+;;; -*-scheme-*-
+
+;;; Mes --- Maxwell Equations of Software
+;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
+;;;
+;;; mes.mes: This file is part of Mes.
+;;;
+;;; Mes is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; Mes is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with Mes. If not, see <http://www.gnu.org/licenses/>.
+
+;; The Maxwell Equations of Software -- John McCarthy page 13
+;; http://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf
+
+(define (caar x) (car (car x)))
+(define (cadr x) (car (cdr x)))
+(define (cdar x) (cdr (car x)))
+(define (cddr x) (cdr (cdr x)))
+(define (caadr x) (car (car (cdr x))))
+(define (caddr x) (car (cdr (cdr x))))
+(define (cddar x) (cdr (cdr (car x))))
+(define (cdadr x) (cdr (car (cdr x))))
+(define (cadar x) (car (cdr (car x))))
+(define (cdddr x) (cdr (cdr (cdr x))))
+
+;; Page 12
+(define (pairlis x y a)
+ (cond
+ ((null? x) a)
+ ((atom? x) (cons (cons x y) a))
+ (#t (cons (cons (car x) (car y))
+ (pairlis (cdr x) (cdr y) a)))))
+
+(define (assq x a)
+ (cond
+ ((null? a) #f)
+ ((eq? (caar a) x) (car a))
+ (#t (assq x (cdr a)))))
+
+;; Page 13
+(define (evcon c a)
+ (cond
+ ((null? c) *unspecified*)
+ ;; single-statement cond
+ ;; ((eval (caar c) a) (eval (cadar c) a))
+ ((eval (caar c) a)
+ (cond ((null? (cddar c)) (eval (cadar c) a))
+ (#t (eval (cadar c) a)
+ (evcon
+ (cons (cons #t (cddar c)) '())
+ a))))
+ (#t (evcon (cdr c) a))))
+
+(define (evlis m a)
+ (cond
+ ((null? m) '())
+ (#t (cons (eval (car m) a) (evlis (cdr m) a)))))
+
+
+(define (apply-env fn x a)
+ (cond
+ ((atom? fn)
+ (cond
+ ((eq? fn 'current-module)
+ (c:apply-env current-module '() a))
+ ((eq? fn 'call-with-values)
+ (c:apply-env 'call-with-values x a))
+ ((builtin? fn)
+ (call fn x))
+ (#t (apply-env (eval fn a) x a))))
+ ((eq? (car fn) 'lambda)
+ (begin-env (cddr fn) (pairlis (cadr fn) x a)))
+ ((eq? (car fn) 'label) (apply-env (caddr fn) x (cons (cons (cadr fn)
+ (caddr fn)) a)))))
+
+(define (begin-env body a)
+ (cond ((null? body) *unspecified*)
+ ((null? (cdr body)) (eval (car body) a))
+ (#t (eval (car body) a)
+ (begin-env (cdr body) a))))
+
+(define (set-env! x e a)
+ (set-cdr! (assq x a) e))
+
+(define (eval e a)
+ (cond
+ ((eq? e #t) #t)
+ ((eq? e #f) #f)
+ ((char? e) e)
+ ((number? e) e)
+ ((string? e) e)
+ ((vector? e) e)
+ ((atom? e) (cdr (assq e a)))
+ ((builtin? e) e)
+ ((atom? (car e))
+ (cond
+ ((eq? (car e) 'quote) (cadr e))
+ ((eq? (car e) 'begin) (begin-env (cdr e) a))
+ ((eq? (car e) 'lambda) e)
+ ((eq? (car e) 'set!) (set-env! (cadr e) (caddr e) a))
+ ((eq? (car e) 'unquote) (eval (cadr e) a))
+ ((eq? (car e) 'quasiquote) (eval-quasiquote (cadr e) a))
+ ((eq? (car e) 'cond) (evcon (cdr e) a))
+ ((pair? (assq (car e) (cdr (assq '*macro* a))))
+ (c:eval
+ (c:apply-env
+ (cdr (assq (car e) (cdr (assq '*macro* a))))
+ (cdr e)
+ a)
+ a))
+ (#t (apply-env (car e) (evlis (cdr e) a) a))))
+ (#t (apply-env (car e) (evlis (cdr e) a) a))))
+
+(define (eval-quasiquote e a)
+ (cond ((null? e) e)
+ ((atom? e) e)
+ ((atom? (car e)) (cons (car e) (eval-quasiquote (cdr e) a)))
+ ((eq? (caar e) 'unquote) (cons (eval (cadar e) a) '()))
+ ((eq? (caar e) 'quote) (cons (cadar e) '()))
+ ((eq? (caar e) 'quasiquote) (cons (cadar e) '()))
+ (#t (cons (car e) (eval-quasiquote (cdr e) a)))))
+
+(define (readenv a)
+ (readword (read-byte) '() a))
+
+(define (readword c w a)
+ (cond ((eq? c -1) ;; eof
+ (cond ((eq? w '()) '())
+ (#t (lookup w a))))
+ ((eq? c 10) ;; \n
+ (cond ((eq? w '()) (readword (read-byte) w a))
+ ;; DOT ((eq? w '(*dot*)) (car (readword (read-byte) '() a)))
+ (#t (lookup w a))))
+ ((eq? c 32) ;; \space
+ (readword 10 w a))
+ ((eq? c 40) ;; (
+ (cond ((eq? w '()) (readlist a))
+ (#t (unread-byte c) (lookup w a))))
+ ((eq? c 41) ;; )
+ (cond ((eq? w '()) (unread-byte c) w)
+ (#t (unread-byte c) (lookup w a))))
+ ((eq? c 39) ;; '
+ (cond ((eq? w '())
+ (cons (lookup (cons c '()) a)
+ (cons (readword (read-byte) w a) '())))
+ (#t (unread-byte c) (lookup w a))))
+ ((eq? c 59) ;; ;
+ (readcomment c)
+ (readword 10 w a))
+ ((eq? c 35) ;; #
+ (cond ((eq? (peek-byte) 33) ;; !
+ (read-byte)
+ (readblock (read-byte))
+ (readword 10 w a))
+ ;; TODO: char, vector
+ (#t (readword (read-byte) (append2 w (cons c '())) a))))
+ (#t (readword (read-byte) (append2 w (cons c '())) a))))
+
+(define (readblock c)
+ (cond ((eq? c 33) (cond ((eq? (peek-byte) 35) (read-byte))
+ (#t (readblock (read-byte)))))
+ (#t (readblock (read-byte)))))
+
+(define (eat-whitespace)
+ (cond ((eq? (peek-byte) 10) (read-byte) (eat-whitespace))
+ ((eq? (peek-byte) 32) (read-byte) (eat-whitespace))
+ ((eq? (peek-byte) 35) (read-byte) (eat-whitespace))
+ (#t #t)))
+
+(define (readlist a)
+ (eat-whitespace)
+ (cond ((eq? (peek-byte) 41) ;; )
+ (read-byte)
+ '())
+ ;; TODO *dot*
+ (#t (cons (readword (read-byte) '() a) (readlist a)))))
+
+(define (readcomment c)
+ (cond ((eq? c 10) ;; \n
+ c)
+ (#t (readcomment (read-byte)))))