0d7a02f25106afb075763d0e36b598f9237f984a
[ghc.git] / docs / users_guide / packages.xml
1 <?xml version="1.0" encoding="iso-8859-1"?>
2 <sect1 id="packages">
3 <title>
4 Packages
5 </title>
6 <indexterm><primary>packages</primary></indexterm>
7
8 <para>A package is a library of Haskell modules known to the
9 compiler. GHC comes with several packages: see the accompanying
10 <ulink url="../libraries/index.html">library
11 documentation</ulink>. More packages to install can be obtained
12 from <ulink
13 url="http://hackage.haskell.org/packages/hackage.html">HackageDB</ulink>.</para>
14
15 <para>Using a package couldn't be simpler: if you're using
16 <option>--make</option> or GHCi, then most of the installed packages will be
17 automatically available to your program without any further options. The
18 exceptions to this rule are covered below in <xref
19 linkend="using-packages" />.</para>
20
21 <para>Building your own packages is also quite straightforward: we provide
22 the <ulink url="http://www.haskell.org/cabal/">Cabal</ulink> infrastructure which
23 automates the process of configuring, building, installing and distributing
24 a package. All you need to do is write a simple configuration file, put a
25 few files in the right places, and you have a package. See the
26 <ulink url="../Cabal/index.html">Cabal documentation</ulink>
27 for details, and also the Cabal libraries (<ulink url="../libraries/Cabal/Distribution-Simple.html">Distribution.Simple</ulink>,
28 for example).</para>
29
30 <sect2 id="using-packages">
31 <title>Using Packages
32 </title>
33 <indexterm><primary>packages</primary>
34 <secondary>using</secondary></indexterm>
35
36 <para>GHC only knows about packages that are
37 <emphasis>installed</emphasis>. To see which packages are installed, use
38 the <literal>ghc-pkg</literal> command:</para>
39
40 <screen>
41 $ ghc-pkg list
42 /usr/lib/ghc-6.4/package.conf:
43 base-1.0, haskell98-1.0, template-haskell-1.0, mtl-1.0, unix-1.0,
44 Cabal-1.0, haskell-src-1.0, parsec-1.0, network-1.0,
45 QuickCheck-1.0, HUnit-1.1, fgl-1.0, X11-1.1, HGL-3.1, OpenGL-2.0,
46 GLUT-2.0, stm-1.0, readline-1.0, (lang-1.0), (concurrent-1.0),
47 (posix-1.0), (util-1.0), (data-1.0), (text-1.0), (net-1.0),
48 (hssource-1.0), rts-1.0
49 </screen>
50
51 <para>An installed package is either <emphasis>exposed</emphasis> or <emphasis>hidden</emphasis>
52 by default. Packages hidden by default are listed in
53 parentheses (eg. <literal>(lang-1.0)</literal>) in the output above. Command-line flags, described below, allow you to expose a hidden package
54 or hide an exposed one.
55 Only modules from exposed packages may be imported by your Haskell code; if
56 you try to import a module from a hidden package, GHC will emit an error
57 message.</para>
58
59 <para>To see which modules are provided by a package use the
60 <literal>ghc-pkg</literal> command (see <xref linkend="package-management"/>):</para>
61
62 <screen>
63 $ ghc-pkg field network exposed-modules
64 exposed-modules: Network.BSD,
65 Network.CGI,
66 Network.Socket,
67 Network.URI,
68 Network
69 </screen>
70
71 <para>The GHC command line options that control packages are:</para>
72
73 <variablelist>
74 <varlistentry>
75 <term>
76 <option>-package <replaceable>P</replaceable></option>
77 <indexterm><primary><option>-package</option></primary></indexterm>
78 </term>
79 <listitem>
80 <para>This option causes the installed
81 package <replaceable>P</replaceable> to be exposed. The
82 package <replaceable>P</replaceable> can be specified in
83 full with its version number
84 (e.g. <literal>network-1.0</literal>) or the version
85 number can be omitted if there is only one version of the
86 package installed. If there are multiple versions
87 of <replaceable>P</replaceable> installed, then all other
88 versions will become hidden.</para>
89
90 <para>The <option>-package <replaceable>P</replaceable></option>
91 option also causes package <replaceable>P</replaceable> to
92 be linked into the resulting executable or shared
93 object. Whether a packages' library is linked statically
94 or dynamically is controlled by the flag
95 pair <option>-static</option>/<option>-dynamic</option>.</para>
96
97 <para>In <option>&ndash;&ndash;make</option> mode
98 and <option>&ndash;&ndash;interactive</option> mode (see
99 <xref linkend="modes" />), the compiler normally
100 determines which packages are required by the current
101 Haskell modules, and links only those. In batch mode
102 however, the dependency information isn't available, and
103 explicit
104 <option>-package</option> options must be given when linking. The one other time you might need to use
105 <option>-package</option> to force linking a package is
106 when the package does not contain any Haskell modules (it
107 might contain a C library only, for example). In that
108 case, GHC will never discover a dependency on it, so it
109 has to be mentioned explicitly.</para>
110
111 <para>For example, to link a program consisting of objects
112 <filename>Foo.o</filename> and <filename>Main.o</filename>, where
113 we made use of the <literal>network</literal> package, we need to
114 give GHC the <literal>-package</literal> flag thus:
115
116 <screen>$ ghc -o myprog Foo.o Main.o -package network</screen>
117
118 The same flag is necessary even if we compiled the modules from
119 source, because GHC still reckons it's in batch mode:
120
121 <screen>$ ghc -o myprog Foo.hs Main.hs -package network</screen></para>
122 </listitem>
123 </varlistentry>
124
125 <varlistentry>
126 <term><option>-hide-all-packages</option>
127 <indexterm><primary><option>-hide-package</option></primary>
128 </indexterm></term>
129 <listitem>
130 <para>Ignore the exposed flag on installed packages, and hide them
131 all by default. If you use
132 this flag, then any packages you require (including
133 <literal>base</literal>) need to be explicitly exposed using
134 <option>-package</option> options.</para>
135
136 <para>This is a good way to insulate your program from
137 differences in the globally exposed packages, and being
138 explicit about package dependencies is a Good Thing.
