minor edits

book.tex

@@ -4199,12 +4199,6 @@ the procedure call stack. These addresses are called the \emph{root
 transitively reachable from the root set. Thus, it is safe for the
 garbage collector to reclaim the tuples that are not reachable in this
 way.
-%
-\footnote{The sitation in Figure~\ref{fig:copying-collector}, with a
-  cycle, cannot be created by a well-typed program in $R_3$. However,
-  creating cycles will be possible once we get to $R_6$.  We design
-  the garbage collector to deal with cycles to begin with, so we will
-  not need to revisit this issue.}
 
 So the goal of the garbage collector is twofold:
 \begin{enumerate}
@@ -4214,17 +4208,22 @@ So the goal of the garbage collector is twofold:
   \emph{garbage}.
 \end{enumerate}
 A copying collector accomplishes this by copying all of the live
-objects into the ToSpace and then performs a slight of hand, treating
-the ToSpace as the new FromSpace and the old FromSpace as the new
-ToSpace.  In the example of Figure~\ref{fig:copying-collector}, there
-are three pointers in the root set, one in a register and two on the
-stack.  All of the live objects have been copied to the ToSpace (the
-right-hand side of Figure~\ref{fig:copying-collector}) in a way that
-preserves the pointer relationships. For example, the pointer in the
-register still points to a 2-tuple whose first element is a 3-tuple
-and second element is a 2-tuple.  There are four tuples that are not
-reachable from the root set and therefore do not get copied into the
-ToSpace.
+objects from the FromSpace into the ToSpace and then performs a slight
+of hand, treating the ToSpace as the new FromSpace and the old
+FromSpace as the new ToSpace.  In the example of
+Figure~\ref{fig:copying-collector}, there are three pointers in the
+root set, one in a register and two on the stack.  All of the live
+objects have been copied to the ToSpace (the right-hand side of
+Figure~\ref{fig:copying-collector}) in a way that preserves the
+pointer relationships. For example, the pointer in the register still
+points to a 2-tuple whose first element is a 3-tuple and second
+element is a 2-tuple.  There are four tuples that are not reachable
+from the root set and therefore do not get copied into the ToSpace.
+(The sitation in Figure~\ref{fig:copying-collector}, with a
+cycle, cannot be created by a well-typed program in $R_3$. However,
+creating cycles will be possible once we get to $R_6$.  We design
+the garbage collector to deal with cycles to begin with, so we will
+not need to revisit this issue.)
 
 \begin{figure}[tbp]
 \centering
@@ -4234,11 +4233,6 @@ ToSpace.
 \label{fig:copying-collector}
 \end{figure}
 
-%% \margincomment{\tiny Need to add comment somewhere about the goodness
-%%  of copying collection, especially that it doesn't touch
-%%  the garbage, so its time complexity only depends on the
-%%  amount of live data.\\ --Jeremy}
-
 There are many alternatives to copying collectors (and their older
 siblings, the generational collectors) when its comes to garbage
 collection, such as mark-and-sweep and reference counting.  The