cite Cardelli

book.tex

@@ -6476,17 +6476,19 @@ point where the \code{lambda} is applied. Referring again to
 Figure~\ref{fig:lexical-scoping}, the binding of \code{x} to \code{5}
 needs to be used in the application of \code{g} to \code{11}, but the
 binding of \code{x} to \code{3} needs to be used in the application of
-\code{h} to \code{15}. The solution is to bundle the values of the
+\code{h} to \code{15}. An efficient solution to the problem, due to
+\citet{Cardelli:1983aa}, is to bundle into a vector the values of the
 free variables together with the function pointer for the lambda's
-code into a data structure called a \emph{closure}. Fortunately, we
-already have the appropriate ingredients to make closures,
-Chapter~\ref{ch:tuples} gave us tuples and Chapter~\ref{ch:functions}
-gave us function pointers. The function pointer shall reside at index
-$0$ and the values for free variables will fill in the rest of the
-tuple. Figure~\ref{fig:closures} depicts the two closures created by
-the two calls to \code{f} in Figure~\ref{fig:lexical-scoping}.
-Because the two closures came from the same \key{lambda}, they share
-the same code but differ in the values for free variable \code{x}.
+code, an arrangement called a \emph{flat closure} (which we shorten to
+just ``closure'') . Fortunately, we have all the ingredients to make
+closures, Chapter~\ref{ch:tuples} gave us vectors and
+Chapter~\ref{ch:functions} gave us function pointers. The function
+pointer shall reside at index $0$ and the values for free variables
+will fill in the rest of the vector. Figure~\ref{fig:closures} depicts
+the two closures created by the two calls to \code{f} in
+Figure~\ref{fig:lexical-scoping}.  Because the two closures came from
+the same \key{lambda}, they share the same function pointer but differ
+in the values for the free variable \code{x}.
 
 \begin{figure}[tbp]
 \centering \includegraphics[width=0.6\textwidth]{figs/closures}