From: Jim Pryor Date: Sun, 19 Sep 2010 22:11:02 +0000 (-0400) Subject: week2 tweak X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=5da5bda6005474c49ec76ad89dfd92959388b030 week2 tweak Signed-off-by: Jim Pryor --- diff --git a/week2.mdwn b/week2.mdwn index 13d1d449..88058389 100644 --- a/week2.mdwn +++ b/week2.mdwn @@ -36,9 +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:

-	λ ... ___ ...
-	^      |
-	|______|
+	(λ. λ. z x) y
+    ^  ^  | |
+    |  |__| |
+    |_______|
 
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.