=head1 NAME

Inline - Write Perl subroutines in other programming languages.

=head1 SYNOPSIS

    use Inline C;

    print "9 + 16 = ", add(9, 16), "\n";
    print "9 - 16 = ", subtract(9, 16), "\n";

    __END__
    __C__
    int add(int x, int y) {
      return x + y;
    }

    int subtract(int x, int y) {
      return x - y;
    }

=head1 DESCRIPTION

The Inline module allows you to put source code from other programming
languages directly "inline" in a Perl script or module. The code is
automatically compiled as needed, and then loaded for immediate access
from Perl.

Inline saves you from the hassle of having to write and compile your own
glue code using facilities like XS or SWIG. Simply type the code where
you want it and run your Perl as normal. All the hairy details are
handled for you. The compilation and installation of your code chunks
all happen transparently; all you will notice is the delay of
compilation on the first run.

The Inline code only gets compiled the first time you run it (or
whenever it is modified) so you only take the performance hit once. Code
that is Inlined into distributed modules (like on the CPAN) will get
compiled when the module is installed, so the end user will never notice
the compilation time.

Best of all, it works the same on both Unix and Microsoft Windows. See
L<Inline-Support> for support information.

=head2 Why Inline?

Do you want to know "Why would I use other languages in Perl?" or "Why
should I use Inline to do it?"? I'll try to answer both.

=over 4

=item Why would I use other languages in Perl?

The most obvious reason is performance. For an interpreted language,
Perl is very fast. Many people will say "Anything Perl can do, C can do
faster". (They never mention the development time :-) Anyway, you may be
able to remove a bottleneck in your Perl code by using another language,
without having to write the entire program in that language. This keeps
your overall development time down, because you're using Perl for all of
the non-critical code.

Another reason is to access functionality from existing API-s that use
the language. Some of this code may only be available in binary form.
But by creating small subroutines in the native language, you can
"glue" existing libraries to your Perl. As a user of the CPAN, you know
that code reuse is a good thing. So why throw away those Fortran
libraries just yet?

If you are using Inline with the C language, then you can access the
full internals of Perl itself. This opens up the floodgates to both
extreme power and peril.

Maybe the best reason is "Because you want to!". Diversity keeps the
world interesting. TMTOWTDI!

=item Why should I use Inline to do it?

There are already two major facilities for extending Perl with C. They
are XS and SWIG. Both are similar in their capabilities, at least as far
as Perl is concerned. And both of them are quite difficult to learn
compared to Inline.

There is a big fat learning curve involved with setting up and using the
XS environment. You need to get quite intimate with the following docs:

 * perlxs
 * perlxstut
 * perlapi
 * perlguts
 * perlmod
 * h2xs
 * xsubpp
 * ExtUtils::MakeMaker

With Inline you can be up and running in minutes. There is a C Cookbook
with lots of short but complete programs that you can extend to your
real-life problems. No need to learn about the complicated build
process going on in the background. You don't even need to compile the
code yourself. Inline takes care of every last detail except writing
the C code.

Perl programmers cannot be bothered with silly things like compiling.
"Tweak, Run, Tweak, Run" is our way of life. Inline does all the dirty
work for you.

Another advantage of Inline is that you can use it directly in a script.
You can even use it in a Perl one-liner. With XS and SWIG, you always
set up an entirely separate module. Even if you only have one or two
functions. Inline makes easy things easy, and hard things possible. Just
like Perl.

Finally, Inline supports several programming languages (not just C and
C++). As of this writing, Inline has support for C, C++, Java, Python,
Ruby, Tcl, Assembler, Basic, Guile, Befunge, Octave, Awk, BC, TT
(Template Toolkit), WebChat and even PERL. New Inline Language Support
Modules (ILSMs) are regularly being added. See L<Inline-API> for details
on how to create your own ILSM.

=back

=head1 Using the Inline.pm Module

Inline is a little bit different than most of the Perl modules that you
are used to. It doesn't import any functions into your namespace and it
doesn't have any object oriented methods. Its entire interface (with two
minor exceptions) is specified through the C<'use Inline ...'> command.

