X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=exercises%2F_assignment4.mdwn;h=127ecc39d0d9fbe6e38f02cac5acc081f8ade4a2;hp=f998e7ac73a33c66d353463a62b91aa7b403d710;hb=cd8b8c25ea0a23ef2ef148a8504913aef8428ac1;hpb=ea4c96609b8d02f5e83a8027cf567bab5562cb5b

diff --git a/exercises/_assignment4.mdwn b/exercises/_assignment4.mdwn
index f998e7ac..127ecc39 100644
--- a/exercises/_assignment4.mdwn
+++ b/exercises/_assignment4.mdwn
@@ -99,7 +99,7 @@ point, i.e., demonstrate that `succ ξ <~~> ξ`.
     We've had surprising success embedding normal arithmetic in the Lambda
 Calculus, modeling the natural numbers, addition, multiplication, and
 so on.  But one thing that some versions of arithmetic supply is a
-notion of infinity, which we'll write as `inf`.  This object usually
+notion of infinity, which we'll write as `inf`.  This object sometimes
 satisfies the following constraints, for any finite natural number `n`:
 
         n + inf == inf
@@ -107,7 +107,7 @@ satisfies the following constraints, for any finite natural number `n`:
         n ^ inf == inf
         leq n inf == true
 
-    (Note, though, that with *some* notions of infinite numbers, like [[!wikipedia ordinal numbers]], operations like `+` and `*` are defined in such a way that `inf + n` is different from `n + inf`, and does exceed `inf`.)
+    (Note, though, that with *some* notions of infinite numbers, like [[!wikipedia ordinal numbers]], operations like `+` are defined in such a way that `inf + n` is different from `n + inf`, and does exceed `inf`; similarly for `*` and `^`. With other notions of infinite numbers, like the [[!wikipedia cardinal numbers]], even less familiar arithmetic operations are employed.)
 
 9. Prove that `add ξ 1 <~~> ξ`, where `ξ` is the fixed
 point you found in (1).  What about `add ξ 2 <~~> ξ`?