1 <?xml version="1.0" encoding="iso-8859-1"?>
6 <indexterm><primary>packages</primary></indexterm>
8 <para>A package is a library of Haskell modules known to the compiler. GHC
9 comes with several packages: see the accompanying
10 <ulink url="../libraries/index.html">library documentation</ulink>.</para>
12 <para>Using a package couldn't be simpler: if you're using
13 <option>--make</option> or GHCi, then most of the installed packages will be
14 automatically available to your program without any further options. The
15 exceptions to this rule are covered below in <xref
16 linkend="using-packages" />.</para>
18 <para>Building your own packages is also quite straightforward: we provide
19 the <ulink url="http://www.haskell.org/cabal/">Cabal</ulink> infrastructure which
20 automates the process of configuring, building, installing and distributing
21 a package. All you need to do is write a simple configuration file, put a
22 few files in the right places, and you have a package. See the
23 <ulink url="../Cabal/index.html">Cabal documentation</ulink>
24 for details, and also the Cabal libraries (<ulink url="../libraries/Cabal/Distribution-Simple.html">Distribution.Simple</ulink>,
27 <sect2 id="using-packages">
30 <indexterm><primary>packages</primary>
31 <secondary>using</secondary></indexterm>
33 <para>To see which packages are installed, use the
34 <literal>ghc-pkg</literal> command:</para>
38 /usr/lib/ghc-6.4/package.conf:
39 base-1.0, haskell98-1.0, template-haskell-1.0, mtl-1.0, unix-1.0,
40 Cabal-1.0, haskell-src-1.0, parsec-1.0, network-1.0,
41 QuickCheck-1.0, HUnit-1.1, fgl-1.0, X11-1.1, HGL-3.1, OpenGL-2.0,
42 GLUT-2.0, stm-1.0, readline-1.0, (lang-1.0), (concurrent-1.0),
43 (posix-1.0), (util-1.0), (data-1.0), (text-1.0), (net-1.0),
44 (hssource-1.0), rts-1.0
47 <para>Packages are either exposed or hidden. Only
48 modules from exposed packages may be imported by your Haskell code; if
49 you try to import a module from a hidden package, GHC will emit an error
52 <para>Each package has an exposed flag, which says whether it is exposed by
53 default or not. Packages hidden by default are listed in
54 parentheses (eg. <literal>(lang-1.0)</literal>) in the output from
55 <literal>ghc-pkg list</literal>. To expose a package which is hidden by
56 default, use the <option>-package</option>
57 flag (see below).</para>
59 <para>To see which modules are exposed by a package:</para>
62 $ ghc-pkg field network exposed-modules
63 exposed-modules: Network.BSD,
70 <para>In general, packages containing hierarchical modules are usually
71 exposed by default. However, it is possible for two packages to contain
72 the same module: in this case, only one of the packages should be
73 exposed. It is an error to import a module that belongs to more than one
74 exposed package.</para>
76 <para>The GHC command line options that control packages are:</para>
81 <option>-package <replaceable>P</replaceable></option>
82 <indexterm><primary><option>-package</option></primary></indexterm>
85 <para>This option causes package <replaceable>P</replaceable> to be
86 exposed. The package <replaceable>P</replaceable> can be specified
87 in full with its version number
88 (e.g. <literal>network-1.0</literal>) or the version number can be
89 omitted if there is only one version of the package
92 <para>If there are multiple versions of <replaceable>P</replaceable>
93 installed, then all other versions will become hidden.</para>
95 <para>The <option>-package <replaceable>P</replaceable></option>
96 option also causes package <replaceable>P</replaceable> to be
97 linked into the resulting executable. In
98 <option>––make</option> mode and GHCi, the compiler
99 normally determines which packages are required by the current
100 Haskell modules, and links only those. In batch mode however, the
101 dependency information isn't available, and explicit
102 <option>-package</option> options must be given when linking.</para>
104 <para>For example, to link a program consisting of objects
105 <filename>Foo.o</filename> and <filename>Main.o</filename>, where
106 we made use of the <literal>network</literal> package, we need to
107 give GHC the <literal>-package</literal> flag thus:
109 <screen>$ ghc -o myprog Foo.o Main.o -package network</screen>
111 The same flag is necessary even if we compiled the modules from
112 source, because GHC still reckons it's in batch mode:
