Bootstrap Scheme is a quick and very dirty Scheme interpreter. Its *only* intended use is to compile a self-compiling Scheme-to-Assembly or Scheme-to-C compiler the first time.
Bootstrap Scheme doesn't have many features a Scheme system usually has. It doesn't have numbers other than integers. It doesn't have vectors. It definitely doesn't have a module system, call/cc, macros, dynamic-wind or any other advanced Scheme features.
Bootstrap Scheme is slow. The implementation is an abstract syntax tree node walker with no optimizations. There is no point in making a node walking interpreter any better than the absolute base necessity as the fundamental design of a node walker would never be used in production. Small, easy to read source code is far more important than anything else.
Bootstrap Scheme revels in the opportunity to be very dirty Scheme.
----
Example build and use.
$ cd bootstrap
$ make
cc -Wall -ansi -o scheme scheme.c
$ ./scheme
Welcome to your Scheme REPL. Use ctrl-c to exit.
> #t
#t
> -123
-123
> #\c
#\c
> "adsf"
"asdf"
> (quote ())
()
> (quote (0 . 1))
(0 . 1)
> (quote (0 1 2 3))
(0 1 2 3)
> (quote asdf)
asdf
> (define a 1)
ok
> a
1
> (set! a 2)
ok
> a
2
> (if #t 1 2)
1
> (+ 1 2 3)
6
> +
#<procedure>
> ((lamba (x) x) 1)
1
> (define (add x y) (+ x y))
ok
> (add 1 2)
3
> add
#<procedure>
> (define c ((lambda (x) (lambda () x)) 3))
ok
> (c)
3
> (begin 1 2)
2
> (cond (#f 1)
((eq? #t #t) 2)
(else 3))
2
> (let ((x (+ 1 1))
(y (- 5 2)))
(+ x y))
5
> (and 1 2 #f 3)
#f
> (or #f #f 3 #f)
3
> (apply + '(1 2 3))
6
> (define env (environment))
ok
> (eval '(define z 25) env)
ok
> (eval 'z env)
25
> (define out (open-output-port "asdf.txt"))
ok
> (write-car #\c out)
ok
> (close-output-port out)
ok
> (load "program.scm")
program-loaded
> (error "bad move")
"bad move"
exiting
$
----
For more information see:
http://peter.michaux.ca/articles/scheme-from-scratch-introduction
----
See the LICENSE file for legal information.
I went to convert the README's text to a test file. For half an hour I wondered why the line that applies an anonymous identity function to 1 was resulting in a message "unbound variable lamba".
Yeah, and when I manually entered a line that did the same thing I was always typing lambda correctly and so I was really puzzled when the test file would error out.
Hello Peter,
just to inform you I managed to rewrite the source using K&R style.
It works... it's a little bit slower (with only 62KB of RAM available), and to compile/assemble/link the interpreter, with Aztec C compiler, it takes 10 mins.