-<Chapter id="utils">
-<Title>Other Haskell utility programs
-</Title>
-
-<IndexTerm><Primary>utilities, Haskell</Primary></IndexTerm>
-
-<Para>
-This section describes other program(s) which we distribute, that help
-with the Great Haskell Programming Task.
-</Para>
-
-<Sect1 id="hstags">
-<Title>Emacs `TAGS' for Haskell: <Command>hstags</Command>
-</Title>
-
-<Para>
-<IndexTerm><Primary>hstags</Primary></IndexTerm>
-<IndexTerm><Primary>TAGS for Haskell</Primary></IndexTerm>
-</Para>
-
-<Para>
-`Tags' is a facility for indexing the definitions of
-programming-language things in a multi-file program, and then using
-that index to jump around among these definitions.
-</Para>
-
-<Para>
-Rather than scratch your head, saying “Now where did we define
-`foo'?”, you just do (in Emacs) <Literal>M-. foo RET</Literal>, and You're There!
-Some people go wild over this stuff…
-</Para>
-
-<Para>
-GHC comes with a program <Command>hstags</Command>, which build Emacs-able TAGS files. The invocation syntax is:
-
-<Screen>
-hstags [GHC-options] file [files...]
-</Screen>
+<chapter id="utils">
+ <title>Other Haskell utility programs</title>
+ <indexterm><primary>utilities, Haskell</primary></indexterm>
+
+ <para>This section describes other program(s) which we distribute,
+ that help with the Great Haskell Programming Task.</para>
+
+<!-- comment: hstags doesn't work anymore
+
+ <sect1 id="hstags">
+ <title>Emacs `TAGS' for Haskell: <command>hstags</command></title>
+ <indexterm><primary><command>hstags</command></primary></indexterm>
+ <indexterm><primary>TAGS for Haskell</primary></indexterm>
-</Para>
+ <para>`Tags' is a facility for indexing the definitions of
+ programming-language things in a multi-file program, and then
+ using that index to jump around among these definitions.</para>
+
+ <para>Rather than scratch your head, saying “Now where did
+ we define `foo'?”, you just do (in Emacs) <Literal>M-. foo
+ RET</Literal>, and You're There! Some people go wild over this
+ stuff…</para>
+
+ <para>GHC comes with a program <command>hstags</command>, which
+ build Emacs-able TAGS files. The invocation syntax is:</para>
+
+<screen>
+hstags [GHC-options] file [files...]
+</screen>
-<Para>
-The best thing is just to feed it your GHC command-line flags.
-A good Makefile entry might be:
+ <para>The best thing is just to feed it your GHC command-line
+ flags. A good Makefile entry might be:</para>
-<ProgramListing>
+<programlisting>
tags:
$(RM) TAGS
hstags $(GHC_FLAGS) *.lhs
-</ProgramListing>
-
-</Para>
-
-<Para>
-The only flags of its own are: <Option>-v</Option> to be verbose; <Option>-a</Option> to
-<Emphasis>APPEND</Emphasis> to the TAGS file, rather than write to it.
-</Para>
-
-<Para>
-Shortcomings: (1) Instance declarations don't get into the TAGS file
-(but the definitions inside them do); as instances aren't named, this
-is probably just as well. (2) Data-constructor definitions don't get
-in. Go for the corresponding type constructor instead.
-</Para>
-
-<Para>
-(Actually, GHC also comes with <Command>etags</Command> [for C], and <Command>perltags</Command>
-[for You Know What]. And—I cannot tell a lie—there is Denis
-Howe's <Command>fptags</Command> [for Haskell, etc.] in the <Filename>ghc/CONTRIB</Filename>
-section…)
-</Para>
-
-</Sect1>
-
-<Sect1 id="happy">
-<Title>“Yacc for Haskell”: <Command>happy</Command>
-</Title>
-
-<Para>
-<IndexTerm><Primary>happy</Primary></IndexTerm>
-<IndexTerm><Primary>Yacc for Haskell</Primary></IndexTerm>
-<IndexTerm><Primary>parser generator for Haskell</Primary></IndexTerm>
-Andy Gill and Simon Marlow have written a parser-generator for
-Haskell, called <Command>happy</Command>.<IndexTerm><Primary>happy parser generator</Primary></IndexTerm> <Command>Happy</Command>
-is to Haskell what <Command>Yacc</Command> is to C.