114 <screen>$ ghc -o myprog Foo.hs Main.hs -package network</screen>
116 In <literal>--make</literal> and <literal>--interactive</literal>
117 modes (<xref linkend="modes" />), however, GHC figures out the
118 packages required for linking without further assistance.</para>
120 <para>The one other time you might need to use
121 <option>-package</option> to force linking a package is when the
122 package does not contain any Haskell modules (it might contain a C
123 library only, for example). In that case, GHC
124 will never discover a dependency on it, so it has to be mentioned
130 <term><option>-hide-all-packages</option>
131 <indexterm><primary><option>-hide-package</option></primary>
134 <para>Ignore the exposed flag on installed packages, and hide them
135 all by default. If you use
136 this flag, then any packages you require (including
137 <literal>base</literal>) need to be explicitly exposed using
138 <option>-package</option> options.</para>
140 <para>This is a good way to insulate your program from differences
141 in the globally exposed packages, and being explicit about package
142 dependencies is a Good Thing.</para>
147 <term><option>-hide-package</option> <replaceable>P</replaceable>
148 <indexterm><primary><option>-hide-package</option></primary>
151 <para>This option does the opposite of <option>-package</option>: it
152 causes the specified package to be <firstterm>hidden</firstterm>,
153 which means that none of its modules will be available for import
154 by Haskell <literal>import</literal> directives.</para>
156 <para>Note that the package might still end up being linked into the
157 final program, if it is a dependency (direct or indirect) of
158 another exposed package.</para>
163 <term><option>-ignore-package</option> <replaceable>P</replaceable>
164 <indexterm><primary><option>-ignore-package</option></primary>
167 <para>Causes the compiler to behave as if package
168 <replaceable>P</replaceable>, and any packages that depend on
169 <literal>P</literal>, are not installed at all.</para>
171 <para>Saying <literal>-ignore-package P</literal> is the same as
172 giving <literal>-hide-package</literal> flags for
173 <literal>P</literal> and all the packages that depend on
174 <literal>P</literal>. Sometimes we don't know ahead of time which
175 packages will be installed that depend on <literal>P</literal>,
176 which is when the <literal>-ignore-package</literal> flag can be
183 <sect2 id="package-overlaps">
184 <title>The module overlap restriction</title>
186 <para>The module names in a Haskell program must be distinct.
187 This doesn't sound like a severe restriction, but in a Haskell program
188 using multiple packages with interdependencies, difficulties can start to
189 arise. You should be aware of what the module overlap
190 restriction means, and how to avoid it.</para>
192 <para>GHC knows which packages are <emphasis>in use</emphasis> by your
193 program: a package is in use if you imported something from it, or if it
194 is a dependency of some other package in use. There must be no conflicts
195 between the packages in use; a conflict is when two packages contain
196 a module with the same name. If
197 GHC detects a conflict, it will issue a message stating which packages
198 are in conflict, and which modules are overlapping.</para>
200 <para>For example, a conflict might arise if you use two packages, say P
201 and Q, which respectively depend on two different versions of another
202 package, say <literal>R-1.0</literal> and <literal>R-2.0</literal>. The
203 two versions of <literal>R</literal> are likely to contain at least some
204 of the same modules, so this situation would be a conflict.</para>
207 <sect2 id="package-databases">
208 <title>Package Databases</title>
210 <para>A package database is a file, normally called
211 <literal>package.conf</literal> which contains descriptions of installed
212 packages. GHC usually knows about two package databases:</para>
216 <para>The global package database, which comes with your GHC
220 <para>A package database private to each user. On Unix
222 <filename>$HOME/.ghc/<replaceable>arch</replaceable>-<replaceable>os</replaceable>-<replaceable>version</replaceable>/package.conf</filename>, and on
223 Windows it will be something like
224 <filename>C:\Documents And Settings\<replaceable>user</replaceable>\ghc</filename>.
