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

[Scott Turner]

It installed and worked on my Nexus 5.

On 2014-07-04 00:43, Dominick Samperi wrote:
> 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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