139 Cabal always passes the
140 <option>-hide-all-packages</option> flag to GHC, for
141 exactly this reason.</para>
142 </listitem>
143 </varlistentry>
144
145 <varlistentry>
146 <term><option>-hide-package</option> <replaceable>P</replaceable>
147 <indexterm><primary><option>-hide-package</option></primary>
148 </indexterm></term>
149 <listitem>
150 <para>This option does the opposite of <option>-package</option>: it
151 causes the specified package to be <firstterm>hidden</firstterm>,
152 which means that none of its modules will be available for import
153 by Haskell <literal>import</literal> directives.</para>
154
155 <para>Note that the package might still end up being linked into the
156 final program, if it is a dependency (direct or indirect) of
157 another exposed package.</para>
158 </listitem>
159 </varlistentry>
160
161 <varlistentry>
162 <term><option>-ignore-package</option> <replaceable>P</replaceable>
163 <indexterm><primary><option>-ignore-package</option></primary>
164 </indexterm></term>
165 <listitem>
166 <para>Causes the compiler to behave as if package
167 <replaceable>P</replaceable>, and any packages that depend on
168 <literal>P</literal>, are not installed at all.</para>
169
170 <para>Saying <literal>-ignore-package P</literal> is the same as
171 giving <literal>-hide-package</literal> flags for
172 <literal>P</literal> and all the packages that depend on
173 <literal>P</literal>. Sometimes we don't know ahead of time which
174 packages will be installed that depend on <literal>P</literal>,
175 which is when the <literal>-ignore-package</literal> flag can be
176 useful.</para>
177 </listitem>
178 </varlistentry>
179
180 <varlistentry>
181 <term><option>-package-name</option> <replaceable>foo</replaceable>
182 <indexterm><primary><option>-package-name</option></primary>
183 </indexterm></term>
184 <listitem>
185 <para>Tells GHC the the module being compiled forms part of
186 package <replaceable>foo</replaceable>.
187 If this flag is omitted (a very common case) then the
188 default package <literal>main</literal> is assumed.</para>
189 <para>Note: the argument to <option>-package-name</option>
190 should be the full package identifier for the package,
191 that is it should include the version number. For example:
192 <literal>-package mypkg-1.2</literal>.</para>
193 </listitem>
194 </varlistentry>
195 </variablelist>
196 </sect2>
197
198 <sect2 id="package-main">
199 <title>The main package</title>
200
201 <para>Every complete Haskell program must define <literal>main</literal> in
202 module <literal>Main</literal>
203 in package <literal>main</literal>. (Omitting the <option>-package-name</option> flag compiles
204 code for package <literal>main</literal>.) Failure to do so leads to a somewhat obscure
205 link-time error of the form:
206 <programlisting>
207 /usr/bin/ld: Undefined symbols:
208 _ZCMain_main_closure
209 ___stginit_ZCMain
210 </programlisting>
211 </para>
212
213 </sect2>
214
215 <sect2 id="package-overlaps">
216 <title>Consequences of packages</title>
217
218 <para>It is possible that by using packages you might end up with
219 a program that contains two modules with the same name: perhaps
220 you used a package P that has a <emphasis>hidden</emphasis> module
221 M, and there is also a module M in your program. Or perhaps the
222 dependencies of packages that you used contain some overlapping
223 modules. Perhaps the program even contains multiple versions of a
224 certain package, due to dependencies from other packages.</para>
225
226 <para>None of these scenarios gives rise to an error on its
227 own<footnote><para>it used to in GHC 6.4, but not since
228 6.6</para></footnote>, but they may have some interesting
229 consequences. For instance, if you have a type
230 <literal>M.T</literal> from version 1 of package
231 <literal>P</literal>, then this is <emphasis>not</emphasis> the
232 same as the type <literal>M.T</literal> from version 2 of package
233 <literal>P</literal>, and GHC will report an error if you try to
234 use one where the other is expected.</para>
235
236 <para>Formally speaking, in Haskell 98, an entity (function, type
237 or class) in a program is uniquely identified by the pair of the
238 module name in which it is defined and its name. In GHC, an
239 entity is uniquely defined by a triple: package, module, and
240 name.</para>
241 </sect2>
242
243 <sect2 id="package-databases">
244 <title>Package Databases</title>
245
246 <para>A package database is a file, normally called
247 <literal>package.conf</literal> which contains descriptions of installed
248 packages. GHC usually knows about two package databases:</para>
249
250 <itemizedlist>
251 <listitem>
252 <para>The global package database, which comes with your GHC
253 installation.</para>
254 </listitem>
255 <listitem>
256 <para>A package database private to each user. On Unix
257 systems this will be
258 <filename>$HOME/.ghc/<replaceable>arch</replaceable>-<replaceable>os</replaceable>-<replaceable>version</replaceable>/package.conf</filename>, and on
259 Windows it will be something like
260 <filename>C:\Documents&nbsp;And&nbsp;Settings\<replaceable>user</replaceable>\ghc</filename>.
261 The <literal>ghc-pkg</literal> tool knows where this file should be
262 located, and will create it if it doesn't exist (see <xref linkend="package-management" />).</para>
263 </listitem>
264 </itemizedlist>
265
266 <para>When GHC starts up, it reads the contents of these two package
267 databases, and builds up a list of the packages it knows about. You can
268 see GHC's package table by running GHC with the <option>-v</option>
269 flag.</para>
270
271 <para>Package databases may overlap: for example, packages in the user
272 database will override those of the same name in the global
273 database.</para>
274
275 <para>You can control the loading of package databases using the following
276 GHC options:</para>
277
278 <variablelist>
279 <varlistentry>
280 <term>
281 <option>-package-conf <replaceable>file</replaceable></option>
282 <indexterm><primary><option>-package-conf</option></primary></indexterm>
283 </term>
284 <listitem>
285 <para>Read in the package configuration file
286 <replaceable>file</replaceable> in addition to the system
287 default file and the user's local file. Packages in additional
288 files read this way will override those in the global and user
289 databases.</para>
290 </listitem>
291 </varlistentry>
292
293 <varlistentry>
294 <term><option>-no-user-package-conf</option>
