Tell HN: Meet CoffeeScript

http://jashkenas.github.com/coffee-script/#overview

by grandalf • 16 years ago

87 40 16 years ago

jashkenas.github.com

david927• 16 years ago

In a word: cool.

hackoder• 16 years ago

Beautiful to look at.

For anyone who uses this in an app, my guess is that it makes debugging (in firebug etc) kinda annoying? I mean, even though it maps directly to JavaScript, the mental context switch between what you see in firebug and the code you've written would take getting used to?

jashkenas11• 16 years ago

We're trying to be pretty careful about keeping the compiled JS debuggable. To that end:

* The compiled output is pretty-printed instead of minified.

* Comments are passed through in-place to JavaScript.

* All functions are named functions, so instead of a stacktrace full of "anonymous", you can situate yourself.

* There's a "no special functions" rule -- CoffeeScript translates directly into JS without a standard library, which means that theres a one-to-one correspondence between your source code and its JavaScript equivalent, so it's not too hard to untangle.

That said, the temporary variable that we need to generate for some features are a little ugly, and sometimes we need to generate extra safety checks because we don't know certain things at compile time (such as, for example if a range counts upwards or down). Any suggestions for how to make the compiled JS more easily readable would be warmly welcomed.

johnnybgoode• 16 years ago

My dream would be to be able to decompile JS into CoffeeScript, so I could make changes in either form. That would probably be difficult to do for some of the more advanced features, though.

10ren• 16 years ago

To make the line numbers in JS error messages more informative, you could make the line numbers coincide.

i.e. by minifying the JS where coffee:js lines are 1:m and adding blanks when m:1, instead of always pretty-printing.

It's a trade-off of js-readability for error-readability - a hard call, but very cool to be able to go directly to the line in question.

jashkenas11• 16 years ago

Oops. I was hoping to post this to HN in a couple of days when it's finished, but the latest commits to CoffeeScript on Github include a compiler that's written entirely in CoffeeScript. It's been compiling itself since Friday.

This means that you can compile scripts in the browser, should you choose to, or within Node.js on the server, and greatly increases the speed of the interactive REPL. It's also a nice showcase for what's possible in CoffeeScript.

For example, take a peek at the Jison parser, using a little DSL function that makes for a nice style of grammar declaration:

http://github.com/jashkenas/coffee-script/blob/master/src/gr...

If you'd like to play with the CoffeeScript-in-CoffeeScript implementation, use bin/node_coffee when you check out the source. bin/coffee remains the Ruby implementation until the CoffeeScript side is up to feature parity.

Here's the original post, things have come a long way since then:

http://news.ycombinator.com/item?id=1014080

grandalf2• 16 years ago

Sorry about posting it early :) I must have missed the original story and when I discovered it today I thought it merited sharing with HN.

bprater• 16 years ago

Brilliant. I was turned off by the need to compile separately with Ruby.

Now I can play with it without that overhead and always compile down when done with development for speed. Kudos!

makmanalp• 16 years ago

Repost, but great job. I really like how crud-free it is compared to the javascript versions of the same scripts.

jashkenas11• 16 years ago

Alright, just pushed a quick update to the documentation page that includes the self-compiler. You can try compiling CoffeeScript expressions in the browser right here:

http://jashkenas.github.com/coffee-script/#try_coffee

fnid22• 16 years ago

The script syntax is less intuitive than javascript and doesn't save that many lines, so I'm not sure it's something I'd ever use.

brehaut2• 16 years ago

Not 'less intuitive', it is 'less familiar'. These sorts of comments are largely subjective. See also C family programmers looking at Lisp or ML family languages.

fnid22• 16 years ago

You are going to have a very hard time convincing me that anyone who doesn't know Coffeescript syntax is going to undertand what this means:

   number: -42 if opposite_day

however, almost anyone, even non-programmers can understand this:

  if (opposite_day) {
    number = -42;
  }

qeorge• 16 years ago

I love the syntax for lambdas and existence checking.

axod2• 16 years ago

So it's almost identical, but with worse (IMHO) syntax!

It's all a matter of taste, but I can't see this as being more tasteful than js.

Also it's comparing to crappy js.

For example

  // Splats:
  race = function race(winner) {
    var runners;
    runners = Array.prototype.slice.call(arguments, 1);
    return print(winner, runners);
  };

Could be rewritten

  race = function race(winner) {
    return print(winner, Array.prototype.slice.call(arguments, 1));
  }

zefhous• 16 years ago

The JavaScript examples don't show what you would write in JavaScript, they show the compiled JavaScript output when you write it in CoffeScript.

jashkenas11• 16 years ago

There's no question that the generated JavaScript is never going to be as pretty as handwritten JS. But that said, choosing splats as your example of bad syntax isn't the best choice, because there isn't a syntactic equivalent in JavaScript.