This section will explain all of the different ways to C<use Inline>. If
you want to begin using C with Inline immediately, see
L<Inline::C-Cookbook>.

=head2 The Basics

The most basic form for using Inline is:

    use Inline X => "X source code";

where 'X' is one of the supported Inline programming languages. The
second parameter identifies the source code that you want to bind
to Perl. The source code can be specified using any of the
following syntaxes:

=over 4

=item The DATA Keyword.

    use Inline Java => 'DATA';

    # Perl code goes here ...

    __DATA__
    __Java__
    /* Java code goes here ... */

The easiest and most visually clean way to specify your source code in
an Inline Perl program is to use the special C<DATA> keyword. This tells
Inline to look for a special marker in your C<DATA> filehandle's input
stream. In this example the special marker is C<__Java__>, which is the
programming language surrounded by double underscores.

In case you've forgotten, the C<DATA> pseudo file is comprised of all
the text after the C<__END__> or C<__DATA__> section of your program. If
you're working outside the C<main> package, you'd best use the
C<__DATA__> marker or else Inline will not find your code.

Using this scheme keeps your Perl code at the top, and all the ugly Java
stuff down below where it belongs. This is visually clean and makes for
more maintainable code. An excellent side benefit is that you don't have
to escape any characters like you might in a Perl string. The source
code is verbatim. For these reasons, I prefer this method the most.

The only problem with this style is that since Perl can't read the
C<DATA> filehandle until runtime, it obviously can't bind your functions
until runtime. The net effect of this is that you can't use your Inline
functions as barewords (without predeclaring them) because Perl has no
idea they exist during compile time.

=item The FILE and BELOW keywords.

    use Inline::Files;
    use Inline Java => 'FILE';

    # Perl code goes here ...

    __JAVA__
    /* Java code goes here ... */

This is the newest method of specifying your source code. It makes use
of the Perl module C<Inline::Files> written by Damian Conway. The basic
style and meaning are the same as for the C<DATA> keyword, but there are
a few syntactic and semantic twists.

First, you must say 'use Inline::Files' before you 'use Inline' code
that needs those files. The special 'C<DATA>' keyword is replaced by
either 'C<FILE>' or 'C<BELOW>'. This allows for the bad pun idiom of:

    use Inline C => 'BELOW';

You can omit the C<__DATA__> tag now. Inline::Files is a source filter
that will remove these sections from your program before Perl compiles
it. They are then available for Inline to make use of. And since this
can all be done at compile time, you don't have to worry about the
caveats of the 'DATA' keyword.

This module has a couple small gotchas. Since Inline::Files only
recognizes file markers with capital letters, you must specify the
capital form of your language name. Also, there is a startup time
penalty for using a source code filter.

At this point Inline::Files is alpha software and use of it is
experimental. Inline's integration of this module is also fledgling at
the time being. One of things I plan to do with Inline::Files is to get
line number info so when an extension doesn't compile, the error
messages will point to the correct source file and line number.

My best advice is to use Inline::Files for testing (especially as
support for it improves), but use DATA for production and
distributed/CPAN code.

=item Strings

    use Inline Java => <<'END';

    /* Java code goes here ... */
    END

    # Perl code goes here ...

You also just specify the source code as a single string. A handy way to
write the string is to use Perl's "here document" style of quoting. This
is ok for small functions but can get unwieldy in the large. On the
other hand, the string variant probably has the least startup penalty
and all functions are bound at compile time.

If you wish to put the string into a scalar variable, please be aware
that the C<use> statement is a compile time directive. As such, all the
variables it uses must also be set at compile time, C<before> the 'use
Inline' statement. Here is one way to do it:

    my $code;
    BEGIN {
        $code = <<END;

    /* Java code goes here ... */
    END
    }
    use Inline Java => $code;

    # Perl code goes here ...

=item The bind() Function

An alternative to using the BEGIN block method is to specify the source
code at run time using the 'Inline->bind()' method. (This is one of the
interface exceptions mentioned above) The C<bind()> method takes the
same arguments as C<'use Inline ...'>.

    my $code = <<END;

    /* Java code goes here ... */
    END

    Inline->bind(Java => $code);

You can think of C<bind()> as a way to C<eval()> code in other
programming languages.

