struct.zp

(define-syntax define-struct
  (syntax-rules "define a data type <par>id</par> with the fields <par>fields</par>.
  The macro also automatically defines field accessor, a type predicate and a constructor.

  Example:
  <zepto>
    (define-struct pair (fst snd))
    ; this will define the functions:
    ; (pair:make-pair fst snd) (constructor)
    ; (pair:pair? obj) (type predicate)
    ; (pair:get-fst pair) (field getter)
    ; (pair:set-fst pair) (field setter)
    ; (pair:get-snd pair) (field getter)
    ; (pair:set-snd pair) (field setter)
  </zepto>

  params:
    - id: the name of the data type
    - fields: a list of field names
  complexity: O(n) where n is the length of <par>fields</par>
  returns: the last function" ()
    ((define-struct "intern" id (field))
      (list `(field ,(->symbol id ":get-" field) ,(->symbol id ":set-" field))))
    ((define-struct "intern" id (field fields ...))
      (++
        (list `(field ,(->symbol id ":get-" field) ,(->symbol id ":set-" field)))
        (define-struct "intern" id (fields ...))))
    ((define-struct id (fields ...))
      (let* ((env (current-env))
             (make (->symbol id ":make-" id))
             (check (->symbol id ":" id "?"))
             (template (++ `(id
                             (,make fields ...)
                             ,check)
                            (define-struct "intern" id (fields ...)))))
            (eval (macro-expand (cons 'define-record-type template)) env)))))