+++ /dev/null
-<?xml version="1.0" encoding="iso-8859-1"?>
-<chapter id="introduction-GHC">
- <title>Introduction to GHC</title>
-
- <para>This is a guide to using the Glasgow Haskell Compiler (GHC):
- an interactive and batch compilation system for the <ulink
- url="http://www.haskell.org/">Haskell 98</ulink>
- language.</para>
-
- <para>GHC has two main components: an interactive Haskell
- interpreter (also known as GHCi), described in <xref
- linkend="ghci"/>, and a batch compiler, described throughout <xref
- linkend="using-ghc"/>. In fact, GHC consists of a single program
- which is just run with different options to provide either the
- interactive or the batch system.</para>
-
- <para>The batch compiler can be used alongside GHCi: compiled
- modules can be loaded into an interactive session and used in the
- same way as interpreted code, and in fact when using GHCi most of
- the library code will be pre-compiled. This means you get the best
- of both worlds: fast pre-compiled library code, and fast compile
- turnaround for the parts of your program being actively
- developed.</para>
-
- <para>GHC supports numerous language extensions, including
- concurrency, a foreign function interface, exceptions, type system
- extensions such as multi-parameter type classes, local universal and
- existential quantification, functional dependencies, scoped type
- variables and explicit unboxed types. These are all described in
- <xref linkend="ghc-language-features"/>.</para>
-
- <para>GHC has a comprehensive optimiser, so when you want to Really
- Go For It (and you've got time to spare) GHC can produce pretty fast
- code. Alternatively, the default option is to compile as fast as
- possible while not making too much effort to optimise the generated
- code (although GHC probably isn't what you'd describe as a fast
- compiler :-).</para>
-
- <para>GHC's profiling system supports “cost centre
- stacks”: a way of seeing the profile of a Haskell program in a
- call-graph like structure. See <xref linkend="profiling"/> for more
- details.</para>
-
- <para>GHC comes with a large collection of libraries, with
- everything from parser combinators to networking. The libraries are
- described in separate documentation.</para>
-
- <sect1 id="mailing-lists-GHC">
- <title>Meta-information: Web sites, mailing lists, etc.</title>
-
- <indexterm><primary>mailing lists, Glasgow Haskell</primary></indexterm>
- <indexterm><primary>Glasgow Haskell mailing lists</primary></indexterm>
-
- <para>On the World-Wide Web, there are several URLs of likely
- interest:</para>
-
- <itemizedlist>
- <listitem>
- <para><ulink url="http://www.haskell.org/" >Haskell home
- page</ulink></para>
- </listitem>
-
- <listitem>
- <para><ulink url="http://www.haskell.org/ghc/">GHC home
- page</ulink></para>
- </listitem>
-
- <listitem>
- <para><ulink
- url="http://www.cs.nott.ac.uk/~gmh/faq.html">comp.lang.functional
- FAQ</ulink></para>
- </listitem>
-
- </itemizedlist>
-
- <para>We run the following mailing lists about Glasgow Haskell.
- We encourage you to join, as you feel is appropriate.</para>
-
- <variablelist>
- <varlistentry>
- <term>glasgow-haskell-users:</term>
- <listitem>
- <para>This list is for GHC users to chat among themselves.
