GHCJS now runs Template Haskell on node.js - Any interest in out of process TH for general cross compilation?

[Dominick Samperi]

Hello John,
I tried to install the Haskell demo Cube on my Nexus 7
and got: Error: package file was not signed correctly.
D

On Thu, Jul 3, 2014 at 4:47 PM, John Meacham <john at repetae.net> wrote:
> In case anyone wanted to start writing haskell android code now, jhc
> fully supports android as a target. here is an app made with it
>
> https://play.google.com/store/apps/details?id=org.metasepi.ajhc.android.cube
>
> this was made with Kiwamu's ajhc branch but code has been merged back
> into the main tree.
>
> On Wed, Jul 2, 2014 at 5:54 PM, Carter Schonwald
> <carter.schonwald at gmail.com> wrote:
>> This would probably be a great boon for those trying to use haskell for
>> Android and IOS right? how might the emulation setup work for those?
>>
>>
>>
>>
>> On Wed, Jul 2, 2014 at 2:20 PM, Carter Schonwald
>> <carter.schonwald at gmail.com> wrote:
>>>
>>> wow, this is great work!
>>>
>>> If theres a clear path to getting the generic tooling into 7.10, i'm all
>>> for it :) (and willing to help on concrete mechanical subtasks)
>>>
>>>
>>> On Wed, Jul 2, 2014 at 12:14 PM, Luite Stegeman <stegeman at gmail.com>
>>> wrote:
>>>>
>>>> hi all,
>>>>
>>>> I've added some code [1] [2] to GHCJS to make it run Template Haskell
>>>> code on node.js, rather than using the GHC linker. GHCJS has supported TH
>>>> for a long time now, but so far always relied on native (host) code for it.
>>>> This is the main reason that GHCJS always builds native and JavaScript code
>>>> for everything (another is that Cabal Setup.hs scripts need to be compiled
>>>> to some host-runnable form, but that can also be JavaScript if you have
>>>> node.js)
>>>>
>>>> Now besides the compiler having to do twice the work, this has some other
>>>> disadvantages:
>>>>
>>>> - Our JavaScript code has the same dependencies (packages) as native
>>>> code, which means packages like unix or Win32 show up somewhere, depending
>>>> on the host environment. This also limits our options in choosing
>>>> JS-specific packages.
>>>> - The Template Haskell code runs on the host environment, which might be
>>>> slightly different from the target, for example in integer size or operating
>>>> system specific constants.
>>>>
>>>> Moreover, building native code made the GHCJS installation procedure more
>>>> tricky, making end users think about libgmp or libiconv locations, since it
>>>> basically required the same preparation as building GHC from source. This
>>>> change will make installing much easier and more reliable (we still have to
>>>> update the build scripts).
>>>>
>>>> How it works is pretty simple:
>>>>
>>>> - When any code needs to be run on the target (hscCompileCoreExpr,
>>>> through the Hooks API new in GHC 7.8), GHCJS starts a node.js process with
>>>> the thrunner.js [3] script,
>>>> - GHCJS sends its RTS and the Template Haskell server code [1] to
>>>> node.js, the script starts a Haskell thread running the server,
>>>> - for every splice, GHCJS compiles it to JavaScript and links it using
>>>> its incremental linking functionality. The code for the splice, including
>>>> dependencies that have not yet been sent to the runner (for earlier
>>>> splices), is then sent in a RunTH [4] message,
>>>> - the runner loads and runs the code in the Q monad, can send queries to
>>>> GHCJS for reification,
>>>> - the runner sends back the result as a serialized Template Haskell AST
>>>> (using GHC.Generics for the Binary instances).
>>>>
>>>> All Template Haskell functionality is supported, including recent
>>>> additions for reifying modules and annotations. I still need to clean up and
>>>> push the patches for the directory and process packages, but after that, the
>>>> TH code can read/write files, run processes and interact with them and make
>>>> network connections, all through node.js.
>>>>
>>>> Now since this approach is in no way specific to JavaScript, I was
>>>> wondering if there's any interest in getting this functionality into GHC
>>>> 7.10 for general cross compilation. The runner would be a native (target)
>>>> program with dynamic libraries (or object files) being sent over to the
>>>> target machine (or emulator) for the splices.
>>>>
>>>> Thanks to Andras Slemmer from Prezi who helped build the initial proof of
>>>> concept (without reification) at BudHac.
>>>>
>>>> cheers,
>>>>
>>>> Luite
>>>>
>>>> [1]
>>>> https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a/src/Gen2/TH.hs
>>>> [2]
>>>> https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d4f9a4/GHCJS/Prim/TH/Eval.hs
>>>> [3]
>>>> https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a/lib/etc/thrunner.js
>>>> [4]
>>>> https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d4f9a4/GHCJS/Prim/TH/Types.hs#L29
>>>>
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>>>>
>>>
>>
>>
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>
>
>
> --
> John Meacham - http://notanumber.net/
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