-</Para>
-
-<Para>
-You can get <Command>happy</Command> from <ulink
-url="http://www.haskell.org/happy/">the Happy Homepage</ulink>.
-</Para>
-
-<Para>
-<Command>Happy</Command> is at its shining best when compiled by GHC.
-</Para>
-
-</Sect1>
-
-<Sect1 id="pphs">
-<Title>Pretty-printing Haskell: <Command>pphs</Command>
-</Title>
-
-<Para>
-<IndexTerm><Primary>pphs</Primary></IndexTerm>
-<IndexTerm><Primary>pretty-printing Haskell code</Primary></IndexTerm>
-</Para>
-
-<Para>
-Andrew Preece has written
-<Command>pphs</Command>,<IndexTerm><Primary>pphs</Primary></IndexTerm><IndexTerm><Primary>pretty-printing Haskell</Primary></IndexTerm>
-a utility to pretty-print Haskell code in LaTeX documents.
-Keywords in bolds, variables in italics—that sort of thing. It is
-good at lining up program clauses and equals signs, things that are
-very tiresome to do by hand.
-</Para>
-
-<Para>
-The code is distributed with GHC in <Filename>ghc/CONTRIB/pphs</Filename>.
-</Para>
-
-</Sect1>
-
-</Chapter>
+</programlisting>
+
+ <para>The only flags of its own are: <Option>-v</Option> to be
+ verbose; <Option>-a</Option> to <Emphasis>APPEND</Emphasis> to the
+ TAGS file, rather than write to it.</para>
+
+ <para>Shortcomings: (1) Instance declarations don't get into
+ the TAGS file (but the definitions inside them do); as instances
+ aren't named, this is probably just as well.
+ (2) Data-constructor definitions don't get in. Go for the
+ corresponding type constructor instead.</para>
+
+ <para>Actually, GHC also comes with <command>etags</command>
+ [for C], and <Command>perltags</Command> [for You
+ Know What]. And—I cannot tell a lie—there is
+ Denis Howe's <Command>fptags</Command> [for Haskell,
+ etc.] in the <Filename>ghc/CONTRIB</Filename>
+ section…)</para>
+
+ </sect1>
+-->
+
+ <sect1 id="happy">
+ <title>“Yacc for Haskell”: <command>happy</command></title>
+
+ <indexterm><primary>Happy</primary></indexterm>
+ <indexterm><primary>Yacc for Haskell</primary></indexterm>
+ <indexterm><primary>parser generator for Haskell</primary></indexterm>
+
+ <para>Andy Gill and Simon Marlow have written a parser-generator
+ for Haskell, called
+ <Command>happy</Command>.<IndexTerm><Primary>happy parser
+ generator</Primary></IndexTerm> <command>Happy</command> is to
+ Haskell what <command>Yacc</command> is to C.</para>
+
+ <para>You can get <Command>happy</Command> from <ulink
+ url="http://www.haskell.org/happy/">the Happy
+ Homepage</ulink>.</para>
+
+ <para><command>Happy</command> is at its shining best when
+ compiled by GHC.</para>
+
+ </sect1>
+
+<!-- we don't distribute this anymore
+ <sect1 id="pphs">
+ <title>Pretty-printing Haskell: <Command>pphs</Command></title>
+ <indexterm><primary>pphs</primary></indexterm>
+ <indexterm><primary>pretty-printing Haskell code</primary></indexterm>
+
+ <para>Andrew Preece has written
+ <Command>pphs</Command>,<IndexTerm><Primary>pphs</Primary></IndexTerm><IndexTerm><Primary>pretty-printing
+ Haskell</Primary></IndexTerm> a utility to pretty-print Haskell
+ code in LaTeX documents. Keywords in bolds, variables in
+ italics—that sort of thing. It is good at lining up program
+ clauses and equals signs, things that are very tiresome to do by
+ hand.</para>
+
+ <para>The code is distributed with GHC in
+ <Filename>ghc/CONTRIB/pphs</Filename>.</para>
+ </sect1>
+-->
+
+ <sect1 id="hs2c">
+ <title>Writing Haskell interfaces to C code:
+ <command>hs2c</command></title>
+ <indexterm><primary><command>hs2c</command></primary>
+ </indexterm>
+
+ <para>The <command>hs2c</command> command can be used to automate
+ some parts of the process of writing Haskell bindings to C code.
