week2 tweak

[lambda.git] / week2.mdwn

diff --git a/week2.mdwn b/week2.mdwn
index 8805838..f978678 100644 (file)
--- a/week2.mdwn
+++ b/week2.mdwn
@@ -36,10 +36,10 @@ Another way to think of it is to identify expressions not with particular alphab
 A third way to think is to identify the lambda formula not with classes of alphabetic sequences, but rather with abstract structures that we might draw like this:
 
 <pre><code>
-       (&lambda;. &lambda;. z x) y
-    ^  ^  | |
-    |  |__| |
-    |_______|
+       (&lambda;. &lambda;. _ _) y
+     ^  ^  | |
+     |  |__| |
+     |_______|
 </code></pre>
 
 Here there are no bound variables, but there are *bound positions*. We can regard formula like (a) and (b) as just helpfully readable ways to designate these abstract structures.