295 <indexterm><primary><option>-no-user-package-conf</option></primary>
296 </indexterm>
297 </term>
298 <listitem>
299 <para>Prevent loading of the user's local package database.</para>
300 </listitem>
301 </varlistentry>
302 </variablelist>
303
304 <para>To create a new package database, just create
305 a new file and put the string
306 <quote><literal>[]</literal></quote> in it. Packages can be
307 added to the file using the
308 <literal>ghc-pkg</literal> tool, described in <xref
309 linkend="package-management"/>.</para>
310
311 <sect3 id="ghc-package-path">
312 <title>The <literal>GHC_PACKAGE_PATH</literal> environment variable</title>
313 <indexterm><primary>Environment variable</primary><secondary><literal>GHC_PACKAGE_PATH</literal></secondary>
314 </indexterm>
315 <indexterm><primary><literal>GHC_PACKAGE_PATH</literal></primary></indexterm>
316 <para>The <literal>GHC_PACKAGE_PATH</literal> environment variable may be
317 set to a <literal>:</literal>-separated (<literal>;</literal>-separated
318 on Windows) list of files containing package databases. This list of
319 package databases is used by GHC and ghc-pkg, with earlier databases in
320 the list overriding later ones. This order was chosen to match the
321 behaviour of the <literal>PATH</literal> environment variable; think of
322 it as a list of package databases that are searched left-to-right for
323 packages.</para>
324
325 <para>If <literal>GHC_PACKAGE_PATH</literal> ends in a separator, then
326 the default user and system package databases are appended, in that
327 order. e.g. to augment the usual set of packages with a database of
328 your own, you could say (on Unix):
329 <screen>
330 $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:</screen>
331 (use <literal>;</literal> instead of <literal>:</literal> on
332 Windows).</para>
333
334 <para>To check whether your <literal>GHC_PACKAGE_PATH</literal> setting
335 is doing the right thing, <literal>ghc-pkg list</literal> will list all
336 the databases in use, in the reverse order they are searched.</para>
337
338 </sect3>
339 </sect2>
340
341 <sect2 id="building-packages">
342 <title>Building a package from Haskell source</title>
343 <indexterm><primary>packages</primary>
344 <secondary>building</secondary></indexterm>
345
346 <para>We don't recommend building packages the hard way. Instead, use the
347 <ulink url="../Cabal/index.html">Cabal</ulink> infrastructure
348 if possible. If your package is particularly complicated or requires a
349 lot of configuration, then you might have to fall back to the low-level
350 mechanisms, so a few hints for those brave souls follow.</para>
351
352 <para>You need to build an "installed package info" file for
353 passing to <literal>ghc-pkg</literal> when installing your
354 package. The contents of this file are described in
355 <xref linkend="installed-pkg-info" />.</para>
356
357 <para>The Haskell code in a package may be built into one or more
358 archive libraries (e.g. <filename>libHSfoo.a</filename>), or a
359 single shared object
360 (e.g. <filename>libHSfoo.dll/.so/.dylib</filename>). The
361 restriction to a single shared object is because the package
362 system is used to tell the compiler when it should make an
363 inter-shared-object call rather than an intra-shared-object-call
364 call (inter-shared-object calls require an extra
365 indirection).</para>
366 <itemizedlist>
367 <listitem><para>Building a static library is done by using the
368 <literal>ar</literal> tool, like so:</para>
369
370 <screen>ar cqs libHSfoo-1.0.a A.o B.o C.o ...</screen>
371
372 <para>where <filename>A.o</filename>,
373 <filename>B.o</filename> and so on are the compiled Haskell
374 modules, and <filename>libHSfoo.a</filename> is the library you
375 wish to create. The syntax may differ slightly on your system,
376 so check the documentation if you run into difficulties.</para>
377 </listitem>
378 <listitem>
379 <para>Versions of the Haskell libraries for use with GHCi may also
380 abe included: GHCi cannot load <literal>.a</literal> files
381 directly, instead it will look for an object file
382 called <filename>HSfoo.o</filename> and load that. On some
383 systems, the <literal>ghc-pkg</literal> tool can automatically
384 build the GHCi version of each library, see
385 <xref linkend="package-management"/>. To build these libraries
386 by hand from the <literal>.a</literal> archive, it is possible
387 to use GNU <command>ld</command> as follows:</para>
388
389 <screen>ld -r &ndash;&ndash;whole-archive -o HSfoo.o libHSfoo.a</screen>
390
391 <para>(replace
392 <literal>&ndash;&ndash;whole-archive</literal> with
393 <literal>&ndash;all_load</literal> on MacOS X)</para>
394 </listitem>
395 <listitem>
396 <para>When building the package as shared object, GHC wraps
397 out the underlying linker so that the user gets a common
398 interface to all shared object variants that are supported
399 by GHC (DLLs, ELF DSOs, and Mac OS dylibs). The shared
400 object must be named in specific way for two reasons: (1)
401 the name must contain the GHC compiler version, so that two
402 library variants don't collide that are compiled by
403 different versions of GHC and that therefore are most likely
404 incompatible with respect to calling conventions, (2) it
405 must be different from the static name otherwise we would
406 not be able to control the linker as precisely as necessary
407 to make
408 the <option>-static</option>/<option>-dynamic</option> flags
409 work, see <xref linkend="options-linker" />.</para>
410
411 <screen>ghc -shared libHSfoo-1.0-ghc<replaceable>GHCVersion</replaceable>.so A.o B.o C.o</screen>
412 <para>Using GHC's version number in the shared object name
413 allows different library versions compiled by different GHC
414 versions to be installed in standard system locations,
415 e.g. under *nix /usr/lib. To obtain the version number of
416 GHC invoke <literal>ghc --numeric-version</literal> and use
417 its output in place
418 of <replaceable>GHCVersion</replaceable>. See also
419 <xref linkend="options-codegen" /> on how object files must
420 be prepared for shared object linking.</para>
421 </listitem>
422 </itemizedlist>
423
424 <para>GHC does not maintain detailed cross-package dependency
425 information. It does remember which modules in other packages
426 the current module depends on, but not which things within
427 those imported things.</para>
428
429 <para>To compile a module which is to be part of a new package,
430 use the <literal>-package-name</literal> option (<xref linkend="using-packages"/>).