+ It reads an almost-Haskell source with embedded special
+ constructs, and outputs a real Haskell file with these constructs
+ processed, based on information taken from some C headers. The
+ extra constructs deal with accessing C data from Haskell.</para>
+
+ <para>It may also output a C file which contains additional C
+ functions to be linked into the program, together with a C header
+ that gets included into the C code to which the Haskell module
+ will be compiled (when compiled via C) and into the C file. These
+ two files are created when the <literal>#def</literal> construct
+ is used.</para>
+
+ <para>Actually <command>hs2c</command> does not output the Haskell
+ file directly. It creates a C program that includes the headers,
+ gets automatically compiled and run. That program outputs the
+ Haskell code.</para>
+
+ <para>In the following, “Haskell file” is the main
+ output (usually a <literal>.hs</literal> file), “compiled
+ Haskell file” is the Haskell file after
+ <command>ghc</command> has compiled it to C (i.e. a
+ <literal>.hc</literal> file), “C program” is the
+ program that outputs the Haskell file, “C file” is the
+ optionally generated C file, and “C header” is its
+ header file.</para>
+
+ <sect2>
+ <title>Command line syntax</title>
+
+ <para>glue-hsc takes input files as arguments, and flags that
+ modify its behavior:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><literal>-t FILE</literal> or
+ <literal>--template=FILE</literal></term>
+ <listitem>
+ <para>The template file (see below).</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>--cc=PROG</literal></term>
+ <listitem>
+ <para>The C compiler to use (default:
+ <command>ghc</command>)</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>--ld=PROG</literal></term>
+ <listitem>
+ <para>The linker to use (default:
+ <command>gcc</command>).</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>--cflag=FLAG</literal></term>
+ <listitem>
+ <para>An extra flag to pass to the C compiler.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>--lflag=FLAG</literal></term>
+ <listitem>
+ <para>An extra flag to pass to the linker.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>--help</literal></term>
+ <listitem>
+ <para>Display a summary of the available flags.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>The input file should end with .hsc. Output files get
+ names with the <literal>.hsc</literal> suffix replaced:</para>
+
+ <informaltable>
+ <tgroup cols=2>
+ <tbody>
+ <row>
+ <entry><literal>.hs</literal></entry>
+ <entry>Haskell file</entry>
+ </row>
+ <row>
+ <entry><literal>_hsc.h</literal></entry>
+ <entry>C header</entry>
+ </row>
+ <row>
+ <entry><literal>_hsc.c</literal></entry>
+ <entry>C file</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+
+ <para>The C program is compiled using the Haskell compiler. This
+ provides the include path to <filename>HsFFI.h</filename> which
+ is automatically included into the C program.</para>
+
+ </sect2>
+ <sect2><title>Input syntax</title>
+
+ <para>All special processing is triggered by the
+ <literal>#</literal> character. To output a literal
+ <literal>#</literal>, write it twice: <literal>##</literal>.</para>
+
+ <para>Otherwise <literal>#</literal> is followed by optional
+ spaces and tabs, an alphanumeric key that describes the kind of
+ processing, and its arguments. Arguments look like C expressions
+ and extend up to the nearest unmatched <literal>)</literal>,
+ <literal>]</literal>, or <literal>}</literal>, or to the end of
+ line outside any <literal>() [] {} '' "" /* */</literal>. Any
+ character may be preceded by a backslash and will not be treated
+ specially.</para>
+
+ <para>Meanings of specific keys:</para>
+
+ <variablelist>
+
+ <varlistentry>
+ <term><literal>#include <file.h></literal></term>
+ <term><literal>#include "file.h"</literal></term>
+ <listitem>
+ <para>The specified file gets included into the C program,
+ the compiled Haskell file, and the C
+ header. <literal><HsFFI.h></literal> is included
+ automatically.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#define name</literal></term>
+ <term><literal>#define name value</literal></term>
+ <listitem>