225 The <literal>ghc-pkg</literal> tool knows where this file should be
226 located, and will create it if it doesn't exist (see <xref linkend="package-management" />).</para>
230 <para>When GHC starts up, it reads the contents of these two package
231 databases, and builds up a list of the packages it knows about. You can
232 see GHC's package table by running GHC with the <option>-v</option>
235 <para>Package databases may overlap: for example, packages in the user
236 database will override those of the same name in the global
239 <para>You can control the loading of package databses using the following
245 <option>-package-conf <replaceable>file</replaceable></option>
246 <indexterm><primary><option>-package-conf</option></primary></indexterm>
249 <para>Read in the package configuration file
250 <replaceable>file</replaceable> in addition to the system
251 default file and the user's local file. Packages in additional
252 files read this way will override those in the global and user
258 <term><option>-no-user-package-conf</option>
259 <indexterm><primary><option>-no-user-package-conf</option></primary>
263 <para>Prevent loading of the user's local package database.</para>
268 <para>To create a new package database, just create
269 a new file and put the string
270 <quote><literal>[]</literal></quote> in it. Packages can be
271 added to the file using the
272 <literal>ghc-pkg</literal> tool, described in <xref
273 linkend="package-management"/>.</para>
275 <sect3 id="ghc-package-path">
276 <title>The <literal>GHC_PACKAGE_PATH</literal> environment variable</title>
277 <indexterm><primary>Environment variable</primary><secondary><literal>GHC_PACKAGE_PATH</literal></secondary>
279 <indexterm><primary><literal>GHC_PACKAGE_PATH</literal></primary></indexterm>
280 <para>The <literal>GHC_PACKAGE_PATH</literal> environment variable may be
281 set to a <literal>:</literal>-separated (<literal>;</literal>-separated
282 on Windows) list of files containing package databases. This list of
283 package databases is used by GHC and ghc-pkg, with earlier databases in
284 the list overriding later ones. This order was chosen to match the
285 behaviour of the <literal>PATH</literal> environment variable; think of
286 it as a list of package databases that are searched left-to-right for
289 <para>If <literal>GHC_PACKAGE_PATH</literal> ends in a separator, then
290 the default user and system package databases are appended, in that
291 order. e.g. to augment the usual set of packages with a database of
292 your own, you could say (on Unix):
294 $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:</screen>
295 (use <literal>;</literal> instead of <literal>:</literal> on
298 <para>To check whether your <literal>GHC_PACKAGE_PATH</literal> setting
299 is doing the right thing, <literal>ghc-pkg list</literal> will list all
300 the databases in use, in the reverse order they are searched.</para>
304 <sect2 id="building-packages">
305 <title>Building a package from Haskell source</title>
306 <indexterm><primary>packages</primary>
307 <secondary>building</secondary></indexterm>
309 <para>We don't recommend building packages the hard way. Instead, use the
310 <ulink url="../Cabal/index.html">Cabal</ulink> infrastructure
311 if possible. If your package is particularly complicated or requires a
312 lot of configuration, then you might have to fall back to the low-level
313 mechanisms, so a few hints for those brave souls follow.</para>
317 <para>You need to build an "installed package info" file for
318 passing to <literal>ghc-pkg</literal> when installing your
319 package. The contents of this file are described in <xref
320 linkend="installed-pkg-info" />.</para>
324 <para>The Haskell code in a package may be built into one or
325 more archive libraries
326 (e.g. <filename>libHSfoo.a</filename>), or a single DLL on
327 Windows (e.g. <filename>HSfoo.dll</filename>). The
328 restriction to a single DLL on Windows is because the
329 package system is used to tell the compiler when it should
330 make an inter-DLL call rather than an intra-DLL call
331 (inter-DLL calls require an extra
332 indirection). <emphasis>Building packages as DLLs doesn't
333 work at the moment; see <xref linkend="win32-dlls-create"/>
334 for the gory details.</emphasis>
337 <para>Building a static library is done by using the
338 <literal>ar</literal> tool, like so:</para>
340 <screen>ar cqs libHSfoo.a A.o B.o C.o ...</screen>
342 <para>where <filename>A.o</filename>,
