continue week1 summary, add week2 pages

Signed-off-by: Jim Pryor <profjim@jimpryor.net>

diff --git a/week1.mdwn b/week1.mdwn
index 8124ffe..729b14d 100644 (file)
--- a/week1.mdwn
+++ b/week1.mdwn
@@ -167,7 +167,7 @@ For instance:
 
 >      T is defined to be `(x (\x (\y (x (y z)))))`
 
-The first occurrence of `x` in `T` is free.  The `\x` we won't regard as being an occurrence of `x`. The next occurrence of `x` occurs within a form that begins with `\x`, so it is bound as well. The occurrence of `y` is bound; and the occurrence of `z` is free.
+The first occurrence of `x` in T is free.  The `\x` we won't regard as being an occurrence of `x`. The next occurrence of `x` occurs within a form that begins with `\x`, so it is bound as well. The occurrence of `y` is bound; and the occurrence of `z` is free.
 
 Here's an example of beta-reduction:
 
@@ -185,7 +185,7 @@ Different authors use different notations. Some authors use the term "contractio
 
        M ~~> N
 
-We'll mean that you can get from M to N by one or more reduction steps. Hankin uses the symbol -> for one-step contraction, and the symbol ->> for zero-or-more step reduction. Hindley and Seldin use (triangle..sub1) and (triangle).
+We'll mean that you can get from M to N by one or more reduction steps. Hankin uses the symbol &rarr; for one-step contraction, and the symbol &rarr;> for zero-or-more step reduction. Hindley and Seldin use <code>|&gt;<sub>1</sub></code> and <code>|&gt;</code>.
 
 When M and N are such that there's some P that M reduces to by zero or more steps, and that N also reduces to by zero or more steps, then we say that M and N are **beta-convertible**. We'll write that like this:
 
@@ -193,7 +193,7 @@ When M and N are such that there's some P that M reduces to by zero or more step
 
 This is what plays the role of equality in the lambda calculus. Hankin uses the symbol `=` for this. So too do Hindley and Seldin.
 
-In the metatheory, it's also sometimes useful to talk about formulas that are syntactically equivalent *before any reductions take place*. Hankin uses the symbol (three bars) for this. So too do Hindley and Seldin. We'll use that too, and will avoid using `=` when discussing metatheory for the lambda calculus. Instead we'll use `<~~>` as we said above. When we want to introduce a stipulative definition, we'll write it out longhand, as in:
+In the metatheory, it's also sometimes useful to talk about formulas that are syntactically equivalent *before any reductions take place*. Hankin uses the symbol &equiv; for this. So too do Hindley and Seldin. We'll use that too, and will avoid using `=` when discussing metatheory for the lambda calculus. Instead we'll use `<~~>` as we said above. When we want to introduce a stipulative definition, we'll write it out longhand, as in:
 
 >      T is defined to be `(M N)`.