ghc

Original I'm trying to aggregate a CSV file and experiencing [what I consider to be] excessive memory usage and/or GC effort. The issue seems to arise when the number of groups increases. There is no problem when the keys are in the hundreds or thousands, but quickly starts spending a majority of time in the GC when the keys reach tens of thousands. Update Moving from Data.ByteString.Lazy.ByteString to Data.ByteString.Short.ShortByteString significantly reduced the memory consumption (to a level I think is reasonable). However, the amount of time spent in the GC still seems far higher than I

I made small C module to improve performance, but GHC doesn't inline foreign functions, and calls cost eliminates the acceleration. For example, test.h : int inc (int x); test.c : #include "test.h" int inc(int x) {return x + 1;} Test.hc : {-# LANGUAGE ForeignFunctionInterface #-} module Test (inc) where import Foreign import Foreign.C foreign import ccall unsafe "test.h inc" c_inc :: CInt -> CInt inc = fromIntegral . c_inc . fromIntegral {-# INLINE c_inc #-} {-# INLINE inc #-} Main.hs : import System.Environment import Test main = do {args <- getArgs; putStrLn . show . inc . read . head $ args

This question already has answers here : Haskell: How to only generate .hi file with ghc? (2 answers) Closed last year . Usually, when ghc is compiling a source code, it will produce at least an .o (object) and a .hi (interface) file. In the interest of diminishing compilation time, if I only need an interface file, can I somehow order ghc to abandon everything else and just give me said interface file? Or, otherwise, obtain that interface by any kind of lowly guile? I found this ghc user guide part and it says nothing of such. This one doesn't even mention " interface " anywhere in its text.

Following the GHC tutorial posted here and alterations to this code following the advice in a previous stack overflow question I asked , I have created a program which is able to compile and run a module in Test.hs with a function print to print a string to the screen: import GHC import GHC.Paths import DynFlags import Unsafe.Coerce main :: IO () main = defaultErrorHandler defaultLogAction $ do func <- runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags dflags target <- guessTarget "Test.hs" Nothing addTarget target r <- load LoadAllTargets case r of Failed -> error

I noticed that GHC wanted a type signature which I think should be inferred. I minimized my example down to this, which almost certainly does nothing meaningful (I don't recommend running it on your favorite types): {-# LANGUAGE GADTs, RankNTypes, ScopedTypeVariables, TypeOperators, NoMonomorphismRestriction #-} module Foo where import Data.Typeable data Bar rp rq data Foo b = Foo (Foo b) rebar :: forall rp rq rp' rp'' . (Typeable rp', Typeable rp'') => Proxy rp' -> Proxy rp'' -> Foo rp -> Foo (Bar rp rq) rebar p1 p2 (Foo x) = -- The signature for y should be inferred... let y = rebar p1 p2 x

Consider the following simple code: import Crypto.Hash.SHA1 (hashlazy) import qualified Data.ByteString as BS main = return () I installed cabal install --global bytestring and then I obtain (on a newly installed Ubuntu 12.04 machine using ghc 7.4.1): GHCi runtime linker: fatal error: I found a duplicate definition for symbol fps_minimum whilst processing object file /usr/local/lib/bytestring-0.10.0.1/ghc-7.4.1/HSbytestring-0.10.0.1.o This could be caused by: * Loading two different object files which export the same symbol * Specifying the same object file twice on the GHCi command line * An

I'm trying to run this simple example that I got from the Haskell wiki . import GHC import GHC.Paths ( libdir ) import DynFlags main = defaultErrorHandler defaultFatalMessager defaultFlushOut $ do runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags dflags target <- guessTarget "test_main.hs" Nothing setTargets [target] load LoadAllTargets The error messages I'm getting are: amy@wombat$ ghc --make amy15.hs amy15.hs:1:8: Could not find module ‘GHC’ It is a member of the hidden package ‘ghc-7.8.3’. Use -v to see a list of the files searched for. amy15.hs:3:8: Could not find

Suppose I have the following code: {-# LANGUAGE GADTs, DeriveDataTypeable, StandaloneDeriving #-} import Data.Typeable class Eq t => OnlyEq t class (Eq t, Typeable t) => BothEqAndTypeable t data Wrapper a where Wrap :: BothEqAndTypeable a => a -> Wrapper a deriving instance Eq (Wrapper a) deriving instance Typeable1 Wrapper Then, the following instance declaration works, without a constraint on t : instance OnlyEq (Wrapper t) and does what I expect it to do. But the following instance declaration doesn't work: instance BothEqAndTypeable (Wrapper t) since GHC - I'm using 7.6.1 - complains that:

I just installed GHC from the latest sources, and now my program gives me an error message about a "delayed read on closed handle". What does this mean? dfeuer The fundamental lazy I/O primitive, hGetContents , produces a String lazily—it only reads from the handle as needed to produce the parts of the string your program actually demands. Once the handle has been closed, however, it is no longer possible to read from the handle, and if you try to inspect a part of the string that was not yet read, you will get this exception. For example, suppose you write main = do most <- withFile "myfile"