343 <filename>B.o</filename> and so on are the compiled Haskell
344 modules, and <filename>libHSfoo.a</filename> is the library
345 you wish to create. The syntax may differ slightly on your
346 system, so check the documentation if you run into
349 <para>Versions of the Haskell libraries for use with GHCi
350 may also be included: GHCi cannot load <literal>.a</literal>
351 files directly, instead it will look for an object file
352 called <filename>HSfoo.o</filename> and load that. On some
353 systems, the <literal>ghc-pkg</literal> tool can
354 automatically build the GHCi version of each library, see
355 <xref linkend="package-management"/>. To build these
356 libraries by hand from the <literal>.a</literal> archive, it
357 is possible to use GNU <command>ld</command> as
360 <screen>ld -r ––whole-archive -o HSfoo.o libHSfoo.a</screen>
363 <literal>––--whole-archive</literal> with
364 <literal>–all_load</literal> on MacOS X)</para>
366 <para>GHC does not maintain detailed cross-package
367 dependency information. It does remember which modules in
368 other packages the current module depends on, but not which
369 things within those imported things.</para>
373 <para>It is worth noting that on Windows, when each package
374 is built as a DLL, since a reference to a DLL costs an extra
375 indirection, intra-package references are cheaper than
376 inter-package references. Of course, this applies to the
377 <filename>Main</filename> package as well.</para>
380 <sect2 id="package-management">
381 <title>Package management (the <literal>ghc-pkg</literal> command)</title>
382 <indexterm><primary>packages</primary>
383 <secondary>management</secondary></indexterm>
385 <para>The <literal>ghc-pkg</literal> tool allows packages to be
386 added or removed from a package database. By default,
387 the system-wide package database is modified, but alternatively
388 the user's local package database or another specified
389 file can be used.</para>
391 <para>To see what package databases are in use, say
392 <literal>ghc-pkg list</literal>. The stack of databases that
393 <literal>ghc-pkg</literal> knows about can be modified using the
394 <literal>GHC_PACKAGE_PATH</literal> environment variable (see <xref
395 linkend="ghc-package-path" />, and using
396 <literal>--package-conf</literal> options on the
397 <literal>ghc-pkg</literal> command line.</para>
399 <para>When asked to modify a database, <literal>ghc-pkg</literal> modifies
400 the global database by default. Specifying <option>--user</option>
401 causes it to act on the user database, or <option>--package-conf</option>
402 can be used to act on another database entirely. When multiple of these
403 options are given, the rightmost one is used as the database to act
406 <para>The <literal>ghc-pkg</literal> program may be run in the ways listed
407 below. Where a package name is required, the package can be named in
408 full including the version number
409 (e.g. <literal>network-1.0</literal>), or without the version number.
410 Naming a package without the version number matches all versions of the
411 package; the specified action will be applied to all the matching
412 packages. A package specifier that matches all version of the package
413 can also be written <replaceable>pkg</replaceable><literal>-*</literal>,
414 to make it clearer that multiple packages are being matched.</para>
418 <term><literal>ghc-pkg register <replaceable>file</replaceable></literal></term>
420 <para>Reads a package specification from
421 <replaceable>file</replaceable> (which may be “<literal>-</literal>”
422 to indicate standard input),
423 and adds it to the database of installed packages. The syntax of
424 <replaceable>file</replaceable> is given in <xref
425 linkend="installed-pkg-info" />.</para>
427 <para>The package specification must be a package that isn't already
433 <term><literal>ghc-pkg update <replaceable>file</replaceable></literal></term>
435 <para>The same as <literal>register</literal>, except that if a
436 package of the same name is already installed, it is
437 replaced by the new one.</para>
442 <term><literal>ghc-pkg unregister <replaceable>P</replaceable></literal></term>
444 <para>Remove the specified package from the database.</para>
449 <term><literal>ghc-pkg expose <replaceable>P</replaceable></literal></term>
451 <para>Sets the <literal>exposed</literal> flag for package
452 <replaceable>P</replaceable> to <literal>True</literal>.</para>
457 <term><literal>ghc-pkg hide <replaceable>P</replaceable></literal></term>
