## CL-WHO - Yet another Lisp markup language

> ### Abstract

> There are plenty of Lisp Markup Languages out there - every Lisp programmer seems to write at least one during his career - and CL-WHO (where WHO means "with-html-output" for want of a better acronym) is probably just as good or bad as the next one. They are all more or less similar in that they provide convenient means to convert S-expressions intermingled with code into (X)HTML, XML, or whatever but differ with respect to syntax, implementation, and API. So, if you haven't made a choice yet, check out the alternatives as well before you begin to use CL-WHO just because it was the first one you came across. (Was that repelling enough?) If you're looking for a slightly different approach you might also want to look at HTML-TEMPLATE.

> I wrote this one in 2002 although at least Tim Bradshaw's htout and AllegroServe's HTML generation facilities by John Foderaro of Franz Inc. were readily available. Actually, I don't remember why I had to write my own library - maybe just because it was fun and didn't take very long. The syntax was obviously inspired by htout although it is slightly different.

> CL-WHO tries to create efficient code in that it makes constant strings as long as possible. In other words, the code generated by the CL-WHO macros will usually be a sequence of `WRITE-STRING` forms for constant parts of the output interspersed with arbitrary code inserted by the user of the macro. CL-WHO will make sure that there aren't two adjacent `WRITE-STRING` forms with constant strings. CL-WHO's output is either XHTML (default), 'plain' (SGML) HTML or HTML5 (using HTML syntax) — depending on what you've set `HTML-MODE` to.

> CL-WHO is intended to be portable and should work with all conforming Common Lisp implementations. Let us know if you encounter any problems.

> It comes with a BSD-style license so you can basically do with it whatever you want.

> Download shortcut: https://github.com/edicl/cl-who/releases.

### Contents

1. Example usage
2. Download and installation
3. Support
4. Syntax and Semantics
5. The CL-WHO dictionary
   1. `with-html-output`
   2. `with-html-output-to-string`
   3. `*attribute-quote-char*`
   4. `*downcase-tokens-p*`
   5. `*html-empty-tag-aware-p*`
   6. `*html-empty-tags*`
   7. `*html-no-indent-tags*`
   8. `*prologue*`
   9. `esc`
   10. `fmt`
   11. `htm`
   12. `str`
   13. `html-mode`
   14. `escape-string`
   15. `escape-char`
   16. `*escape-char-p*`
   17. `escape-string-minimal`
   18. `escape-string-minimal-plus-quotes`
   19. `escape-string-iso-8859-1`
   20. `escape-string-all`
   21. `escape-char-minimal`
   22. `escape-char-minimal-plus-quotes`
   23. `escape-char-iso-8859-1`
   24. `escape-char-all`
   25. `conc`
   26. `convert-tag-to-string-list`
   27. `convert-attributes`
6. Acknowledgements

### Example usage

Let's assume that `*HTTP-STREAM*` is the stream your web application is supposed to write to. Here are some contrived code snippets together with the Lisp code generated by CL-WHO and the resulting HTML output.

    (with-html-output (*http-stream*)
      (loop for (link . title) in '(("http://zappa.com/" . "Frank Zappa")
                                    ("http://marcusmiller.com/" . "Marcus Miller")
                                    ("http://www.milesdavis.com/" . "Miles Davis"))
            do (htm (:a :href link
                      (:b (str title)))
                    :br)))
| Frank Zappa Marcus Miller Miles Davis
    ;; code generated by CL-WHO (simplified)

