Added expression sequences to macro expander.

[scheme.forth.jl.git] / README.md

diff --git a/README.md b/README.md
index 415a146..52b4b6f 100644 (file)
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ Scheme](https://github.com/petermichaux/bootstrap-scheme) (as described in
 [this wonderful series of blog
 posts](http://peter.michaux.ca/articles/scheme-from-scratch-introduction)) from
 C to forth, but also includes variadic compound function support, mark-sweep
-garbage collection, quasiquotation, and a very basic (non-hygenic) macro
+garbage collection, quasiquotation, and a basic (non-hygienic) macro
 system.
 
 In future, I plan to also implement a more complete numerical tower to bring it closer to
@@ -21,8 +21,8 @@ the majority of the exercises found in [SICP](http://sarabander.github.io/sicp/)
 Running the interpreter
 =======================
 
-To run this Scheme interpreter, first open Julia from the directory that contains
-this README file. If you've not done so already, install forth.jl using the
+To run this Scheme interpreter, first open Julia from the src directory contained
+in this repository.  If you've not done so already, install forth.jl using the
 following command:
 
     julia> Pkg.clone("https://github.com/tgvaughan/forth.jl")
@@ -53,6 +53,51 @@ At this point you can start entering Scheme commands.  For example,
     > (factorial 5)
     ; 120
 
+Metacircular Evaluator
+======================
+
+Of course, one of the things you can do in Scheme (or of course any programming
+language, this is the fundamental thing) is implement an interpreter for
+another programming language.  The examples directory in this repository
+contains a verbatim copy of the source for the "metacircular" scheme interpreter
+from SICP. To load it, use the following command:
+
+    > (load "../examples/metacirc.scm")
+    ; ok
+
+Be prepared to wait a couple of minutes. When the interpreter finally loads, enter
+the following command to run it:
+
+    > (driver-loop)
+
+You'll then be greeted by the following prompt:
+
+    ;; M-Eval input:
+
+At this point you can start entering Scheme commands... but be prepared to wait
+a _long_ time for the result.  For instance, the following example from SICP
+defines and demonstrates a recursive list append procedure:
+
+    (define (append x y)
+       (if (null? x)
+           y
+           (cons (car x)
+                 (append (cdr x) y))))
+
+     ;;; M-Eval value:
+     ok
+
+     ;;; M-Eval input:
+     (append '(a b c) '(d e f))
+
+     ;;; M-Eval value:
+     (a b c d e f)
+
+Be prepared to wait 20 min or more for the final result to be printed.  (Given
+that at this point we have a program running in a Scheme interpreter running
+inside another Scheme interpreter which is itself running on a Forth system
+that is implemented in Julia, this should not be a surprise.)
+
 License
 =======