Tutorial on JS with Haskell: Fay or GHCJS?

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Tutorial on JS with Haskell: Fay or GHCJS?

Alejandro Serrano Mena
Hi,
I'm currently writing a tutorial on web applications using Haskell. I know the pros and cons of each server-side library (Yesod, Snap, Scotty, Warp, Happstack), but I'm looking for the right choice for client-side programming that converts Haskell to JavaScript. I've finally come to Fay vs. GHCJS, and would like your opinion on what's the best to tackle. My current list of pros and cons is:

Fay
===
Pros:
- Does not need GHC 7.8
- Easy FFI with JS
- Has libraries for integration with Yesod and Snap

Cons:
- Only supports a subset of GHC (in particular, no type classes)


GHCJS
======
Pros:
- Supports full GHC
- Easy FFI with JS
- Highly opinionated point: will stay longer than Fay (but it's very important for not having a tutorial that is old in few months)

Cons:
- Needs GHC 7.8 (but provides a Vagrant image)

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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Niklas Hambüchen
Hi, I'm also interested in that.

Have you already evaluated haste?

It does not seem to have any of your cons, but maybe others.

What I particularly miss from all solutions is the ability to simply
call parts written in Haskell from Javascript, e.g. to write `fib` and
then integrate it into an existing Javascript application (they are all
more interested in doing the other direction).

On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:

> Hi,
> I'm currently writing a tutorial on web applications using Haskell. I
> know the pros and cons of each server-side library (Yesod, Snap,
> Scotty, Warp, Happstack), but I'm looking for the right choice for
> client-side programming that converts Haskell to JavaScript. I've
> finally come to Fay vs. GHCJS, and would like your opinion on what's
> the best to tackle. My current list of pros and cons is:
>
> Fay
> ===
> Pros:
> - Does not need GHC 7.8
> - Easy FFI with JS
> - Has libraries for integration with Yesod and Snap
>
> Cons:
> - Only supports a subset of GHC (in particular, no type classes)
>
>
> GHCJS
> ======
> Pros:
> - Supports full GHC
> - Easy FFI with JS
> - Highly opinionated point: will stay longer than Fay (but it's very
> important for not having a tutorial that is old in few months)
>
> Cons:
> - Needs GHC 7.8 (but provides a Vagrant image)
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> [hidden email]
> http://www.haskell.org/mailman/listinfo/haskell-cafe

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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Alejandro Serrano Mena
I haven't looked at Haste too much, I'll give it a try.

My main problem is that I would like to find a solution that will continue working in years (somehow, that will became "the" solution for generating JS from Haskell code). That's why I see GHCJS (which just includes some patches to mainstream GHC) as the preferred solution, because it seems the most probable to continue working when new versions of GHC appear.


2013/9/4 Niklas Hambüchen <[hidden email]>
Hi, I'm also interested in that.

Have you already evaluated haste?

It does not seem to have any of your cons, but maybe others.

What I particularly miss from all solutions is the ability to simply
call parts written in Haskell from Javascript, e.g. to write `fib` and
then integrate it into an existing Javascript application (they are all
more interested in doing the other direction).

On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:
> Hi,
> I'm currently writing a tutorial on web applications using Haskell. I
> know the pros and cons of each server-side library (Yesod, Snap,
> Scotty, Warp, Happstack), but I'm looking for the right choice for
> client-side programming that converts Haskell to JavaScript. I've
> finally come to Fay vs. GHCJS, and would like your opinion on what's
> the best to tackle. My current list of pros and cons is:
>
> Fay
> ===
> Pros:
> - Does not need GHC 7.8
> - Easy FFI with JS
> - Has libraries for integration with Yesod and Snap
>
> Cons:
> - Only supports a subset of GHC (in particular, no type classes)
>
>
> GHCJS
> ======
> Pros:
> - Supports full GHC
> - Easy FFI with JS
> - Highly opinionated point: will stay longer than Fay (but it's very
> important for not having a tutorial that is old in few months)
>
> Cons:
> - Needs GHC 7.8 (but provides a Vagrant image)
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> [hidden email]
> http://www.haskell.org/mailman/listinfo/haskell-cafe


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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Nathan Hüsken
In my opinion haste is somewhere between Fay and ghcjs. It supports more than Fay, but in difference to ghcjs some PrimOps are not supported (weak pointers for example).

