X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=week9.mdwn;fp=week9.mdwn;h=f854d27326a4caff8c92167d58a1ad36678437d0;hp=a9f168b903e707f236293fae5b83b7bbe94711a7;hb=624de393ea56a7ab1e802c02b2423ee02b31944a;hpb=9bbf07372e325d2ef5f4ccf09864456e6b8b27df

diff --git a/week9.mdwn b/week9.mdwn
index a9f168b9..f854d273 100644
--- a/week9.mdwn
+++ b/week9.mdwn
@@ -228,6 +228,8 @@ If however you called `factory` twice, you'd have different `getter`/`setter` pa
 
 Here, the call to `setter` only mutated the reference cell associated with the `getter`/`setter` pair. The reference cell associated with `getter'` hasn't changed, and so `getter' ()` will still evaluate to 1.
 
+If you've got a copy of *The Seasoned Schemer*, which we recommended for the seminar, see the discussion at pp. 91-117 and 127-137.
+
 Notice in these fragments that once we return from inside the call to `factory`, the `free_var` mutable variable is no longer accessible, except through the helper functions `getter` and `setter` that we've provided. This is another way in which a thunk like `getter` can be useful: it still has access to the `free_var` reference cell that was created when it was, because its free variables are interpreted relative to the context in which `getter` was built, even if that context is otherwise no longer accessible. What `getter ()` evaluates to, however, will very much depend on *when* we evaluate it---in particular, it will depend on which calls to the corresponding `setter` were evaluated first.
 
 ##Referential opacity##