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

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... [2] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... [3] https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a... [4] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...

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
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... [2] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... [3] https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a... [4] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...
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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 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 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...
[2]
https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...
[3]
https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a...
[4]
https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... _______________________________________________
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Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

I think GHC could use more or less the same communication method as GHCJS
now does: Start some user-specifiied process and send messages through
pipes (GHCJS uses stdin/stderr of the node process), with the difference
that it would get dynamic libraries for the target rather than blobs of JS
code. That user process is then responsible for setting up the actual
communication with the runner on the emulator or development device.
A requirement for complete TH support is that more code can be loaded at
runtime, so that multiple splices can be run by the same runner (because of
the persistent map, qGetQ / qPutQ), I'm not sure if this is problematic on
iOS.
On Thu, Jul 3, 2014 at 2:54 AM, Carter Schonwald 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@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 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...
[2]
https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...
[3]
https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a...
[4]
https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... _______________________________________________
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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
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
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
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... [2] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... [3] https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a... [4] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...
_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
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-- John Meacham - http://notanumber.net/

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
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
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
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
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... [2] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... [3] https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a... [4] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...
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_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
-- John Meacham - http://notanumber.net/ _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

Hmm.. It works on my nexus 4. Kiwamu of the metasepi
http://ajhc.metasepi.org/ is the one that uploaded the demo. Perhaps
he needs to update the key or something.
On Thu, Jul 3, 2014 at 9:43 PM, 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
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
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
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
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... [2] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... [3] https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a... [4] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...
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_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
-- John Meacham - http://notanumber.net/ _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
-- John Meacham - http://notanumber.net/

Yes! This would definitely be of great interest to users of the Android cross compilers. It should be quite feasible to drive a TH runner process on a development device or emulator. Having genuine TH support would be a huge improvement to the usefulness of GHC in a cross compiling scenario. I would love to start work on integrating TH runner support into ghc-android. On 2014-07-02 18:14, Luite Stegeman wrote:
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.
-- CJ van den Berg mailto:cj@vdbonline.com xmpp:neurocyte@gmail.com

Luite I lack the bandwidth to respond at any technical depth, but I’d like to make encouraging noises. If you can figure out a way to make GHC do these things without making the compiler terribly complicated and making maintaining it harder, then I’m open to your proposals. Several people seem to have said “oh yes, that’d be interesting”. Simon From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Luite Stegeman Sent: 02 July 2014 17:14 To: ghc-devs; glasgow-haskell-users@haskell.org Subject: GHCJS now runs Template Haskell on node.js - Any interest in out of process TH for general cross compilation? 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... [2] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d... [3] https://github.com/ghcjs/ghcjs/blob/414eefb2bb8825b3c4c5cddfec4d79a142bc261a... [4] https://github.com/ghcjs/ghcjs-prim/blob/2dffdc2d732b044377037e1d6ebeac2812d...

On Thu, Jul 3, 2014 at 6:18 PM, Simon Peyton Jones
Luite
I lack the bandwidth to respond at any technical depth, but I’d like to make encouraging noises. If you can figure out a way to make GHC do these things without making the compiler terribly complicated and making maintaining it harder, then I’m open to your proposals.
I think most of the communication code could go into a separate executable that can be built by the user for the target-specific communication. The GHC API facing part of the implementation in GHCJS is under 300 lines and that includes some non-exported code duplicated from GHC, so I'm reasonably optimistic that it can be done without too much impact. Unfortunately I won't have much time in the near future, since a GHCJS release is well overdue (mostly because I keep adding features like this...) and I want to focus on that first, but getting it ready before 7.10 should be doable (especially if other people want to help!) luite
participants (6)
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Carter Schonwald
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CJ van den Berg
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Dominick Samperi
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John Meacham
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Luite Stegeman
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Simon Peyton Jones