build.zp

(define (build-json stream)
  (if (null? stream)
    '()
    (let* ((token (car stream))
           (token-key (car token))
           (token-val (cadr token)))
        (cond
          ((in? ["json-string" "json-num"] token-key)
            (build-json-simple token))
          ((eq? token-key "json-null") (nil))
          ((eq? token-key "json-array") (build-json-array token-val))
          ((eq? token-key "json-object") (build-json-object token-val))))))

(define (build-json-all stream)
  (define (build-all-json tokens acc)
    (if (null? tokens)
      acc
      (begin
        (define tuple (build-json (car tokens)))
        (build-all-json (cdr tokens) (++ acc tuple)))))
  (build-json stream '()))

(define (build-json-simple value)
  (let ((key (car value))
        (val (cadr value)))
  (cond
    ((eq? key "json-string") val)
    ((eq? key "json-num") (string->number val)))))

(define (build-json-array values)
  (if (null? values)
    '()
    (let* ((element (car values))
           (element-key (car element)))
      (case element-key
        (("json-string" "json-num")
            (cons (build-json-simple element)
                  (build-json-array (cdr values))))
        (("json-object")
            (cons (build-json (list element))
                  (build-json-array (cdr values))))
        (else (build-json-array (cdr values)))))))

(define (build-json-object values)
  (if (null? values)
    #{}
    (let* ((key (car values))
           (value (list:ref values 2)))
           (if (> (length values) 3)
            (make-hash (build-json-simple key) (build-json (list value))
                       (build-json-object (cddddr values)))
            (make-hash (build-json-simple key) (build-json (list value))
                       (build-json-object (cdddr values)))))))