    (let ((*http-stream* *http-stream*))
      (progn
        nil
        (loop for (link . title) in '(("http://zappa.com/" . "Frank Zappa")
                                      ("http://marcusmiller.com/" . "Marcus Miller")
                                      ("http://www.milesdavis.com/" . "Miles Davis"))
              do (progn
                   (write-string "<a href='" *http-stream*)
                   (princ link *http-stream*)
                   (write-string "'><b>" *http-stream*)
                   (princ title *http-stream*)
                   (write-string "</b></a><br />" *http-stream*)))))
    (with-html-output (*http-stream*)
      (:table :border 0 :cellpadding 4
       (loop for i below 25 by 5
             do (htm
                 (:tr :align "right"
                  (loop for j from i below (+ i 5)
                        do (htm
                            (:td :bgcolor (if (oddp j)
                                            "pink"
                                            "green")
                                 (fmt "~@R" (1+ j))))))))))
I | II | III | IV | V
VI | VII | VIII | IX | X
XI | XII | XIII | XIV | XV
XVI | XVII | XVIII | XIX | XX
XXI | XXII | XXIII | XXIV | XXV
    ;; code generated by CL-WHO (simplified)

    (let ((*http-stream* *http-stream*))
      (progn
        nil
        (write-string "<table border='0' cellpadding='4'>" *http-stream*)
        (loop for i below 25 by 5
              do (progn
                   (write-string "<tr align='right'>" *http-stream*)
                   (loop for j from i below (+ i 5)
                         do (progn
                              (write-string "<td bgcolor='" *http-stream*)
                              (princ (if (oddp j) "pink" "green") *http-stream*)
                              (write-string "'>" *http-stream*)
                              (format *http-stream* "~@r" (1+ j))
                              (write-string "</td>" *http-stream*)))
                   (write-string "</tr>" *http-stream*)))
        (write-string "</table>" *http-stream*)))
    (with-html-output (*http-stream*)
      (:h4 "Look at the character entities generated by this example")
       (loop for i from 0
             for string in '("Fête" "Sørensen" "naïve" "Hühner" "Straße")
             do (htm
                 (:p :style (conc "background-color:" (case (mod i 3)
                                                        ((0) "red")
                                                        ((1) "orange")
                                                        ((2) "blue")))
                  (htm (esc string))))))
| #### Look at the character entities generated by this example Fête Sørensen naïve Hühner Straße
    ;; code generated by CL-WHO (simplified)

    (let ((*http-stream* *http-stream*))
      (progn
        nil
        (write-string
         "<h4>Look at the character entities generated by this example</h4>"
         *http-stream*)
        (loop for i from 0 for string in '("Fête" "Sørensen" "naïve" "Hühner" "Straße")
              do (progn
                   (write-string "<p style='" *http-stream*)
                   (princ (conc "background-color:"
                                (case (mod i 3)
                                  ((0) "red")
                                  ((1) "orange")
                                  ((2) "blue")))
                          *http-stream*)
                   (write-string "'>" *http-stream*)
                   (progn (write-string (escape-string string) *http-stream*))
                   (write-string "</p>" *http-stream*)))))

### Download and installation

CL-WHO together with this documentation can be downloaded from http://weitz.de/files/cl-who.tar.gz. The current version is 1.1.3.

The preferred method to fetch, compile and load CL-WHO is via Quicklisp. Install Quicklisp, then run

    (ql:quickload :cl-who)

The current development version of CL-WHO can be found at https://github.com/edicl/cl-who. This is the one to send patches against. Use at your own risk.

Luís Oliveira maintains an unofficial darcs repository of CL-WHO at http://common-lisp.net/~loliveira/ediware/.

You can run a test suite which tests some (but not all) aspects of the library with

    (asdf:oos 'asdf:test-op :cl-who)

### Support and mailing lists

The development version of cl-who can be found on github. Please use the github issue tracking system to submit bug reports. Patches are welcome, please use GitHub pull requests. If you want to make a change, please read this first.

### Syntax and Semantics

CL-WHO is essentially just one macro, `WITH-HTML-OUTPUT`, which transforms the body of code it encloses into something else obeying the following rules (which we'll call transformation rules) for the body's forms:

- A string will be printed verbatim. To be more precise, it is transformed into a form which'll print this string to the stream the user provides.

      "foo" => (write-string "foo" s)

  (Here and for the rest of this document the red arrow means '... will be converted to code equivalent to ...' where equivalent means that all output is sent to the "right" stream.)
- Each list beginning with a keyword is transformed into an (X)HTML tag of the same (usually downcased) name by the following rules:
  - If the list contains nothing but the keyword, the resulting tag will be empty.

