X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=exercises%2F_assignment4.mdwn;h=7df06052a7d951fd663438b1b9cfbc5181238bed;hp=0ff4b2c3130d20a7d11b91599be16299d65c3684;hb=89121328344917225949cb675a6706cbcd0f83d9;hpb=1557d471b7e1c4c8723ab78f0fa6492f59554ba1
diff --git a/exercises/_assignment4.mdwn b/exercises/_assignment4.mdwn
index 0ff4b2c3..7df06052 100644
--- a/exercises/_assignment4.mdwn
+++ b/exercises/_assignment4.mdwn
@@ -12,7 +12,7 @@ and prove that it is a fixed point.
never gets around to noticing whether it has an argument, let alone
doing anything with that argument. If so, how could Ω have a
fixed point? That is, how could there be an `X` such that
-Ω X <~~> &Omegea;(Ω X)
? To answer this
+Ω X <~~> Ω(Ω X)
? To answer this
question, begin by constructing YΩ
. Prove that
YΩ
is a fixed point for Ω.
@@ -29,18 +29,18 @@ The factorial `n! = n * (n - 1) * (n - 2) * ... * 3 * 2 * 1`.
For instance, `fac 0 ~~> 1`, `fac 1 ~~> 1`, `fac 2 ~~> 2`, `fac 3 ~~>
6`, and `fac 4 ~~> 24`.
- let true = \then else. then in
- let false = \then else. else in
- let iszero = \n. n (\x. false) true in
- let pred = \n f z. n (\u v. v (u f)) (K z) I in
- let succ = \n f z. f (n f z) in
- let add = \n m .n succ m in
- let mult = \n m.n(add m)0 in
- let Y = \h . (\f . h (f f)) (\f . h (f f)) in
+ let true = \then else. then in
+ let false = \then else. else in
+ let iszero = \n. n (\x. false) true in
+ let pred = \n f z. n (\u v. v (u f)) (K z) I in
+ let succ = \n f z. f (n f z) in
+ let add = \n m .n succ m in
+ let mult = \n m.n(add m)0 in
+ let Y = \h . (\f . h (f f)) (\f . h (f f)) in
- let fac = ... in
+ let fac = ... in
- fac 4
+ fac 4
## Arithmetic infinity? ##