README: add more details.

README.md

@@ -1,17 +1,57 @@
 # mal - Make a Lisp
 
-See mal/presentation.mal
+## Description
+
+Mal is an interpreter for a subset of the Clojure programming
+language. Mal is implemetated from scratch in 10 different languages:
+
+* Javascript
+* Python
+* Clojure
+* C
+* Java
+* PHP
+* Bash shell
+* GNU Make
+* mal itself
+* Postscript (in-progress)
+
+
+Mal is also a learning tool. Each implentation of mal is separated
+into 11 incremental, self-contained (and testable) steps that
+demonstrate core concepts of Lisp. The last step is capable of
+self-hosting (running the mal implemenation of mal).
+
+The mal (make a lisp) steps are:
+
+* step0_repl
+* step1_read_print
+* step2_eval
+* step3_env
+* step4_if_fn_do
+* step5_tco
+* step6_file
+* step7_quote
+* step8_macros
+* step9_interop
+* stepA_more
+
+
+Mal was presented publicly for the first time in a lightning talk at
+Clojure West 2014 (unfortunately there is no video). See
+mal/clojurewest2014.mal for the presentation that was given at the
+conference (yes the presentation is a mal program).
 
 ## Building/running implementations
 
-* Bash 4
+### Bash 4
 
 ```
 cd bash
 bash stepX_YYY.sh
 ```
 
-* C
+### C
 
 ```
 cd c
@@ -19,14 +59,14 @@ make
 ./stepX_YYY
 ```
 
-* Clojure
+### Clojure
 
 ```
 cd clojure
 lein with-profile +stepX trampoline run
 ```
 
-* Java 1.7
+### Java 1.7
 
 ```
 cd java
@@ -36,14 +76,14 @@ mvn -quiet exec:java -Dexec.mainClass=mal.stepX_YYY
 mvn -quiet exec:java -Dexec.mainClass=mal.stepX_YYY -Dexec.args="CMDLINE_ARGS"
 ```
 
-* Javascript/Node
+### Javascript/Node
 
 ```
 cd js
 node stepX_YYY.js
 ```
 
-* Mal
+### Mal
 
 Running the mal implementation of mal involves running stepA of one of
 the other implementations and passing the mal step to run as a command
@@ -55,28 +95,28 @@ IMPL_STEPA_CMD ../mal/stepX_YYY.mal
 
 ```
 
-* GNU Make 3.81
+### GNU Make 3.81
 
 ```
 cd make
 make -f stepX_YYY.mk
 ```
 
-* PHP 5.3
+### PHP 5.3
 
 ```
 cd php
 php stepX_YYY.php
 ```
 
-* Postscript Level 2/3
+### Postscript Level 2/3
 
 ```
 cd ps
 gs -q -dNODISPLAY stepX_YYY.ps
 ```
 
-* Python 2.X
+### Python 2.X
 
 ```
 cd python