It is a little bit more "direct" than ghcjs, in the sense that it does not need such a big rts written in js.

I like haste :).

What I wonder is how the outputs of these 3 compilers compare speed wise.

On 09/04/2013 11:11 AM, Alejandro Serrano Mena wrote:
I haven't looked at Haste too much, I'll give it a try.

My main problem is that I would like to find a solution that will continue working in years (somehow, that will became "the" solution for generating JS from Haskell code). That's why I see GHCJS (which just includes some patches to mainstream GHC) as the preferred solution, because it seems the most probable to continue working when new versions of GHC appear.


2013/9/4 Niklas Hambüchen <[hidden email]>
Hi, I'm also interested in that.

Have you already evaluated haste?

It does not seem to have any of your cons, but maybe others.

What I particularly miss from all solutions is the ability to simply
call parts written in Haskell from Javascript, e.g. to write `fib` and
then integrate it into an existing Javascript application (they are all
more interested in doing the other direction).

On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:
> Hi,
> I'm currently writing a tutorial on web applications using Haskell. I
> know the pros and cons of each server-side library (Yesod, Snap,
> Scotty, Warp, Happstack), but I'm looking for the right choice for
> client-side programming that converts Haskell to JavaScript. I've
> finally come to Fay vs. GHCJS, and would like your opinion on what's
> the best to tackle. My current list of pros and cons is:
>
> Fay
> ===
> Pros:
> - Does not need GHC 7.8
> - Easy FFI with JS
> - Has libraries for integration with Yesod and Snap
>
> Cons:
> - Only supports a subset of GHC (in particular, no type classes)
>
>
> GHCJS
> ======
> Pros:
> - Supports full GHC
> - Easy FFI with JS
> - Highly opinionated point: will stay longer than Fay (but it's very
> important for not having a tutorial that is old in few months)
>
> Cons:
> - Needs GHC 7.8 (but provides a Vagrant image)
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> [hidden email]
> http://www.haskell.org/mailman/listinfo/haskell-cafe



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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Adam Bergmark


On Wed, Sep 4, 2013 at 12:36 PM, Nathan Hüsken <[hidden email]> wrote:
In my opinion haste is somewhere between Fay and ghcjs. It supports more than Fay, but in difference to ghcjs some PrimOps are not supported (weak pointers for example).

It is a little bit more "direct" than ghcjs, in the sense that it does not need such a big rts written in js.

I like haste :).

What I wonder is how the outputs of these 3 compilers compare speed wise.


On 09/04/2013 11:11 AM, Alejandro Serrano Mena wrote:
I haven't looked at Haste too much, I'll give it a try.

My main problem is that I would like to find a solution that will continue working in years (somehow, that will became "the" solution for generating JS from Haskell code). That's why I see GHCJS (which just includes some patches to mainstream GHC) as the preferred solution, because it seems the most probable to continue working when new versions of GHC appear.


2013/9/4 Niklas Hambüchen <[hidden email]>
Hi, I'm also interested in that.

Have you already evaluated haste?

It does not seem to have any of your cons, but maybe others.

What I particularly miss from all solutions is the ability to simply
call parts written in Haskell from Javascript, e.g. to write `fib` and
then integrate it into an existing Javascript application (they are all
more interested in doing the other direction).

On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:
> Hi,
> I'm currently writing a tutorial on web applications using Haskell. I
> know the pros and cons of each server-side library (Yesod, Snap,
> Scotty, Warp, Happstack), but I'm looking for the right choice for
> client-side programming that converts Haskell to JavaScript. I've
> finally come to Fay vs. GHCJS, and would like your opinion on what's
> the best to tackle. My current list of pros and cons is:
>
> Fay
> ===
> Pros:
> - Does not need GHC 7.8
> - Easy FFI with JS
> - Has libraries for integration with Yesod and Snap
>
> Cons:
> - Only supports a subset of GHC (in particular, no type classes)
>
>
> GHCJS
> ======
> Pros:
> - Supports full GHC
> - Easy FFI with JS
> - Highly opinionated point: will stay longer than Fay (but it's very
> important for not having a tutorial that is old in few months)
>
> Cons:
> - Needs GHC 7.8 (but provides a Vagrant image)
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> [hidden email]
> http://www.haskell.org/mailman/listinfo/haskell-cafe



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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Adam Bergmark
Here are some points I'd like to emphasize in addition to the threads above, with the disclaimer that I'm the maintainer of Fay.