        (:br) => (write-string "<br />" s)

    With `HTML-MODE` set to `:SGML` an empty element is written this way:

        (:br) => (write-string "<br>" s)

  - The initial keyword can be followed by another keyword which will be interpreted as the name of an attribute. The next form which will be taken as the attribute's value. (If there's no next form it'll be as if the next form had been `NIL`.) The form denoting the attribute's value will be treated as follows. (Note that the behaviour with respect to attributes is incompatible with versions earlier than 0.3.0!)
    - If it is a string it will be printed literally.

          (:td :bgcolor "red") => (write-string "<td bgcolor='red' />" s)

    - If it is `T` and `HTML-MODE` is `:XML` (default) the attribute's value will be the attribute's name (following XHTML convention to denote attributes which don't have a value in HTML).

          (:td :nowrap t) => (write-string "<td nowrap='nowrap' />" s)

      With `HTML-MODE` set to `:SGML` or `:HTML5`:

          (:td :nowrap t) => (write-string "<td nowrap>" s)

      Attribute minimization is controlled by `*EMPTY-ATTRIBUTE-SYNTAX*`
    - If it is `NIL` the attribute will be left out completely.

          (:td :nowrap nil) => (write-string "<td />" s)

    - If it is a constant form, the result of evaluating it will be inserted into the resulting string as if printed with the format string `"~A"` at macro expansion time.

          (:table :border 3) => (write-string "<table border='3' />" s)

    - If it is any other form it will be left as is and later evaluated at run time and printed like with `PRINC` unless the value is `T` or `NIL` which will be treated as above. (It is the application developer's job to provide the correct printer control variables.)

          ;; simplified example, see function CHECKBOX below
          ;; note that this form is not necessarily CONSTANTP in all Lisps

          (:table :border (+ 1 2)) => (write-string "<table border='" s)
                                        (princ (+ 1 2) s)
                                        (write-string "' />" s)

  - Once an attribute/value pair has been worked up another one can follow, i.e. if the form following an attribute's value is again a keyword it will again be treated as an attribute and so on.

        (:table :border 0 :cellpadding 5 :cellspacing 5)
              => (write-string "<table border='0' cellpadding='5' cellspacing='5' />" s)

  - The first form following either the tag's name itself or an attribute value which is not a keyword determines the beginning of the tag's content. This and all the following forms are subject to the transformation rules we're just describing.

        (:p "Paragraph") => (write-string "<p>Paragraph</p>" s)
        (:p :class "foo" "Paragraph") => (write-string "<p class='foo'>Paragraph</p>" s)
        (:p :class "foo" "One" " " "long" " " "sentence") => (write-string "<p class='foo'>One long sentence</p>" s)
        (:p :class "foo" "Visit " (:a :href "http://www.cliki.net/" "CLiki"))
            => (write-string "<p class='foo'>Visit <a href='http://www.cliki.net/'>CLiki</a></p>" s)

  - Beginning with version 0.4.0 you can also use a syntax like that of LHTML where the tag and all attribute/value pairs are enclosed in an additional list:

        ((:p) "Paragraph") => (write-string "<p>Paragraph</p>" s)
        ((:p :class "foo") "Paragraph") => (write-string "<p class='foo'>Paragraph</p>" s)
        ((:p :class "foo" :name "humpty-dumpty") "One" " " "long" " " "sentence")
            => (write-string "<p class='foo' name='humpty-dumpty'>One long sentence</p>" s)
        ((:p :class "foo") "Visit " ((:a :href "http://www.cliki.net/") "CLiki"))
            => (write-string "<p class='foo'>Visit <a href='http://www.cliki.net/'>CLiki</a></p>" s)

  Here's a slightly more elaborate example:

      * (defun checkbox (stream name checked &optional value)
          (with-html-output (stream)
            (:input :type "checkbox" :name name :checked checked :value value)))

