[Haskell-cafe] Re: Hot-Swap with Haskell

[Andy Stewart]

Martin Hilbig <martin at mhilbig.de> writes:

> hi,
>
> if been thinking about an haskell interpreter to, because of erlang's otp. its syntax is a mess, but
> its scalability is win.
>
> since erlang runs in its vm ("interpreted") is there a need for a real haskell interpreter, or can
> there be a compiled haskell/otp with hotswapping, scaling and stuff?
>
> now back on topic, i wrote "real" haskell interpreter because there is the hint[1] package, which
> wrappes the ghc api.
>
> now i dont know what more the plugin package provides, but i thought hint is like is successor
> (since lambdabot used plugins and now uses mueval, which in turn uses hint ;). please correct me.
Yes, "haskell interpreter" maybe is solution, because Emacs is use this
solution:
"Static C core ++ elisp interpreter", then all elisp hot-swapping is
base on elisp interpreter.

IMO, "haskell interpreter" is perfect solution for samll script job. But
i'm afraid "haskell interpreter" is slow for *large code*, i don't know,
i haven't try this way...

Thanks for your suggestion, i will consider it.

  -- Andy

>
> have fun
> martin
>
> [1]: http://hackage.haskell.org/package/hint
>
> On 16.07.2010 06:06, Andy Stewart wrote:
>> Don Stewart<dons at galois.com>  writes:
>>
>>> lazycat.manatee:
>>>> Hi all,
>>>>
>>>> I'm research to build a hot-swap Haskell program to developing itself in
>>>> Runtime, like Emacs.
>>>>
>>>> Essentially, Yi/Xmonad/dyre solution is "replace currently executing"
>>>> technology:
>>>>
>>>>     re-compile new code with new binary entry
>>>>
>>>>     when re-compile success
>>>>        $ do
>>>>            save state before re-launch new entry
>>>>            replace current entry with new binary entry (executeFile)
>>>>            store state after re-launch new entry
>>>>
>>>> There are some problems with re-compile solution:
>>>>
>>>> 1) You can't save *all* state with some FFI code, such as gtk2hs, you
>>>> can't save state of GTK+ widget. You will lost some state after
>>>> re-launch new entry.
>>>>
>>>> 2) Sometimes re-execute is un-acceptable, example, you running some command
>>>> in temrinal before you re-compile, you need re-execute command to
>>>> restore state after re-launch, in this situation re-execute command is un-acceptable.
>>>>
>>>> I wonder have a better way that hot-swapping new code without
>>>> re-compile/reboot.
>>>>
>>>
>>> Well, the other approach to reloadable modules, using either object code
>>> plugins, or bytecode plugins, giving you module-level granularity.
>> Thanks for your reply.
>>
>> I have read your papers : "Dynamic Application From the Group Up" and  "Plugging Haskell In"
>>
>> In "Dynamic Application From the Group Up", you introduction how to use
>> re-compile technology implement source-code level hot-swapping.
>>
>> In "Plugging Haskell In", you introduction to how to buld hot-swapping
>> with object-code level.
>>
>> Yes, Dynamic linking can add new code to a running program, but how to
>> replace existing binding with new ones?
>> Looks you still need some reboot when you do *replace* and not just *add*.
>>
>> Infact, reboot is okay, only problem is *keep state*, some *static state*
>> is easier to re-build, example, if you want restore editor buffer state, you
>> just need save (filepath, cursorPosition), you can re-open file and
>> restore cursor position after reboot process.
>>
>> Difficult is *Stream State*, such as:
>>    delete operation in file-manager
>>    command running in temrinal
>>    network communications in browser
>> It's really difficult to restore those state, and re-execute is
>> un-acceptable sometimes.
>>
>> You can found the screenshot of my project at http://www.flickr.com/photos/48809572@N02/
>>
>> Currently, the closest library to implement dynamic linking is your
>> plugins package (http://hackage.haskell.org/package/plugins-1.4.1),
>> i really want to write some code to test it, unfortunately, it's
>> broken with Cabal-1.8.0.4 that can't compile with ghc-6.12.x/ghc-6.12.3,
>> can you fix it if you have time? It's so great package...
>>
>> I'm looking for some paper about "Haskell and hot-swapping".
>> Any paper or suggestion are welcome!
>>
>>    -- Andy
>>
>>
>>
>>
>>
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