fixing typo in interp-R0 error, thanks to onelharrison

book.tex

@@ -851,7 +851,7 @@ $R_0$ expressions.
     [(Prim 'read '())
      (define r (read))
      (cond [(fixnum? r) r]
-           [else (error 'interp-R1 "expected an integer" r)])]
+           [else (error 'interp-R0 "expected an integer" r)])]
     [(Prim '- (list e))
      (define v (interp-exp e))
      (fx- 0 v)]
@@ -1254,11 +1254,11 @@ criteria in the following diagram.
 In the next section we introduce enough of the x86 assembly
 language to compile $R_1$.
 
-\section{The x86 Assembly Language}
+\section{The x86$_0$ Assembly Language}
 \label{sec:x86}
 
 Figure~\ref{fig:x86-0-concrete} defines the concrete syntax for the subset of
-the x86 assembly language needed for this chapter.
+the x86 assembly language needed for this chapter, which we call x86$_0$.
 %
 An x86 program begins with a \code{main} label followed by a sequence
 of instructions.  In the grammar, the superscript $+$ is used to
@@ -1317,7 +1317,7 @@ the x86 instructions used in this book.
 \]
 \end{minipage}
 }
-\caption{The concrete syntax of the $x86_0$ assembly language (AT\&T syntax).}
+\caption{The concrete syntax of the x86$_0$ assembly language (AT\&T syntax).}
 \label{fig:x86-0-concrete}
 \end{figure}
 
@@ -1492,7 +1492,7 @@ returns the stack pointer to where it was prior to the procedure call.
 
 The compiler needs a convenient representation for manipulating x86
 programs, so we define an abstract syntax for x86 in
-Figure~\ref{fig:x86-0-ast}. We refer to this language as $x86_0$ with
+Figure~\ref{fig:x86-0-ast}. We refer to this language as x86$_0$ with
 a subscript $0$ because later we introduce extended versions of this
 assembly language. The main difference compared to the concrete syntax
 of x86 (Figure~\ref{fig:x86-0-concrete}) is that it does not allow labeled
@@ -1527,7 +1527,7 @@ x86_0 &::= & \PROGRAM{\itm{info}}{\CFG{\key{(}\itm{label} \,\key{.}\, \Block \ke
 \]
 \end{minipage}
 }
-\caption{The abstract syntax of $x86_0$ assembly.}
+\caption{The abstract syntax of x86$_0$ assembly.}
 \label{fig:x86-0-ast}
 \end{figure}
 
@@ -1813,7 +1813,7 @@ C_0 & ::= & \PROGRAM{\itm{info}}{\CFG{\key{(}\itm{label}\,\key{.}\,\Tail\key{)}^
 \subsection{The dialects of x86}
 
 The x86$^{*}_0$ language, pronounced ``pseudo x86'', is the output of
-the pass \key{select-instructions}. It extends $x86_0$ with an
+the pass \key{select-instructions}. It extends x86$_0$ with an
 unbounded number of program-scope variables and has looser rules
 regarding instruction arguments. The x86$^{\dagger}$ language, the
 output of \key{print-x86}, is the concrete syntax for x86.
@@ -2852,8 +2852,10 @@ sets shown between each instruction to make the figure easy to read.
 \begin{exercise}\normalfont
 Implement the compiler pass named \code{uncover-live} that computes
 the live-after sets. We recommend storing the live-after sets (a list
-of lists of variables) in the $\itm{info}$ field of the \key{Block}
-structure.
+of a set of variables) in the $\itm{info}$ field of the \key{Block}
+structure. We recommend using the
+\href{https://docs.racket-lang.org/reference/sets.html}{\code{racket/set}}
+package for representing sets of variables.
 %
 We recommend organizing your code to use a helper function that takes
 a list of instructions and an initial live-after set (typically empty)
@@ -4052,7 +4054,7 @@ modern computer architectures.
 \end{exercise}
 
 
-\section{XOR, Comparisons, and Control Flow in x86}
+\section{The x86$_1$ Language}
 \label{sec:x86-1}
 
 To implement the new logical operations, the comparison operations,
@@ -4115,7 +4117,7 @@ x86_1 &::= & \gray{\PROGRAM{\itm{info}}{\CFG{\key{(}\itm{label} \,\key{.}\, \Blo
 \]
 \end{minipage}
 }
-\caption{The abstract syntax of $x86_1$ (extends x86$_0$ of Figure~\ref{fig:x86-0-ast}).}
+\caption{The abstract syntax of x86$_1$ (extends x86$_0$ of Figure~\ref{fig:x86-0-ast}).}
 \label{fig:x86-1}
 \end{figure}
 
@@ -5788,7 +5790,7 @@ start:
 
 \clearpage
 
-\section{Select Instructions}
+\section{Select Instructions and the x86$_2$ Language}
 \label{sec:select-instructions-gc}
 
 %% void (rep as zero)
@@ -5893,7 +5895,7 @@ x86_2 &::= & \gray{  (\key{program} \;\itm{info} \;(\key{type}\;\itm{type})\; \I
 \end{figure}
 
 The syntax of the $x86_2$ language is defined in
-Figure~\ref{fig:x86-2}.  It differs from $x86_1$ just in the addition
+Figure~\ref{fig:x86-2}.  It differs from x86$_1$ just in the addition
 of the form for global variables.
 %
 Figure~\ref{fig:select-instr-output-gc} shows the output of the
@@ -6560,7 +6562,7 @@ where $\itm{mainDef}$ is
 \end{lstlisting}
 
 
-\section{Reveal Functions}
+\section{Reveal Functions and the $F_1$ language}
 \label{sec:reveal-functions-r4}
 
 Going forward, the syntax of $R_4$ is inconvenient for purposes of
@@ -6711,7 +6713,7 @@ processing function definitions. Each function definition in $C_3$ has
 its own set of local variables, so the code for function definitions
 should be similar to the case for the \code{program} form in $C_2$.
 
-\section{Select Instructions}
+\section{Select Instructions and the x86$_3$ Language}
 \label{sec:select-r4}
 
 The output of select instructions is a program in the x86$_3$