- If you have a specific question about GHC, please check the
- <ulink
- url="http://hackage.haskell.org/trac/ghc/wiki/FAQ">FAQ</ulink>
- first.</para>
-
- <variablelist>
- <varlistentry>
- <term>list email address:</term>
- <listitem>
- <para><email>glasgow-haskell-users@haskell.org</email></para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>subscribe at:</term>
- <listitem>
- <para><ulink
- url="http://www.haskell.org/mailman/listinfo/glasgow-haskell-users"><literal>http://www.haskell.org/mailman/listinfo/glasgow-haskell-users</literal></ulink>.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>admin email address:</term>
- <listitem>
- <para><email>glasgow-haskell-users-admin@haskell.org</email></para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>list archives:</term>
- <listitem>
- <para><ulink
- url="http://www.haskell.org/pipermail/glasgow-haskell-users/"><literal>http://www.haskell.org/pipermail/glasgow-haskell-users/</literal></ulink></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>glasgow-haskell-bugs:</term>
- <listitem>
- <para>Send bug reports for GHC to this address! The sad and
- lonely people who subscribe to this list will muse upon
- what's wrong and what you might do about it.</para>
-
- <variablelist>
- <varlistentry>
- <term>list email address:</term>
- <listitem>
- <para><email>glasgow-haskell-bugs@haskell.org</email></para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>subscribe at:</term>
- <listitem>
- <para><ulink
- url="http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs"><literal>http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs</literal></ulink>.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>admin email address:</term>
- <listitem>
- <para><email>glasgow-haskell-bugs-admin@haskell.org</email></para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>list archives:</term>
- <listitem>
- <para><ulink
- url="http://www.haskell.org/pipermail/glasgow-haskell-bugs/"><literal>http://www.haskell.org/pipermail/glasgow-haskell-bugs/</literal></ulink></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>cvs-ghc:</term>
- <listitem>
- <para>The hardcore GHC developers hang out here. This list
- also gets commit message from the CVS repository. There are
- several other similar lists for other parts of the CVS
- repository (eg. <literal>cvs-hslibs</literal>,
- <literal>cvs-happy</literal>, <literal>cvs-hdirect</literal>
- etc.)</para>
-
- <variablelist>
- <varlistentry>
- <term>list email address:</term>
- <listitem>
- <para><email>cvs-ghc@haskell.org</email></para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>subscribe at:</term>
- <listitem>
- <para><ulink
- url="http://www.haskell.org/mailman/listinfo/cvs-ghc"><literal>http://www.haskell.org/mailman/listinfo/cvs-ghc</literal></ulink>.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>admin email address:</term>
- <listitem>
- <para><email>cvs-ghc-admin@haskell.org</email></para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>list archives:</term>
- <listitem>
- <para><ulink
- url="http://www.haskell.org/pipermail/cvs-ghc/"><literal>http://www.haskell.org/pipermail/cvs-ghc/</literal></ulink></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>There are several other haskell and GHC-related mailing
- lists served by <literal>www.haskell.org</literal>. Go to <ulink
- url="http://www.haskell.org/mailman/listinfo/"><literal>http://www.haskell.org/mailman/listinfo/</literal></ulink>
- for the full list.</para>
-
- <para>Some Haskell-related discussion also takes place in the
- Usenet newsgroup <literal>comp.lang.functional</literal>.</para>
-
- </sect1>
-
- <sect1 id="bug-reporting">
- <title>Reporting bugs in GHC</title>
- <indexterm><primary>bugs</primary><secondary>reporting</secondary>
- </indexterm>
- <indexterm><primary>reporting bugs</primary>
- </indexterm>
-
- <para>Glasgow Haskell is a changing system so there are sure to be
- bugs in it. </para>
-
- <para>To report a bug, either:</para>
-
- <itemizedlist>
- <listitem>
- <para>Preferred: <ulink
- url="http://hackage.haskell.org/trac/ghc/newticket?type=bug">Create
- a new bug</ulink>, and enter your bug report. You can also
- search the bug database here to make sure your bug hasn't already
- been reported (if it has, it might still help to add information
- from your experience to the existing report).</para>
- </listitem>
- <listitem>
- <para>Bug reports can also be emailed to
- <email>glasgow-haskell-bugs@haskell.org</email>. </para>
- </listitem>
- </itemizedlist>
-
- <sect2>
- <title>How do I tell if I should report my bug?</title>
-
- <para>Take a look at the <ulink
- url="http://hackage.haskell.org/trac/ghc/wiki/FAQ">FAQ</ulink> and <xref
- linkend="wrong"/>, which will give you some guidance as to
- whether the behaviour you're seeing is really a bug or
- not.</para>
-
- <para>If it is a bug, then it might have been reported before:
- try searching on the <ulink
- url="http://hackage.haskell.org/trac/ghc">bug tracker</ulink>,
- and failing that, try <ulink
- url="http://www.google.com">Google</ulink>.</para>
-
- <para>If in doubt, just report it.</para>
- </sect2>
-
- <sect2>
- <title>What to put in a bug report</title>
