Thanks! hint works good! On Tue, Jul 20, 2010 at 9:29 PM, Andy Stewart <lazycat.mana...@gmail.com>wrote:
> Hongmin Fan <hongmin.fan.li...@gmail.com> writes: > > > Thanks Andy! Yes, I do need the second approach you listed here. I think > the plugin package actually > > uses GHC API to load > > too. > > > > My problem here is more technical than theoretical. The type safety isn't > the primary issue for me, > > because I'm trying to > > implement a certain genetic programming system (there is some papers like > this one: > > http://citeseerx.ist.psu.edu/viewdoc/ > > summary?doi=10.1.1.98.7686), which generates functions that I'm going to > dynamically evaluate. I'm > > hoping to use GHC API to > > avoid writing my own evaluator. The func generation component actually is > designed to generate > > functions of the specific > > type, so no worries about type safty. > > > > I'm looking for a clean/correct way to use GHC API to reload the module, > maybe there is some option > > I should set but I > > didn't? Being new to Haskell, the source code for GHCi isn't so > accessible... Thanks! > If you want dynamic evaluation, you can try hint : Runtime Haskell > interpreter (GHC API wrapper) > > At http://hackage.haskell.org/package/hint > > Cheers, > > -- Andy > > > > > On Tue, Jul 20, 2010 at 1:01 AM, Andy Stewart <lazycat.mana...@gmail.com> > wrote: > > > > Hi Hongmin, > > > > I think you're looking for how to hot-swap Haskell program. > > > > There are two approach to reach target: > > > > 1) Source-Code level: > > Recompile source code to build new execute cache file, if > re-compile > > successful, use executeFile to switch new entry. You perhaps need > use > > Binary instance to save/restore state between re-launch new execute > > file. > > > > 2) Dynamic Linking object code. > > Compile plugins code to object file, the use .o and .hi file to > > dynamic linking object code to running Haskell application. > > Because .hi file have type/depend information, we can do type-check > > when dynamic linking .o file. > > > > First way is simpler, but you perhaps will lost state after reboot, > > because you can't serialize state (such as FFI) sometimes. > > > > Second way is more complicated, but you can present all state when > hot-swapping. > > > > Looks you need second way, from your code, that's wrong, you can't > > dynamic link object file without type-check, and expect everything > will > > be fine. > > If you don't type-check when linking code, it's very dangerous, it > willl *crash* your > > program once type mismatch or runtime error occur. > > > > Infact, Don Stewart has implement a complete solution to dynamic > > linking in Haskell program, at > > http://hackage.haskell.org/package/plugins-1.4.1 > > Unfortunately, it's broken with ghc-6.12.x > > > > Before Don fix plugins package, i recommend you read Don's new paper > > > > (http://www.cse.unsw.edu.au/~dons/papers/dons-phd-thesis.pdf<http://www.cse.unsw.edu.au/%7Edons/papers/dons-phd-thesis.pdf> > ) > > You will know every detail that how to dynamic extension Haskell > > program. > > > > Hope above will help you. :) > > > > -- Andy > > > > Hongmin Fan <hongmin.fan.li...@gmail.com> writes: > > > > > Hi, > > > > > > I'm using GHC API to dynamically load some module, and evaluate it; > and later change the > > content of > > > the module, and > > > re-evaluate it. But I found unless I delete the object file created > by previous compilation, > > the > > > module seems not reloaded. > > > I have set ghcLink = LinkInMemory as an older post suggested > > > > > > To illustrate what I'm saying, here is a piece of code (sorry for > any naivety in the code, new > > to > > > Haskell too) > > > > > > import System.IO (IOMode(..),hClose,hPutStr,openFile) > > > import Directory (removeFile) > > > import GHC > > > import GHC.Paths > > > import DynFlags > > > import Unsafe.Coerce > > > > > > src_file = "Target.hs" > > > obj_file = "Target.o" > > > > > > main = do > > > writeTarget "arg" > > > func0 <- compileTarget > > > putStrLn $ show $ func0 2 > > > > > > writeTarget "arg*2" > > > func1 <- compileTarget > > > putStrLn $ show $ func1 2 > > > > > > writeTarget input = do > > > -- removeFile obj_file `catch` (const $ return ()) -- uncomment > this line to have correct > > results > > > h <- openFile src_file WriteMode > > > hPutStr h "module Target (Target.target) where\n" > > > hPutStr h "target::Double -> Double\n" > > > hPutStr h "target arg = \n " > > > hPutStr h input > > > hClose h > > > > > > compileTarget = > > > defaultErrorHandler defaultDynFlags $ do > > > func <- runGhc (Just libdir) $ do > > > -- setup dynflags > > > dflags <- getSessionDynFlags > > > setSessionDynFlags dflags { ghcLink = LinkInMemory } > > > > > > -- load target module > > > target <- guessTarget src_file Nothing > > > setTargets [target] > > > r <- load LoadAllTargets > > > case r of > > > Failed -> error "Compilation failed" > > > Succeeded -> do > > > m <- findModule (mkModuleName "Target") Nothing > > > -- set context and compile > > > setContext [] [m] > > > value <- compileExpr ("Target.target") > > > do > > > let value' = (unsafeCoerce value) :: Double > -> Double > > > return value' > > > return func > > > > > > The code basically write to a Haskell source file twice with > different content, and hoping to > > get > > > different results, but > > > unless I uncomment the line with removeFile, the output of 2 runs > are the same; using 'touch' > > to > > > touch the source file being > > > written between 2 runs also gives the correct results. So maybe > caused by some caching > > mechanism? > > > > > > I'm using GHC 6.12.1 in Ubuntu 10.04. I have this workaround of > deleting the obj file, but I'm > > > wondering the "correct" way > > > of doing it. Did some search on GHC API, but never got something > relevant. > > > > > > Thanks, > > > Hongmin > > > > > > _______________________________________________ > > > Haskell-Cafe mailing list > > > Haskell-Cafe@haskell.org > > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe@haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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