further reading for closures

book.tex

@@ -463,8 +463,9 @@ organization of the course made it difficult for students to
 understand the rationale for the compiler design. Ghuloum proposed the
 incremental approach~\citep{Ghuloum:2006bh}.
 
-We thank Bor-Yuh Chang, John Clements, Jay McCarthy, Nate Nystrom, and
-Michael Wollowski for teaching courses based on early drafts.
+We thank Bor-Yuh Chang, John Clements, Jay McCarthy, Joseph Near, Nate
+Nystrom, and Michael Wollowski for teaching courses based on early
+drafts.
 
 We thank Ronald Garcia for being Jeremy's partner when they took the
 compiler course in the early 2000's and especially for finding the bug
@@ -9384,6 +9385,27 @@ These exercises only scratches the surface of optimizing of
 closures. A good next step for the interested reader is to look at the
 work of \citet{Keep:2012ab}.
 
+\section{Further Reading}
+
+The notion of lexically scoped anonymous functions predates modern
+computers by about a decade. They were invented by
+\citet{Church:1932aa}, who proposed the $\lambda$ calculus as a
+foundation for logic. Anonymous functions were included in the
+LISP~\citep{McCarthy:1960dz} programming language but were initially
+dynamically scoped. The Scheme dialect of LISP adopted lexical scoping
+and \citet{Guy-L.-Steele:1978yq} demonstrated how to efficiently
+compile Scheme programs. However, environments were represented as
+linked lists, so variable lookup was linear in the size of the
+environment. In this chapter we represent environments using flat
+closures, which were invented by
+\citet{Cardelli:1983aa,Cardelli:1984aa} for the purposes of compiling
+the ML language~\citep{Gordon:1978aa,Milner:1990fk}. With flat
+closures, variable lookup is constant time but the time to create a
+closure is proportional to the number of its free variables.  Flat
+closures were reinvented by \citet{Dybvig:1987ab} in his Ph.D. thesis
+and used in Chez Scheme version 1~\citep{Dybvig:2006aa}.
+
+
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 \chapter{Dynamic Typing}
 \label{ch:Rdyn}