From 6c019df6b459c86bf5de4fd817db2316038935da Mon Sep 17 00:00:00 2001
From: Tim Vaughan <tgvaughan@gmail.com>
Date: Mon, 1 May 2017 21:15:43 +1200
Subject: [PATCH] Updated README.
---
README.md | 45 +++++++++++++++++++++++++++++++++++++++++++
examples/metacirc.scm | 4 ++--
2 files changed, 47 insertions(+), 2 deletions(-)
diff --git a/README.md b/README.md
index 2f78b7e..52b4b6f 100644
--- a/README.md
+++ b/README.md
@@ -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
=======
diff --git a/examples/metacirc.scm b/examples/metacirc.scm
index a1ad1dd..fe4c965 100644
--- a/examples/metacirc.scm
+++ b/examples/metacirc.scm
@@ -2,6 +2,8 @@
;; Mandatory SICP Metacircular Evaluator ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; To use, simply (load "metacirc.scm") and run the (driver-loop) command.
+
(define apply-in-underlying-scheme apply)
(define true #t)
(define false #f)
@@ -367,5 +369,3 @@
(define the-global-environment (setup-environment))
-
-(driver-loop)
--
2.20.1