(in-package :ps)
;;;# 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.
(ps
(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.
(ps
(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 Lisp
;;; macros and ParenScript macros to coexist without interfering with
;;; each other. For example, the `1+' construct is implemented using
;;; a ParenScript macro:
(defpsmacro 1+ (form)
`(+ ,form 1))
;;; ParenScript allows the creation of JavaScript objects in a Lispy
;;; way, using keyword arguments.
(ps
(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.
(ps
(defun add-div (name href link-text)
(document.write
(ps-html ((:div :id name)
"The link is: "
((:a :href href) link-text))))))
;; compiles to
"
function addDiv(name, href, linkText) {
document.write('');
}
"
;;; In order to have a complete web application framework available in
;;; Lisp, ParenScript also provides a sexp-based syntax for CSS
;;; stylesheets. 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 using the
;;; AllegroServe HTMLGEN library:
(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