check

book.tex

@@ -25,7 +25,7 @@
 
 \def\racketEd{0}
 \def\pythonEd{1}
-\def\edition{0}
+\def\edition{1}
 
 % material that is specific to the Racket edition of the book
 \newcommand{\racket}[1]{{\if\edition\racketEd{#1}\fi}}
@@ -11162,6 +11162,16 @@ class TypeCheckLtup(TypeCheckLwhile):
 \section{Garbage Collection}
 \label{sec:GC}
 
+
+%% Def. The *live data* are all of the tuples that might be accessed by
+%% the program in the future. We can overapproximate this as all of the
+%% tuples that are reachable, transitively, from the registers or
+%% procedure call stack. We refer to the registers and stack collectively
+%% as the *root set*.
+
+%% The goal of a garbage collector is to reclaim the data that is not
+%% live.
+
 Here we study a relatively simple algorithm for garbage collection
 that is the basis of state-of-the-art garbage
 collectors~\citep{Lieberman:1983aa,Ungar:1984aa,Jones:1996aa,Detlefs:2004aa,Dybvig:2006aa,Tene:2011kx}. In