# HG changeset patch
# User Robert McIntyre <rlm@mit.edu>
# Date 1318775541 25200
# Node ID 1c7ace5054ac5254a16099f34beee8b0d75f5fd7

initial commit

diff -r 000000000000 -r 1c7ace5054ac .hgignore
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.hgignore	Sun Oct 16 07:32:21 2011 -0700
@@ -0,0 +1,3 @@
+syntax: glob
+src*
+html*
\ No newline at end of file
diff -r 000000000000 -r 1c7ace5054ac org/no_parens.org
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org/no_parens.org	Sun Oct 16 07:32:21 2011 -0700
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+#+title: Calling it quits without parentheses
+#+author: Robert McIntyre & Dylan Holmes
+#+EMAIL:     rlm@mit.edu
+#+MATHJAX: align:"left" mathml:t path:"../MathJax/MathJax.js"
+#+STYLE: <link rel="stylesheet" type="text/css" href="../css/aurellem.css" />
+#+OPTIONS:   H:3 num:t toc:t \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
+#+SETUPFILE: ../templates/level-0.org
+#+INCLUDE: ../templates/level-0.org
+
+[TABLE-OF-CONTENTS]
+
+# * Calling it quits without parentheses
+Is it possible to make a =quit= command for Clojure such that simply
+typing the word =quit= at an REPL exits the REPL?  An intuitive =quit=
+command would be especially useful for people new to Lisp syntax or
+the REPL; the challenge is to make a genuine Clojure command that
+executes without being called with parentheses. We found three
+solutions.
+
+#+srcname: header
+#+begin_src clojure :results silent
+(ns abomination.no-parens
+  (:use clojure.contrib.def))
+#+end_src
+
+* By modifying =toString=
+#+srcname: toString
+#+begin_src clojure
+(in-ns 'abomination.no-parens)
+(gen-class :name abomination.no-parens.Quit
+	   :prefix quit-)
+
+(defn quit-toString
+  [this]
+  (System/exit 0))
+
+(defvar quit (abomination.no-parens.Quit.)
+  "a sneaky way to support a `quit` command")
+#+end_src
+
+When you type any variable at the REPL, the REPL attempts to print it as a nicely-formatted string by calling its =toString=
+method. Our trick is to define a class with a =toString= method
+that exits the REPL; this trick ensures that any variable of that class will close
+the REPL when the REPL attempts to print it.
+
+First, we use =gen-class= to make a new class named Quit; in that same line, we use
+=:prefix= to establish the convention that any function named
+=quit-[something]= will be adopted as the =[something]= method for the
+newly-defined Quit class. We use this convention to write our own
+=toString= method for Quit.
+
+Next, we define a suitable =toString= method for the Quit class so that
+attempting to print an instance of the Quit class has the effect of
+closing the REPL. We do this by defining a function =quit-toString=
+which closes the REPL; by the convention established above, the Quit
+class automatically adopts  =quit-toString= as its =toString= method.
+
+Finally, we use =defvar= to create an instance of the Quit class; we
+name this instance =quit=. Now when you type =quit= into the REPL, the
+REPL executes the =toString= method of the Quit class, exiting the REPL instead of returning a
+string.
+
+#+begin_src clojure :exports both
+(binding [*compile-path* "/home/r/aurellem/classes"]
+  (compile 'abomination.no-parens))
+#+end_src
+
+#+results:
+: abomination.no-parens
+
+* By wrapping the command in a lazy sequence
+#+srcname: lazy-seq
+#+begin_src clojure :results silent
+(in-ns 'abomination.no-parens)
+(defvar quit* (lazy-seq :the-great-bringer-of-death! (System/exit 0))
+  "the first time it's evaulated it will kill the JVM")
+#+end_src
+  
+* By =delay=-ing the command 
+#+srcname: delay
+#+begin_src clojure :results silent
+(in-ns 'abomination.no-parens)
+(defvar quit** (delay (System/exit 0))
+  "when this is evaulated at the REPL, it will exit the JVM.")
+#+end_src
+
+The same thing, accomplished in a much more elegant and clojureish
+way.
+
+#+begin_src clojure :tangle no_parens.clj :results silent :exports none :noweb yes
+<<header>>
+<<toString>>
+<<lazy-seq>>
+<<delay>>
+#+end_src
+
+# STUD CRUFT PIZZA
+
+#+begin_quote
+And death i think is no parenthesis
+\mdash{}E. E. Cummings
+#+end_quote
diff -r 000000000000 -r 1c7ace5054ac readme.txt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/readme.txt	Sun Oct 16 07:32:21 2011 -0700
@@ -0,0 +1,2 @@
+Here, Dylan and I use some neat tricks to give a "quit" command to
+clojure which can be called with no parens.