X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=assignment3.mdwn;h=e240b732b1405e176d696bbab3c5974a1d125f35;hp=4da627a53691f776e2a6a4a5aaac63a29856ba01;hb=aab06ee4eafe7ac322521e4cef1b1704a9258900;hpb=74821f8f77cf5c5a67bce44ab8944dff92678e30

diff --git a/assignment3.mdwn b/assignment3.mdwn
index 4da627a5..e240b732 100644
--- a/assignment3.mdwn
+++ b/assignment3.mdwn
@@ -10,9 +10,9 @@ originally read
 	let tb = (make_list t12 t3) in
 
 This has been corrected below, and in the preloaded evaluator for 
-working on assignment 3.
-
+working on assignment 3, available here: [[assignment 3 evaluator]].
 
+<hr>
 
 Once again, the lambda evaluator will make working through this
 assignment much faster and more secure.
@@ -42,6 +42,7 @@ Recall that version 1 style lists are constructed like this (see
 	; church numerals
 	let iszero = \n. n (\x. false) true in
 	let succ = \n s z. s (n s z) in
+	let add = \l r. l succ r in
 	let mul = \m n s. m (n s) in
 	let pred = (\shift n. n shift (make\_pair 0 0) get\_snd) (\p. p (\x y. make\_pair (succ x) x)) in
 	let leq = \m n. iszero(n pred m) in
@@ -50,6 +51,7 @@ Recall that version 1 style lists are constructed like this (see
 	; a fixed-point combinator for defining recursive functions
 	let Y = \f. (\h. f (h h)) (\h. f (h h)) in
 	let length = Y (\length l. isempty l 0 (succ (length (tail l)))) in
+	let fold = Y (\f l g z. isempty l z (g (head l)(f (tail l) g z))) in
 	
 	eq 2 2 yes no