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-macro (if expr then . else)
  `(cond
    (,expr ,then)
    (#t (cond (,(pair? else) ((lambda () ,@else)))))))

(define-macro (when expr . body)
  `(if ,expr
       ((lambda () ,@body))))

(define (list . rest) rest)

(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 (simple-let bindings rest)
  `((lambda ,(split-params bindings '()) ,@rest)
    ,@(split-values bindings '())))

(define-macro (let-loop label bindings . rest)
  `(let ((,label *unspecified*))
     (let ((,label (lambda ,(split-params bindings '()) ,@rest)))
       (,label ,@(split-values bindings '())))))

(define-macro (let-loop label bindings rest)
  `((lambda (,label)
      (set! ,label (lambda ,(split-params bindings '()) ,@rest))
      (,label ,@(split-values bindings '())))
    *unspecified*))

(define-macro (let bindings-or-label . rest)
  `(cond (,(symbol? bindings-or-label)
          (let-loop ,bindings-or-label ,(car rest) ,(cdr rest)))
         (#t (simple-let ,bindings-or-label ,rest))))

(define-macro (or2 x y)
  `(cond (,x ,x) (#t ,y)))

(define-macro (and2 x y)
  `(cond (,x ,y) (#t #f)))

(define-macro (or . x)
  (cond
   ((null? x) #f)
   ((null? (cdr x)) (car x))
   (#t `(cond (,(car x))
              (#t (or ,@(cdr x)))))))

(define-macro (and . x)
  (cond ((null? x) #t)
        ((null? (cdr x)) (car x))
        (#t `(cond (,(car x) (and ,@(cdr x)))
                   (#t #f)))))

(define (expand-let* bindings body)
  (cond ((null? bindings)
         `((lambda () ,@body)))
        (#t `((lambda (,(caar bindings))
                ,(expand-let* (cdr bindings) body))
              ,@(cdar bindings)))))

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

(define (equal? a b) ;; FIXME: only 2 arg
  (cond ((and (null? a) (null? b)) #t)
        ((and (pair? a) (pair? b))
         (and (equal? (car a) (car b))
              (equal? (cdr a) (cdr b))))
        ((and (string? a) (string? b))
         (eq? (string->symbol a) (string->symbol b)))
        ((and (vector? a) (vector? b))
         (equal? (vector->list a) (vector->list b)))
        (#t (eq? a b))))

(define (vector . rest) (list->vector rest))
(define (make-vector n . x)
  (let ((fill (if (pair? x) (cdr x) *unspecified*)))
    (list->vector (let loop ((n n))
                    (if (= 0 n) '()
                        (cons fill (loop (- n 1))))))))

(define-macro (defined? x)
  `(assq ,x (cddr (current-module))))

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

(define integer? number?)

(define (assq-set! alist key val)
  (let ((entry (assq key alist)))
    (cond (entry (set-cdr! entry val)
                 alist)
          (#t (cons (cons key val) alist)))))

(define (assq-ref alist key)
  (let ((entry (assq key alist)))
    (if entry (cdr entry)
        #f)))

(define assv assq)

(define (assoc key alist)
  (cond ((null? alist) #f)
        ((equal? key (caar alist)) (car alist))
        (#t (assoc key (cdr alist)))))

(define (memq x lst)
  (cond ((null? lst) #f)
        ((eq? x (car lst)) lst)
        (#t (memq x (cdr lst)))))
(define memv memq)

(define (member x lst)
  (cond ((null? lst) #f)
        ((equal? x (car lst)) lst)
        (#t (member x (cdr lst)))))

(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 (identity x) x)
(define (for-each f l . r)
  (cond ((null? l) '())
        ((null? r) (f (car l)) (for-each f (cdr l)))
        ((null? (cdr r))
         (for-each f (cdr l) (cdar r)))))

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

(define (<= a b) ;; FIXME: only 2 arg
  (or (< a b)
      (= a b)))

(define (>= a b) ;; FIXME: only 2 arg
  (or (> a b)
      (= a b)))

(define (list? x)
  (or (null? x)
      (and (pair? x) (list? (cdr x)))))

(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)
  `(let ,(unspecified-bindings bindings '())
     ,@(letrec-setters bindings '())
     ,@body))

(define gensym
  (let ((counter 0))
    (lambda (. rest)
      (let ((value (number->string counter)))
        (set! counter (+ counter 1))
        (string->symbol (string-append "g" value))))))

(define else #t)

(define (error who . rest)
  (display "error:")
  (display who)
  (display ":")
  (display rest)
  (display newline))

(define (syntax-error message . rest)
  (display "syntax-error:")
  (display message)
  (display ":")
  (display rest)
  (newline))

;; srfi-1
(define (last-pair lst)
  (let loop ((lst lst))
    (if (or (null? lst) (null? (cdr lst))) lst
        (loop (cdr lst)))))

(define (reverse lst)
  (if (null? lst) '()
      (append (reverse (cdr lst)) (cons (car lst) '()))))