459 <para>Sets the <literal>exposed</literal> flag for package
460 <replaceable>P</replaceable> to <literal>False</literal>.</para>
465 <term><literal>ghc-pkg list [<replaceable>P</replaceable>] [<option>--simple-output</option>]</literal></term>
467 <para>This option displays the currently installed
468 packages, for each of the databases known to
469 <literal>ghc-pkg</literal>. That includes the global database, the
470 user's local database, and any further files specified using the
471 <option>-f</option> option on the command line.</para>
473 <para>Hidden packages (those for which the <literal>exposed</literal>
474 flag is <literal>False</literal>) are shown in parentheses in the
475 list of packages.</para>
477 <para>If an optional package identifier <replaceable>P</replaceable>
478 is given, then only packages matching that identifier are
481 <para>If the option <option>--simple-output</option> is given, then
482 the packages are listed on a single line separated by spaces, and
483 the database names are not included. This is intended to make it
484 easier to parse the output of <literal>ghc-pkg list</literal> using
490 <term><literal>ghc-pkg latest <replaceable>P</replaceable></literal></term>
492 <para>Prints the latest available version of package
493 <replaceable>P</replaceable>.</para>
498 <term><literal>ghc-pkg describe <replaceable>P</replaceable></literal></term>
500 <para>Emit the full description of the specified package. The
501 description is in the form of an
502 <literal>InstalledPackageInfo</literal>, the same as the input file
503 format for <literal>ghc-pkg register</literal>. See <xref
504 linkend="installed-pkg-info" /> for details.</para>
509 <term><literal>ghc-pkg field <replaceable>P</replaceable> <replaceable>field</replaceable></literal></term>
511 <para>Show just a single field of the installed package description
512 for <literal>P</literal>.</para>
517 <para>Additionally, the following flags are accepted by
518 <literal>ghc-pkg</literal>:</para>
523 <option>––auto-ghci-libs</option><indexterm><primary><option>––auto-ghci-libs</option></primary>
527 <para>Automatically generate the GHCi
528 <filename>.o</filename> version of each
529 <filename>.a</filename> Haskell library, using GNU ld (if
530 that is available). Without this option,
531 <literal>ghc-pkg</literal> will warn if GHCi versions of
532 any Haskell libraries in the package don't exist.</para>
534 <para>GHCi <literal>.o</literal> libraries don't
535 necessarily have to live in the same directory as the
536 corresponding <literal>.a</literal> library. However,
537 this option will cause the GHCi library to be created in
538 the same directory as the <literal>.a</literal>
545 <option>-f</option> <replaceable>file</replaceable>
546 <indexterm><primary><option>-f</option></primary>
550 <option>-package-conf</option> <replaceable>file</replaceable>
551 <indexterm><primary><option>-package-conf</option></primary>
555 <para>Adds <replaceable>file</replaceable> to the stack of package
556 databases. Additionally, <replaceable>file</replaceable> will
557 also be the database modified by a <literal>register</literal>,
558 <literal>unregister</literal>, <literal>expose</literal> or
559 <literal>hide</literal> command, unless it is overriden by a later
560 <option>--package-conf</option>, <option>--user</option> or
561 <option>--global</option> option.</para>
567 <option>––force</option>
569 <option>––force</option>
570 </primary></indexterm>
573 <para>Causes <literal>ghc-pkg</literal> to ignore missing
574 dependencies, directories and libraries when registering a package,
575 and just go ahead and add it anyway. This might be useful if your
576 package installation system needs to add the package to
577 GHC before building and installing the files.</para>
583 <option>––global</option><indexterm><primary><option>––global</option></primary>
587 <para>Operate on the global package database (this is the default).
588 This flag affects the <literal>register</literal>,
589 <literal>update</literal>, <literal>unregister</literal>,
590 <literal>expose</literal>, and <literal>hide</literal>
597 <option>––help</option><indexterm><primary><option>––help</option></primary>
601 <option>-?</option><indexterm><primary><option>-?</option></primary>
605 <para>Outputs the command-line syntax.</para>
611 <option>––user</option><indexterm><primary><option>––user</option></primary>
615 <para>Operate on the current user's local package database.
