import Text.Coffee
Gives you coffescript templates like Julius. But it isn't truly a first
class citizen yet- you can't just use it anywhere javascript is used yet.
That ability is slated for the next release. You might also be interested in
lambdascript (basically a direct translation of haskell to javascript) or
jmacro (more like your suggestion).
Greg Weber
On Thu, May 12, 2011 at 1:08 PM, Neil Mitchell
Hi,
I am thinking of doing a project using Hamlet (and perhaps a little of Yesod, I'm not quite sure). As I was reading through the book (excellent resource!) I was surprised by the syntax for $maybe, in particular that you get case matching on only the Maybe type. Being used to Haskell I'm a fan of general solutions, so I commented on the book (http://www.yesodweb.com/book/templates#c5). Since book comments aren't really the right place to discuss something technical I thought I'd move it here.
Currently Hamlet has:
$if a; $elseif b; $else
$maybe x <- ma; $nothing
I think if $if was expanded to be pattern guards, rather than boolean expressions, it would be more powerful, yet remain just as easy to use. So, I'd like:
$if Just x <- ma
To be equivalent to:
$maybe x <- ma
Then $else and $nothing also become equivalent.
If you also allow commas you can write things like:
$if Just x <- age, x > 18 adults $else kids
These have a very simple explanation - they're just pattern guards. Michael wants Hamlet to remain simple, in order to allow designers to use it without knowing programming. I think that's a reasonable goal, but I don't think a richer syntax for $if would make it any harder in the common case. I also think that if inexperienced people have to do more advanced tricks - i.e. converting their ADT into nested Maybe values in order to do some case analysis, it's going to end up harder in the long run.
I had two other, smaller thoughts, while reading the book:
1) $for x <- xs, x > 12 could be used to generalise $for to list comps. However, I notice you've got $for working over anything Foldable, rather than just lists, so it's not necessarily such a clear conversion. It's probably also less useful - since filter isn't too bad - and you can always do $for x <- [x | x <- xs, x > 12]
2) CoffeeScript makes Javascript much more useful. It would be very cool if as well as Julius there was something more like CoffeeScript, or perhaps exactly CoffeeScript. I also idly wondered if you could translate Haskell syntax to Javascript (without the types), but perhaps that isn't such a great idea.
Thanks, Neil
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