> t1 (elem1 elem1 elem2) (elem2 elem1 elem2)
 			<~~> t1 (Y1 t1 t2) (Y2 t1 t2)
+			 === t1 X1 X2
 
 			and
 
-	Y2 t1 t2 ~~> elem2 elem1 elem2
+	X2 === Y2 t1 t2 ~~> elem2 elem1 elem2
 			 === (\elem1 elem2. t2 (elem1 elem1 elem2) (elem2 elem1 elems2)) elem1 elem2
 			 ~~> t2 (elem1 elem1 elem2) (elem2 elem1 elem2)
 			<~~> t2 (Y1 t1 t2) (Y2 t1 t2)
+			 === t2 X1 X2