indirectly, by the topmost module, and load them all in dependency
order.</para>
- <sect2>
+ <sect2 id="ghci-modules-filenames">
<title>Modules vs. filenames</title>
<indexterm><primary>modules</primary><secondary>and filenames</secondary></indexterm>
<indexterm><primary>filenames</primary><secondary>of modules</secondary></indexterm>
which GHCi can't find a source file, even if there are object
and interface files for the module, you'll get an error
message.</para>
-
- <para>One final note: if you load a module called Main, it must
- contain a <literal>main</literal> function, just like in
- GHC.</para>
</sect2>
<sect2>
<title>Packages</title>
<indexterm><primary>packages</primary><secondary>with GHCi</secondary></indexterm>
- <para>GHCi can make use of all the packages that come with GHC,
- For example, to start up GHCi with the <literal>network</literal>
- package loaded:</para>
+ <para>Most packages (see <xref linkend="using-packages">) are
+ available without needing to specify any extra flags at all:
+ they will be automatically loaded the first time they are
+ needed.</para>
+
+ <para>For non-auto packages, however, you need to request the
+ package be loaded by using the <literal>-package</literal> flag:</para>
<screen>
-$ ghci -package network
+$ ghci -package data
___ ___ _
/ _ \ /\ /\/ __(_)
- / /_\// /_/ / / | | GHC Interactive, version 5.04, for Haskell 98.
+ / /_\// /_/ / / | | GHC Interactive, version 5.05, for Haskell 98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.
Loading package base ... linking ... done.
Loading package haskell98 ... linking ... done.
-Loading package network ... linking ... done.
+Loading package lang ... linking ... done.
+Loading package concurrent ... linking ... done.
+Loading package readline ... linking ... done.
+Loading package unix ... linking ... done.
+Loading package posix ... linking ... done.
+Loading package util ... linking ... done.
+Loading package data ... linking ... done.
Prelude>
-</screen>
-
- <para>Note that GHCi will also automatically load any packages
- on which the requested package depends.</para>
+</screen>
<para>The following command works to load new packages into a
running GHCi:</para>
<para>But note that doing this will cause all currently loaded
modules to be unloaded, and you'll be dumped back into the
- Prelude.</para>
+ <literal>Prelude</literal>.</para>
</sect2>
<sect2>
<para>Extra libraries may be specified on the command line using
the normal <literal>-l<replaceable>lib</replaceable></literal>
- option. For example, to load the “m” library:</para>
+ option. (The term <emphasis>library</emphasis> here refers to
+ libraries of foreign object code; for using libraries of Haskell
+ source code, see <xref linkend="ghci-modules-filenames">.) For
+ example, to load the “m” library:</para>
<screen>
$ ghci -lm
<variablelist>
<varlistentry>
- <term>GHCi complains about <function>main</function> not being
- in scope when I load a module.</term>
- <indexterm><primary><function>main</function></primary><secondary>with GHCi</secondary>
- </indexterm>
- <listitem>
- <para>You probably omitted the <literal>module</literal>
- declaration at the top of the module, which causes the
- module name to default to <literal>Main</literal>. In
- Haskell, the <literal>Main</literal> module must define a
- function called <function>main</function>. Admittedly this
- doesn't make a great deal of sense for an interpreter, but
- the rule was kept for compatibility with GHC.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
<term>The interpreter can't load modules with foreign export
declarations!</term>
<listitem>