Although bind() is a powerful feature, it is not recommended for use in
Inline based modules. In fact, it won't work at all for installable
modules. See instructions below for creating modules with Inline.

=item Other Methods

The source code for Inline can also be specified as an external
filename, a reference to a subroutine that returns source code, or a
reference to an array that contains lines of source code. (Note that
if the external source file is in the current directory it must be
specified with a leading './' - ie './file.ext' instead of simply
'file.ext'.) These methods are less frequently used but may be useful
in some situations.

=item Shorthand

If you are using the 'DATA' or 'FILE' methods described above B<and>
there are no extra parameters, you can omit the keyword altogether.
For example:

    use Inline 'Java';

    # Perl code goes here ...

    __DATA__
    __Java__
    /* Java code goes here ... */

or

    use Inline::Files;
    use Inline 'Java';

    # Perl code goes here ...

    __JAVA__
    /* Java code goes here ... */

=back

=head2 More about the DATA Section

If you are writing a module, you can also use the DATA section for POD
and AutoLoader subroutines. Just be sure to put them before the first
Inline marker. If you install the helper module C<Inline::Filters>, you
can even use POD inside your Inline code. You just have to specify a
filter to strip it out.

You can also specify multiple Inline sections, possibly in different
programming languages. Here is another example:

    # The module Foo.pm
    package Foo;
    use AutoLoader;

    use Inline C;
    use Inline C => DATA => FILTERS => 'Strip_POD';
    use Inline Python;

    1;

    __DATA__

    sub marine {
        # This is an autoloaded subroutine
    }

    =head1 External subroutines

    =cut

    __C__
    /* First C section */

    __C__
    /* Second C section */
    =head1 My C Function

    Some POD doc.

    =cut

    __Python__
    """A Python Section"""

An important thing to remember is that you need to have one "use
Inline Foo => 'DATA'" for each "__Foo__" marker, and they must be in
the same order. This allows you to apply different configuration
options to each section.

=head2 Configuration Options

Inline trys to do the right thing as often as possible. But
sometimes you may need to override the default actions. This is easy
to do. Simply list the Inline configuration options after the
regular Inline parameters. All congiguration options are specified
as (key, value) pairs.

    use Inline (C => 'DATA',
                DIRECTORY => './inline_dir',
                LIBS => '-lfoo',
                INC => '-I/foo/include',
                PREFIX => 'XXX_',
                WARNINGS => 0,
               );

You can also specify the configuration options on a separate Inline call
like this:

    use Inline (C => Config =>
                DIRECTORY => './inline_dir',
                LIBS => '-lfoo',
                INC => '-I/foo/include',
                PREFIX => 'XXX_',
                WARNINGS => 0,
               );
    use Inline C => <<'END_OF_C_CODE';

The special keyword C<'Config'> tells Inline that this is a
configuration-only call. No source code will be compiled or bound to
Perl.

If you want to specify global configuration options that don't apply
to a particular language, just leave the language out of the call.
Like this:

    use Inline Config => WARNINGS => 0;

The Config options are inherited and additive. You can use as many
Config calls as you want. And you can apply different options to
different code sections. When a source code section is passed in,
Inline will apply whichever options have been specified up to that
point. Here is a complex configuration example:

    use Inline (Config =>
                DIRECTORY => './inline_dir',
               );
    use Inline (C => Config =>
                LIBS => '-lglobal',
               );
    use Inline (C => 'DATA',         # First C Section
                LIBS => ['-llocal1', '-llocal2'],
               );
    use Inline (Config =>
                WARNINGS => 0,
               );
    use Inline (Python => 'DATA',    # First Python Section
                LIBS => '-lmypython1',
               );
    use Inline (C => 'DATA',         # Second C Section
                LIBS => [undef, '-llocal3'],
               );

The first C<Config> applies to all subsequent calls. The second
C<Config> applies to all subsequent C<C> sections (but not C<Python>
sections). In the first C<C> section, the external libraries C<global>,
C<local1> and C<local2> are used. (Most options allow either string or
array ref forms, and do the right thing.) The C<Python> section does not
use the C<global> library, but does use the same C<DIRECTORY>, and has
warnings turned off. The second C<C> section only uses the C<local3>
library. That's because a value of C<undef> resets the additive
behavior.

