added example about interaction between shrink and explicate

book.tex

@@ -4704,6 +4704,55 @@ blocks $B_3$ and $B_4$ to obtain the result $B_5$.
 B_5
 \]
 
+Finally, note that the way in which the \code{shrink} pass transforms
+logical operations such as \code{and} and \code{or} can impact the
+quality of code generated by \code{explicate-control}. For example,
+consider the following program.
+\begin{lstlisting}
+(if (and (eq? (read) 0) (eq? (read) 1))
+    0
+    42)  
+\end{lstlisting}
+The \code{and} operation should transform into something that the
+\code{explicat-pred} function can still analyze and descend through to
+reach the underlying \code{eq?} conditions. Ideally, your
+\code{explicate-control} pass should generate code similar to the
+following for the above program.\footnote{If the trivial blocks 17,
+  18, and 20 bother you, take a look at the challenge problem in
+  Section~\ref{sec:opt-jumps}.}
+\begin{center}
+\begin{minipage}{0.45\textwidth}
+\begin{lstlisting}
+start:
+    tmp13 = (read);
+    if (eq? tmp13 0)
+       goto block19;
+    else
+       goto block20;
+block19:
+    tmp14 = (read);
+    if (eq? tmp14 1)
+       goto block17;
+    else
+       goto block18;
+\end{lstlisting}
+\end{minipage}
+\begin{minipage}{0.45\textwidth}
+\begin{lstlisting}
+block20:
+    goto block16;
+block17:
+    goto block15;
+block18:
+    goto block16;
+block15:
+    return 0;
+block16:
+    return 42;
+\end{lstlisting}
+\end{minipage}
+\end{center}
+
 \begin{exercise}\normalfont
   Implement the pass \code{explicate-control} by adding the cases for
   \key{if} to the functions for tail and assignment contexts, and
@@ -7088,7 +7137,7 @@ and changes the top \code{ProgramDefsExp} form to
 \end{lstlisting}
 where $\itm{mainDef}$ is
 \begin{lstlisting}
-(Def main () Integer () |$\Exp'$|)
+(Def 'main '() 'Integer '() |$\Exp'$|)
 \end{lstlisting}