User's Guide The Cabal aims to simplify the distribution of Haskell software. It does this by specifying a number of interfaces between package authors, builders and users, as well as providing a library implementing these interfaces. A package is the unit of distribution for the Cabal. Its purpose, when installed, is to make available either or both of: A library, exposing a number of Haskell modules. A library may also contain hidden modules, which are used internally but not available to clients. Hugs doesn't support module hiding. One or more Haskell programs. However having both a library and executables in a package does not work very well; if the executables depend on the library, they must explicitly list all the modules they directly or indirectly import from that library. Internally, the package may consist of much more than a bunch of Haskell modules: it may also have C source code and header files, source code meant for preprocessing, documentation, test cases, auxiliary tools etc. A package is identified by a globally-unique package name, an identifier containing no spaces. Chaos will result if two distinct packages with the same name are installed on the same system, but there is not yet a mechanism for allocating these names. A particular version of the package is distinguished by a version number, consisting of a sequence of one or more integers. These can be combined to form a single text string called the package ID, using a hyphen to separate the version from the name, and dots to separate the version components, e.g. HUnit-1.1. Packages are not part of the Haskell language; they simply populate the hierarchical space of module names. It is still the case that all the modules of a program must have distinct module names, regardless of the package they come from, and whether they are exposed or hidden. This also means that although some implementations (i.e. GHC) may allow several versions of a package to be installed at the same time, a program cannot use two packages, P and Q that depend on different versions of the same underlying package R. Suppose you have a directory hierarchy containing the source files that make up your package. You will need to add two more files to the root directory of the package: package.cabal a text file containing a package description (for details of the syntax of this file, see ), and Setup.hs or Setup.lhs a single-module Haskell program to perform various setup tasks (with the interface described in ). This module should import only modules that will be present in all Haskell implementations, including modules of the Cabal library. In most cases it will be trivial, calling on the Cabal library to do most of the work. Once you have these, you can create a source bundle of this directory for distribution. Building of the package is discussed in . The HUnit package contains a file HUnit.cabal containing: Name: HUnit Version: 1.1 License: BSD3 Author: Dean Herington Homepage: http://hunit.sourceforge.net/ Category: Testing Build-Depends: base Synopsis: Unit testing framework for Haskell Exposed-modules: Test.HUnit, Test.HUnit.Base, Test.HUnit.Lang, Test.HUnit.Terminal, Test.HUnit.Text Extensions: CPP and the following Setup.hs: import Distribution.Simple main = defaultMain Name: TestPackage Version: 0.0 License: BSD3 Author: Angela Author Synopsis: Small package with two programs Build-Depends: HUnit Executable: program1 Main-Is: Main.hs Hs-Source-Dir: prog1 Executable: program2 Main-Is: Main.hs Hs-Source-Dir: prog2 Other-Modules: Utils with Setup.hs the same as above. Name: TestPackage Version: 0.0 License: BSD3 Author: Angela Author Synopsis: Package with library and two programs Build-Depends: HUnit Exposed-Modules: A, B, C Executable: program1 Main-Is: Main.hs Hs-Source-Dir: prog1 Other-Modules: A, B Executable: program2 Main-Is: Main.hs Hs-Source-Dir: prog2 Other-Modules: A, C, Utils with Setup.hs the same as above. The trivial setup script used in these examples uses the simple build infrastructure provided by the Cabal library (see &Simple;). The simplicity lies in its interface rather that its implementation. It automatically handles preprocessing with standard preprocessors, and builds packages for all the Haskell implementations (except nhc98, for now). The simple build infrastructure can also handle packages where building is governed by system-dependent parameters, if you specify a little more (see ). A few packages require more elaborate solutions (see ). The package description file should have a name ending in .cabal. There must be exactly one such file in the directory, and the first part of the name is immaterial, but it is conventional to use the package name. This file should contain several stanzas separated by blank lines. Each stanza consists of a number of field/value pairs, with a syntax like mail message headers. case is not significant in field names to continue a field value, indent the next line to get a blank line in a field value, use an indented . Lines beginning with -- are treated as comments and ignored. The syntax of the value depends on the field. Field types include: token filename directory Either a sequence of one or more non-space non-comma characters, or a quoted string in Haskell 98 lexical syntax. Unless otherwise stated, relative filenames and directories are interpreted from the package root directory. freeform URL address An arbitrary, uninterpreted string. identifier A letter followed by zero or more alphanumerics or underscores. Some fields take lists of values, which are optionally separated by commas, except for the build-depends field, where the commas are mandatory. Some fields are marked as required. All others are optional, and unless otherwise specified have empty default values. The first stanza describes the package as a whole, as well as the library it contains (if any), using the following fields: name: identifier (required) The