add SML README

impls/sml/README.md

@@ -0,0 +1,34 @@
+# SML-MAL
+
+This is Make-A-Lisp in Standard ML.
+
+## Building
+
+Just run `make`.
+
+Building requires a Standard ML compiler with basis library. This MAL
+implementation has been tested and works with Poly/ML, MLton, and Moscow ML.
+
+On Ubuntu, you can run `apt-get install polyml libpolyml-dev`.
+
+By setting `sml_MODE` to `polyml`, `mosml`, or `mlton` on invoking `make` you
+can select which compiler to use. The Makefile has some hacks to figure out
+how to make the different compilers build everything.
+
+## Running
+
+You can build a `mal` binary from the final step with `make dist`:
+
+```
+$ make dist
+$ ./mal
+Mal [sml]
+user> (map (fn* (x) (println "Odelay!")) [1 2 3 4 5])
+Odelay!
+Odelay!
+Odelay!
+Odelay!
+Odelay!
+(nil nil nil nil nil)
+user> 
+```