From a19ca9df4191bdac91748cf54df7fa42a00c1c42 Mon Sep 17 00:00:00 2001
From: ben <benjaminlgreenman@gmail.com>
Date: Fri, 11 Mar 2016 08:13:11 -0500
Subject: [PATCH] [icfp] checkpoint: usage intro

---
 icfp-2016/Makefile        |  2 +-
 icfp-2016/common.rkt      |  4 +-
 icfp-2016/fig-staging.tex | 13 +++++++
 icfp-2016/paper.scrbl     |  4 +-
 icfp-2016/texstyle.tex    |  1 +
 icfp-2016/usage.scrbl     | 79 ++++++++++++++++++++++++++++++++++++++-
 6 files changed, 97 insertions(+), 6 deletions(-)
 create mode 100644 icfp-2016/fig-staging.tex

diff --git a/icfp-2016/Makefile b/icfp-2016/Makefile
index adec061..fd54d1c 100644
--- a/icfp-2016/Makefile
+++ b/icfp-2016/Makefile
@@ -6,7 +6,7 @@ compiled/paper_scrbl.zo: *.rkt *.scrbl
 	raco make -v $(PAPER).scrbl
 
 paper.pdf: pkg compiled/paper_scrbl.zo texstyle.tex
-	scribble ++style texstyle.tex --pdf $(PAPER).scrbl
+	scribble ++extra fig-staging.tex ++style texstyle.tex --pdf $(PAPER).scrbl
 
 paper.tex: pkg compiled/paper_scrbl.zo texstyle.tex
 	scribble ++style texstyle.tex --latex $(PAPER).scrbl
diff --git a/icfp-2016/common.rkt b/icfp-2016/common.rkt
index a14e992..ed7096c 100644
--- a/icfp-2016/common.rkt
+++ b/icfp-2016/common.rkt
@@ -136,5 +136,5 @@
 (define (id x)
   (make-element plain @format["~a" x]))
 
-(define (todo . x)
-  (make-element 'bold (list x)))
+(define (todo . x*)
+  (make-element 'bold (cons "TODO:" x*)))
diff --git a/icfp-2016/fig-staging.tex b/icfp-2016/fig-staging.tex
new file mode 100644
index 0000000..ccb16a3
--- /dev/null
+++ b/icfp-2016/fig-staging.tex
@@ -0,0 +1,13 @@
+\begin{center}
+\begin{tikzpicture}
+  \node (0) {$\bullet$};
+  \node (1) [right of=0,xshift=0.5cm]{$\bullet$};
+  \node (2) [right of=1,xshift=0.8cm] {$\bullet$};
+  \node (3) [right of=2,xshift=0.8cm] {$\bullet$};
+
+  \draw[->] (0) edge[bend left=50] node[above]{\emph{read}} (1);
+  \draw[<-] (0) edge[bend right=50] node[below]{\emph{expand}} (1);
+  \draw[->] (1) -- node[above]{\emph{typecheck}} (2);
+  \draw[->] (2) -- node[above]{\emph{compile}} (3);
+\end{tikzpicture}
+\end{center}
diff --git a/icfp-2016/paper.scrbl b/icfp-2016/paper.scrbl
index 9b1b5ec..c6dc11f 100644
--- a/icfp-2016/paper.scrbl
+++ b/icfp-2016/paper.scrbl
@@ -37,8 +37,8 @@
 
 @include-section{intro.scrbl}
 @include-section{solution.scrbl}
-@;@include-section{usage.scrbl}
-@;@include-section{experience.scrbl} @; Merge with usage?
+@include-section{usage.scrbl}
+@include-section{experience.scrbl} @; Merge with usage?
 @;@include-section{implementation.scrbl}
 @;@include-section{correctness.scrbl}
 @;@include-section{related.scrbl}
diff --git a/icfp-2016/texstyle.tex b/icfp-2016/texstyle.tex
index 4a2a643..6458e63 100644
--- a/icfp-2016/texstyle.tex
+++ b/icfp-2016/texstyle.tex
@@ -5,6 +5,7 @@
 \lstset{language=ML}
 \usepackage[usenames,dvipsnames]{xcolor}
 \usepackage{multicol}
+\usepackage{tikz}
 