unique name of the package, without the version number. version: numbers (required) The package version number, usually consisting of a sequence of natural numbers separated by dots. license: identifier (default: AllRightsReserved) The type of license under which this package is distributed. License names are the constants of the &License; type. license-file: filename The name of a file containing the precise license for this package. copyright: freeform The content of a copyright notice, typically the name of the holder of the copyright on the package and the year(s) from which copyright is claimed. author: freeform The original author of the package. maintainer: address The current maintainer or maintainers of the package. This is an e-mail address to which users should send bug reports, feature requests and patches. stability: freeform The stability level of the package, e.g. alpha, experimental, provisional, stable. homepage: URL The package homepage. package-url: URL The location of a source bundle for the package. The distribution should be a Cabal package. synopsis: freeform A very short description of the package, for use in a table of packages. This is your headline, so keep it short (one line) but as informative as possible. Save space by not including the package name or saying it's written in Haskell. description: freeform Description of the package. This may be several paragraphs, and should be aimed at a Haskell programmer who has never heard of your package before. category: freeform A classification category for future use by the package catalogue Hackage. These categories have not yet been specified, but the upper levels of the module hierarchy make a good start. tested-with: compiler list A list of compilers and versions against which the package has been tested (or at least built). build-depends: package list A list of packages, possibly annotated with versions, needed to build this one, e.g. foo > 1.2, bar. If no version constraint is specified, any version is assumed to be acceptable. exposed-modules: identifier list (required if this package contains a library) A list of modules added by this package. Module names may correspond to Haskell source files, i.e. with names ending in .hs or .lhs, or to inputs for various Haskell preprocessors. The simple build infrastructure understands .gc (GreenCard), .chs (c2hs), .hsc (hsc2hs), .y and .ly (happy), .x (alex) and .cpphs (cpphs). In such cases the appropriate preprocessor will be run automatically as required. This stanza may also contain build information fields (see ) relating to the library. Subsequent stanzas (if present) describe executable programs contained in the package, using the following fields, as well as build information fields (see ). executable: freeform (required) The name of the executable program. main-is: filename (required) The name of the source file containing the Main module, relative to the hs-source-dir directory. The following fields may be optionally present in any stanza, and give information for the building of the corresponding library or executable. See also for a way to supply system-dependent values for these fields. buildable: Boolean (default: True) Is the component buildable? Like some of the other fields below, this field is more useful with the slightly more elaborate form of the simple build infrastructure described in . other-modules: identifier list A list of modules used by the component but not exposed to users. For a library component, these would be hidden modules of the library. For an executable, these would be auxiliary modules to be linked with the file named in the main-is field. hs-source-dir: directory (default: .) The name of root directory of the module hierarchy. extensions: identifier list A list of Haskell extensions used by every module. Extension names are the constructors of the &Extension; type. These determine corresponding compiler options. In particular, CPP specifies that Haskell source files are to be preprocessed with a C preprocessor. Extensions used only by one module may be specified by placing a LANGUAGE pragma in the source file affected, e.g.: {-# LANGUAGE CPP, MultiParamTypeClasses #-} ghc-options: token list Additional options for GHC. You can often achieve the same effect using the extensions field, which is preferred. Options required only by one module may be specified by placing an OPTIONS_GHC pragma in the source file affected. hugs-options: token list Additional options for Hugs. You can often achieve the same effect using the extensions field, which is preferred. Options required only by one module may be specified by placing an OPTIONS_HUGS pragma in the source file affected. nhc-options: token list Additional options for nhc98. You can often achieve the same effect using the extensions field, which is preferred. Options required only by one module may be specified by placing an OPTIONS_NHC pragma in the source file affected. includes: filename list A list of header files from standard include directories or those listed in include-dirs, to be included in any compilations via C. These files typically contain function prototypes for foreign imports used by the package. include-dirs: directory list A list of directories to search for header files, both when using a C preprocessor and when compiling via C. c-sources: filename list A list of C source files to be compiled and linked with the Haskell files. If you use this field, you should also name the C files in CFILES pragmas in the Haskell source files that use them, e.g.: {-# CFILES dir/file1.c dir/file2.c #-} These are ignored by the compilers, but needed by Hugs. extra-libraries: token list A list of extra libraries to link with. extra-lib-dirs: directory list A list of directories to search for libraries. cc-options: token list Command-line arguments to be passed to the C compiler. Since the arguments are compiler-dependent, this