The C<DIRECTORY> and C<WARNINGS> options are generic Inline options. All
other options are language specific. To find out what the C<C> options
do, see C<Inline::C>.

=head2 On and Off

If a particular config option has value options of 1 and 0, you can use
the ENABLE and DISABLE modifiers. In other words, this:

    use Inline Config =>
               FORCE_BUILD => 1,
               CLEAN_AFTER_BUILD => 0;

could be reworded as:

    use Inline Config =>
               ENABLE => FORCE_BUILD,
               DISABLE => CLEAN_AFTER_BUILD;

=head2 Playing 'with' Others

Inline has a special configuration syntax that tells it to get more
configuration options from other Perl modules. Here is an example:

    use Inline with => 'Event';

This tells Inline to load the module C<Event.pm> and ask it for
configuration information. Since C<Event> has a C API of its own, it can
pass Inline all of the information it needs to be able to use C<Event> C
callbacks seamlessly.

That means that you don't need to specify the typemaps, shared
libraries, include files and other information required to get
this to work.

You can specify a single module or a list of them. Like:

    use Inline with => qw(Event Foo Bar);

Currently, C<Event> is the only module that works I<with> Inline.

=head2 Inline Shortcuts

Inline lets you set many configuration options from the command line.
These options are called 'shortcuts'. They can be very handy, especially
when you only want to set the options temporarily, for say, debugging.

For instance, to get some general information about your Inline code in
the script C<Foo.pl>, use the command:

    perl -MInline=INFO Foo.pl

If you want to force your code to compile, even if its already done, use:

    perl -MInline=FORCE Foo.pl

If you want to do both, use:

    perl -MInline=INFO -MInline=FORCE Foo.pl

or better yet:

    perl -MInline=INFO,FORCE Foo.pl

=head2 The Inline DIRECTORY

Inline needs a place to build your code and to install the results of
the build. It uses a single directory named C<'.Inline/'> under normal
circumstances. If you create this directory in your home directory, the
current directory or in the directory where your program resides, Inline
will find and use it. You can also specify it in the environment
variable C<PERL_INLINE_DIRECTORY> or directly in your program, by using
the C<DIRECTORY> keyword option. If Inline cannot find the directory in
any of these places it will create a C<'_Inline/'> directory in either
your current directory or the directory where your script resides.

One of the key factors to using Inline successfully, is understanding
this directory. When developing code it is usually best to create this
directory (or let Inline do it) in your current directory. Remember that
there is nothing sacred about this directory except that it holds your
compiled code. Feel free to delete it at any time. Inline will simply
start from scratch and recompile your code on the next run. If you have
several programs that you want to force to recompile, just delete your
C<'.Inline/'> directory.

It is probably best to have a separate C<'.Inline/'> directory for each
project that you are working on. You may want to keep stable code in the
<.Inline/> in your home directory. On multi-user systems, each user
should have their own C<'.Inline/'> directories. It could be a security
risk to put the directory in a shared place like C</tmp/>.

=head2 Debugging Inline Errors

All programmers make mistakes. When you make a mistake with Inline, like
writing bad C code, you'll get a big error report on your screen. This
report tells you where to look to do the debugging. Some languages may also
dump out the error messages generated from the build.

When Inline needs to build something it creates a subdirectory under
your C<DIRECTORY/build/> directory. This is where it writes all the
components it needs to build your extension. Things like XS files,
Makefiles and output log files.

If everything goes OK, Inline will delete this subdirectory. If there is
an error, Inline will leave the directory intact and print its location.
The idea is that you are supposed to go into that directory and figure
out what happened.

Read the doc for your particular Inline Language Support Module for more
information.

=head2 The 'config' Registry File

Inline keeps a cached file of all of the Inline Language Support
Module's meta data in a file called C<config>. This file can be found in
your C<DIRECTORY> directory. If the file does not exist, Inline creates
a new one. It will search your system for any module beginning with
C<Inline::>. It will then call that module's C<register()> method to get
useful information for future invocations.

