I'm trying to set up Haskell from scratch, on Ubuntu 11.04, without using the outdated Debian repository or Haskell-Platform.
I've installed GHC-7.0.4 from source with no problem, and now need to install Cabal (which appears to already be included in GHC in /usr/local/lib/ghc-7.0.4/Cabal-1.10.2.0) and Cabal Install.
The latter specifies several dependencies (parsec and network), each of which has several dependencies of their own (mtl, text, etc).
What's the command to install these packages, that I downloaded from hackage in tar.gz form?
Unpack, then runhaskell doesn't work.
I see Setup.lhs, but it's not clear what that's for or how to use it.
Most of the Haskell documentation I've found assumes you've installed from a repo or Haskell-Package and doesn't really explain this well.
cabal-install has a shell script that does this. If you download it from hackage and install it, you can start bootstrap.sh to install cabal-install. You can then use it to install other packages.
There are two different packages: Cabal and cabal-install. Cabal is a library, and cabal-install is an executable named cabal.
To install a package, cabal-install is an optional convenience wrapper around Cabal, but Cabal is required.
According to http://hackage.haskell.org/trac/ghc/wiki/Commentary/Libraries , Cabal is a 'zero-boot' package, so when you build GHC, Cabal and its dependencies are built for you automatically.
You can use ghc-pkg executable to check which packages are already installed:
# ghc-pkg list
Check if Cabal is in the list after you build GHC. If yes, you can install more packages without cabal-install using this documentation:
http://haskell.org/haskellwiki/Cabal/How_to_install_a_Cabal_package
I suggest you to install cabal-install first, and then install everything else using cabal-install executable. A usual commandine for global installation is this:
# runhaskell Setup configure
# runhaskell Setup build
# sudo runhaskell Setup install
Unpack a package tarball and run the commands in the folder with Setup.hs or Setup.lhs files. Note that a per-user non-root installation is also supported - Use runhaskell Setup configure --user
When you install cabal executable and its dependencies this way, use cabal install {package-name} to install more packages.
Note that Haskell Platform exists mostly because of the pain of installing cabal-install by yourself.
Related
The commands install, v1-install, v2-install and new-install are simply described to "Install packages" when running man cabal. Are they different from one another? Which is the preferred option?
For modern versions of cabal-install, install, new-install and v2-install are the same. v1-install and the other v1- commands are obsolete and should not be used anymore.
Notice that, when developing a cabal package, the install command is largely unnecessary. Running cabal build and cabal repl will automatically install the required dependencies (listed in the build-depends: section of the cabal file).
cabal install is still useful in cases like the following:
Installing an executable from a package. Like the warp executable from the package wai-app-static. In those cases, the options --overwrite-policy, --install-method and --installdir are useful.
Creating a local package environment in some folder, so that "bare" invocations of ghc and ghci see some desired set of libraries. Like this. In those cases, the options --lib and --package-env are useful.
I try to install "System.Random" by cabal through Powershell & Git Bash.
getting this result.
PS C:\Users\xxx> cabal install random
Resolving dependencies...
Up to date
Warning: You asked to install executables, but there are no executables in
target: random. Perhaps you want to use --lib to install libraries instead.
And then I try to input like this
cabal install --lib random
Resolving dependencies...
and
cabal install random --lib
both output Resolving dependencies... Up to date without warning.
but ghci Could not find module `System.Random'
input cabal install random still having the same result with warning.
It is a bad idea to install packages globally, so cabal install doesn't do that. The package is built and placed into the Cabal package database, but GHC won't find it unless you specifically tell Cabal to point GHC at it:
cabal repl -b random # -b is short for --build-depends
# Note that cabal install isn't really necessary: the above command would have installed random if it wasn't there already
I think your Cabal/GHC installation might be outdated, however. When you do cabal install --lib random, recent versions of Cabal should write out an "environment file" at %APPDATA%\ghc\arch-os-ghcversion\environments\default, which GHC should then automatically read (GHCi should say something like Loaded package environment from ...), and it should then find the installed package. If you are using the latest version of everything,
cabal install --lib random
ghci
should work.
I am trying latest Haskell from here on Windows7. I downloaded ghc-8.8.1-x86_64-unknown-mingw32.tar.xz (377.3 MB) and untarred it in a folder and added bin folder path to environment.
Now I can run ghc but cabal or cabal-install are not there.
Although I:\ghc-8.8.1\lib\Cabal-3.0.0.0 is there in package but there is no cabal.exe or cabal-install.exe
How can I get an run cabal in this setup? Thanks for your help.
GHC is just the compiler and a set of core libraries and executables, of which cabal-the-program is not one. The Cabal you found is a library for package management. The cabal program is part of the cabal-install package, and it depends on the Cabal library. Without cabal-install installed, you cannot cabal install cabal-install. Instead, you have to manually download the cabal program from the website. You can build it from source or you can use one of the pre-built binaries.
If I install a package using cabal install pkg then cabal will install all packages that pkg depends on. If there is a conflict with already installed packages then cabal shows which packages have to be installed freshly, which ones are updated and which installed ones will be broken.
Is there a way to get this list unconditionally instead of running the install procedure?
cabal install <pkg> --dry-run will print the packages that will be installed without actually performing any of the installation. It will not show this information though if the package is installed or similar.
I'm a newbie to haskell and cabal, so I'm probably missing something simple.
I updated cabal-install:
sudo cabal install cabal-install
Password:
Resolving dependencies...
Configuring cabal-install-1.22.0.0...
Building cabal-install-1.22.0.0...
Installed cabal-install-1.22.0.0
Updating documentation index
However cabal --version says:
cabal-install version 1.18.0.5
using version 1.18.1.4 of the Cabal library
What happened to cabal-install 1.22.0.0?
There are two ways of making cabal install packages globally. Note that, as a result, cabal may require sudo.
This command will install <PACKAGE> globally:
$ cabal install <PACKAGE> --global
As a more general solution, edit the file ~/.cabal/config and set user-install to False. This will automatically set the --global flag so you can just write cabal install <PACKAGE> without any worry. Here's a snippet of my config file:
...
-- split-objs: False
-- executable-stripping: True
user-install: False
-- package-db:
-- flags:
...
You may also want to set root-cmd to sudo if it's not already, so that cabal will automatically prompt for the root password when it encounters a permission problem.
There's some more info online here.
I see that there's an updated cabal at ~/Library/Haskell/bin, so I could replace /usr/bin/cabal with a symbolic link to this copy or I could copy this binary to /usr/bin.
I'm still interested if there is a more elegant/canonical way to make sure the new cabal is what gets used by default.
TLDR: Try running hash -r
Bash has a PATH hashtable that maps commands to the location of binaries. You may still have an old version of cabal installed somewhere in your PATH (possibly in a sandbox). Since cabal is not a new command, the hashtable will keep serving up the old version. hash -r rebuilds the hashtable, so the shell will correctly find the new version (providing it appears earlier in your path than the old one).