      CHECKBOX
      * (with-output-to-string (s) (checkbox s "foo" t))

      "<input type='checkbox' name='foo' checked='checked' />"
      * (with-output-to-string (s) (checkbox s "foo" nil))

      "<input type='checkbox' name='foo' />"
      * (with-output-to-string (s) (checkbox s "foo" nil "bar"))

      "<input type='checkbox' name='foo' value='bar' />"
      * (with-output-to-string (s) (checkbox s "foo" t "bar"))

      "<input type='checkbox' name='foo' checked='checked' value='bar' />"

- A keyword alone will be treated like a list containing only this keyword.

      :hr => (write-string "<hr />" s)

- A form which is neither a string nor a keyword nor a list beginning with a keyword will be left as is except for the following local macros:
  - Forms that look like `(str form)` will be substituted with `(let ((result form)) (when result (princ result s)))`.

        (loop for i below 10 do (str i)) =>
        (loop for i below 10 do
           (let ((#:result i))
             (when #:result (princ #:result *standard-output*))))

  - Forms that look like `(fmt form*)` will be substituted with `(format s form*)`.

        (loop for i below 10 do (fmt "~R" i)) => (loop for i below 10 do (format s "~R" i))

  - Forms that look like `(esc form)` will be substituted with `(let ((result form)) (when result (write-string (escape-string result s))))`.
  - If a form looks like `(htm form*)` then each of the `forms` will be subject to the transformation rules we're just describing, i.e. this is the body is wrapped with another invocation of `WITH-HTML-OUTPUT`.

        (loop for i below 100 do (htm (:b "foo") :br))
            => (loop for i below 100 do (progn (write-string "<b>foo</b><br />" s)))

- That's all. Note in particular that CL-WHO knows nothing about HTML or XHTML, i.e. it doesn't check whether you mis-spelled tag names or use attributes which aren't allowed. CL-WHO doesn't care if you use, say, `:foobar` instead of `:hr`.

### The CL-WHO dictionary

CL-WHO exports the following symbols:

[Macro]
with-html-output (var `&optional` stream `&key` prologue indent) declaration* form* => result*

> This is the main macro of CL-WHO. It will transform its body by the transformation rules described in Syntax and Semantics such that the output generated is sent to the stream denoted by `var` and `stream`. `var` must be a symbol. If `stream` is `NIL` it is assumed that `var` is already bound to a stream, if `stream` is not `NIL` `var` will be bound to the form `stream` which will be evaluated at run time. `prologue` should be a string (or `NIL` for the empty string which is the default) which is guaranteed to be the first thing sent to the stream from within the body of this macro. If `prologue` is `T` the prologue string is the value of `*PROLOGUE*`.

> CL-WHO will usually try not to insert any unnecessary whitespace in order to save bandwidth. However, if `indent` is true line breaks will be inserted and nested tags will be indented properly. The value of `indent` - if it is an integer - will be taken as the initial indentation. If it is not an integer it is assumed to mean `0`. Value of `*HTML-NO-INDENT-TAGS*` controls which tag-contents are excempt from indentation: by default contents of `PRE` and `TEXTAREA` tags are not indented to avoid spurious layout changes. (Note: in certain situations additional whitespace may change the layout of tables.)

> The `results` are the values returned by the `forms`.

> Note that the keyword arguments `prologue` and `indent`, and the associated variables are used at macro expansion time.