 % Override Scribble's default SecRef to numeric only
 \renewcommand{\SecRef}[2]{~#1}
diff --git a/icfp-2016/usage.scrbl b/icfp-2016/usage.scrbl
index 481cb14..d1d4f7a 100644
--- a/icfp-2016/usage.scrbl
+++ b/icfp-2016/usage.scrbl
@@ -1,6 +1,40 @@
 #lang scribble/sigplan
+@require["common.rkt"]
 
-@title{Usage}
+@title[#:tag "sec:usage"]{Real-World Metaprogramming}
+
+We have defined useful letter-of-values transformations for a variety of
+ common programming tasks ranging from type-safe string formatting to
+ constant-folding of arithmetic.
+These transformations are implemented in Typed Racket@~cite[TypedRacket],
+ which inherits Racket's powerful macro system@~cite[plt-tr1].
+
+Our exposition does not assume any knowledge of Racket or Typed Racket, but
+ a key design choice of the Typed Racket language model bears mentioning:
+ evaluation of a Typed Racket program happens across three distinct stages,
+ shown in @Figure-ref{fig:staging}.
+First the program is read and macro-expanded; as expanding a macro introduces
+ new code, the result is recursively read and expanded until no macros remain.
+Next, the @emph{fully-expanded} Typed Racket program is type checked.
+If checking succeeds, types are erased and the program is handed to the Racket
+ compiler.
+For us, this means that we can implement @exact|{$\trans\ $}|
+ functions as macros referencing @exact|{$\interp\ $}| functions and rely
+ on the macro expander to invoke our transformations before the type checker runs.
+
+@figure["fig:staging"
+  @list{Typed Racket language model}
+  @exact|{\input{fig-staging}}|
+]
+
+Though we describe each of the following transformations using in-line constant
+ values, our implementation applies @exact|{$\interp\ $}| functions to every
+ definition and let-binding in the program and then associates compile-time
+ data with the bound identifier.
+When a defined value flows into a function like @racket[printf] without being
+ mutated along the way, we retrieve this cached information.
+The macro system features used to implement this behavior are described in
+ @Secref{sec:implementation}.
 
 @; regexp-match
 @; format
@@ -8,6 +42,41 @@
 @; vectors
 @; arity
 
+@section{Regexp}
+Regular expression patterns are another common value whose structure is not
+ expressed by conventional type systems.
+Consider the function @racket[regexp-match] from Typed Racket:
+
+@interaction[
+  (regexp-match #rx"types" "types@ccs.neu.edu")
+
+  (regexp-match #rx"lambda" "types@ccs.neu.edu")
+
+  (regexp-match #rx"(.*)@(.*)" "types@ccs.neu.edu")
+]
+@; TODO note that nested groups cannot fail.
+
+When called with a pattern @racket[p] and string @racket[s] to match with,
+ @racket[(regexp-match p s)] returns a list of all substrings in @racket[s]
+ matching groups in the pattern @racket[p].
+The pattern itself counts for one group and parentheses within @racket[p]
+ delimit nested groups.
+Hence the third example returns a list of three elements.
+A match can also fail, in which case the value @racket[#f] is returned.
+
+Although Typed Racket's @racket[regexp-match] has the type@note{Assuming that a
+    successful match implies that all nested groups successfully match.}
+ @racket[(Regexp String -> (U #f (Listof String)))], the number of strings
+ in the result list is determined by the number of groups in the input regular
+ expression.
+Like the arity of a function or the size of a tuple, the number of groups
+ in a pattern is often clear to the programmer.
+We could imagine using
+ an indexed family of @racket[regexp-match] functions for patterns of
+ two, three, or more groups.
+Ideally though, the programming language should understand
+ these unconventional or domain-specific flavors of polymorphism.
+
 
 @section{Database}
 @; db
@@ -55,7 +124,15 @@ Calls to generic operations like @racket[query-row] are then specialized to
 @; - no changes to underlying library / type system
 @; - compile-time validation of query strings
 
+Incidentally, @racket[regexp-match:] is useful for parsing queries.
+We also implemented @racket[query-row] to return a sized vector.
+
+
 While light years away from LINQ, this technique provides at least basic
  safety guarantees for an existing library and demonstrates the generality of
  our technique.
 
+
+@section{}
+@; identifier macros
+@; rename transformers