431 Failure to use the <literal>-package-name</literal> option
432 when compiling a package will probably result in disaster, but
433 you will only discover later when you attempt to import modules
434 from the package. At this point GHC will complain that the
435 package name it was expecting the module to come from is not the
436 same as the package name stored in the <literal>.hi</literal>
437 file.</para>
438
439 <para>It is worth noting with shared objects, when each package
440 is built as a single shared object file, since a reference to a shared object costs an extra
441 indirection, intra-package references are cheaper than
442 inter-package references. Of course, this applies to the
443 <filename>main</filename> package as well.</para>
444 </sect2>
445
446 <sect2 id="package-management">
447 <title>Package management (the <literal>ghc-pkg</literal> command)</title>
448 <indexterm><primary>packages</primary>
449 <secondary>management</secondary></indexterm>
450
451 <para>The <literal>ghc-pkg</literal> tool allows packages to be
452 added or removed from a package database. By default,
453 the system-wide package database is modified, but alternatively
454 the user's local package database or another specified
455 file can be used.</para>
456
457 <para>To see what package databases are in use, say
458 <literal>ghc-pkg&nbsp;list</literal>. The stack of databases that
459 <literal>ghc-pkg</literal> knows about can be modified using the
460 <literal>GHC_PACKAGE_PATH</literal> environment variable (see <xref
461 linkend="ghc-package-path" />, and using
462 <literal>--package-conf</literal> options on the
463 <literal>ghc-pkg</literal> command line.</para>
464
465 <para>When asked to modify a database, <literal>ghc-pkg</literal> modifies
466 the global database by default. Specifying <option>--user</option>
467 causes it to act on the user database, or <option>--package-conf</option>
468 can be used to act on another database entirely. When multiple of these
469 options are given, the rightmost one is used as the database to act
470 upon.</para>
471
472 <para>Commands that query the package database (list, latest,
473 describe, field) operate on the list of databases specified by
474 the flags <option>--user</option>, <option>--global</option>, and
475 <option>--package-conf</option>. If none of these flags are
476 given, the default is <option>--global</option>
477 <option>--user</option>.</para>
478
479 <para>If the environment variable <literal>GHC_PACKAGE_PATH</literal> is
480 set, and its value does not end in a separator (<literal>:</literal> on
481 Unix, <literal>;</literal> on Windows), then the last database is
482 considered to be the global database, and will be modified by default by
483 <literal>ghc-pkg</literal>. The intention here is that
484 <literal>GHC_PACKAGE_PATH</literal> can be used to create a virtual
485 package environment into which Cabal packages can be installed without
486 setting anything other than <literal>GHC_PACKAGE_PATH</literal>.</para>
487
488 <para>The <literal>ghc-pkg</literal> program may be run in the ways listed
489 below. Where a package name is required, the package can be named in
490 full including the version number
491 (e.g. <literal>network-1.0</literal>), or without the version number.
492 Naming a package without the version number matches all versions of the
493 package; the specified action will be applied to all the matching
494 packages. A package specifier that matches all version of the package
495 can also be written <replaceable>pkg</replaceable><literal>-*</literal>,
496 to make it clearer that multiple packages are being matched.</para>
497
498 <variablelist>
499 <varlistentry>
500 <term><literal>ghc-pkg register <replaceable>file</replaceable></literal></term>
501 <listitem>
502 <para>Reads a package specification from
503 <replaceable>file</replaceable> (which may be &ldquo;<literal>-</literal>&rdquo;
504 to indicate standard input),
505 and adds it to the database of installed packages. The syntax of
506 <replaceable>file</replaceable> is given in <xref
507 linkend="installed-pkg-info" />.</para>
508
509 <para>The package specification must be a package that isn't already
510 installed.</para>
511 </listitem>
512 </varlistentry>
513
514 <varlistentry>
515 <term><literal>ghc-pkg update <replaceable>file</replaceable></literal></term>
516 <listitem>
517 <para>The same as <literal>register</literal>, except that if a
518 package of the same name is already installed, it is
519 replaced by the new one.</para>
520 </listitem>
521 </varlistentry>
522
523 <varlistentry>
524 <term><literal>ghc-pkg unregister <replaceable>P</replaceable></literal></term>
525 <listitem>
526 <para>Remove the specified package from the database.</para>
527 </listitem>
528 </varlistentry>
529
530 <varlistentry>
531 <term><literal>ghc-pkg expose <replaceable>P</replaceable></literal></term>
532 <listitem>
533 <para>Sets the <literal>exposed</literal> flag for package
534 <replaceable>P</replaceable> to <literal>True</literal>.</para>
535 </listitem>
536 </varlistentry>
537
538 <varlistentry>
539 <term><literal>ghc-pkg check</literal></term>
540 <listitem>
541 <para>Check consistency of dependencies in the package
542 database, and report packages that have missing
543 dependencies.</para>
544 </listitem>
545 </varlistentry>
546
547 <varlistentry>
548 <term><literal>ghc-pkg hide <replaceable>P</replaceable></literal></term>
549 <listitem>
550 <para>Sets the <literal>exposed</literal> flag for package
551 <replaceable>P</replaceable> to <literal>False</literal>.</para>
552 </listitem>
553 </varlistentry>
554
555 <varlistentry>
556 <term><literal>ghc-pkg list [<replaceable>P</replaceable>] [<option>--simple-output</option>]</literal></term>
557 <listitem>
558 <para>This option displays the currently installed
559 packages, for each of the databases known to
560 <literal>ghc-pkg</literal>. That includes the global database, the
561 user's local database, and any further files specified using the
562 <option>-f</option> option on the command line.</para>
563
564 <para>Hidden packages (those for which the <literal>exposed</literal>
565 flag is <literal>False</literal>) are shown in parentheses in the
566 list of packages.</para>
567
568 <para>If an optional package identifier <replaceable>P</replaceable>
569 is given, then only packages matching that identifier are
570 shown.</para>
571
572 <para>If the option <option>--simple-output</option> is given, then
573 the packages are listed on a single line separated by spaces, and
574 the database names are not included. This is intended to make it
575 easier to parse the output of <literal>ghc-pkg list</literal> using
576 a script.</para>
577 </listitem>
578 </varlistentry>
579
580 <varlistentry>
581 <term><literal>ghc-pkg find-module <replaceable>M</replaceable> [<option>--simple-output</option>]</literal></term>
582 <listitem>
583 <para>This option lists registered packages exposing module
584 <replaceable>M</replaceable>. Examples:</para>
585 <screen>
586 $ ghc-pkg find-module Var
587 c:/fptools/validate/ghc/driver/package.conf.inplace:
588 (ghc-6.9.20080428)
589
590 $ ghc-pkg find-module Data.Sequence
591 c:/fptools/validate/ghc/driver/package.conf.inplace:
592 containers-0.1
593 </screen>
594 <para>Otherwise, it behaves like <literal>ghc-pkg list</literal>,
595 including options.</para>
596 </listitem>
597 </varlistentry>
598
599
600 <varlistentry>
601 <term><literal>ghc-pkg latest <replaceable>P</replaceable></literal></term>
602 <listitem>
603 <para>Prints the latest available version of package
604 <replaceable>P</replaceable>.</para>
605 </listitem>
606 </varlistentry>
607
608 <varlistentry>
609 <term><literal>ghc-pkg describe <replaceable>P</replaceable></literal></term>
610 <listitem>
611 <para>Emit the full description of the specified package. The
612 description is in the form of an
613 <literal>InstalledPackageInfo</literal>, the same as the input file
614 format for <literal>ghc-pkg register</literal>. See <xref
615 linkend="installed-pkg-info" /> for details.</para>
616
617 <para>If the pattern matches multiple packages, the
618 description for each package is emitted, separated by the
619 string <literal>---</literal> on a line by itself.</para>
620 </listitem>
621 </varlistentry>
622
623 <varlistentry>
624 <term><literal>ghc-pkg field <replaceable>P</replaceable> <replaceable>field</replaceable>[,<replaceable>field</replaceable>]*</literal></term>
625 <listitem>
626 <para>Show just a single field of the installed package description
627 for <literal>P</literal>. Multiple fields can be selected by separating
628 them with commas</para>
629 </listitem>
630 </varlistentry>
631
632 <varlistentry>
633 <term><literal>ghc-pkg dump</literal></term>
634 <listitem>
635 <para>Emit the full description of every package, in the
636 form of an <literal>InstalledPackageInfo</literal>.