>     * (with-html-output (*standard-output* nil :prologue t)
>         (:html (:body "Not much there"))
>         (values))
>     <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html><body>Not much there</body></html>
>     * (with-html-output (*standard-output*)
>         (:html (:body :bgcolor "white"
>                  "Not much there"))
>         (values))
>     <html><body bgcolor='white'>Not much there</body></html>
>     * (with-html-output (*standard-output* nil :prologue t :indent t)
>         (:html (:body :bgcolor "white"
>                  "Not much there"))
>         (values))
>     <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
>     <html>
>       <body bgcolor='white'>
>         Not much there
>       </body>
>     </html>

[Macro]
with-html-output-to-string (var `&optional` string-form `&key` element-type prologue indent) declaration* form* => result*

> This is just a thin wrapper around `WITH-HTML-OUTPUT`. Indeed, the wrapper is so thin that the best explanation probably is to show its definition:

>     (defmacro with-html-output-to-string ((var &optional string-form
>                                                &key (element-type ''character)
>                                                     prologue
>                                                     indent)
>                                           &body body)
>       "Transform the enclosed BODY consisting of HTML as s-expressions
>     into Lisp code which creates the corresponding HTML as a string."
>       `(with-output-to-string (,var ,string-form :element-type ,element-type)
>         (with-html-output (,var nil :prologue ,prologue :indent ,indent)
>           ,@body)))

> Note that the `results` of this macro are determined by the behaviour of `WITH-OUTPUT-TO-STRING`.

[Special variable]
*attribute-quote-char*

> This character is used as the quote character when building attributes. Defaults to the single quote `#\'`. Only other reasonable character is the double quote `#\"`.

[Special variable]
*downcase-tokens-p*

> If the value of this variable is `NIL`, keyword symbols representing a tag or attribute name will not be automatically converted to lowercase. This is useful when one needs to output case sensitive XML. The default is `T`.

[Special variable]
*html-empty-tag-aware-p*

> Set this to `NIL` to if you want to use CL-WHO as a strict XML generator. Otherwise, CL-WHO will only write empty tags listed in `*HTML-EMPTY-TAGS*` as `<tag/>` (XHTML mode) or `<tag>` (SGML mode or HTML mode). For all other tags, it will always generate `<tag></tag>`. The initial value of this variable is `T`.

[Special variable]
*html-empty-tags*

> The list of HTML tags that should be output as empty tags. See `*HTML-EMPTY-TAG-AWARE-P*`. The initial value is the list

>     (:area :atop :audioscope :base :basefont :br :choose :col :command :embed
>      :frame :hr :img :input :isindex :keygen :left :limittext :link :meta :nextid
>      :of :over :param :range :right :source :spacer :spot :tab :track :wbr)

[Special variable]
*html-no-indent-tags*

> The list of HTML tags that should disable indentation inside them even when indentation is requested. The initial value is a list containing only `:pre` and `:texarea`.

[Special variable]
*prologue*

> This is the prologue string which will be printed if the `prologue` keyword argument to `WITH-HTML-OUTPUT` is `T`. Gets changed when you set `HTML-MODE`. Its initial value is

>     "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\">"

[Special variable]
*empty-attribute-syntax*

> This controls the attribute minimization. (also called 'boolean attributes', or 'empty attribute syntax' according to the w3 html standard). Set value to `T` to enable attribute minimization.

> In XHTML attribute minimization is forbidden, and all attributes must have a value. Thus in XHTML boolean attributes must be defined as

>      <input disabled='disabled' />

> In HTML5 and SGML HTML boolean attributes can be defined as

>     <input disabled>

> Gets changed when you set `HTML-MODE`. Its initial value is `NIL`

[Symbol]
esc
[Symbol]
fmt
[Symbol]
htm
[Symbol]
str

> These are just symbols with no bindings associated with them. The only reason they are exported is their special meaning during the transformations described in Syntax and Semantics.

[Accessor]
html-mode => mode
`(setf (`html-mode) mode`)`

> The function `HTML-MODE` returns the current mode for generating HTML. The default is `:XML` for XHTML. You can change this by setting it with `(SETF (HTML-MODE) :SGML)` to pre-XML HTML mode or `(SETF (HTML-MODE) :HTML5)` to HTML5 mode (using HTML syntax).

> Setting it to SGML HTML sets the `*prologue*` to the doctype string for HTML 4.01 transitional:

>     <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

> Code generation in HTML5 and SGML HTML is slightly different from XHTML - there's no need to end empty elements with `/>` and empty attributes are allowed.

