errata ch. 1 from Michael Vanier

book.tex

@@ -514,19 +514,19 @@ definition for integer constants.
 (struct Int (value))
 \end{lstlisting}
 An integer node includes just one thing: the integer value.
-To create a AST node for the integer $8$, we write \code{(Int 8)}.
+To create an AST node for the integer $8$, we write \code{(Int 8)}.
 \begin{lstlisting}
 (define eight (Int 8))
 \end{lstlisting}
 We say that the value created by \code{(Int 8)} is an
 \emph{instance} of the \code{Int} structure.
 
-The following is the \code{struct} definition for primitives operations.
+The following is the \code{struct} definition for primitive operations.
 \begin{lstlisting}
 (struct Prim (op args))
 \end{lstlisting}
 A primitive operation node includes an operator symbol \code{op}
-and a list of children \code{args}. For example, to create
+and a list of child \code{args}. For example, to create
 an AST that negates the number $8$, we write \code{(Prim '- (list eight))}.
 \begin{lstlisting}
 (define neg-eight (Prim '- (list eight)))
@@ -599,7 +599,7 @@ left-hand-side.
 A name such as $\Exp$ that is defined by the grammar rules is a
 \emph{non-terminal}.  \index{non-terminal}
 %
-The name $\Int$ is a also a non-terminal, but instead of defining it
+The name $\Int$ is also a non-terminal, but instead of defining it
 with a grammar rule, we define it with the following explanation.  We
 make the simplifying design decision that all of the languages in this
 book only handle machine-representable integers.  On most modern
@@ -844,7 +844,7 @@ it is defined using a sequence of match clauses that correspond to a
 grammar, and the body of each clause makes a recursive call on each
 child node.\footnote{This principle of structuring code according to
   the data definition is advocated in the book \emph{How to Design
-    Programs} \url{http://www.ccs.neu.edu/home/matthias/HtDP2e/}.}.
+    Programs} \url{https://htdp.org/2020-8-1/Book/index.html}.}.
 Below we also define a second function, named \code{Rint?}, that
 determines whether an AST is an \LangInt{} program.  In general we can
 expect to write one recursive function to handle each non-terminal in