Added defgenerics for all the defmethods

[clinton/parenscript.git] / introduction.lisp

;;;# Introduction
;;;
;;; ParenScript is a simple language that looks a lot like Lisp, but
;;; actually is JavaScript in disguise. Actually, it is JavaScript
;;; embedded in a host Lisp. This way, JavaScript programs can be
;;; seamlessly integrated in a Lisp web application. The programmer
;;; doesn't have to resort to a different syntax, and JavaScript code
;;; can easily be generated without having to resort to complicated
;;; string generation or `FORMAT' expressions.
;;;
;;; An example is worth more than a thousand words. The following Lisp
;;; expression is a call to the ParenScript "compiler". The
;;; ParenScript "compiler" transforms the expression in ParenScript
;;; into an equivalent, human-readable expression in JavaScript.

(js
  (defun foobar (a b)
    (return (+ a b))))

;;; The resulting javascript is:

function foobar(a, b) {
  return a + b;
}

;;; Great care has been given to the indentation and overall
;;; readability of the generated JavaScript code.

;;;# Features
;;;
;;; ParenScript supports all the statements and expressions defined by
;;; the EcmaScript 262 standard. Lisp symbols are converted to
;;; camelcase, javascript-compliant syntax. This idea is taken from
;;; Linj by Antonio Menezes Leitao.  Here are a few examples of Lisp
;;; symbol to JavaScript name conversion:

(js-to-string 'foobar)      => "foobar"
(js-to-string 'foo-bar)     => "fooBar"
(js-to-string 'foo-b-@-r)   => "fooBAtR"
(js-to-string 'foo-b@r)     => "fooBatr"
(js-to-string '*array)      => "Array"
(js-to-string '*math.floor) => "Math.floor"

;;; It also supports additional iteration constructs, relieving the
;;; programmer of the burden of iterating over arrays.
;;; `for' loops can be written using the customary `DO' syntax.

(js
  (do ((i 0 (incf i))
       (j (aref arr i) (aref arr i)))
      ((>= i 10))
    (alert (+ "i is " i " and j is " j))))

; compiles to

for (var i = 0, j = arr[i]; i < 10; i = ++i, j = arr[i]) {
  alert("i is " + i + " and j is " + j);
}

;;; ParenScript uses the Lisp reader, allowing for reader macros. It
;;; also comes with its own macro environment, allowing host macros
;;; and ParenScript to coexist without interfering with each other.
;;; Furthermore, ParenScript uses its own compiler macro system,
;;; allowing for an even further customization of the generation of
;;; JavaScript. For example, the `1+' construct is implemented using a
;;; ParenScript macro:

(defjsmacro 1+ (form)
  `(+ ,form 1))

;;; ParenScript allows the creation of JavaScript objects in a Lispy
;;; way, using keyword arguments.

(js
  (create :foo "foo"
          :bla "bla"))

; compiles to

{ foo : "foo", 
  bla : "bla" }

;;; ParenScript features a HTML generator. Using the same syntax as
;;; the `HTMLGEN' package of Franz, Inc., it can generate JavaScript
;;; string expressions. This allows for a clean integration of HTML in
;;; ParenScript code, instead of writing the tedious and error-prone
;;; string generation code generally found in JavaScript.

(js
  (defun add-div (name href link-text)
    (document.write
     (html ((:div :id name)
            "The link is: "
            ((:a :href href) link-text))))))

; compiles to

function addDiv(name, href, linkText) {
  document.write("<div id=\"" + name + "\">The link is: <a href=\""
                                + href + "\">"
                                + linkText + "</a></div>");
}

;;; In order to have a complete web application framework available in
;;; Lisp, ParenScript also provides a sexp-based syntax for CSS
;;; files. Thus, a complete web application featuring HTML, CSS and
;;; JavaScript documents can be generated using Lisp syntax, allowing
;;; the programmer to use Lisp macros to factor out the redundancies
;;; and complexities of Web syntax. For example, to generate a CSS
;;; inline node in a HTML document:

(html-stream *standard-output* 
  (html
   (:html
    (:head
     (css (* :border "1px solid black")
          (div.bl0rg :font-family "serif")
          (("a:active" "a:hoover") :color "black" :size "200%"))))))

; which produces

<html><head><style type="text/css">
<!--
* {
   border:1px solid black;
}

div.bl0rg {
   font-family:serif;
}

a:active,a:hoover {
   color:black;
   size:200%;
}

-->
</style>
</head>
</html>

;;;# Getting ParenScript
;;;
;;; ParenScript can be obtained from the BKNR subversion repository at

    svn://bknr.net/trunk/bknr/src/js

;;; ParenScript does not depend on any part of BKNR though. You can
;;; download snapshots of ParenScript at the webpage

    http://bknr.net/parenscript

;;; or using asdf-install.

   (asdf-install:install 'parenscript)

;;;
;;; After downloading the ParenScript sourcecode, set up the ASDF
;;; central registry by adding a symlink to "parenscript.asd". Then
;;; use ASDF to load ParenScript. You may want to edit the ASDF file
;;; to remove the dependency on the Allegroserve HTMLGEN facility.

   (asdf:oos 'asdf:load-op :parenscript)

;;; ParenScript was written by Manuel Odendahl. He can be reached at

    manuel@bknr.net