637 Multiple package descriptions are separated by the
638 string <literal>---</literal> on a line by itself.</para>
639
640 <para>This is almost the same as <literal>ghc-pkg describe '*'</literal>, except that <literal>ghc-pkg dump</literal>
641 is intended for use by tools that parse the results, so
642 for example where <literal>ghc-pkg describe '*'</literal>
643 will emit an error if it can't find any packages that
644 match the pattern, <literal>ghc-pkg dump</literal> will
645 simply emit nothing.</para>
646 </listitem>
647 </varlistentry>
648 </variablelist>
649
650 <para>
651 Substring matching is supported for <replaceable>M</replaceable> in
652 <literal>find-module</literal> and for <replaceable>P</replaceable> in
653 <literal>list</literal>, <literal>describe</literal>, and
654 <literal>field</literal>, where a <literal>'*'</literal> indicates open
655 substring ends (<literal>prefix*</literal>, <literal>*suffix</literal>,
656 <literal>*infix*</literal>). Examples (output omitted):
657 </para>
658 <screen>
659 -- list all regex-related packages
660 ghc-pkg list '*regex*' --ignore-case
661 -- list all string-related packages
662 ghc-pkg list '*string*' --ignore-case
663 -- list OpenGL-related packages
664 ghc-pkg list '*gl*' --ignore-case
665 -- list packages exporting modules in the Data hierarchy
666 ghc-pkg find-module 'Data.*'
667 -- list packages exporting Monad modules
668 ghc-pkg find-module '*Monad*'
669 -- list names and maintainers for all packages
670 ghc-pkg field '*' name,maintainer
671 -- list location of haddock htmls for all packages
672 ghc-pkg field '*' haddock-html
673 -- dump the whole database
674 ghc-pkg describe '*'
675 </screen>
676
677 <para>Additionally, the following flags are accepted by
678 <literal>ghc-pkg</literal>:</para>
679
680 <variablelist>
681 <varlistentry>
682 <term>
683 <option>&ndash;&ndash;auto-ghci-libs</option><indexterm><primary><option>&ndash;&ndash;auto-ghci-libs</option></primary>
684 </indexterm>
685 </term>
686 <listitem>
687 <para>Automatically generate the GHCi
688 <filename>.o</filename> version of each
689 <filename>.a</filename> Haskell library, using GNU ld (if
690 that is available). Without this option,
691 <literal>ghc-pkg</literal> will warn if GHCi versions of
692 any Haskell libraries in the package don't exist.</para>
693
694 <para>GHCi <literal>.o</literal> libraries don't
695 necessarily have to live in the same directory as the
696 corresponding <literal>.a</literal> library. However,
697 this option will cause the GHCi library to be created in
698 the same directory as the <literal>.a</literal>
699 library.</para>
700 </listitem>
701 </varlistentry>
702
703 <varlistentry>
704 <term>
705 <option>-f</option> <replaceable>file</replaceable>
706 <indexterm><primary><option>-f</option></primary>
707 </indexterm>
708 </term>
709 <term>
710 <option>-package-conf</option> <replaceable>file</replaceable>
711 <indexterm><primary><option>-package-conf</option></primary>
712 </indexterm>
713 </term>
714 <listitem>
715 <para>Adds <replaceable>file</replaceable> to the stack of package
716 databases. Additionally, <replaceable>file</replaceable> will
717 also be the database modified by a <literal>register</literal>,
718 <literal>unregister</literal>, <literal>expose</literal> or
719 <literal>hide</literal> command, unless it is overridden by a later
720 <option>--package-conf</option>, <option>--user</option> or
721 <option>--global</option> option.</para>
722 </listitem>
723 </varlistentry>
724
725 <varlistentry>
726 <term>
727 <option>&ndash;&ndash;force</option>
728 <indexterm><primary>
729 <option>&ndash;&ndash;force</option>
730 </primary></indexterm>
731 </term>
732 <listitem>
733 <para>Causes <literal>ghc-pkg</literal> to ignore missing
734 dependencies, directories and libraries when registering a package,
735 and just go ahead and add it anyway. This might be useful if your
736 package installation system needs to add the package to
737 GHC before building and installing the files.</para>
738 </listitem>
739 </varlistentry>
740
741 <varlistentry>
742 <term>
743 <option>&ndash;&ndash;global</option><indexterm><primary><option>&ndash;&ndash;global</option></primary>
744 </indexterm>
745 </term>
746 <listitem>
747 <para>Operate on the global package database (this is the default).
748 This flag affects the <literal>register</literal>,
749 <literal>update</literal>, <literal>unregister</literal>,
750 <literal>expose</literal>, and <literal>hide</literal>
751 commands.</para>
752 </listitem>
753 </varlistentry>
754
755 <varlistentry>
756 <term>
757 <option>&ndash;&ndash;help</option><indexterm><primary><option>&ndash;&ndash;help</option></primary>
758 </indexterm>
759 </term>
760 <term>
761 <option>-?</option><indexterm><primary><option>-?</option></primary>
762 </indexterm>
763 </term>
764 <listitem>
765 <para>Outputs the command-line syntax.</para>
766 </listitem>
767 </varlistentry>
768
769 <varlistentry>
770 <term>
771 <option>&ndash;&ndash;user</option><indexterm><primary><option>&ndash;&ndash;user</option></primary>
772 </indexterm>
773 </term>
774 <listitem>
775 <para>Operate on the current user's local package database.