Fay tries to be very simple, the code base is small (~4800 LoC). This really lowers the entry barrier for contributions which I think is very important for open source projects. GHCJS is much more complicated since it tries to do so much. For GHCJS I'd be afraid that the developers might eventually abandon the project and then it'd be pretty hard to take over development. Much easier for someone to take over Fay development. I think you can safely expect to find bugs in all compilers, and if you do and you are in a hurry you might have to fix it yourself. Fay has very simple output that is close to both Haskell and JavaScript so it's pretty easy to just add a breakpoint and start debugging.

Even if GHCJS can successfully compile most of hackage, would we want to have these as dependencies in web projects? An output size of 1MiB is nothing when compiling a binary, but for a public website 1MiB can still be quite a lot, add some transitive dependencies and output will explode. Most people don't optimize their packages to have few dependencies, which makes sense since the abstraction usually heavily outweighs code size. So either way you would probably want to write some specific light-weight versions of libraries you want to use, that's one reason both GHCJS and Fay have their own base packages.

One place I think GHCJS can shine is for non standard web applications such as WEBGL games. Nothing stopping you from using Fay for this, but I expect you can really start to leverage GHCJS's threaded runtime here.

I'm not sure if GHCJS or Haste have any out of the box solutions for doing client<->server communication. In Fay you can just serialize any data type automatically on the front and backend to a json format and then deserialize it automatically again on the other end. You can also leverage phantom types (https://github.com/fpco/yesod-fay/blob/master/Language/Fay/Yesod.hs#L41) to typecheck this communication.

It's hard to know how well GHCJS performs in a real web application. FP Complete uses Fay for their IDE and School of Haskell so it has been battle tested, so if you want something that definitely works today I think Fay is the more reliable option.

It is possible that GHCJS will eventually supercede Fay. But if you want something that's easy to use today you can always write Fay, and then convert it to GHCJS later since Fay is a subset of Haskell.

I think GHCJS needs more time to prove itself. I know the developers are hard at work and I hope they will focus on a lot of learning materials. Once you can `cabal install ghcjs` and just get started I think they will see a lot more interest coming their way.

Let me know if you have more questions. If you decide to use Fay in your tutorial I'd be happy to help out, just send me an e-mail!

- Adam



On Wed, Sep 4, 2013 at 2:46 PM, Adam Bergmark <[hidden email]> wrote:


On Wed, Sep 4, 2013 at 12:36 PM, Nathan Hüsken <[hidden email]> wrote:
In my opinion haste is somewhere between Fay and ghcjs. It supports more than Fay, but in difference to ghcjs some PrimOps are not supported (weak pointers for example).

It is a little bit more "direct" than ghcjs, in the sense that it does not need such a big rts written in js.

I like haste :).

What I wonder is how the outputs of these 3 compilers compare speed wise.


On 09/04/2013 11:11 AM, Alejandro Serrano Mena wrote:
I haven't looked at Haste too much, I'll give it a try.

My main problem is that I would like to find a solution that will continue working in years (somehow, that will became "the" solution for generating JS from Haskell code). That's why I see GHCJS (which just includes some patches to mainstream GHC) as the preferred solution, because it seems the most probable to continue working when new versions of GHC appear.


2013/9/4 Niklas Hambüchen <[hidden email]>
Hi, I'm also interested in that.

Have you already evaluated haste?

It does not seem to have any of your cons, but maybe others.

What I particularly miss from all solutions is the ability to simply
call parts written in Haskell from Javascript, e.g. to write `fib` and
then integrate it into an existing Javascript application (they are all
more interested in doing the other direction).

