X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=README.md;h=f2cc92e6a75cc2e9b96ca30f2e0f2828c2b773c4;hb=50e62272f0453640f022a8dfb70b21c705fda841;hp=c62fbafbad196044f855ffb35b3bcf5909506ebe;hpb=f636021f07e61701c3df7a6ba1b7dac3160c2110;p=scheme.forth.jl.git

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 scheme.forth.jl
 ---------------
 
-A hobby scheme implementation for FORTH 83. Specifically it is targeted at 
-[forth.jl](http://github.com/tgvaughan/forth.jl) which is an implementation
-of FORTH on top of [Julia](http://www.julialang.org), hence the name.  However
-it does not rely on anything but standard FORTH 83 words.
+A hobby Scheme interpreter for FORTH 83. Specifically it is targeted at
+[forth.jl](http://github.com/tgvaughan/forth.jl) which is an implementation of
+FORTH on top of [Julia](http://www.julialang.org), hence the name.  It began
+life as a fairly direct port of Peter Micheaux's [Bootstrap
+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,
+* pre-evaluation syntactic analysis,
+* mark-sweep garbage collection,
+* quasiquotation,
+* a basic (non-hygienic) macro system and
+* first-class continuations via `call-with-current-continuation`.
+
+Running the interpreter
+=======================
+
+To run this Scheme interpreter, first open Julia (**version >=0.6**) 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")
+
+Then, import and run the Forth system:
+
+    julia> import forth
+    julia> forth.run()
+    Welcome to forth.jl!
+
+Once Forth is running, execute the Scheme source and fire up the
+REPL using the following commands:
+
+    include scheme.4th  ok
+    scheme repl
+    Welcome to scheme.forth.jl!
+    Use Ctrl-D to exit.
+
+    >
+
+At this point you can start entering Scheme commands.  For example,
+
+    > (define (factorial n)
+        (if (= n 0)
+          1
+          (* n (factorial (- n 1)))))
+    ; ok
+    > (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 while for each result.  After all, when evaluating commands in the MCE you are
+running a program in a Scheme interpreter running inside another Scheme
+interpreter which is itself running on a Forth system that is implemented atop
+a virtual register machine running in the Julia numerical computing
+environment.  **That's four levels of abstraction more than a native Julia
+program experiences**, so some delay is to be expected!
+
+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)
+
+You may have to wait a minute or so for the final result to be printed.
+
+License
+=======
+
+This software is free (as in freedom) and is distributed under the terms
+of version 3 of the GNU General Public License.  A copy of this license
+is included in this repository in the file COPYING.