mes/scm.mes

;;; -*-scheme-*-

;;; Mes --- Maxwell Equations of Software
;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
;;;
;;; scm.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 (defined? x)
  (assq x (current-module)))

(define (procedure? p)
  (cond ((builtin? p) #t)
        ((pair? p) (eq? (car p) 'lambda))
        (#t #f)))

(define (list . rest) rest)
(define (vector . rest) (list->vector rest))
(define assv assq)
(define (memq x lst)
  (cond ((null? lst) #f)
        ((eq? x (car lst)) lst)
        (#t (memq x (cdr lst)))))
(define memv memq)

(define-macro (and x y)
  (cond (x y)
        (#t #f)))

(define-macro (or x y)
  (cond (x x)
        (#t y)))

(define (split-params bindings params)
  (cond ((null? bindings) params)
        (#t (split-params (cdr bindings)
                          (append params (cons (caar bindings) '()))))))

(define (split-values bindings values)
  (cond ((null? bindings) values)
        (#t (split-values (cdr bindings)
                          (append values (cdar bindings) '())))))

(define-macro (let bindings . body)
  (cons (cons 'lambda (cons (split-params bindings '()) body))
        (split-values bindings '())))

(define (expand-let* bindings body)
  (cond ((null? bindings)
         (cons (cons 'lambda (cons '() body)) '()))
        (#t
         (cons
          (cons 'lambda (cons (cons (caar bindings) '())
                              (cons (expand-let* (cdr bindings) body) '())))
          (cdar bindings)))))

(define-macro (let* bindings . body)
  (expand-let* bindings body))

(define (map f l . r)
  (cond ((null? l) '())
        ((null? r) (cons (f (car l)) (map f (cdr l))))
        ((null? (cdr r))
         (cons (f (car l) (caar r)) (map f (cdr l) (cdar r))))))

(define (not x)
  (cond (x #f)
        (#t #t)))

(define-macro (if expr then . else)
  (cond ((not (eq? (c:eval expr (current-module)) #f))
         then)
        (#t
         (cond ((pair? else) (car else))
               (#t *unspecified*)))))

(define (unspecified-bindings bindings params)
  (cond ((null? bindings) params)
        (#t (unspecified-bindings
             (cdr bindings)
             (append params (cons (cons (caar bindings) '(*unspecified*)) '()))))))

(define (letrec-setters bindings setters)
  (cond ((null? bindings) setters)
        (#t (letrec-setters (cdr bindings)
                            (append setters
                                    (cons (cons 'set! (car bindings)) '()))))))

(define-macro (letrec bindings . body)
  (cons 'let (cons (unspecified-bindings bindings '())
                    (append (letrec-setters bindings '())
                            body)))  )

(define (begin . rest)
  (let () rest))