On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:
> Hi,
> I'm currently writing a tutorial on web applications using Haskell. I
> know the pros and cons of each server-side library (Yesod, Snap,
> Scotty, Warp, Happstack), but I'm looking for the right choice for
> client-side programming that converts Haskell to JavaScript. I've
> finally come to Fay vs. GHCJS, and would like your opinion on what's
> the best to tackle. My current list of pros and cons is:
>
> Fay
> ===
> Pros:
> - Does not need GHC 7.8
> - Easy FFI with JS
> - Has libraries for integration with Yesod and Snap
>
> Cons:
> - Only supports a subset of GHC (in particular, no type classes)
>
>
> GHCJS
> ======
> Pros:
> - Supports full GHC
> - Easy FFI with JS
> - Highly opinionated point: will stay longer than Fay (but it's very
> important for not having a tutorial that is old in few months)
>
> Cons:
> - Needs GHC 7.8 (but provides a Vagrant image)
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> [hidden email]
> http://www.haskell.org/mailman/listinfo/haskell-cafe



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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Joachim Breitner-2
In reply to this post by Adam Bergmark
Hi,

Am Mittwoch, den 04.09.2013, 14:46 +0200 schrieb Adam Bergmark:
> You might be interested in these two comment threads (and maybe the
> rest of the comments as well):
> http://www.reddit.com/r/haskell/comments/1ldqav/thoughts_on_uhc_vs_haste_vs_fay/cbyrhwz
> http://www.reddit.com/r/haskell/comments/1htqi2/announce_haste_the_haskell_to_js_compiler_is_now/cay79g9?context=1

and another data point:
http://www.joachim-breitner.de/blog/archives/602-Running-Circle-Packing-in-the-Browser-using-Haste.html

Greetings,
Joachim


--
Joachim “nomeata” Breitner
  [hidden email]http://www.joachim-breitner.de/
  Jabber: [hidden email]  • GPG-Key: 0x4743206C
  Debian Developer: [hidden email]

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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Daniil Frumin
In reply to this post by Niklas Hambüchen
Hi!

On Sep 4, 2013, at 13:02, Niklas Hambüchen <[hidden email]> wrote:

> Hi, I'm also interested in that.
>
> Have you already evaluated haste?
>
> It does not seem to have any of your cons, but maybe others.
>
> What I particularly miss from all solutions is the ability to simply
> call parts written in Haskell from Javascript, e.g. to write `fib` and
> then integrate it into an existing Javascript application (they are all
> more interested in doing the other direction).
>

So, I don't how Fay handles things but I can say the following about GHCJS:

I have to admit that it's not that easy to call Haskell from
JavaScript as I want it.
However, there are several functions you can use for doing that. GHCJS
supports running actions in "main" asynchronous threads (application
is considered to be terminated when the thread is finished), regular
asynchronous threads and synchronous threads. Since you want to call
pure Haskell code you probably want to use runSync.

One way to do that would be to use an intermediate object to store the
result of calling Fib:

----
fib :: Int -> Int
fib n = fibs !! n
  where fibs = 0:1:zipWith (+) fibs (tail fibs)

fibAction :: JSRef () -> Int -> IO ()
fibAction ref n = do
    res <- toJSRef (fib n)
    setProp ("result"::Text) res ref
----
    function go() {
       var i = parseInt($("#num").val(), 10);
       var o = { result : null };
       var oref = mkJSRefNew(o);
       var act = h$c3( h$ap2_e
                     , h$mainZCMainzifibAction
                     , oref
                     , i );
       h$runSync(act);
       $("#result").text(o.result);
    };
----

You can find the complete sourcecode and a runnable executable here:
<http://co-dan.github.io/ghcjs/examples/Fib.hs> &
<http://co-dan.github.io/ghcjs/examples/Fib/index.html>


I think it's nice that you've raised that question, I will think about
implementing a finer API for calling Haskell from JS.

NB: It also sounds like you might benefit from the non-concurrent
GHCJS runtime and codegen that Luite is now porting to the new API.
Since you plan to implement your interface/interactions in JS you
probably don't need support for concurrency and you can enjoy smaller
code & rts sizes.