616 This flag affects the <literal>register</literal>,
617 <literal>update</literal>, <literal>unregister</literal>,
618 <literal>expose</literal>, and <literal>hide</literal>
625 <option>-V</option><indexterm><primary><option>-V</option></primary>
629 <option>––version</option><indexterm><primary><option>––version</option></primary>
633 <para>Output the <literal>ghc-pkg</literal> version number.</para>
638 <para>When modifying the package database
639 <replaceable>file</replaceable>, a copy of the original file is
640 saved in <replaceable>file</replaceable><literal>.old</literal>,
641 so in an emergency you can always restore the old settings by
642 copying the old file back again.</para>
646 <sect2 id="installed-pkg-info">
648 <literal>InstalledPackageInfo</literal>: a package specification
651 <para>A package specification is a Haskell record; in particular, it is the
653 url="../libraries/Cabal/Distribution-InstalledPackageInfo.html#%tInstalledPackageInfo">InstalledPackageInfo</ulink> in the module Distribution.InstalledPackageInfo, which is part of the Cabal package distributed with GHC.</para>
655 <para>An <literal>InstalledPackageInfo</literal> has a human
656 readable/writable syntax. The functions
657 <literal>parseInstalledPackageInfo</literal> and
658 <literal>showInstalledPackageInfo</literal> read and write this syntax
659 respectively. Here's an example of the
660 <literal>InstalledPackageInfo</literal> for the <literal>unix</literal> package:</para>
663 $ ghc-pkg describe unix
668 maintainer: libraries@haskell.org
676 exposed-modules: System.Posix,
677 System.Posix.DynamicLinker.Module,
678 System.Posix.DynamicLinker.Prim,
679 System.Posix.Directory,
680 System.Posix.DynamicLinker,
685 System.Posix.Process,
686 System.Posix.Resource,
688 System.Posix.Terminal,
692 System.Posix.Signals.Exts
693 import-dirs: /usr/lib/ghc-6.4/libraries/unix
694 library-dirs: /usr/lib/ghc-6.4/libraries/unix
696 extra-libraries: HSunix_cbits, dl
697 include-dirs: /usr/lib/ghc-6.4/libraries/unix/include
702 <para>The full <ulink url="../Cabal/index.html">Cabal documentation</ulink>
703 is still in preparation (at time of writing), so in the meantime
704 here is a brief description of the syntax of this file:</para>
706 <para>A package description consists of a number of field/value pairs. A
707 field starts with the field name in the left-hand column followed by a
708 “<literal>:</literal>”, and the value continues until the next line that begins in the
709 left-hand column, or the end of file.</para>
711 <para>The syntax of the value depends on the field. The various field
716 <term>freeform</term>
718 <para>Any arbitrary string, no interpretation or parsing is
725 <para>A sequence of non-space characters, or a sequence of arbitrary
726 characters surrounded by quotes <literal>"...."</literal>.</para>
730 <term>string list</term>
732 <para>A sequence of strings, separated by commas. The sequence may
738 <para>In addition, there are some fields with special syntax (e.g. package
739 names, version, dependencies).</para>
741 <para>The allowed fields, with their types, are:</para>
746 <literal>name</literal>
747 <indexterm><primary><literal>name</literal></primary><secondary>package specification</secondary></indexterm>
750 <para>The package's name (without the version).</para>
756 <literal>version</literal>
757 <indexterm><primary><literal>version</literal></primary><secondary>package specification</secondary></indexterm>
760 <para>The package's version, usually in the form
761 <literal>A.B</literal> (any number of components are allowed).</para>
767 <literal>license</literal>
768 <indexterm><primary><literal>auto</literal></primary><secondary>package specification</secondary></indexterm>
771 <para>(string) The type of license under which this package is distributed.
772 This field is a value of the <ulink
773 url="../libraries/Cabal/Distribution-License.html#t:License"><literal>License</literal></ulink> type.</para>
779 <literal>license-file</literal>
780 <indexterm><primary><literal>license-file</literal></primary><secondary>package specification</secondary></indexterm>
783 <para>(optional string) The name of a file giving detailed license
784 information for this package.</para>
790 <literal>copyright</literal>
791 <indexterm><primary><literal>copyright</literal></primary><secondary>package specification</secondary></indexterm>
794 <para>(optional freeform) The copyright string.</para>
800 <literal>maintainer</literal>
801 <indexterm><primary><literal>maintainer</literal></primary><secondary>package specification</secondary></indexterm>
804 <para>(optinoal freeform) The email address of the package's maintainer.</para>
810 <literal>stability</literal>
811 <indexterm><primary><literal>stability</literal></primary><secondary>package specification</secondary></indexterm>
814 <para>(optional freeform) A string describing the stability of the package
815 (eg. stable, provisional or experimental).</para>
821 <literal>homepage</literal>
822 <indexterm><primary><literal>homepage</literal></primary><secondary>package specification</secondary></indexterm>
825 <para>(optional freeform) URL of the package's home page.</para>
831 <literal>package-url</literal>
832 <indexterm><primary><literal>package-url</literal></primary><secondary>package specification</secondary></indexterm>