776 This flag affects the <literal>register</literal>,
777 <literal>update</literal>, <literal>unregister</literal>,
778 <literal>expose</literal>, and <literal>hide</literal>
779 commands.</para>
780 </listitem>
781 </varlistentry>
782
783 <varlistentry>
784 <term>
785 <option>-V</option><indexterm><primary><option>-V</option></primary>
786 </indexterm>
787 </term>
788 <term>
789 <option>&ndash;&ndash;version</option><indexterm><primary><option>&ndash;&ndash;version</option></primary>
790 </indexterm>
791 </term>
792 <listitem>
793 <para>Output the <literal>ghc-pkg</literal> version number.</para>
794 </listitem>
795 </varlistentry>
796 </variablelist>
797
798 <para>When modifying the package database
799 <replaceable>file</replaceable>, a copy of the original file is
800 saved in <replaceable>file</replaceable><literal>.old</literal>,
801 so in an emergency you can always restore the old settings by
802 copying the old file back again.</para>
803
804 </sect2>
805
806 <sect2 id="installed-pkg-info">
807 <title>
808 <literal>InstalledPackageInfo</literal>: a package specification
809 </title>
810
811 <para>A package specification is a Haskell record; in particular, it is the
812 record <ulink
813 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>
814
815 <para>An <literal>InstalledPackageInfo</literal> has a human
816 readable/writable syntax. The functions
817 <literal>parseInstalledPackageInfo</literal> and
818 <literal>showInstalledPackageInfo</literal> read and write this syntax
819 respectively. Here's an example of the
820 <literal>InstalledPackageInfo</literal> for the <literal>unix</literal> package:</para>
821
822 <screen>
823 $ ghc-pkg describe unix
824 name: unix
825 version: 1.0
826 license: BSD3
827 copyright:
828 maintainer: libraries@haskell.org
829 stability:
830 homepage:
831 package-url:
832 description:
833 category:
834 author:
835 exposed: True
836 exposed-modules: System.Posix,
837 System.Posix.DynamicLinker.Module,
838 System.Posix.DynamicLinker.Prim,
839 System.Posix.Directory,
840 System.Posix.DynamicLinker,
841 System.Posix.Env,
842 System.Posix.Error,
843 System.Posix.Files,
844 System.Posix.IO,
845 System.Posix.Process,
846 System.Posix.Resource,
847 System.Posix.Temp,
848 System.Posix.Terminal,
849 System.Posix.Time,
850 System.Posix.Unistd,
851 System.Posix.User,
852 System.Posix.Signals.Exts
853 import-dirs: /usr/lib/ghc-6.4/libraries/unix
854 library-dirs: /usr/lib/ghc-6.4/libraries/unix
855 hs-libraries: HSunix
856 extra-libraries: HSunix_cbits, dl
857 include-dirs: /usr/lib/ghc-6.4/libraries/unix/include
858 includes: HsUnix.h
859 depends: base-1.0
860 </screen>
861
862 <para>The full <ulink url="../Cabal/index.html">Cabal documentation</ulink>
863 is still in preparation (at time of writing), so in the meantime
864 here is a brief description of the syntax of this file:</para>
865
866 <para>A package description consists of a number of field/value pairs. A
867 field starts with the field name in the left-hand column followed by a
868 &ldquo;<literal>:</literal>&rdquo;, and the value continues until the next line that begins in the
869 left-hand column, or the end of file.</para>
870
871 <para>The syntax of the value depends on the field. The various field
872 types are:</para>
873
874 <variablelist>
875 <varlistentry>
876 <term>freeform</term>
877 <listitem>
878 <para>Any arbitrary string, no interpretation or parsing is
879 done.</para>
880 </listitem>
881 </varlistentry>
882 <varlistentry>
883 <term>string</term>
884 <listitem>
885 <para>A sequence of non-space characters, or a sequence of arbitrary
886 characters surrounded by quotes <literal>"...."</literal>.</para>
887 </listitem>
888 </varlistentry>
889 <varlistentry>
890 <term>string list</term>
891 <listitem>
892 <para>A sequence of strings, separated by commas. The sequence may
893 be empty.</para>
894 </listitem>
895 </varlistentry>
896 </variablelist>
897
898 <para>In addition, there are some fields with special syntax (e.g. package
899 names, version, dependencies).</para>
900
901 <para>The allowed fields, with their types, are:</para>
902
903 <variablelist>
904 <varlistentry>
905 <term>
906 <literal>name</literal>
907 <indexterm><primary><literal>name</literal></primary><secondary>package specification</secondary></indexterm>
908 </term>
909 <listitem>
910 <para>The package's name (without the version).</para>
911 </listitem>
912 </varlistentry>
913
914 <varlistentry>
915 <term>
916 <literal>version</literal>
917 <indexterm><primary><literal>version</literal></primary><secondary>package specification</secondary></indexterm>
918 </term>
919 <listitem>
920 <para>The package's version, usually in the form
921 <literal>A.B</literal> (any number of components are allowed).</para>
922 </listitem>
923 </varlistentry>
924
925 <varlistentry>
926 <term>
927 <literal>license</literal>
928 <indexterm><primary><literal>auto</literal></primary><secondary>package specification</secondary></indexterm>
929 </term>
930 <listitem>
931 <para>(string) The type of license under which this package is distributed.
