insert missing (list ...) in an example

book.tex

@@ -2174,7 +2174,7 @@ def InterpLvar(InterpLint):
 We return to the troublesome example, repeated here:
 {\if\edition\racketEd  
 \begin{lstlisting}
-(Let 'y (Int 10) (Prim '- (Var 'y)))
+(Let 'y (Int 10) (Prim '- (list (Var 'y))))
 \end{lstlisting}
 \fi}
 {\if\edition\pythonEd\pythonColor
@@ -2183,8 +2183,8 @@ We return to the troublesome example, repeated here:
    print(-y)
 \end{lstlisting}
 \fi}
-\noindent We can invoke the \code{interp\_exp} method for \LangVar{}%
-\racket{on this expression,}
+\noindent We can invoke the \code{interp\_exp} method for \LangVar{}
+\racket{on this expression,}%
 \python{on the \code{-y} expression,}
 %
 which we call \code{e0}, by creating an object of the \LangVar{} class