835 <para>(optional freeform) URL of a downloadable distribution for this
836 package. The distribution should be a Cabal package.</para>
842 <literal>description</literal>
843 <indexterm><primary><literal>description</literal></primary><secondary>package specification</secondary></indexterm>
846 <para>(optional freeform) Description of the package.</para>
852 <literal>category</literal>
853 <indexterm><primary><literal>category</literal></primary><secondary>package specification</secondary></indexterm>
856 <para>(optinoal freeform) Which category the package belongs to. This field
857 is for use in conjunction with a future centralised package
858 distribution framework, tentatively titled Hackage.</para>
864 <literal>author</literal>
865 <indexterm><primary><literal>author</literal></primary><secondary>package specification</secondary></indexterm>
868 <para>(optional freeform) Author of the package.</para>
874 <literal>exposed</literal>
875 <indexterm><primary><literal>exposed</literal></primary><secondary>package specification</secondary></indexterm>
878 <para>(bool) Whether the package is exposed or not.</para>
884 <literal>exposed-modules</literal>
885 <indexterm><primary><literal>exposed-modules</literal></primary><secondary>package specification</secondary></indexterm>
888 <para>(string list) modules exposed by this package.</para>
894 <literal>hidden-modules</literal>
895 <indexterm><primary><literal>hidden-modules</literal></primary><secondary>package specification</secondary></indexterm>
898 <para>(string list) modules provided by this package,
899 but not exposed to the programmer. These modules cannot be
900 imported, but they are still subject to the overlapping constraint:
901 no other package in the same program may provide a module of the
908 <literal>import-dirs</literal>
909 <indexterm><primary><literal>import-dirs</literal></primary><secondary>package specification</secondary></indexterm>
912 <para>(string list) A list of directories containing interface files
913 (<literal>.hi</literal> files) for this package.</para>
915 <para>If the package contains profiling libraries, then
916 the interface files for those library modules should have
917 the suffix <literal>.p_hi</literal>. So the package can
918 contain both normal and profiling versions of the same
919 library without conflict (see also
920 <literal>library_dirs</literal> below).</para>
926 <literal>library-dirs</literal>
927 <indexterm><primary><literal>library-dirs</literal></primary><secondary>package specification</secondary></indexterm>
930 <para>(string list) A list of directories containing libraries for this
937 <literal>hs-libraries</literal>
938 <indexterm><primary><literal>hs-libraries</literal></primary><secondary>package specification</secondary></indexterm>
941 <para>(string list) A list of libraries containing Haskell code for this
942 package, with the <literal>.a</literal> or
943 <literal>.dll</literal> suffix omitted. When packages are
944 built as libraries, the
945 <literal>lib</literal> prefix is also omitted.</para>
947 <para>For use with GHCi, each library should have an
948 object file too. The name of the object file does
949 <emphasis>not</emphasis> have a <literal>lib</literal>
950 prefix, and has the normal object suffix for your
953 <para>For example, if we specify a Haskell library as
954 <filename>HSfoo</filename> in the package spec, then the
955 various flavours of library that GHC actually uses will be
959 <term><filename>libHSfoo.a</filename></term>
961 <para>The name of the library on Unix and Windows
962 (mingw) systems. Note that we don't support
963 building dynamic libraries of Haskell code on Unix
968 <term><filename>HSfoo.dll</filename></term>
970 <para>The name of the dynamic library on Windows
971 systems (optional).</para>
975 <term><filename>HSfoo.o</filename></term>
976 <term><filename>HSfoo.obj</filename></term>
978 <para>The object version of the library used by
988 <literal>extra-libraries</literal>
989 <indexterm><primary><literal>extra-libraries</literal></primary><secondary>package specification</secondary></indexterm>
992 <para>(string list) A list of extra libraries for this package. The
993 difference between <literal>hs-libraries</literal> and
994 <literal>extra-libraries</literal> is that
995 <literal>hs-libraries</literal> normally have several
996 versions, to support profiling, parallel and other build
997 options. The various versions are given different
998 suffixes to distinguish them, for example the profiling
999 version of the standard prelude library is named
1000 <filename>libHSbase_p.a</filename>, with the
1001 <literal>_p</literal> indicating that this is a profiling
1002 version. The suffix is added automatically by GHC for
1003 <literal>hs-libraries</literal> only, no suffix is added
1005 <literal>extra-libraries</literal>.</para>
1007 <para>The libraries listed in
1008 <literal>extra-libraries</literal> may be any libraries
1009 supported by your system's linker, including dynamic
1010 libraries (<literal>.so</literal> on Unix,
1011 <literal>.DLL</literal> on Windows).</para>
1013 <para>Also, <literal>extra-libraries</literal> are placed
1014 on the linker command line after the
1015 <literal>hs-libraries</literal> for the same package. If
1016 your package has dependencies in the other direction (i.e.
