http://codemirror.net/demo/widget.html

I was able to very easily add in inline error messages to nulan.html:

https://github.com/Pauan/nulan/tree/a24a33a864d9e2800fc3c995...

And here's a screenshot of it in action:

http://img687.imageshack.us/img687/2348/screenshot1223201203...

https://github.com/Pauan/nulan/tree/9ffecb5a9aa7a4bd7cbe9680...

Firstly, there's now an interactive tutorial. Just open up "nulan.html", and if you don't see the tutorial, click the "Reset Tutorial" button at the top. Be careful, it'll clobber any changes you've made.

Secondly, you might have noticed that the editor has syntax highlighting now. But it's actually really cool. First, try inputting this:

  $mac foo -> a b c
    a + b + c

  foo 1 2 3


  def foo -> a b c
    a + b + c

  foo 1 2 3

Now try inputting this:

  # Array comprehensions
  box in

  $mac for -> x {('in) n y}
    'y.map -> n x

  $syntax-infix for 0 [ order "right" ]
  $syntax-infix in  0 [ order "right" ]

  (x + 2) for x in {1 2 3}

  $mac ^ -> a b
    a + b

  $syntax-infix ^ 0 [ delimiter %t ]

  prn 1^2

http://pauan.github.com/nulan/doc/tutorial.html

I'm thinking about putting in a redirect for the old URL, but I'm not sure if it's worth it or not.

https://github.com/Pauan/nulan/tree/f88a81563fec518cd740302d...

Or just use the uploaded version:

http://pauan.github.com/nulan/doc/tutorial.html

You'll have to use the "Reset Tutorial" button to see all the changes.

The biggest change is that you can now click on an expression to highlight it. To see what I mean, try clicking on stuff in the tutorial.

But the coolest part is that the highlighting understands boxes. Try inputting this:

  box foo = 5

  foo + 10


  box foo = 20

  foo + 30

  w/box foo = 5
    | foo + 10
    | box foo = 20
    | foo + 30

It's also smart enough to know that the "." syntax is a string, even though it looks like a symbol:

  box foo = []
  
  foo.bar <= 5
  
  foo.bar

a) if-box is a kinda contrived example. Perhaps we can find something better?

b) What's the difference between w/uniq and w/box? Both seem to create boxes. Could I just say this at http://github.com/Pauan/nulan/blob/5dfddacfbb/nulan.html#L44...?

  $mac if-box ->
    w/uniq temp
      'w/box temp = 5
         if temp
           temp + 1

  TypeError: Cannot call method 'chunkSize' of undefined

If you have a better suggestion, I'm all ears. But I settled on that because A) it's simple, B) it's short, C) it's something that does actually come up in practice, so it's not too contrived.

---

"What's the difference between w/uniq and w/box? Both seem to create boxes."

Well, to explain this... unique variables are actually implemented as anonymous boxes. So implementation-wise, there's not much difference.

The difference is in the actual macros "w/box" and "w/uniq". Here's the definition for them:

  $mac w/box -> @args body
    'w/new-scope
       | var ,@args
       | body

  $mac w/uniq -> @args body
    'w/box ,@(args.map -> x 'x = make-uniq;)
       body

  w/box foo = 5
    foo

  w/new-scope
    | var foo = 5
    | foo

  w/uniq foo
    foo

  w/box foo = make-uniq;
    foo

  w/new-scope
    | var foo = make-uniq;
    | foo

They serve exactly the same purpose as "let" and "w/uniq" in Arc.

If you're asking why you can't just do this:

  $mac if-box ->
    w/box temp
      'w/box temp = 5
         if temp
           temp + 1

  $mac foo ->
    w/box bar = 5
      'bar + 2

I thought about having it throw an error for local symbols, which would have required you to write the macro like this:

  $mac foo ->
    w/box bar = 5
      ',bar + 2

---

"I tried running this and got the following"

It works fine for me. And in fact, the code snippet you posted seems exactly the same as what is already in the tutorial. Maybe you intended to paste something else?