Whenever you add a new ILSM, you should delete this file so that Inline
will auto-discover your newly installed language module.

=head1 Configuration Options

This section lists all of the generic Inline configuration options. For
language specific configuration, see the doc for that language.

=head2 DIRECTORY

The C<DIRECTORY> config option is the directory that Inline uses to both
build and install an extension.

Normally Inline will search in a bunch of known places for a directory
called C<'.Inline/'>. Failing that, it will create a directory called
C<'_Inline/'>

If you want to specify your own directory, use this configuration
option.

Note that you must create the C<DIRECTORY> directory yourself. Inline
will not do it for you.

=head2 NAME

You can use this option to set the name of your Inline extension object
module. For example:

    use Inline C => 'DATA',
               NAME => 'Foo::Bar';

would cause your C code to be compiled in to the object:

    lib/auto/Foo/Bar/Bar.so
    lib/auto/Foo/Bar/Bar.inl

(The .inl component contains dependency information to make sure the
source code is in sync with the executable)

If you don't use NAME, Inline will pick a name for you based on your
program name or package name. In this case, Inline will also enable the
AUTONAME option which mangles in a small piece of the MD5 fingerprint
into your object name, to make it unique.

=head2 AUTONAME

This option is enabled whenever the NAME parameter is not specified. To
disable it say:

    use Inline C => 'DATA',
               DISABLE => 'AUTONAME';

AUTONAME mangles in enough of the MD5 fingerprint to make your module
name unique. Objects created with AUTONAME will never get replaced. That
also means they will never get cleaned up automatically.

AUTONAME is very useful for small throw away scripts. For more serious
things, always use the NAME option.

=head2 VERSION

Specifies the version number of the Inline extension object. It is used
B<only> for modules, and it must match the global variable $VERSION.
Additionally, this option should used if (and only if) a module is being
set up to be installed permanently into the Perl sitelib tree. Inline
will croak if you use it otherwise.

The presence of the VERSION parameter is the official way to let Inline
know that your code is an installable/installed module. Inline will
never generate an object in the temporary cache (_Inline/ directory) if
VERSION is set. It will also never try to recompile a module that was
installed into someone's Perl site tree.

So the basic rule is develop without VERSION, and deliver with VERSION.

=head2 WITH

C<WITH> can also be used as a configuration option instead of using the
special 'with' syntax. Do this if you want to use different sections of
Inline code I<with> different modules. (Probably a very rare usage)

    use Event;
    use Inline C => DATA => WITH => 'Event';

Modules specified using the config form of C<WITH> will B<not> be
automatically required. You must C<use> them yourself.

=head2 GLOBAL_LOAD

This option is for compiled languages only. It tells Inline to tell
DynaLoader to load an object file in such a way that its symbols can be
dynamically resolved by other object files. May not work on all
platforms. See the C<GLOBAL> shortcut below.

=head2 UNTAINT

You can use this option whenever you use Perl's C<-T> switch, for taint
checking. This option tells Inline to blindly untaint all tainted
variables. (This is generally considerd to be an appallingly insecure
thing to do, and not to be recommended - but the option is there for
you to use if you want. Please consider using something other than
Inline for scripts that need taint checking.)
It also turns on SAFEMODE by default. See the C<UNTAINT>
shortcut below.
You will see warnings about blindly untainting fields in both %ENV
and Inline objects. If you want to silence these warnings, set the
Config option NO_UNTAINT_WARN => 1.
There can be some problems untainting Inline scripts where older
versions of Cwd, such as those that shipped with early versions of
perl-5.8 (and earlier), are installed. Updating Cwd will probably
solve these problems.

=head2 SAFEMODE

Perform extra safety checking, in an attempt to thwart malicious code.
This option cannot guarantee security, but it does turn on all the
currently implemented checks. (Currently, the only "currently
implemented check" is to ensure that the C<DIRECTORY> option has also
been used.)

There is a slight startup penalty by using SAFEMODE. Also, using UNTAINT
automatically turns this option on. If you need your code to start
faster under C<-T> (taint) checking, you'll need to turn this option off
manually. Only do this if you are not worried about security risks. See
the C<UNSAFE> shortcut below.