field is more useful with the setup described in . ld-options: token list Command-line arguments to be passed to the linker. Since the arguments are compiler-dependent, this field is more useful with the setup described in . frameworks: token list On Darwin/MacOS X, a list of frameworks to link to. See Apple's developer documentation for more details on frameworks. This entry is ignored on all other platforms. For some packages, implementation details and the build procedure depend on the build environment. The simple build infrastructure can handle many such situations using a slightly longer Setup.hs: import Distribution.Simple main = defaultMainWithHooks defaultUserHooks This program differs from defaultMain in two ways: If the package root directory contains a file called configure, the configure step will run that. This configure program may be a script produced by the autoconf system, or may be hand-written. This program typically discovers information about the system and records it for later steps, e.g. by generating system-dependent header files for inclusion in C source files and preprocessed Haskell source files. (Clearly this won't work for Windows without MSYS or Cygwin: other ideas are needed.) If the package root directory contains a file called package.buildinfo after the configuration step, subsequent steps will read it to obtain additional settings for build information fields (see ), to be merged with the ones given in the .cabal file. In particular, this file may be generated by the configure script mentioned above, allowing these settings to vary depending on the build environment. The build information file should have the following structure: buildinfo executable: name buildinfo executable: name buildinfo ... where each buildinfo consists of settings of fields listed in . The first one (if present) relates to the library, while each of the others relate to the named executable. (The names must match the package description, but you don't have to have entries for all of them.) Neither of these files is required. If they are absent, this setup script is equivalent to defaultMain. (This example is for people familiar with the autoconf tools.) In the X11 package, the file configure.ac contains: AC_INIT([Haskell X11 package], [1.1], [libraries@haskell.org], [X11]) # Safety check: Ensure that we are in the correct source directory. AC_CONFIG_SRCDIR([X11.cabal]) # Header file to place defines in AC_CONFIG_HEADERS([include/HsX11Config.h]) # Check for X11 include paths and libraries AC_PATH_XTRA AC_TRY_CPP([#include <X11/Xlib.h>],,[no_x=yes]) # Build the package if we found X11 stuff if test "$no_x" = yes then BUILD_PACKAGE_BOOL=False else BUILD_PACKAGE_BOOL=True fi AC_SUBST([BUILD_PACKAGE_BOOL]) AC_CONFIG_FILES([X11.buildinfo]) AC_OUTPUT Then the setup script will run the configure script, which checks for the presence of the X11 libraries and substitutes for variables in the file X11.buildinfo.in: buildable: @BUILD_PACKAGE_BOOL@ cc-options: @X_CFLAGS@ ld-options: @X_LIBS@ This generates a file X11.buildinfo supplying the parameters needed by later stages: buildable: True cc-options: -I/usr/X11R6/include ld-options: -L/usr/X11R6/lib The configure script also generates a header file include/HsX11Config.h containing C preprocessor defines recording the results of various tests. This file may be included by C source files and preprocessed Haskell source files in the package. For packages that don't fit the simple schemes described above, you have a few options: You can customize the simple build infrastructure using hooks. These allow you to perform additional actions before and after each command is run, and also to specify additional preprocessors. See &Simple; for the details, but note that this interface is experimental, and likely to change in future releases.. You could delegate all the work to make, though this is unlikely to be very portable. Cabal supports this with a trivial setup library &Make;, which simply parses the command line arguments and invokes make. Here Setup.hs looks like import Distribution.Make main = defaultMain The root directory of the package should contain a configure script, and, after that has run, a Makefile with a default target that builds the package, plus targets install, register, unregister, clean, dist and docs. Some options to commands are passed through as follows: The --with-hc, --with-hc-pkg and --prefix options to the configure command are passed on to the configure script. the --copy-prefix option to the copy command becomes a setting of a prefix variable on the invocation of make install. You can write your own setup script conforming to the interface of , possibly using the Cabal library for part of the work. One option is to copy the source of Distribution.Simple, and alter it for your needs. Good luck. After you've unpacked a Cabal package, you can build it by moving into the root directory of the package and using the Setup.hs or Setup.lhs script there: runhaskell Setup.hs command option where runhaskell might be runhugs, runghc or runnhc. The command argument selects a particular step in the build/install process. You can also get a summary of the command syntax with runhaskell Setup.hs --help runhaskell Setup.hs configure --ghc runhaskell Setup.hs build runhaskell Setup.hs install The first line readies the system to build the tool using GHC; for example, it checks that GHC exists on the system. The second line performs the actual building, while the last both copies the build results to some permanent place and registers the package with GHC. runhaskell Setup.hs configure --ghc --prefix=$HOME runhaskell Setup.hs build runhaskell Setup.hs install --user In this case, since the package will be registered in the user's package database, we also install it under the user's home directory. When creating binary packages (e.g. for RedHat or Debian) one needs to create