ghc

Initially I thought I would get install Haskell with couple of commands using apt-get but its seems somehow complex. As I look at the haskell org download page , I downloaded haskell-platform-2013.2.0.0.tar.gz . Then next step is somehow confusing. It ask to install GHC before installing platform but at the same time if one opens GHC download page , it shows some warning e.g Stop ! ..... we recommend installing the Haskell Platform instead of GHC . Please guide me how to install Haskell on Debian Wheezy. Can we build a .deb installation package from this package ? vivian $ sudo apt-get install

Consider the following example: import Data.Constraint class Bar a where bar :: a -> a foo :: (Bar a) => Dict (Bar a) -> a -> a foo Dict = bar GHC has two choices for the dictionary to use when selecting a Bar instance in foo : it could use the dictionary from the Bar a constraint on foo , or it could use the runtime Dict to get a dictionary. See this question for an example where the dictionaries correspond to different instances. Which dictionary does GHC use, and why is it the "correct" choice? GHC just picks one, and this is the correct choice. Any two dictionaries for the same constraint

I'm working on a Haskell daemon that uses POSIX fork/exec together with file locking mechanism. My experiments show that file locks aren't inherited during executeFile with -threaded runtime (see also this thread ), no matter if I use +RTS -N or not. So I'd like to add a check to be sure that the daemon ins't compiled with -threaded . Is there a portable way to detect it? There is a value in Control.Concurrent for this, for example: module Main (main) where import Control.Concurrent main :: IO () main = print rtsSupportsBoundThreads And test: $ ghc -fforce-recomp Test.hs; ./Test [1 of 1]

Edit: It turns out that things generally (not just array/ref operations) slow down the more arrays have been created, so I guess this might just be measuring increased GC times and might not be as strange as I thought. But I'd really like to know (and learn how to find out) what's happening here though, and if there's some way to mitigate this effect in code that creates lots of smallish arrays. Original question follows. In investigating some weird benchmarking results in a library, I stumbled upon some behavior I don't understand, though it might be really obvious. It seems that the time

Possible Duplicate: Small Haskell program compiled with GHC into huge binary Recently I noticed how large Haskell executables are. Everything below was compiled on GHC 7.4.1 with -O2 on Linux. Hello World ( main = putStrLn "Hello World!" ) is over 800 KiB. Running strip over it reduces the filesize to 500 KiB; even adding -dynamic to the compilation doesn't help much, leaving me with a stripped executable around 400 KiB. Compiling a very primitive example involving Parsec yields a 1.7 MiB file. -- File: test.hs import qualified Text.ParserCombinators.Parsec as P import Data.Either (either) --

I ported a little Haskell program I wrote from Mac to Windows. It's a GUI application (wxHaskell, compiled with ghc 6.12.1), so it does not need the command prompt window to open. It does so, anyway, so my question: What must I do so that the program starts without opening a prompt window first? Is there some ghc switch for this? When using wxWidgets with cygwin, you can avoid having a console window appear by passing the -mwindows flag to the linker . You can tell GHC to pass flags to the linker using the -optl prefix , so you could try building with -optl-mwindows and see if that works. I've