From: Jim Pryor
Date: Wed, 15 Sep 2010 20:47:24 +0000 (-0400)
Subject: week1 tweaks
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=dc4a37d3f21dae7e6aceb29c6291fc2e7daa2f5e
week1 tweaks
Signed-off-by: Jim Pryor
---
diff --git a/week1.mdwn b/week1.mdwn
index b864d024..8124ffe6 100644
--- a/week1.mdwn
+++ b/week1.mdwn
@@ -123,7 +123,7 @@ Each variable is an expression. For any expressions M and N and variable a, the
**Abstract**: `(λa M)`

-We'll tend to write `(λa M)`

as just `(\a M)`, so we don't have to write out the markup code for the `λ`

. You can yourself write `(λa M)`

or `(\a M)` or `lambda a M`.
+We'll tend to write `(λa M)`

as just `(\a M)`, so we don't have to write out the markup code for the `λ`

. You can yourself write `(λa M)`

or `(\a M)` or `(lambda a M)`.
**Application**: `(M N)`

@@ -142,7 +142,7 @@ Examples of expressions:
(x (\x x))
((\x (x x)) (\x (x x)))
-The lambda calculus has an associated proof theory. For now, we can regard the proof theory as having just one rule, called the rule of "beta-reduction" or "beta-contraction". Suppose you have some expression of the form:
+The lambda calculus has an associated proof theory. For now, we can regard the proof theory as having just one rule, called the rule of **beta-reduction** or "beta-contraction". Suppose you have some expression of the form:
((\a M) N)
@@ -150,7 +150,7 @@ that is, an application of an abstract to some other expression. This compound f
The rule of beta-reduction permits a transition from that expression to the following:
- M {a:=N}
+ M [a:=N]
What this means is just `M`, with any *free occurrences* inside `M` of the variable `a` replaced with the term `N`.