Thank you very much to everyone who responded on java integration. I have a lot of work to do before I can conclude, but I will give a quick summary just in case there is some general interest. The most common approach appears to be a network interface between separate java and haskell processes. Both JSON and thrift appear to tools to help doing that. That sounds like a good idea if effort is taken properly to plan out the system architecture. In my case, it would probably lead me to write more code in haskell than I had originally planned (for good or for bad). One poster pointed to neurocyte's library of JNI bindings. That's definately something I will look into. At first sight, it looks much easier to get into than I had feared. The most popular proposal was, nevertheless, to use other languages, in particular hybrid languages like scala. In my opinion, that only solves a minor part of the problem. In my opinion, the chief virtue of a pure language like haskell is its simplicity. Yet, I must admit, that option was always on my list. Familiar with python, jython is a serious option, although I would prefer strong and static type checking. Thanks again, everyone :-- George On Thu, May 09, 2013 at 11:48:09AM -0700, Dominic Espinosa wrote:

Hello,

I've had some success with the Thrift library (http://thrift.apache.org/). See this blog post (http://mortenib.wordpress.com/2009/10/29/thrift-and-haskell/) for a basic tutorial on getting started. My project was interfacing a haskell library of machine learning algorithms (which I wrote) with a large Java application I was familiar with but didn't write. So this may be what you're looking for.

Thrift interfaces language X with language Y with a sort of RPC paradigm: you specify the names and types of the possible calls and returns, and Thrift uses this file to generate serialization and transport code for whatever languages you name. You then add this code to the project on each side and things pretty much just work.

On Thu, May 09, 2013 at 04:04:19PM +0100, Hans Georg Schaathun wrote:

...

Hi all,

I am rather new to the café, so I just hope my question fits in.

Does anyone have experience with integrating Haskell and Java? I have done some searching, finding a lot of pointers but hardly anything in terms of evaluation, successes, or caveats.

From what I see Frege looks promising, arguably not haskell I suppose, but does it work? Other projects I have seen appear to have reached a stand-still for ages.

The background for the question is that I will contribute some control algorithms based on machine learning or AI in a larger project. It would save me a lot of time if I could write in Haskell, but only assuming that interfacing with Java afterwards is trivial compared to writing everything in java in the first place. I am, perhaps, particularly worried that a Haskell-lookalike for JVM might be unable to optimise properly, like not being lazy. Any advice?

TIA -- :-- Hans Georg

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-- :-- Hans Georg

I'm also interested in seeing this. Have you ported the Haskell runtime to Android? It seems like this should be able to be done, and through the JNI it seems like you should be able to get the system API (albeit, ugly). However, I'd be really happy to see this setup if you were willing to put it up somewhere so I could hack on it too. Kris On Mon, May 27, 2013 at 8:07 PM, Manuel M T Chakravarty < chak@cse.unsw.edu.au> wrote:

CJ van den Berg :

...

I have successfully written Java/Haskell programs using the Java Native Interface. You can find my JNI to Haskell binding library at https://github.com/neurocyte/foreign-jni. I am primarily using it to write Android Apps with Haskell,

Just out of curiosity, have you got any complete apps that you built that way? Are they in the Google Store?

Manuel

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No, you can go both ways. You can call Haskell from Java and Java from Haskell. Write Android Apps in Haskell will of course be just the same as writing Android Apps in Java. That’s just the price you pay for having full API access. There is of course nothing preventing someone from creating more idiomatic Haskell GUI libraries for Android on top of the API bindings. On 2013-05-28 15:37, Kristopher Micinski wrote:

I guess you can't really go from native -> framework code like this, so this would really make sense only for native methods that are self contained. Is this right? It seems like this would imply that you can only write parts of an app's computation in Haskell, not the whole thing. But maybe I'm wrong. I have seen people that write apps in native / managed code integrating in a reasonable way, but it's very ugly afaik.

Kris

On Tue, May 28, 2013 at 9:35 AM, Kristopher Micinski mailto:krismicinski@gmail.com> wrote:

I'm also interested in seeing this.

Have you ported the Haskell runtime to Android? It seems like this should be able to be done, and through the JNI it seems like you should be able to get the system API (albeit, ugly).

However, I'd be really happy to see this setup if you were willing to put it up somewhere so I could hack on it too.

Kris

On Mon, May 27, 2013 at 8:07 PM, Manuel M T Chakravarty mailto:chak@cse.unsw.edu.au> wrote:

CJ van den Berg mailto:cj@vdbonline.com>: > I have successfully written Java/Haskell programs using the Java > Native Interface. You can find my JNI to Haskell binding library at > https://github.com/neurocyte/foreign-jni. I am primarily using it to > write Android Apps with Haskell,

Just out of curiosity, have you got any complete apps that you built that way? Are they in the Google Store?

Manuel

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-- CJ van den Berg mailto:cj@vdbonline.com xmpp:neurocyte@gmail.com

The RTS was ported to Android, yes. But not by me. I just wrote ghc-android, which is just a build script to help people with setting up the somewhat complex cross-compiler build. IIRC Nathan Hüsken did most of the porting work. Everything you need should be on github. ghc-android and foreign-jni is pretty much it right now. Using the JNI is a bit ugly, yes. But I see it really as just a tool for writing more appealing API bindings, which is what I am working on now. On 2013-05-28 15:35, Kristopher Micinski wrote:

I'm also interested in seeing this.

Have you ported the Haskell runtime to Android? It seems like this should be able to be done, and through the JNI it seems like you should be able to get the system API (albeit, ugly).

However, I'd be really happy to see this setup if you were willing to put it up somewhere so I could hack on it too.

Kris

On Mon, May 27, 2013 at 8:07 PM, Manuel M T Chakravarty mailto:chak@cse.unsw.edu.au> wrote:

CJ van den Berg mailto:cj@vdbonline.com>: > I have successfully written Java/Haskell programs using the Java > Native Interface. You can find my JNI to Haskell binding library at > https://github.com/neurocyte/foreign-jni. I am primarily using it to > write Android Apps with Haskell,

Just out of curiosity, have you got any complete apps that you built that way? Are they in the Google Store?

Manuel

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-- CJ van den Berg mailto:cj@vdbonline.com xmpp:neurocyte@gmail.com