> On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:
>> Hi,
>> I'm currently writing a tutorial on web applications using Haskell. I
>> know the pros and cons of each server-side library (Yesod, Snap,
>> Scotty, Warp, Happstack), but I'm looking for the right choice for
>> client-side programming that converts Haskell to JavaScript. I've
>> finally come to Fay vs. GHCJS, and would like your opinion on what's
>> the best to tackle. My current list of pros and cons is:
>>
>> Fay
>> ===
>> Pros:
>> - Does not need GHC 7.8
>> - Easy FFI with JS
>> - Has libraries for integration with Yesod and Snap
>>
>> Cons:
>> - Only supports a subset of GHC (in particular, no type classes)
>>
>>
>> GHCJS
>> ======
>> Pros:
>> - Supports full GHC
>> - Easy FFI with JS
>> - Highly opinionated point: will stay longer than Fay (but it's very
>> important for not having a tutorial that is old in few months)
>>
>> Cons:
>> - Needs GHC 7.8 (but provides a Vagrant image)
>>
>>
>> _______________________________________________
>> Haskell-Cafe mailing list
>> [hidden email]
>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
> _______________________________________________
> Haskell-Cafe mailing list
> [hidden email]
> http://www.haskell.org/mailman/listinfo/haskell-cafe

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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Luite Stegeman

On Wed, Sep 4, 2013 at 6:32 PM, Daniil Frumin <[hidden email]> wrote:


I think it's nice that you've raised that question, I will think about
implementing a finer API for calling Haskell from JS.


It sounds like something like h$runSyncWithResult (name open for bikeshedding) that takes an IO (JSRef a) and returns the result to the caller, or null (exception?) when the synchronous thread terminated for some reason, would fit the bill. I think this can be implemented in a few lines of JS.

the current API is a bit bare-bones, based around calling main or a few other top-level IO actions and doing the rest from Haskell code. The Haskell code can make callbacks (JS functions that run Haskell when called, see [1] ), but that can be a bit cumbersome to use when wrapping a library with lots of external JavaScript.

If anyone has ideas of how they'd like a call-Haskell-functions-from-JS API to look, I'd be happy to hear and see if we can make something nice.

One thing to keep in mind though is that type information has been erased from the compiled code, making a generic applyHaskellFun(fun,x,y) that would run 'fun x y' and return its result would be rather risky. That's why the syncCallback/asyncCallback actions use JSRef, letting the Haskell side do the conversion. Going through 'foreign export' could work though, or perhaps there are other options that make this safer.

luite

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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Adam Bergmark


On Wed, Sep 4, 2013 at 8:18 PM, Luite Stegeman <[hidden email]> wrote:

On Wed, Sep 4, 2013 at 6:32 PM, Daniil Frumin <[hidden email]> wrote:


I think it's nice that you've raised that question, I will think about
implementing a finer API for calling Haskell from JS.


It sounds like something like h$runSyncWithResult (name open for bikeshedding) that takes an IO (JSRef a) and returns the result to the caller, or null (exception?) when the synchronous thread terminated for some reason, would fit the bill. I think this can be implemented in a few lines of JS.

the current API is a bit bare-bones, based around calling main or a few other top-level IO actions and doing the rest from Haskell code. The Haskell code can make callbacks (JS functions that run Haskell when called, see [1] ), but that can be a bit cumbersome to use when wrapping a library with lots of external JavaScript.

If anyone has ideas of how they'd like a call-Haskell-functions-from-JS API to look, I'd be happy to hear and see if we can make something nice.

One thing to keep in mind though is that type information has been erased from the compiled code, making a generic applyHaskellFun(fun,x,y) that would run 'fun x y' and return its result would be rather risky. That's why the syncCallback/asyncCallback actions use JSRef, letting the Haskell side do the conversion. Going through 'foreign export' could work though, or perhaps there are other options that make this safer.

luite

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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Chris Smith-31
In reply to this post by Nathan Hüsken

I second the recommendation to look at Haste.  It's what I would pick for a project like this today.

In the big picture, Haste and GHCJS are fairly similar.  But when it comes to the ugly details of the runtime system, GHCJS adopts the perspective that it's basically an emulator, where compatibility is the number one goal.  Haste goes for a more native approach; while the evaluation semantics and such are completely faithful to Haskell, it doesn't go out of the way to emulate the gritty details of GHC's runtime system.

On Sep 4, 2013 3:38 AM, "Nathan Hüsken" <[hidden email]> wrote:
In my opinion haste is somewhere between Fay and ghcjs. It supports more than Fay, but in difference to ghcjs some PrimOps are not supported (weak pointers for example).