=head2 FORCE_BUILD

Makes Inline build (compile) the source code every time the program is
run. The default is 0. See the C<FORCE> shortcut below.

=head2 BUILD_NOISY

Tells ILSMs that they should dump build messages to the terminal rather
than be silent about all the build details.

=head2 BUILD_TIMERS

Tells ILSMs to print timing information about how long each build phase
took. Usually requires C<Time::HiRes>.

=head2 CLEAN_AFTER_BUILD

Tells Inline to clean up the current build area if the build was
successful. Sometimes you want to DISABLE this for debugging. Default is
1. See the C<NOCLEAN> shortcut below.

=head2 CLEAN_BUILD_AREA

Tells Inline to clean up the old build areas within the entire Inline
DIRECTORY. Default is 0. See the C<CLEAN> shortcut below.

=head2 PRINT_INFO

Tells Inline to print various information about the source code. Default
is 0. See the C<INFO> shortcut below.

=head2 PRINT_VERSION

Tells Inline to print Version info about itself. Default is 0. See the
C<VERSION> shortcut below.

=head2 REPORTBUG

Puts Inline into 'REPORTBUG' mode, which is what you want if you desire
to report a bug.

=head2 WARNINGS

This option tells Inline whether to print certain warnings. Default is 1.

=head1 Inline Configuration Shortcuts

This is a list of all the shorcut configuration options currently
available for Inline. Specify them from the command line when running
Inline scripts.

    perl -MInline=NOCLEAN inline_script.pl

or

    perl -MInline=Info,force,NoClean inline_script.pl

You can specify multiple shortcuts separated by commas. They are not
case sensitive. You can also specify shorcuts inside the Inline program
like this:

    use Inline 'Info', 'Force', 'Noclean';

NOTE:
If a C<'use Inline'> statement is used to set shortcuts, it can not be
used for additional purposes.

=over 4

=item CLEAN

Tells Inline to remove any build directories that may be lying around in
your build area. Normally these directories get removed immediately
after a successful build. Exceptions are when the build fails, or when
you use the NOCLEAN or REPORTBUG options.

=item FORCE

Forces the code to be recompiled, even if everything is up to date.

=item GLOBAL

Turns on the GLOBAL_LOAD option.

=item INFO

This is a very useful option when you want to know what's going on under
the hood. It tells Inline to print helpful information to C<STDERR>.
Among the things that get printed is a list of which Inline functions
were successfully bound to Perl.

=item NOCLEAN

Tells Inline to leave the build files after compiling.

=item NOISY

Use the BUILD_NOISY option to print messages during a build.

=item REPORTBUG

Puts Inline into 'REPORTBUG' mode, which does special processing when
you want to report a bug. REPORTBUG also automatically forces a build,
and doesn't clean up afterwards. This is so that you can tar and mail
the build directory to me. REPORTBUG will print exact instructions on
what to do. Please read and follow them carefully.

NOTE: REPORTBUG informs you to use the tar command. If your system does not have tar, please use the equivalent C<zip> command.

=item SAFE

Turns SAFEMODE on. UNTAINT will turn this on automatically. While this
mode performs extra security checking, it does not guarantee safety.

=item SITE_INSTALL

This parameter used to be used for creating installable Inline modules.
It has been removed from Inline altogether and replaced with a much
simpler and more powerful mechanism, C<Inline::MakeMaker>. See the
section below on how to create modules with Inline.

=item _TESTING

Used internally by C/t/09parser.t and C/t/10callback.t(in the Inline::C test
suite). Setting this option with Inline::C will mean that files named 'parser_id'
and 'void_test are created in the ./Inline_test directory, creating that
directory if it doesn't already exist. The files (but not the ./Inline_test
directory) are cleaned up by calling Inline::C::_testing_cleanup().

=item TIMERS

Turn on BUILD_TIMERS to get extra diagnostic info about builds.

=item UNSAFE

Turns SAFEMODE off. Use this in combination with UNTAINT for slightly
faster startup time under C<-T>. Only use this if you are sure the
environment is safe.