- <indexterm><primary>bug reports</primary><secondary>contents</secondary></indexterm>
-
- <para>The name of the bug-reporting game is: facts, facts,
- facts. Don't omit them because “Oh, they won't be
- interested…”</para>
-
- <orderedlist>
- <listitem>
- <para>What kind of machine are you running on, and exactly
- what version of the operating system are you using? (on a
- Unix system, <command>uname -a</command> or <command>cat
- /etc/motd</command> will show the desired information.) In
- the bug tracker, this information can be given in the
- “Architecture” and “Operating
- system” fields.</para>
- </listitem>
-
- <listitem>
- <para>What version of GCC are you using? <command>gcc -v</command> will tell you.</para>
- </listitem>
-
- <listitem>
- <para>Run the sequence of compiles/runs that caused the
- offending behaviour, cut-and-paste the whole session into
- the bug report. We'd prefer to see the whole thing.</para>
- </listitem>
-
- <listitem>
- <para>Add the -v flag when running GHC, so we can see exactly
- what was run, what versions of things you have, etc.</para>
- </listitem>
-
- <listitem>
- <para>What is the program behaviour that is wrong, in your
- opinion?</para>
- </listitem>
-
- <listitem>
- <para>If practical, please attach or send enough source
- files for us to duplicate the problem.</para>
- </listitem>
-
- <listitem>
- <para>If you are a Hero and track down the problem in the
- compilation-system sources, please send us patches (either
- <literal>darcs send</literal>, plain patches, or just whole
- files if you prefer).</para>
- </listitem>
- </orderedlist>
- </sect2>
- </sect1>
-
- <sect1 id="version-numbering">
- <title>GHC version numbering policy</title>
- <indexterm><primary>version, of ghc</primary></indexterm>
-
- <para>As of GHC version 6.0, we have adopted the following policy
- for numbering GHC versions:</para>
-
- <variablelist>
- <varlistentry>
- <term>Stable Releases</term>
- <listitem>
- <para>These are numbered <literal><replaceable>x</replaceable>.<replaceable>y</replaceable>.<replaceable>z</replaceable></literal>, where
- <replaceable>y</replaceable> is <emphasis>even</emphasis>, and
- <replaceable>z</replaceable> is the patchlevel number (the trailing
- <literal>.<replaceable>z</replaceable></literal> can be omitted if <replaceable>z</replaceable>
- is zero). Patchlevels are bug-fix releases only, and never
- change the programmer interface to any system-supplied code.
- However, if you install a new patchlevel over an old one you
- will need to recompile any code that was compiled against the
- old libraries.</para>
-
- <para>The value of <literal>__GLASGOW_HASKELL__</literal>
- (see <xref linkend="c-pre-processor"/>) for a major release
- <literal><replaceable>x</replaceable>.<replaceable>y</replaceable>.<replaceable>z</replaceable></literal>
- is the integer <replaceable>xyy</replaceable> (if
- <replaceable>y</replaceable> is a single digit, then a leading zero
- is added, so for example in version 6.2 of GHC,
- <literal>__GLASGOW_HASKELL__==602</literal>).</para>
- <indexterm>
- <primary><literal>__GLASGOW_HASKELL__</literal></primary>
- </indexterm>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Snapshots/unstable releases</term>
- <listitem>
- <para>We may make snapshot releases of the current
- development sources from time to time, and the current
- sources are always available via the CVS repository (see the
- <ulink url="http://www.haskell.org/ghc/">GHC web
- site</ulink> for details).</para>
-
- <para>Snapshot releases are named
- <literal><replaceable>x</replaceable>.<replaceable>y</replaceable>.YYYYMMDD</literal>
- where <literal>YYYYMMDD</literal> is the date of the sources
- from which the snapshot was built. In theory, you can check
- out the exact same sources from the CVS repository using
- this date.</para>
-
- <para>If <replaceable>y</replaceable> is odd, then this is a
- snapshot of the CVS HEAD (the main development branch). If
- <replaceable>y</replaceable> is even, then it is a snapshot
- of the stable branch between patchlevel releases. For
- example, <literal>6.3.20040225</literal> would be a snapshot
- of the HEAD, but <literal>6.2.20040225</literal> would be a
- snapshot of the <literal>6.2</literal> branch.</para>
-
- <para>The value of <literal>__GLASGOW_HASKELL__</literal>
- for a snapshot release is the integer
- <replaceable>xyy</replaceable>. You should never write any
- conditional code which tests for this value, however: since
- interfaces change on a day-to-day basis, and we don't have
- finer granularity in the values of
- <literal>__GLASGOW_HASKELL__</literal>, you should only
- conditionally compile using predicates which test whether
- <literal>__GLASGOW_HASKELL__</literal> is equal to, later
- than, or earlier than a given major release.</para>
- <indexterm>
- <primary><literal>__GLASGOW_HASKELL__</literal></primary>
- </indexterm>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>The version number of your copy of GHC can be found by
- invoking <literal>ghc</literal> with the
- <literal>––version</literal> flag (see <xref
- linkend="options-help"/>).</para>
- </sect1>
-
-
-&relnotes;
-
-</chapter>
-
-<!-- Emacs stuff:
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