more polishing

book.tex

@@ -5493,7 +5493,7 @@ in Figure~\ref{fig:Rif-syntax}. The \LangIf{} language includes all of
 \code{\#f}, and the conditional \code{if} expression. We expand the
 operators to include
 \begin{enumerate}
-\item subtraction on integers \ocaml{OCaml version already had thes},
+\item subtraction on integers \ocaml{(OCaml version already had this)},
 \item the logical operators \key{and}, \key{or} and \key{not},
 \item the \key{eq?} operation for comparing two integers or two Booleans, and
 \item the \key{<}, \key{<=}, \key{>}, and \key{>=} operations for
@@ -6342,7 +6342,11 @@ labeled sequence of code, called a \emph{basic block}, and each edge
 represents a jump to another block. The \key{CProgram} construct of
 \LangCVar{} and \LangCIf{} contains a control flow graph represented
 as an alist mapping labels to basic blocks. Each basic block is
-represented by the $\Tail$ non-terminal.
+represented by the $\Tail$ non-terminal. \ocaml{It is 
+  a little confusing to call this representation a CFG, since it
+  does not make the flow edges explicit (they have to be deduced by looking
+  inside the $\Tail$s). When we get to register assignment for \LangCIf{},
+  we will construct a more explicit CFG data structure.}
 
 Figure~\ref{fig:explicate-control-s1-38} shows the output of the
 \code{remove-complex-opera*} pass and then the