=item UNTAINT

Turn the UNTAINT option on. Used with C<-T> switch.
In terms of secure practices, this is definitely *not* a recommended
way of dealing with taint checking, but it's the *only* option
currently available with Inline. Use it at your own risk.

=item VERSION

Tells Inline to report its release version.

=back

=head1 Writing Modules with Inline

Writing CPAN modules that use C code is easy with Inline. Let's say that
you wanted to write a module called C<Math::Simple>. Start by using the
following command:

    h2xs -PAXn Math::Simple

This will generate a bunch of files that form a skeleton of what you
need for a distributable module. (Read the h2xs manpage to find out what
the options do) Next, modify the C<Simple.pm> file to look like this:

    package Math::Simple;
    $VERSION = '1.23';

    use base 'Exporter';
    @EXPORT_OK = qw(add subtract);
    use strict;

    use Inline C => 'DATA',
               VERSION => '1.23',
               NAME => 'Math::Simple';

    1;

    __DATA__

    =pod

    =cut

    __C__
    int add(int x, int y) {
      return x + y;
    }

    int subtract(int x, int y) {
      return x - y;
    }

The important things to note here are that you B<must> specify a C<NAME>
and C<VERSION> parameter. The C<NAME> must match your module's package
name. The C<VERSION> parameter must match your module's C<$VERSION>
variable and they must be of the form C</^\d\.\d\d$/>.

NOTE:
These are Inline's sanity checks to make sure you know what you're doing
before uploading your code to CPAN. They insure that once the module has
been installed on someone's system, the module would not get
automatically recompiled for any reason. This makes Inline based modules
work in exactly the same manner as XS based ones.

Finally, you need to modify the Makefile.PL. Simply change:

    use ExtUtils::MakeMaker;

to

    use Inline::MakeMaker;

When the person installing C<Math::Simple> does a "C<make>", the
generated Makefile will invoke Inline in such a way that the C code will
be compiled and the executable code will be placed into the C<./blib>
directory. Then when a "C<make install>" is done, the module will be
copied into the appropiate Perl sitelib directory (which is where an
installed module should go).

Now all you need to do is:

    perl Makefile.PL
    make dist

That will generate the file C<Math-Simple-0.20.tar.gz> which is a
distributable package. That's all there is to it.

IMPORTANT NOTE:
Although the above steps will produce a workable module, you still have
a few more responsibilities as a budding new CPAN author. You need to
write lots of documentation and write lots of tests. Take a look at some
of the better CPAN modules for ideas on creating a killer test harness.
Actually, don't listen to me, go read these:

    perldoc perlnewmod
    http://www.cpan.org/modules/04pause.html
    http://www.cpan.org/modules/00modlist.long.html

=head1 How Inline Works

In reality, Inline just automates everything you would need to do if you
were going to do it by hand (using XS, etc).

Inline performs the following steps:

=over 4

=item 1) Receive the Source Code

Inline gets the source code from your script or module with a statements
like the following:

    use Inline C => "Source-Code";

or

    use Inline;
    bind Inline C => "Source-Code";

where C<C> is the programming language of the source code, and
C<Source-Code> is a string, a file name, an array reference, or the
special C<'DATA'> keyword.

Since Inline is coded in a "C<use>" statement, everything is done during
Perl's compile time. If anything needs to be done that will affect the
C<Source-Code>, it needs to be done in a C<BEGIN> block that is
I<before> the "C<use Inline ...>" statement. If you really need to
specify code to Inline at runtime, you can use the C<bind()> method.

Source code that is stowed in the C<'DATA'> section of your code, is
read in by an C<INIT> subroutine in Inline. That's because the C<DATA>
filehandle is not available at compile time.

=item 2) Check if the Source Code has been Built

Inline only needs to build the source code if it has not yet been built.
It accomplishes this seemingly magical task in an extremely simple and
straightforward manner. It runs the source text through the
C<Digest::MD5> module to produce a 128-bit "fingerprint" which is
virtually unique. The fingerprint along with a bunch of other
contingency information is stored in a C<.inl> file that sits next to
your executable object. For instance, the C<C> code from a script called
C<example.pl> might create these files:

    example_pl_3a9a.so
    example_pl_3a9a.inl

If all the contingency information matches the values stored in the
C<.inl> file, then proceed to step 8. (No compilation is necessary)

=item 3) Find a Place to Build and Install

At this point Inline knows it needs to build the source code. The first
thing to figure out is where to create the great big mess associated
with compilation, and where to put the object when it's done.