It is a little bit more "direct" than ghcjs, in the sense that it does not need such a big rts written in js.

I like haste :).

What I wonder is how the outputs of these 3 compilers compare speed wise.

On 09/04/2013 11:11 AM, Alejandro Serrano Mena wrote:
I haven't looked at Haste too much, I'll give it a try.

My main problem is that I would like to find a solution that will continue working in years (somehow, that will became "the" solution for generating JS from Haskell code). That's why I see GHCJS (which just includes some patches to mainstream GHC) as the preferred solution, because it seems the most probable to continue working when new versions of GHC appear.


2013/9/4 Niklas Hambüchen <[hidden email]>
Hi, I'm also interested in that.

Have you already evaluated haste?

It does not seem to have any of your cons, but maybe others.

What I particularly miss from all solutions is the ability to simply
call parts written in Haskell from Javascript, e.g. to write `fib` and
then integrate it into an existing Javascript application (they are all
more interested in doing the other direction).

On Wed 04 Sep 2013 17:14:55 JST, Alejandro Serrano Mena wrote:
> Hi,
> I'm currently writing a tutorial on web applications using Haskell. I
> know the pros and cons of each server-side library (Yesod, Snap,
> Scotty, Warp, Happstack), but I'm looking for the right choice for
> client-side programming that converts Haskell to JavaScript. I've
> finally come to Fay vs. GHCJS, and would like your opinion on what's
> the best to tackle. My current list of pros and cons is:
>
> Fay
> ===
> Pros:
> - Does not need GHC 7.8
> - Easy FFI with JS
> - Has libraries for integration with Yesod and Snap
>
> Cons:
> - Only supports a subset of GHC (in particular, no type classes)
>
>
> GHCJS
> ======
> Pros:
> - Supports full GHC
> - Easy FFI with JS
> - Highly opinionated point: will stay longer than Fay (but it's very
> important for not having a tutorial that is old in few months)
>
> Cons:
> - Needs GHC 7.8 (but provides a Vagrant image)
>
>
> _______________________________________________
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> [hidden email]
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Re: Tutorial on JS with Haskell: Fay or GHCJS?

Dmitry V'yal
In reply to this post by Adam Bergmark
On 09/04/2013 05:39 PM, Adam Bergmark wrote:

> Here are some points I'd like to emphasize in addition to the threads
> above, with the disclaimer that I'm the maintainer of Fay.
>
> Fay tries to be very simple, the code base is small (~4800 LoC). This
> really lowers the entry barrier for contributions which I think is
> very important for open source projects. GHCJS is much more
> complicated since it tries to do so much. For GHCJS I'd be afraid that
> the developers might eventually abandon the project and then it'd be
> pretty hard to take over development. Much easier for someone to take
> over Fay development. I think you can safely expect to find bugs in
> all compilers, and if you do and you are in a hurry you might have to
> fix it yourself. Fay has very simple output that is close to both
> Haskell and JavaScript so it's pretty easy to just add a breakpoint
> and start debugging.
>
> Even if GHCJS can successfully compile most of hackage, would we want
> to have these as dependencies in web projects? An output size of 1MiB
> is nothing when compiling a binary, but for a public website 1MiB can
> still be quite a lot, add some transitive dependencies and output will
> explode. Most people don't optimize their packages to have few
> dependencies, which makes sense since the abstraction usually heavily
> outweighs code size. So either way you would probably want to write
> some specific light-weight versions of libraries you want to use,
> that's one reason both GHCJS and Fay have their own base packages.
>
> One place I think GHCJS can shine is for non standard web applications
> such as WEBGL games. Nothing stopping you from using Fay for this, but
> I expect you can really start to leverage GHCJS's threaded runtime here.
>

Hi Adam!

We found it to be very convenient to use both Hastec and Fay. Since the
former (as well, as GHCJS) is based on GHC, you can be quite sure any
bugs you encounter are yours, not of the compiler. And after your code
works with Hastec and so your idea is tested, you can try to port it to
Fay. Usually it's trivial, but prepare to encounter some minor compiler
deficiencies here and there.

So my proposal to original poster would be to tell a bit about both.
After all, they represent different approaches to JS generation each
with it's own pros and cons.

Regards,
Dmitry

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