mes/syntax.mes

;;(define else #t)
(define (syntax-error message thing)
  (display "syntax-error:")
  (display message)
  (display ":")
  ;;(display thing)
  (newline))

(display "mes:define-syntax...")

;;(define (caddr x) (car (cdr (cdr x))))
;; (define (caddr x)
;;   (display "wanna caddr:")
;;   (display x)
;;   (newline))

;; (define-macro mes:define-syntax
;;   (lambda (form expander)
;;      (expander `(define-macro ,(cadr form)
;;                   (let ((transformer ,(caddr form)))
;;                     (lambda (form expander)
;;                       (expander (transformer form
;;                                              (lambda (x) x)
;;                                              eq?)
;;                                 expander))))
;;                expander)))

;; (define (dinges form expander)
;;   (display "dinges form:")
;;   (display form)
;;   (newline)
;;   `(define-macro BOO ;;;,(cadr form)
;;      (let ((transformer ,(caddr form)))
;;        (lambda (form expander)
;;          (expander (transformer form
;;                                 (lambda (x) x)
;;                                 eq?)
;;                    expander)))))

;; (define-macro (mes:define-syntax form expander)
;;   `(expander (dinges form expander)
;;              expander))

(define-macro (mes:define-syntax macro-name transformer . stuff)
  ;; (display "mes:define-syntax:")
  ;; (newline)
  ;; (display   `(define-macro (,macro-name . args)
  ;;    (,transformer (cons ',macro-name args)
  ;;                  (lambda (x) x)
  ;;                  eq?)))
  ;; (newline)
  `(define-macro (,macro-name . args)
     (,transformer (cons ',macro-name args)
                   (lambda (x) x)
                   eq?)
     ;;"blaat"
     ))

;; (define-macro (mes:define-syntax form expander)
;;   (expander `(define-macro ,(cadr form)
;;                (let ((transformer ,(caddr form)))
;;                  (lambda (form expander)
;;                    (expander (transformer form
;;                                           (lambda (x) x)
;;                                           eq?)
;;                              expander))))
;;             expander))

;; (define-macro (mes:define-syntax form expander)
;;   (expander `(define-macro ((cadr form) form expander) 
;;                (let ((transformer (caddr form)))
;;                  (expander (transformer form
;;                                         (lambda (x) x)
;;                                         eq?)
;;                            expander)))
;;             expander))

(newline)


(display "mes:define-syntax syntax-rules...")
(newline)

(mes:define-syntax syntax-rules
  (let ()
   ;;begin

    (define name? symbol?)

    (define (segment-pattern? pattern)
      (and (segment-template? pattern)
           (or (null? (cddr pattern))
               (syntax-error "segment matching not implemented" pattern))))

    (define (segment-template? pattern)
      (and (pair? pattern)
           (pair? (cdr pattern))
           (memq (cadr pattern) indicators-for-zero-or-more)))

    (define indicators-for-zero-or-more (list (string->symbol "...") '---))
    
    (display "BOOO")

    (lambda (exp r c)

      (define %input (r '%input))     ;Gensym these, if you like.
      (define %compare (r '%compare))
      (define %rename (r '%rename))
      (define %tail (r '%tail))
      (define %temp (r '%temp))

      (define rules (cddr exp))
      (define subkeywords (cadr exp))

      (define (make-transformer rules)
        `(lambda (,%input ,%rename ,%compare)
           (let ((,%tail (cdr ,%input)))
             (cond ,@(map process-rule rules)
                   (#t ;;else
                    (syntax-error
                     "use of macro doesn't match definition"
                     ,%input))))))

      (define (process-rule rule)
        (if (and (pair? rule)
                 (pair? (cdr rule))
                 (null? (cddr rule)))
            (let ((pattern (cdar rule))
                  (template (cadr rule)))
              `((and ,@(process-match %tail pattern))
                (let* ,(process-pattern pattern
                                        %tail
                                        (lambda (x) x))
                  ,(process-template template
                                     0
                                     (meta-variables pattern 0 '())))))
            (syntax-error "ill-formed syntax rule" rule)))

      ;; Generate code to test whether input expression matches pattern

      (define (process-match input pattern)
        (cond ((name? pattern)
               (if (member pattern subkeywords)
                   `((,%compare ,input (,%rename ',pattern)))
                   `()))
              ((segment-pattern? pattern)
               (process-segment-match input (car pattern)))
              ((pair? pattern)
               `((let ((,%temp ,input))
                   (and (pair? ,%temp)
                        ,@(process-match `(car ,%temp) (car pattern))
                        ,@(process-match `(cdr ,%temp) (cdr pattern))))))
              ((or (null? pattern) (boolean? pattern) (char? pattern))
               `((eq? ,input ',pattern)))
              (#t ;;else
               `((equal? ,input ',pattern)))))

      (define (process-segment-match input pattern)
        (let ((conjuncts (process-match '(car l) pattern)))
          (if (null? conjuncts)
              `((list? ,input))                        ;+++
              `((let loop ((l ,input))
                  (or (null? l)
                      (and (pair? l)
                           ,@conjuncts
                           (loop (cdr l)))))))))

      ;; Generate code to take apart the input expression
      ;; This is pretty bad, but it seems to work (can't say why).

