From: Jim Pryor <profjim@jimpryor.net>
Date: Sun, 3 Oct 2010 23:02:10 +0000 (-0400)
Subject: fixed assignment3 pred
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=2950fbdc81547d95aa8fda13cc3e042ca264e0e6;hp=d6c90390eadec4c8ec2c7728269ca063e9e45de0

fixed assignment3 pred

Signed-off-by: Jim Pryor <profjim@jimpryor.net>
---

diff --git a/assignment3.mdwn b/assignment3.mdwn
index f84d07f9..289f818a 100644
--- a/assignment3.mdwn
+++ b/assignment3.mdwn
@@ -30,7 +30,7 @@ Recall that version 1 style lists are constructed like this (see
 	let iszero = \n. n (\x. false) true in
 	let succ = \n s z. s (n s z) in
 	let mul = \m n s. m (n s) in
-	let pred = \n. iszero n 0 (length (tail (n (\p. make_list junk p) empty))) 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
 	let eq = \m n. and (leq m n)(leq n m) in
 	
diff --git a/assignment_3_evaluator.mdwn b/assignment_3_evaluator.mdwn
index 496003d0..c910064a 100644
--- a/assignment_3_evaluator.mdwn
+++ b/assignment_3_evaluator.mdwn
@@ -21,7 +21,7 @@ let mylist = make\_list 1 (make\_list 2 (make\_list 3 empty)) in
 let iszero = \n. n (\x. false) true in
 let succ = \n s z. s (n s z) in
 let mul = \m n s. m (n s) in
-let pred = \n. iszero n 0 (length (tail (n (\p. make\_list junk p) empty))) 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
 let eq = \m n. and (leq m n)(leq n m) in
 ;