1017 <literal>extra-libraries</literal> depends on
1018 <literal>hs-libraries</literal>), and the libraries are
1019 static, you might need to make two separate
1026 <literal>include-dirs</literal>
1027 <indexterm><primary><literal>include-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1030 <para>(string list) A list of directories containing C includes for this
1037 <literal>includes</literal>
1038 <indexterm><primary><literal>includes</literal></primary><secondary>package specification</secondary></indexterm>
1041 <para>(string list) A list of files to include for via-C compilations
1042 using this package. Typically the include file(s) will
1043 contain function prototypes for any C functions used in
1044 the package, in case they end up being called as a result
1045 of Haskell functions from the package being
1052 <literal>depends</literal>
1053 <indexterm><primary><literal>depends</literal></primary><secondary>package specification</secondary></indexterm>
1056 <para>(package name list) Packages on which this package depends. This field contains
1057 packages with explicit versions are required, except that when
1058 submitting a package to <literal>ghc-pkg register</literal>, the
1059 versions will be filled in if they are unambiguous.</para>
1065 <literal>hugs-options</literal>
1066 <indexterm><primary><literal>hugs-options</literal></primary><secondary>package specification</secondary></indexterm>
1069 <para>(string list) Options to pass to Hugs for this package.</para>
1075 <literal>cc-options</literal>
1076 <indexterm><primary><literal>cc-options</literal></primary><secondary>package specification</secondary></indexterm>
1079 <para>(string list) Extra arguments to be added to the gcc command line
1080 when this package is being used (only for via-C
1081 compilations).</para>
1087 <literal>ld-options</literal>
1088 <indexterm><primary><literal>ld-options</literal></primary><secondary>package specification</secondary></indexterm>
1091 <para>(string list) Extra arguments to be added to the
1092 <command>gcc</command> command line (for linking) when
1093 this package is being used.</para>
1099 <literal>framework-dirs</literal>
1100 <indexterm><primary><literal>framework-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1103 <para>(string list) On Darwin/MacOS X, a list of directories containing
1104 frameworks for this package. This corresponds to the
1105 <option>-framework-path</option> option. It is ignored on all other
1112 <literal>frameworks</literal>
1113 <indexterm><primary><literal>frameworks</literal></primary><secondary>package specification</secondary></indexterm>
1116 <para>(string list) On Darwin/MacOS X, a list of frameworks to link to. This
1117 corresponds to the <option>-framework</option> option. Take a look
1118 at Apple's developer documentation to find out what frameworks
1119 actually are. This entry is ignored on all other platforms.</para>
1125 <literal>haddock-interfaces</literal>
1126 <indexterm><primary><literal>haddock-interfaces</literal></primary><secondary>package specification</secondary></indexterm>
1129 <para>(string list) A list of filenames containing <ulink
1130 url="http://www.haskell.org/haddock/">Haddock</ulink> interface
1131 files (<literal>.haddock</literal> files) for this package.</para>
1137 <literal>haddock-html</literal>
1138 <indexterm><primary><literal>haddock-html</literal></primary><secondary>package specification</secondary></indexterm>
1141 <para>(optional string) The directory containing the Haddock-generated HTML
1142 for this package.</para>
1147 <!-- This isn't true any more. I'm not sure if we still need it -SDM
1149 The <literal>ghc-pkg</literal> tool performs expansion of
1150 environment variables occurring in input package specifications.
1151 So, if the <literal>mypkg</literal> was added to the package
1152 database as follows:
1155 $ installdir=/usr/local/lib ghc-pkg -a < mypkg.pkg
1159 The occurrence of <literal>${installdir}</literal> is replaced
1160 with <literal>/usr/local/lib</literal> in the package data that
1161 is added for <literal>mypkg</literal>.
1165 This feature enables the distribution of package specification
1166 files that can be easily configured when installing.
1169 <para>For examples of more package specifications, take a look
1170 at the <literal>package.conf</literal> in your GHC
1171 installation.</para>
1179 ;;; Local Variables: ***
1181 ;;; sgml-parent-document: ("users_guide.xml" "book" "chapter" "sect1") ***