C_1 grammar update

book.tex

@@ -2912,7 +2912,7 @@ arguments unconditionally.
 \begin{array}{lcl}
 \Arg &::=& \ldots \mid \key{\#t} \mid \key{\#f} \\
 \Exp &::= & \ldots \mid (\key{not}\;\Arg) \mid (\key{eq?}\;\Arg\;\Arg) \\
-\Stmt &::=& \ldots \mid \IF{\Exp}{\Stmt^{*}}{\Stmt^{*}} \\
+\Stmt &::=& \ldots \mid \IF{\Arg}{\Stmt^{*}}{\Stmt^{*}} \\
 C_1 & ::= & (\key{program}\;(\Var^{*})\;\Stmt^{+})
 \end{array}
 \]