...])
;;; - OUT is either a port or #t for the current input port.
;;; - Each attribute is either a (name . value) pair, which is printed as
;;; name="value"
;;; or a single symbol or string, which is simply printed as-is
;;; (this is useful for attributes that don't have values, such as the
;;; ISMAP attribute in ![]()
tags).
;;;
(define (emit-tag out tag . attrs)
(let ((out (fmt->port out)))
(display "<" out)
(display tag out)
(for-each (lambda (attr)
(display #\space out)
(cond ((pair? attr) ; name="val"
(display (car attr) out)
(display "=\"" out) ; Should check for
(display (cdr attr) out) ; internal double-quote
(display #\" out)) ; etc.
(else
(display attr out)))) ; name
attrs)
(display #\> out)))
;;;
(define (emit-close-tag out tag)
(format out "" tag))
;;;
(define (emit-p . args) ; (emit-p [out attr1 ...])
(receive (out attrs) (if (pair? args)
(let* ((out (car args)))
(values (if (eq? out #t) (current-output-port) out)
(cdr args)))
(values (current-output-port) args))
(apply emit-tag out 'p attrs)))
;;;
Make Money Fast!!!
(define (emit-title out title) ; Takes no attributes.
(format out "~a~%" title))
(define (emit-header out level text . attribs)
(apply with-tag* out (string-append "h" (number->string level))
(lambda () (display text (fmt->port out)))
attribs))
;;; ...and so forth. Could stand to define a bunch of little emitters for the
;;; various tags. (define-tag-emitter ...)
;;; Printing out balanced ... pairs.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; (with-tag out tag (attr-elt ...) body ...)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Execute the body forms between a ... pair.
;;; The (ATTR-ELT ...) list specifies the attributes for the .
;;; It is rather like a LET-list, having the form
;;; ((name val) ...)
;;; Each NAME must be a symbol, and each VAL must be a Scheme expression
;;; whose value is the string to use as attribute NAME's value. Attributes
;;; that have no value (e.g., ISMAP) can be specified as attr-elt NAME,
;;; instead of (NAME VALUE).
;;;
;;; For example,
;;; (let ((hp-url "http://clark.lcs.mit.edu/~shivers")) ; My home page.
;;; (with-tag port a ((href hp-url) (name "hp"))
;;; (display "home page" port)))
;;; outputs
;;; home page
(define-syntax with-tag
(syntax-rules ()
((with-tag out tag (attr-elt ...) body ...)
(with-tag* out 'tag (lambda () body ...)
(%hack-attr-elt attr-elt)
...))))
;;; Why does this have to be top-level?
;;; Why can't this be a LET-SYNTAX inside of WITH-TAG?
(define-syntax %hack-attr-elt
(syntax-rules (xmlnsdecl-attr) ; Build attribute-list element:
((%hack-attr-elt (name val)) ; (name elt) => (cons 'name elt)
(cons 'name val))
((%hack-attr-elt xmlnsdecl-attr)
xmlnsdecl-attr)
((%hack-attr-elt name) 'name))) ; name => 'name
;;; Execute THUNK between a ... pair.
(define (with-tag* out tag thunk . attrs)
(apply emit-tag out tag attrs)
(let ((out (fmt->port out)))
(newline out)
(call-with-values thunk
(lambda results
(newline out)
(emit-close-tag out tag)
(apply values results)))))
(define (fmt->port x)
(if (eq? x #t) (current-output-port) x))
;;; Translate text to HTML, mapping special chars such as <, >, &, and
;;; double-quote to their HTML escape sequences.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Note iso8859-1 above 127 is perfectly OK
(define *html-entity-alist*
(list
(cons (ascii->char 60) "<")
(cons (ascii->char 62) ">")
(cons (ascii->char 38) "&")
(cons (ascii->char 34) """)))
(define *html-entities*
(list->char-set (map car *html-entity-alist*)))
(define *html-entity-table*
(let ((v (make-vector 256 #f)))
(for-each (lambda (entry)
(vector-set! v
(char->ascii (car entry))
(cdr entry)))
*html-entity-alist*)
v))
(define (string-set-substring! t start s)
(let* ((l (string-length s))
(end (+ l start)))
(do ((i start (+ 1 i)))
((= i end) t)
(string-set! t i (string-ref s (- i start))))))
(define (escape-html s)
(let ((target-length
(string-fold (lambda (c i)
(+ i
(if (char-set-contains? *html-entities* c)
(string-length
(vector-ref *html-entity-table*
(char->ascii c)))
1)))
0
s)))
(if (= target-length (string-length s))
s
(let ((target (make-string target-length)))
(string-fold
(lambda (c i)
(+ i
(if (char-set-contains? *html-entities* c)
(let ((entity (vector-ref *html-entity-table* (char->ascii c))))
(string-set-substring! target i entity)
(string-length entity))
(begin
(string-set! target i c)
1))))
0
s)
target))))
(define (emit-text s . maybe-port)
(if (null? maybe-port)
(write-string (escape-html s))
(write-string (escape-html s) (fmt->port (car maybe-port)))))