(define (maprev f l)
  (if (null? l)
      '()
      (cons (f (car l))
            (maprev f (cdr l)))))

(define (tag->html tag)
  (let ((name (car tag))
        (attrs (cadr tag))
        (content (cddr tag)))
    (display "<")
    (display name)
    (attribute->html attrs)
    (if (null? content)
        (display "/>")
        (begin
          (display ">")
          (content->html content)
          (display "</")
          (display name)
          (display ">")))))

(define (non-closing-tag? tag-name)
  (member tag-name '(area base br col command embed hr img input keygen link meta param source track wbr)))

(define (content->html content)
  (if (null? content)
      #t
      (maprev to-html content)))

(define (to-html element)
  (cond ((string? element) (display element))
        ((list? element) (if (symbol? (car element))
                             (tag->html element)
                             (content->html element)))
        (else (display #f))))

(define (make-html tree)
  (to-html tree))

(define (attribute->html attrs)
  (for-each (lambda (attr)
              (let ((key (car attr))
                    (value (cadr attr)))
                (display " ")
                (display key)
                (display "=\"")
                (display value)
                (display "\"")))
            attrs))