a tarball that can be sent to another system for unpacking in the root directory: runhaskell Setup.hs configure --ghc --prefix=/usr runhaskell Setup.hs build runhaskell Setup.hs copy --copy-prefix=/tmp/mypkg/usr (cd /tmp/mypkg; tar cf - .) | gzip -9 >mypkg.tar.gz If the package contains a library, you need two additional steps: runhaskell Setup.hs register --gen-script runhaskell Setup.hs unregister --gen-script This creates shell scripts register.sh and unregister.sh, which must also be sent to the target system. After unpacking there, the package must be registered by running the register.sh script. The unregister.sh script would be used in the uninstall procedure of the package. Similar steps may be used for creating binary packages for Windows. The following options are understood by all commands: --help, -h or -? List the available options for the command. --verbose=n or -vn Set the verbosity level (0-5). The normal level is 1; a missing n defaults to 3. The various commands and the additional options they support are described below. In the simple build infrastructure, any other options will be reported as errors, except in the case of the configure command. Prepare to build the package. Typically, this step checks that the target platform is capable of building the package, and discovers platform-specific features that are needed during the build. In addition to the general options, this command recognizes the following --prefix=dir Specify the installation prefix (default: /usr/local on Unix systems). --ghc or -g --nhc or -n --hugs Specify which Haskell implementation to use to build the package. At most one of these flags may be given. If none is given, the implementation under which the setup script was compiled or interpreted is used. --with-compiler=path or -wpath Specify the path to a particular compiler. If given, this must match the implementation selected above. The default is to search for the usual name of the selected implementation. --with-hc-pkg=path Specify the path to the package tool, e.g. ghc-pkg. --with-haddock=path Specify the path to &Haddock;. --with-happy=path Specify the path to happy. --with-alex=path Specify the path to alex. --with-hsc2hs=path Specify the path to hsc2hs. --with-cpphs=path Specify the path to cpphs. --user Allow dependencies to be satisfied by the user package database, in addition to the global database. --global (default) Dependencies must be satisfied by the global package database. In the simple build infrastructure, an additional option is recognized: --builddir=dir or -bdir Specify the directory into which the package will be built (default: dist/build). In the simple build infrastructure, the values supplied via these options are recorded in a private file for use by later stages. If a user-supplied configure script is run (see ), it is passed the --prefix option and any unrecognized options. Perform any preprocessing or compilation needed to make this package ready for installation. Build the interface documentation for a library using &Haddock;. Copy the files into the install locations and (for library packages) register the package with the compiler, i.e. make the modules it contains available to programs. This command takes the following options: --global Register this package in the system-wide database. (This is the default.) --user Register this package in the user's local package database. Copy the files without registering them. This command is mainly of use to those creating binary packages. This command takes the following option: --copy-prefix=path Specify the directory under which to place installed files. If this is not given, the argument of the --prefix option to configure is used. Register this package with the compiler, i.e. make the modules it contains available to programs. This only makes sense for library packages. Note that the install command incorporates this action. The main use of this separate command is in the post-installation step for a binary package. This command takes the following options: --global Register this package in the system-wide database. (This is the default.) --user Register this package in the user's local package database. --gen-script Instead of registering the package, generate a script containing commands to perform the registration. On Unix, this file is called register.sh, on Windows, register.bat. This script might be included in a binary bundle, to be run after the bundle is unpacked on the target system. Deregister this package with the compiler. This command takes the following options: --global Deregister this package in the system-wide database. (This is the default.) --user Deregister this package in the user's local package database. --gen-script Instead of deregistering the package, generate a script containing commands to perform the deregistration. On Unix, this file is called unregister.sh, on Windows, unregister.bat. This script might be included in a binary bundle, to be run on the target system. Remove any files created during the configure or build steps. Create a system- and compiler-independent source distribution in a file package-version.tgz that can be distributed to package builders. When unpacked, the commands listed in this section will be available. However this command is not yet working in the simple build infrastructure. All these should be fixed in future versions: In the simple build infrastructure, the sdist command does not work. The scheme described in will not work on Windows without MSYS or Cygwin. Cabal has some limitations both running under Hugs and building packages for it: Cabal does not work with the current stable release (Nov 2003), just the development version. It doesn't work with Windows. The --user option is unavailable. There is no hugs-pkg tool. Though the library runs under Nhc98, it cannot build packages for Nhc98. Please report any other flaws to libraries@haskell.org.