By default Inline will try to build and install under the first place
that meets one of the following conditions:

    A) The DIRECTORY= config option; if specified
    B) The PERL_INLINE_DIRECTORY environment variable; if set
    C) .Inline/ (in current directory); if exists and $PWD != $HOME
    D) bin/.Inline/ (in directory of your script); if exists
    E) ~/.Inline/; if exists
    F) ./_Inline/; if exists
    G) bin/_Inline; if exists
    H) Create ./_Inline/; if possible
    I) Create bin/_Inline/; if possible

Failing that, Inline will croak. This is rare and easily remedied by
just making a directory that Inline will use;

If the module option is being compiled for permanent installation, then
Inline will only use C<./_Inline/> to build in, and the
C<$Config{installsitearch}> directory to install the executable in. This
action is caused by Inline::MakeMaker, and is intended to be used in
modules that are to be distributed on the CPAN, so that they get
installed in the proper place.

=item 4) Parse the Source for Semantic Cues

Inline::C uses the module C<Parse::RecDescent> to parse through your
chunks of C source code and look for things that it can create run-time
bindings to. In C<C> it looks for all of the function definitions and
breaks them down into names and data types. These elements are used to
correctly bind the C<C> function to a C<Perl> subroutine. Other Inline
languages like Python and Java actually use the C<python> and C<javac>
modules to parse the Inline code.

=item 5) Create the Build Environment

Now Inline can take all of the gathered information and create an
environment to build your source code into an executable. Without going
into all the details, it just creates the appropriate directories,
creates the appropriate source files including an XS file (for C) and a
C<Makefile.PL>.

=item 6) Build the Code and Install the Executable

The planets are in alignment. Now for the easy part. Inline just does
what you would do to install a module. "C<perl Makefile.PL && make &&
make test && make install>". If something goes awry, Inline will croak
with a message indicating where to look for more info.

=item 7) Tidy Up

By default, Inline will remove all of the mess created by the build
process, assuming that everything worked. If the build fails, Inline
will leave everything intact, so that you can debug your errors. Setting
the C<NOCLEAN> shortcut option will also stop Inline from cleaning up.

=item 8) DynaLoad the Executable

For C (and C++), Inline uses the C<DynaLoader::bootstrap> method to pull
your external module into C<Perl> space. Now you can call all of your
external functions like Perl subroutines.

Other languages like Python and Java, provide their own loaders.

=back

=head1 SEE ALSO

For information about using Inline with C see L<Inline::C>.

For sample programs using Inline with C see L<Inline::C-Cookbook>.

For "Formerly Answered Questions" about Inline, see L<Inline-FAQ>.

For information on supported languages and platforms see
L<Inline-Support>.

For information on writing your own Inline Language Support Module, see
L<Inline-API>.

Inline's mailing list is inline@perl.org

To subscribe, send email to inline-subscribe@perl.org

=head1 BUGS AND DEFICIENCIES

When reporting a bug, please do the following:

 - Put "use Inline REPORTBUG;" at the top of your code, or
   use the command line option "perl -MInline=REPORTBUG ...".
 - Run your code.
 - Follow the printed directions.

=head1 AUTHOR

Brian Ingerson <INGY@cpan.org>

Neil Watkiss <NEILW@cpan.org> is the author of C<Inline::CPP>,
C<Inline::Python>, C<Inline::Ruby>, C<Inline::ASM>, C<Inline::Struct>
and C<Inline::Filters>. He is known in the innermost Inline circles as
the "Boy Wonder".

Sisyphus <sisyphus@cpan.org> fixed some bugs and is current co-maintainer.

=head1 COPYRIGHT

Copyright (c) 2000-2002. Brian Ingerson.

Copyright (c) 2008, 2010, 2011. Sisyphus.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

See http://www.perl.com/perl/misc/Artistic.html

=cut
