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

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

Martin Hilbig writes: 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:

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Don Stewart writes:

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lazycat.manatee:

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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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