This CoffeeScript:

    send_letter: (name, addresses...) ->
      # more code...

Where the array of addresses can be referenced and used as many times as you like within the function body, would need to be translated as this JavaScript:

    var send_letter = function send_letter(name) {
      var addresses = Array.prototype.slice.call(arguments, 1);
      # more code...
    };

Which is both a good bit more to type, as well as more work -- you need to figure out the index from which to slice. The only difference with the generated JS is that the variable declaration is on a separate line -- a feature that allows all assignments to be used as part of a larger expression.

jrockway• 16 years ago

You hate everything. Maybe you should just not read this type of article.

axod2• 16 years ago

Yeah you're right. I'll try hard to ignore the "language syntax sucks/rocks/is so important" articles.

TheSOB88• 16 years ago

Why are braces needed in the Math declaration? Is this not Pythonlike enough to use the indentation, or is there something else?

jashkenas11• 16 years ago

The braces are there because JavaScript's object literals are already pretty nice. But it would certainly be an interesting feature, if assigning to a block implied an object literal.

    obj:
      prop: value
      prop2: value2

edit: I've opened a ticket for this, here:

http://github.com/jashkenas/coffee-script/issues/issue/146

grayrest2• 16 years ago

Is there any reason the object comprehensions can't be rewritten from:

    ages = (function() {
      __a = []; __b = years_old;
      for (child in __b) {
        age = __b[child];
        if (__hasProp.call(__b, child)) {
          __a.push(child + " is " + age);
        }
      }
      return __a;
    }).call(this);

to:

    ages = (function() {
      __a = []; __b = years_old;
      for (child in __b) if (__hasProp.call(__b, child)) {
        age = __b[child];
        __a.push(child + " is " + age);
      }
      return __a;
    }).call(this);

It's fairly minor but saves a few assignments and generates slightly less noise.

jashkenas11• 16 years ago

Thanks, grayrest. That's a nice improvement that has the lovely side effect of simplifying the code generation needed to implement comprehensions.

I've pushed a patch that implements your suggestion, and all the tests are passing:

http://github.com/jashkenas/coffee-script/commit/7667e167322...

Thanks for that.

Tichy2• 16 years ago

Is there a chance to add macros? Don't know enough about macros to know if it was doable for CoffeeScript, but only today I run into a situation where I thought it would be nice to have them in JS.

jashkenas11• 16 years ago

Mind explaining the situation that you encountered? Maybe we can come up with something.

Tichy2• 16 years ago

I am afraid it already slipped my mind as it was several hours ago. But I am sure another situation will arise. Where would be a good place to discuss it, as this thread will long have been gone stale by then?

winter_blue• 16 years ago

Okay, enough of these metalanguages. These languages might make it slightly easier to write your program, but the inability to use standard development tools with it results in you loosing more time in the end.

drats• 16 years ago

Excellent work Jashkenas! I think what would really let you achieve liftoff (and a book deal with a tech publisher) would be a Sinatra-like framework based on this. The Sinatra core is very small and has wowed a lot of people, replicating it so that people are using coffeescript serverside and also in the client would be amazing. I imagine a 300 page book equally divided between the language, server-side and client-side would sell really well with a 1.0 release. I can easily picture a rails-like ecosystem (with associated business and publishing opportunities) surrounding this in the future.

grayrest2• 16 years ago

There's no real shortage of sinatra clones for js:

http://www.fabjs.org/ http://code.quirkey.com/sammy/ http://github.com/visionmedia/express/

and there's no real trick to using them:

    require 'express'
    require 'express/plugins'

    configure ->
        use MethodOverride
        use ContentLength
        set 'root', __dirname

    get '/hello', ->
        @contentType('html')
        '<h1>Hello World </h1>'

    get '/user/:id?', (id) ->
        @render 'user.haml.html', {
            locals: {
                name: if id? then 'User '+id else 'You'
            }
        }

theschwa• 16 years ago

So far, one of my favorite features of CoffeeScript is how responsive you are to questions comments and concerns jashkenas.

jashkenas11• 16 years ago

If anyone wants to try tweaking the grammar and recompiling the language, you can run this:

    bin/node_coffee src/*.coffee --output lib/coffee_script

Just be careful, if you break it you'll have to check out the 'lib' directory again to get a working compiler back.

camccann• 16 years ago

Ah, the existential accessor operator is lovely. It really warms the heart to see variations on the Maybe monad sneaking into other languages--if there's one thing from Haskell I miss elsewhere, it's that.

Tell HN: Meet CoffeeScript

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