> Setting it to HTML5 sets the `*prologue*` to the following doctype string:

>     <!DOCTYPE html>

[Function]
escape-string string `&key` test => escaped-string

> This function will accept a string `string` and will replace every character for which `test` returns true with its character entity. The numeric character entities use decimal instead of hexadecimal values when `HTML-MODE` is set to `:SGML` because of compatibility reasons with old clients. `test` must be a function of one argument which accepts a character and returns a generalized boolean. The default is the value of `*ESCAPE-CHAR-P*`. Note the `ESC` shortcut described in Syntax and Semantics.

>     * (escape-string "<Hühner> 'naïve'")
>     "&lt;H&#xFC;hner&gt; &#x27;na&#xEF;ve&#x27;"
>     * (with-html-output-to-string (s)
>         (:b (esc "<Hühner> 'naïve'")))
>     "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\"<b>&lt;H&#xFC;hner&gt; &#x27;na&#xEF;ve&#x27;</b>"

[Function]
escape-char character `&key` test => escaped-string

> This function works identical to `ESCAPE-STRING`, except that it operates on characters instead of strings.

[Special variable]
*escape-char-p*

> This is the default for the `test` keyword argument to `ESCAPE-STRING` and `ESCAPE-CHAR`. Its initial value is

>     #'(lambda (char)
>         (or (find char "<>&'\"")
>             (> (char-code char) 127)))

[Function]
escape-string-minimal string => escaped-string
[Function]
escape-string-minimal-plus-quotes string => escaped-string
[Function]
escape-string-iso-8859-1 string => escaped-string
[Function]
escape-string-all string => escaped-string
[Function]
escape-char-minimal character => escaped-string
[Function]
escape-char-minimal-plus-quotes character => escaped-string
[Function]
escape-char-iso-8859-1 character => escaped-string
[Function]
escape-char-all character => escaped-string

> These are convenience function based on `ESCAPE-STRING` and `ESCAPE-CHAR`. The string functions are defined in a way similar to this one:

>     (defun escape-string-minimal (string)
>       "Escape only #\<, #\>, and #\& in STRING."
>       (escape-string string :test #'(lambda (char) (find char "<>&"))))

>     (defun escape-string-minimal-plus-quotes (string)
>       "Like ESCAPE-STRING-MINIMAL but also escapes quotes."
>       (escape-string string :test #'(lambda (char) (find char "<>&'\""))))

>     (defun escape-string-iso-8859-1 (string)
>       "Escapes all characters in STRING which aren't defined in ISO-8859-1."
>       (escape-string string :test #'(lambda (char)
>                                       (or (find char "<>&'\"")
>                                           (> (char-code char) 255)))))

>     (defun escape-string-all (string)
>       "Escapes all characters in STRING which aren't in the 7-bit ASCII
>     character set."
>       (escape-string string :test #'(lambda (char)
>                                       (or (find char "<>&'\"")
>                                           (> (char-code char) 127)))))

> The character functions are defined in an analogous manner.

[Function]
conc `&rest` string-list => string

> Utility function to concatenate all arguments (which should be strings) into one string. Meant to be used mainly with attribute values.

>     * (conc "This" " " "is" " " "a" " " "sentence")
>     "This is a sentence"
>     * (with-html-output-to-string (s)
>         (:div :style (conc "padding:"
>                            (format nil "~A" (+ 3 2)))
>          "Foobar"))
>     "<div style='padding:5'>Foobar</div>"

[Generic Function]
convert-tag-to-string-list tag attr-list body body-fn => strings-or-forms

> This function exposes some of CL-WHO's internals so users can customize its behaviour. It is called whenever a tag is processed and must return a corresponding list of strings or Lisp forms. The idea is that you can specialize this generic function in order to process certain tags yourself.

> `tag` is a keyword symbol naming the outer tag, `attr-list` is an alist of its attributes (the car is the attribute's name as a keyword, the cdr is its value), `body` is the tag's body, and `body-fn` is a function which should be applied to the body to further process it. Of course, if you define your own methods you can ignore `body-fn` if you want.

