fix links to v4 lists

[lambda.git] / week4.mdwn

diff --git a/week4.mdwn b/week4.mdwn
index e69832f..e3f0fb9 100644 (file)
--- a/week4.mdwn
+++ b/week4.mdwn
@@ -6,11 +6,11 @@ A: That's easy: let `T` be an arbitrary term in the lambda calculus.  If
 `T` has a fixed point, then there exists some `X` such that `X <~~>
 TX` (that's what it means to *have* a fixed point).
 
-<pre>
-let W = \x.T(xx) in
-let X = WW in
-X = WW = (\x.T(xx))W = T(WW) = TX
-</pre>
+<pre><code>
+let L = \x. T (x x) in
+let X = L L in
+X &equiv; L L &equiv; (\x. T (x x)) L ~~> T (L L) &equiv; T X
+</code></pre>
 
 Please slow down and make sure that you understand what justified each
 of the equalities in the last line.
@@ -437,7 +437,7 @@ of the list multiplied to, because that would affect the answer you passed
 along to the continue-leftwards handler.
 
 A **version 5** list encodes the kind of fold operation we're envisaging here, in
-the same way that v3 (and [v4](/advanced/#v4)) lists encoded the simpler fold operation.
+the same way that v3 (and [v4](/advanced/#index1h1)) lists encoded the simpler fold operation.
 Roughly, the list `[5;4;3;2;1]` would look like this:
 
 
@@ -566,6 +566,6 @@ detail](http://okmij.org/ftp/Streams.html#enumerator-stream).
                                larger_computation
 
 3.     To extract tails efficiently, too, it'd be nice to fuse the apparatus developed
-       in these v5 lists with the ideas from [v4](/advanced/#v4) lists.
+       in these v5 lists with the ideas from [v4](/advanced/#index1h1) lists.
        But that also is left as an exercise.