+ <para>Similar to <literal>#include</literal>. Note that
+ <literal>#includes</literal> and
+ <literal>#defines</literal> may be put in the same file
+ twice so they should not assume otherwise.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#option opt</literal></term>
+ <listitem>
+ <para>The specified Haskell compiler command-line option
+ is placed in the <literal>{-# OPTIONS #-}</literal> pragma
+ at the top of the Haskell file (see <xref
+ linkend="source-file-options">). This is needed because
+ glue-hsc emits its own <literal>OPTIONS</literal> pragma,
+ and only one such pragma is interpreted by GHC.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#def C_definition</literal></term>
+ <listitem>
+ <para>The definition (of a function, variable, struct or
+ typedef) is written to the C file, and its prototype or
+ extern declaration to the C header. Inline functions are
+ handled correctly. struct definitions and typedefs are
+ written to the C program too. The
+ <literal>inline</literal>, <literal>struct</literal> or
+ <literal>typedef</literal> keyword must come just after
+ <literal>def</literal>.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#if condition</literal></term>
+ <term><literal>#ifdef name</literal></term>
+ <term><literal>#ifndef name</literal></term>
+ <term><literal>#elif condition</literal></term>
+ <term><literal>#else</literal></term>
+ <term><literal>#endif</literal></term>
+ <listitem>
+ <para>Conditional compilation directives are passed
+ unmodified to the C program, C file, and C header. Putting
+ them in the C program means that appropriate parts of the
+ Haskell file will be skipped.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#const C_expression</literal></term>
+ <listitem>
+ <para>The expression must be convertible to
+ <literal>long</literal> or <literal>unsigned
+ long</literal>. Its value (literal or negated literal)
+ will be output.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#const_str C_expression</literal></term>
+ <listitem>
+ <para>The expression must be convertible to const char
+ pointer. Its value (string literal) will be output.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#type C_type</literal></term>
+ <listitem>
+ <para>A Haskell equivalent of the C numeric type will be
+ output. It will be one of
+ <literal>{Int,Word}{8,16,32,64}</literal>,
+ <literal>Float</literal>, <literal>Double</literal>,
+ <literal>LDouble</literal>.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#peek struct_type, field</literal></term>
+ <listitem>
+ <para>A function that peeks a field of a C struct will be
+ output. It will have the type
+ <literal>Storable b => Ptr a -> IO b</literal>.
+
+ The intention is that <literal>#peek</literal> and
+ <literal>#poke</literal> can be used for implementing the
+ operations of class <literal>Storable</literal> for a
+ given C struct (see <xref linkend="sec-Storable">).</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#poke struct_type, field</literal></term>
+ <listitem>
+ <para>Similarly for poke. It will have the type
+ <literal>Storable b => Ptr a -> b -> IO ()</literal>.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>#ptr struct_type, field</literal></term>
+ <listitem>
+ <para>Makes a pointer to a field struct. It will have the type
+ <literal>Ptr a -> Ptr b</literal>.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ </sect2>
+
+ <sect2>
+ <title>Custom constructs</title>
+
+ <para><literal>#const</literal>, <literal>#type</literal>,
+ <literal>#peek</literal>, <literal>#poke</literal> and
+ <literal>#ptr</literal> are not hardwired into the
+ <command>hs2c</command>, but are defined in a C template that is
+ included in the C program: <filename>template-hsc.h</filename>.
+ Custom constructs and templates can be used too. Any
+ <literal>#</literal>-construct with unknown key is expected to
+ be handled by a C template.</para>
+
+ <para>A C template should define a macro or function with name
+ prefixed by <literal>hsc_</literal> that handles the construct
+ by emitting the expansion to stdout. See
+ <filename>template-hsc.h</filename> for examples.</para>
+
+ </sect2>
+
+ </sect1>
+
+</chapter>
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