      (define (process-pattern pattern path mapit)
        (cond ((name? pattern)
               (if (memq pattern subkeywords)
                   '()
                   (list (list pattern (mapit path)))))
              ((segment-pattern? pattern)
               (process-pattern (car pattern)
                                %temp
                                (lambda (x)        ;temp is free in x
                                  (mapit (if (eq? %temp x)
                                             path ;+++
                                             `(map (lambda (,%temp) ,x)
                                                   ,path))))))
              ((pair? pattern)
               (append (process-pattern (car pattern) `(car ,path) mapit)
                       (process-pattern (cdr pattern) `(cdr ,path) mapit)))
              (#t ;;else
               '())))

      ;; Generate code to compose the output expression according to template

      (define (process-template template rank env)
        (cond ((name? template)
               (let ((probe (assq template env)))
                 (if probe
                     (if (<= (cdr probe) rank)
                         template
                         (syntax-error "template rank error (too few ...'s?)"
                                       template))
                     `(,%rename ',template))))
              ((segment-template? template)
               (let ((vars
                      (free-meta-variables (car template) (+ rank 1) env '())))
                 (if (null? vars)
                     (syntax-error "too many ...'s" template)
                     (let* ((x (process-template (car template)
                                                 (+ rank 1)
                                                 env))
                            (gen (if (equal? (list x) vars)
                                     x        ;+++
                                     `(map (lambda ,vars ,x)
                                           ,@vars))))
                       (if (null? (cddr template))
                           gen                ;+++
                           `(append ,gen ,(process-template (cddr template)
                                                            rank env)))))))
              ((pair? template)
               `(cons ,(process-template (car template) rank env)
                      ,(process-template (cdr template) rank env)))
              (#t ;;else
               `(quote ,template))))

      ;; Return an association list of (var . rank)

      (define (meta-variables pattern rank vars)
        (cond ((name? pattern)
               (if (memq pattern subkeywords)
                   vars
                   (cons (cons pattern rank) vars)))
              ((segment-pattern? pattern)
               (meta-variables (car pattern) (+ rank 1) vars))
              ((pair? pattern)
               (meta-variables (car pattern) rank
                               (meta-variables (cdr pattern) rank vars)))
              (#t ;;else
               vars)))

      ;; Return a list of meta-variables of given higher rank

      (define (free-meta-variables template rank env free)
        (cond ((name? template)
               (if (and (not (memq template free))
                        (let ((probe (assq template env)))
                          (and probe (>= (cdr probe) rank))))
                   (cons template free)
                   free))
              ((segment-template? template)
               (free-meta-variables (car template)
                                    rank env
                                    (free-meta-variables (cddr template)
                                                         rank env free)))
              ((pair? template)
               (free-meta-variables (car template)
                                    rank env
                                    (free-meta-variables (cdr template)
                                                         rank env free)))
              (#t ;;else
               free)))

      c ;ignored

      (display "HELLO")
      (newline)

      ;; Kludge for Scheme48 linker.
      ;; `(cons ,(make-transformer rules)
      ;;          ',(find-free-names-in-syntax-rules subkeywords rules))

      (make-transformer rules))))


(mes:define-syntax mes:or
  (syntax-rules ()
    ((mes:or) #f)
    ((mes:or e) e)
    ((mes:or e1 e ...) (let ((temp e1))
                      (if temp temp (or e ...))))))

(display "(mes:or #f (= 0 1) 'hello-syntax-world): ")
(display (mes:or #f (= 0 1) 'hello-syntax-world))
(display (mes:or #f '==>baaa))
(newline)

(mes:define-syntax mes:when
  (syntax-rules ()
    ((when condition exp ...)
     (if condition
         (begin exp ...)))))

(display (mes:when #t "when:hello syntax world"))

;; (define-macro (when cond exp . rest)
;;   `(if ,cond
;;        (begin ,exp . ,rest)))


;; (define-macro (when clause . rest)
;;   (list 'cond (list clause (list 'let '() rest))))
(newline)
'syntax-dun