/lava-script

Lisp oozes like molten rock

Primary LanguageJavaScript

Copyright 2011 Evan R. Murphy

LavaScript

A lispy language that compiles into JavaScript.

Try LavaScript

You can now try LavaScript in your web-browser. Many thanks to Ross Angle (a.k.a. rocketnia) for implementing this!! He has also made the source code available.

Todo

LavaScript is incomplete. It still needs:

  • rest parameters and unquote-splicing

  • better reader (support strings!)

  • npm packaging

  • syntactic conveniences

      [1 2 3]             [1,2,3]
  {a 1 b 2}           {a:1,b:2}
  h.k  and (.k h)     h.k
  h[k] and ([k] h)    h[k]

  • access to other features of javascript, like loops and try/catch

  • more sophisticated macros, quasiquote or compile-time evaluation? see arc forum thread

  • pretty-printed output

  • idiomatic output (semi-colon instead of comma)

  • file extension: .lava, .ls, .lavascript?

LavaScript Challenge

We're not there yet, but this could be LavaScript's entry into the Arc Challenge, once the language gets sufficiently developed:

($ (fn ()
  (.html ($ 'body)
    (+ (<input>)
       (<button> "submit")))
  (.click ($ 'button) (fn ()
    (= said (.val ($ 'input) ()))
    (.html ($ 'body)
      (<a> href '#))
    (.click ($ 'a) (fn ()
      (.html ($ 'body)
        (+ "you said: " said))))))))

And the JavaScript output would be:

$(function() {
  $('body').html(
    '<input></input>' +
    '<button>submit</button>');
  $('button').click(function() {
    said = $('input').val();
    $('body').html(
      '<a href="#">click here</a>');
    $('a').click(function() {
      $('body').html("you said: " + said);
    });
  });
});

It depends on jQuery and a hypothetical HTML library that can generate strings like '<tag attr1="val1">body</tag>' from calls like (<tag> attr1 'val1 "body").

Now, with a few macros to abstract away common jQuery patterns and a softer HTML lib, you could rewrite this more concisely. The macros:

(mac ready body
  `($ (fn () ,@body)))

(mac trigger (selector event args...)
  `(. ($ ,selector) (,event ,@args)))

(mac draw body
  `(trigger 'body html 
    (+ ,@body)))

(mac handler (selector event body...)
  `(trigger ,selector ,event (fn ()
    ,@body)))

And the rewrite:

(ready
  (draw (input)
        (button "submit"))
  (handler 'button click
    (= said (trigger 'input val))
    (draw (a href '# "click here"))
    (handler 'a click
      (draw "you said: " said)))))))