932 This field is a value of the <ulink
933 url="../libraries/Cabal/Distribution-License.html#t:License"><literal>License</literal></ulink> type.</para>
934 </listitem>
935 </varlistentry>
936
937 <varlistentry>
938 <term>
939 <literal>license-file</literal>
940 <indexterm><primary><literal>license-file</literal></primary><secondary>package specification</secondary></indexterm>
941 </term>
942 <listitem>
943 <para>(optional string) The name of a file giving detailed license
944 information for this package.</para>
945 </listitem>
946 </varlistentry>
947
948 <varlistentry>
949 <term>
950 <literal>copyright</literal>
951 <indexterm><primary><literal>copyright</literal></primary><secondary>package specification</secondary></indexterm>
952 </term>
953 <listitem>
954 <para>(optional freeform) The copyright string.</para>
955 </listitem>
956 </varlistentry>
957
958 <varlistentry>
959 <term>
960 <literal>maintainer</literal>
961 <indexterm><primary><literal>maintainer</literal></primary><secondary>package specification</secondary></indexterm>
962 </term>
963 <listitem>
964 <para>(optinoal freeform) The email address of the package's maintainer.</para>
965 </listitem>
966 </varlistentry>
967
968 <varlistentry>
969 <term>
970 <literal>stability</literal>
971 <indexterm><primary><literal>stability</literal></primary><secondary>package specification</secondary></indexterm>
972 </term>
973 <listitem>
974 <para>(optional freeform) A string describing the stability of the package
975 (eg. stable, provisional or experimental).</para>
976 </listitem>
977 </varlistentry>
978
979 <varlistentry>
980 <term>
981 <literal>homepage</literal>
982 <indexterm><primary><literal>homepage</literal></primary><secondary>package specification</secondary></indexterm>
983 </term>
984 <listitem>
985 <para>(optional freeform) URL of the package's home page.</para>
986 </listitem>
987 </varlistentry>
988
989 <varlistentry>
990 <term>
991 <literal>package-url</literal>
992 <indexterm><primary><literal>package-url</literal></primary><secondary>package specification</secondary></indexterm>
993 </term>
994 <listitem>
995 <para>(optional freeform) URL of a downloadable distribution for this
996 package. The distribution should be a Cabal package.</para>
997 </listitem>
998 </varlistentry>
999
1000 <varlistentry>
1001 <term>
1002 <literal>description</literal>
1003 <indexterm><primary><literal>description</literal></primary><secondary>package specification</secondary></indexterm>
1004 </term>
1005 <listitem>
1006 <para>(optional freeform) Description of the package.</para>
1007 </listitem>
1008 </varlistentry>
1009
1010 <varlistentry>
1011 <term>
1012 <literal>category</literal>
1013 <indexterm><primary><literal>category</literal></primary><secondary>package specification</secondary></indexterm>
1014 </term>
1015 <listitem>
1016 <para>(optinoal freeform) Which category the package belongs to. This field
1017 is for use in conjunction with a future centralised package
1018 distribution framework, tentatively titled Hackage.</para>
1019 </listitem>
1020 </varlistentry>
1021
1022 <varlistentry>
1023 <term>
1024 <literal>author</literal>
1025 <indexterm><primary><literal>author</literal></primary><secondary>package specification</secondary></indexterm>
1026 </term>
1027 <listitem>
1028 <para>(optional freeform) Author of the package.</para>
1029 </listitem>
1030 </varlistentry>
1031
1032 <varlistentry>
1033 <term>
1034 <literal>exposed</literal>
1035 <indexterm><primary><literal>exposed</literal></primary><secondary>package specification</secondary></indexterm>
1036 </term>
1037 <listitem>
1038 <para>(bool) Whether the package is exposed or not.</para>
1039 </listitem>
1040 </varlistentry>
1041
1042 <varlistentry>
1043 <term>
1044 <literal>exposed-modules</literal>
1045 <indexterm><primary><literal>exposed-modules</literal></primary><secondary>package specification</secondary></indexterm>
1046 </term>
1047 <listitem>
1048 <para>(string list) modules exposed by this package.</para>
1049 </listitem>
1050 </varlistentry>
1051
1052 <varlistentry>
1053 <term>
1054 <literal>hidden-modules</literal>
1055 <indexterm><primary><literal>hidden-modules</literal></primary><secondary>package specification</secondary></indexterm>
1056 </term>
1057 <listitem>
1058 <para>(string list) modules provided by this package,
1059 but not exposed to the programmer. These modules cannot be
1060 imported, but they are still subject to the overlapping constraint:
1061 no other package in the same program may provide a module of the
1062 same name.</para>
1063 </listitem>
1064 </varlistentry>
1065
1066 <varlistentry>
1067 <term>
1068 <literal>import-dirs</literal>
1069 <indexterm><primary><literal>import-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1070 </term>
1071 <listitem>
1072 <para>(string list) A list of directories containing interface files
1073 (<literal>.hi</literal> files) for this package.</para>
1074
1075 <para>If the package contains profiling libraries, then
1076 the interface files for those library modules should have
1077 the suffix <literal>.p_hi</literal>. So the package can
1078 contain both normal and profiling versions of the same
1079 library without conflict (see also
1080 <literal>library_dirs</literal> below).</para>
1081 </listitem>
1082 </varlistentry>
1083
1084 <varlistentry>
1085 <term>
1086 <literal>library-dirs</literal>
1087 <indexterm><primary><literal>library-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1088 </term>
1089 <listitem>
1090 <para>(string list) A list of directories containing libraries for this
1091 package.</para>
1092 </listitem>
1093 </varlistentry>
1094
1095 <varlistentry>
1096 <term>
1097 <literal>hs-libraries</literal>
1098 <indexterm><primary><literal>hs-libraries</literal></primary><secondary>package specification</secondary></indexterm>
1099 </term>
1100 <listitem>
1101 <para>(string list) A list of libraries containing Haskell code for this
1102 package, with the <literal>.a</literal> or
1103 <literal>.dll</literal> suffix omitted. When packages are
1104 built as libraries, the
1105 <literal>lib</literal> prefix is also omitted.</para>
1106
1107 <para>For use with GHCi, each library should have an
1108 object file too. The name of the object file does
1109 <emphasis>not</emphasis> have a <literal>lib</literal>
1110 prefix, and has the normal object suffix for your
1111 platform.</para>
1112
1113 <para>For example, if we specify a Haskell library as
1114 <filename>HSfoo</filename> in the package spec, then the
1115 various flavours of library that GHC actually uses will be
1116 called:</para>
1117 <variablelist>
1118 <varlistentry>
1119 <term><filename>libHSfoo.a</filename></term>
1120 <listitem>
1121 <para>The name of the library on Unix and Windows
1122 (mingw) systems. Note that we don't support
1123 building dynamic libraries of Haskell code on Unix
1124 systems.</para>
1125 </listitem>
1126 </varlistentry>
1127 <varlistentry>
1128 <term><filename>HSfoo.dll</filename></term>
1129 <listitem>
1130 <para>The name of the dynamic library on Windows
1131 systems (optional).</para>
1132 </listitem>
1133 </varlistentry>
1134 <varlistentry>
1135 <term><filename>HSfoo.o</filename></term>
1136 <term><filename>HSfoo.obj</filename></term>
1137 <listitem>
1138 <para>The object version of the library used by
1139 GHCi.</para>
1140 </listitem>
1141 </varlistentry>
1142 </variablelist>
1143 </listitem>
1144 </varlistentry>
1145
1146 <varlistentry>
1147 <term>
1148 <literal>extra-libraries</literal>
1149 <indexterm><primary><literal>extra-libraries</literal></primary><secondary>package specification</secondary></indexterm>
1150 </term>
1151 <listitem>
1152 <para>(string list) A list of extra libraries for this package. The
1153 difference between <literal>hs-libraries</literal> and
1154 <literal>extra-libraries</literal> is that
1155 <literal>hs-libraries</literal> normally have several
1156 versions, to support profiling, parallel and other build
1157 options. The various versions are given different
1158 suffixes to distinguish them, for example the profiling
1159 version of the standard prelude library is named
1160 <filename>libHSbase_p.a</filename>, with the
1161 <literal>_p</literal> indicating that this is a profiling
1162 version. The suffix is added automatically by GHC for
1163 <literal>hs-libraries</literal> only, no suffix is added
1164 for libraries in
1165 <literal>extra-libraries</literal>.</para>
1166
1167 <para>The libraries listed in
1168 <literal>extra-libraries</literal> may be any libraries
1169 supported by your system's linker, including dynamic
1170 libraries (<literal>.so</literal> on Unix,
1171 <literal>.DLL</literal> on Windows).</para>
1172
1173 <para>Also, <literal>extra-libraries</literal> are placed
1174 on the linker command line after the
1175 <literal>hs-libraries</literal> for the same package. If
1176 your package has dependencies in the other direction (i.e.