> Here are some simple examples:

>     * (defmethod convert-tag-to-string-list ((tag (eql :red)) attr-list body body-fn)
>         (declare (ignore attr-list))
>         (nconc (cons "<font color='red'>" (funcall body-fn body)) (list "</font>")))
>     ; Compiling LAMBDA (PCL::.PV-CELL. PCL::.NEXT-METHOD-CALL. TAG ATTR-LIST BODY BODY-FN):
>     ; Compiling Top-Level Form:

>     #<STANDARD-METHOD CONVERT-TAG-TO-STRING-LIST ((EQL :RED) T T T) {582B268D}>
>     * (with-html-output (*standard-output*)
>         (:red (:b "Bold and red"))
>         (values))
>     <font color='red'><b>Bold and red</b></font>
>     * (show-html-expansion (s)
>         (:red :style "spiffy" (if (foo) (htm "Attributes are ignored"))))

>     (LET ((S S))
>       (PROGN
>        NIL
>        (WRITE-STRING "<font color='red'>" S)
>        (IF (FOO) (PROGN (WRITE-STRING "Attributes are ignored" S)))
>        (WRITE-STRING "</font>" S)))
>     * (defmethod convert-tag-to-string-list ((tag (eql :table)) attr-list body body-fn)
>         (cond ((cdr (assoc :simple attr-list))
>                (nconc (cons "<table"
>                             (convert-attributes (remove :simple attr-list :key #'car)))
>                       (list ">")
>                       (loop for row in body
>                             collect "<tr>"
>                             nconc (loop for col in row
>                                         collect "<td>"
>                                         when (constantp col)
>                                           collect (format nil "~A" col)
>                                         else
>                                           collect col
>                                         collect "</td>")
>                             collect "</tr>")
>                       (list "</table>")))
>               (t
>                 ;; you could as well invoke CALL-NEXT-METHOD here, of course
>                 (nconc (cons "<table "
>                              (convert-attributes attr-list))
>                        (list ">")
>                        (funcall body-fn body)
>                        (list "</table>")))))
>     ; Compiling LAMBDA (PCL::.PV-CELL. PCL::.NEXT-METHOD-CALL. TAG ATTR-LIST BODY BODY-FN):
>     ; Compiling Top-Level Form:

>     #<STANDARD-METHOD CONVERT-TAG-TO-STRING-LIST ((EQL :TABLE) T T T) {58AFB7CD}>
>     * (with-html-output (*standard-output*)
>         (:table :border 0 (:tr (:td "1") (:td "2")) (:tr (:td "3") (:td "4"))))
>     <table  border='0'><tr><td>1</td><td>2</td></tr><tr><td>3</td><td>4</td></tr></table>
>     "</td></tr></table>"
>     * (show-html-expansion (s)
>         (:table :simple t :border 0
>                 (1 2) (3 (fmt "Result = ~A" (compute-result)))))

>     (LET ((S S))
>       (PROGN
>        NIL
>        (WRITE-STRING
>         "<table border='0'><tr><td>1</td><td>2</td></tr><tr><td>3</td><td>"
>         S)
>        (FORMAT S "Result = ~A" (COMPUTE-RESULT))
>        (WRITE-STRING "</td></tr></table>" S)))

[Function]
convert-attributes attr-list => strings-or-forms

> This is a helper function which can be called from `CONVERT-TAG-TO-STRING-LIST` to process the list of attributes.

### Acknowledgements

Thanks to Tim Bradshaw and John Foderaro for the inspiration provided by their libraries mentioned above. Thanks to Jörg-Cyril Höhle for his suggestions with respect to attribute values. Thanks to Kevin Rosenberg for the LHTML patch. Thanks to Stefan Scholl for the 'old school' patch. Thanks to Mac Chan for several useful additions.

$Header: /usr/local/cvsrep/cl-who/doc/index.html,v 1.68 2009/03/09 21:54:11 edi Exp $

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