1177 <literal>extra-libraries</literal> depends on
1178 <literal>hs-libraries</literal>), and the libraries are
1179 static, you might need to make two separate
1180 packages.</para>
1181 </listitem>
1182 </varlistentry>
1183
1184 <varlistentry>
1185 <term>
1186 <literal>include-dirs</literal>
1187 <indexterm><primary><literal>include-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1188 </term>
1189 <listitem>
1190 <para>(string list) A list of directories containing C includes for this
1191 package.</para>
1192 </listitem>
1193 </varlistentry>
1194
1195 <varlistentry>
1196 <term>
1197 <literal>includes</literal>
1198 <indexterm><primary><literal>includes</literal></primary><secondary>package specification</secondary></indexterm>
1199 </term>
1200 <listitem>
1201 <para>(string list) A list of files to include for via-C compilations
1202 using this package. Typically the include file(s) will
1203 contain function prototypes for any C functions used in
1204 the package, in case they end up being called as a result
1205 of Haskell functions from the package being
1206 inlined.</para>
1207 </listitem>
1208 </varlistentry>
1209
1210 <varlistentry>
1211 <term>
1212 <literal>depends</literal>
1213 <indexterm><primary><literal>depends</literal></primary><secondary>package specification</secondary></indexterm>
1214 </term>
1215 <listitem>
1216 <para>(package name list) Packages on which this package depends. This field contains
1217 packages with explicit versions are required, except that when
1218 submitting a package to <literal>ghc-pkg register</literal>, the
1219 versions will be filled in if they are unambiguous.</para>
1220 </listitem>
1221 </varlistentry>
1222
1223 <varlistentry>
1224 <term>
1225 <literal>hugs-options</literal>
1226 <indexterm><primary><literal>hugs-options</literal></primary><secondary>package specification</secondary></indexterm>
1227 </term>
1228 <listitem>
1229 <para>(string list) Options to pass to Hugs for this package.</para>
1230 </listitem>
1231 </varlistentry>
1232
1233 <varlistentry>
1234 <term>
1235 <literal>cc-options</literal>
1236 <indexterm><primary><literal>cc-options</literal></primary><secondary>package specification</secondary></indexterm>
1237 </term>
1238 <listitem>
1239 <para>(string list) Extra arguments to be added to the gcc command line
1240 when this package is being used (only for via-C
1241 compilations).</para>
1242 </listitem>
1243 </varlistentry>
1244
1245 <varlistentry>
1246 <term>
1247 <literal>ld-options</literal>
1248 <indexterm><primary><literal>ld-options</literal></primary><secondary>package specification</secondary></indexterm>
1249 </term>
1250 <listitem>
1251 <para>(string list) Extra arguments to be added to the
1252 <command>gcc</command> command line (for linking) when
1253 this package is being used.</para>
1254 </listitem>
1255 </varlistentry>
1256
1257 <varlistentry>
1258 <term>
1259 <literal>framework-dirs</literal>
1260 <indexterm><primary><literal>framework-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1261 </term>
1262 <listitem>
1263 <para>(string list) On Darwin/MacOS X, a list of directories containing
1264 frameworks for this package. This corresponds to the
1265 <option>-framework-path</option> option. It is ignored on all other
1266 platforms.</para>
1267 </listitem>
1268 </varlistentry>
1269
1270 <varlistentry>
1271 <term>
1272 <literal>frameworks</literal>
1273 <indexterm><primary><literal>frameworks</literal></primary><secondary>package specification</secondary></indexterm>
1274 </term>
1275 <listitem>
1276 <para>(string list) On Darwin/MacOS X, a list of frameworks to link to. This
1277 corresponds to the <option>-framework</option> option. Take a look
1278 at Apple's developer documentation to find out what frameworks
1279 actually are. This entry is ignored on all other platforms.</para>
1280 </listitem>
1281 </varlistentry>
1282
1283 <varlistentry>
1284 <term>
1285 <literal>haddock-interfaces</literal>
1286 <indexterm><primary><literal>haddock-interfaces</literal></primary><secondary>package specification</secondary></indexterm>
1287 </term>
1288 <listitem>
1289 <para>(string list) A list of filenames containing <ulink
1290 url="http://www.haskell.org/haddock/">Haddock</ulink> interface
1291 files (<literal>.haddock</literal> files) for this package.</para>
1292 </listitem>
1293 </varlistentry>
1294
1295 <varlistentry>
1296 <term>
1297 <literal>haddock-html</literal>
1298 <indexterm><primary><literal>haddock-html</literal></primary><secondary>package specification</secondary></indexterm>
1299 </term>
1300 <listitem>
1301 <para>(optional string) The directory containing the Haddock-generated HTML
1302 for this package.</para>
1303 </listitem>
1304 </varlistentry>
1305 </variablelist>
1306
1307 <!-- This isn't true any more. I'm not sure if we still need it -SDM
1308 <para>
1309 The <literal>ghc-pkg</literal> tool performs expansion of
1310 environment variables occurring in input package specifications.
1311 So, if the <literal>mypkg</literal> was added to the package
1312 database as follows:
1313 </para>
1314 <screen>
1315 $ installdir=/usr/local/lib ghc-pkg -a &lt; mypkg.pkg
1316 </screen>
1317
1318 <para>
1319 The occurrence of <literal>${installdir}</literal> is replaced
1320 with <literal>/usr/local/lib</literal> in the package data that
1321 is added for <literal>mypkg</literal>.
1322 </para>
1323
1324 <para>
1325 This feature enables the distribution of package specification
1326 files that can be easily configured when installing.
1327 </para>
1328
1329 <para>For examples of more package specifications, take a look
1330 at the <literal>package.conf</literal> in your GHC
1331 installation.</para>
1332
1333 -->
1334
1335 </sect2>
1336 </sect1>
1337
1338 <!-- Emacs stuff:
1339 ;;; Local Variables: ***
1340 ;;; mode: xml ***
1341 ;;; sgml-parent-document: ("users_guide.xml" "book" "chapter" "sect1") ***
1342 ;;; End: ***
1343 -->