=head1 NAME
Inline::Ruby - Write Perl subroutines and classes in Ruby.
=head1 SYNOPSIS
print "9 + 16 = ", add(9, 16), "\n";
print "9 - 16 = ", subtract(9, 16), "\n";
use Inline Ruby;
__END__
__Ruby__
def add(a, b)
a + b
end
def subtract(a, b)
a - b
end
=head1 DESCRIPTION
The C<Inline::Ruby> module allows you to put Ruby source code directly
"inline" in a Perl script or module. It sets up an in-process Ruby
interpreter, runs your code, and then examines Ruby's symbol table, looking
for things to bind to Perl.
The process of interrogating the Ruby interpreter only occurs the first time
you run your Ruby code. The namespace is cached, and subsequent calls use
the cached version. Of course, your Ruby code must still be run every time
your run the Perl script -- but Inline::Ruby already knows the results of
running it.
=head1 Using the Inline::Ruby Module
Using Inline::Ruby will seem very similar to using any other Inline language,
thanks to Inline's consistent look and feel.
This section will explain the different ways to use Inline::Ruby. For more
details on C<Inline>, see 'perldoc Inline'.
=head2 Importing Functions
Using functions defined in Ruby is just like using Perl subs. You just supply
the source code to Inline::Ruby, and then use them.
use Inline Ruby => <<'END';
def doit
...
end
END
doit();
=head2 Importing Classes
If you're written a library in Ruby, it's probably object-oriented. Binding
Ruby classes to Perl is as easy as telling Ruby to import the class library.
use Inline Ruby;
my $obj = SomeClass->new;
__END__
__Ruby__
# Pretend SomeClass is defined in an external library
require 'SomeClass'
=head1 Ruby Configuration Options
For information on how to specify Inline configuration options, see L<Inline>.
This section describes each of the configuration options available for Ruby.
=head2 BIND_TYPE or BIND_TYPES
Normally, Inline::Ruby binds classes, modules, and functions into Perl. That
can be really big namespace polluter, so you can tell Inline::Ruby to ignore
functions, for example:
use Inline Ruby => DATA => BIND_TYPES => [undef, qw(classes modules)];
=head2 ITER
When Inline::Ruby binds a Ruby class, module, or function into a Perl package,
it also binds a function named C<iter> to the package. C<iter> is used to set
up an iterator block when calling Ruby methods.
It's conceivable that the word C<iter> will conflict with an actual function
in the class -- if that happens, you can override the name of the C<iter>
function using this configuration option.
use Inline Ruby => DATA => ITER => 'my_iter';
=head2 FILTERS
Like several other Inline languages, Inline::Ruby allows you to preprocess
your Inline::Ruby code with a custom filter:
use Inline Ruby => DATA => FILTER => \&my_filter;
=head1 Inline::Ruby Features
There are several cool topics worth mentioning specially:
=over 4
=item 1
Perl Subs as Iterator Blocks
=item 2
Perl Subs as Proc Objects
=item 3
Exceptions
=back
The following few sections describe each topic and give examples.
=head2 Perl Subs as Iterator Blocks
Ruby has very primitive looping support -- all the libraries and builtins use
iterators, which provide the same functionality with more power.
Here's an example of iterating over the elements of an Array in Ruby:
array = [1, 2, 3]
array.each { |x|
print "array.each printing array element: #{x}\n"
}
Here's an example writing a function which calls an iterator:
def call_iter
yield "hello, iterator!"
end
Ruby's C<yield> keyword invokes the block passed the the function. There can
only be one block passed to each function. A function can invoke the block
several times, though. Like Perl's anonymous subroutines, Ruby's blocks are
closures: they remember the context in which they were defined, so they have
access to local variables defined at that point.
Inline::Ruby allows you to pass a Perl subroutine reference as an iterator
block. That means whenever C<yield> is called, the Perl subroutine will be
called with the arguments to C<yield>.
Here's an example:
use Inline Ruby;
sub block { print "Ruby says: @_\n" }
no_iter();
iter(\&block)->call_iter;
__END__
__Ruby__
def no_iter
print "no block\n"
end
def call_iter
yield "hello, block!"
end
As you can see, calling a global function with an iterator is slightly more
complicated than just calling a regular function. Why not just pass the
subroutine in the parameter list? Because that would actually pass it as a
Proc object, which is also supported in Ruby (see L<"Perl Subs as Proc
Objects">).
That was functions. What about methods?
use Inline Ruby;
$obj = Iterator->new(1, "2", [3, 4], {5 => 6});
$obj->iter(\&my_iter)->each;
sub iter {
use Data::Dumper;
print Dumper \@_;
}
__END__
__Ruby__
class Iterator
def initialize(*elements)
@elements = elements
end
def each
for i in @elements
yield i
end
end
end
That example showed an instance method being called. Class methods are very
similar -- you just call the method on the class, not an instance of it:
Iterator->iter(\&my_iter)->some_class_iterator(@args);
There are six combinations of iterators and function types, all supported by
Inline::Ruby:
global_function();
iter(\&my_iter)->global_iterator();
Class->class_method();
Class->iter(\&my_iter)->class_iterator();
$obj->instance_method();
$obj->iter(\&my_iter)->instance_iterator();
Ruby also allows you to prototype a function definition to pass the block in
as an argument:
def function(arg1, arg2, arg3, &b)
b.call(arg1, arg2, arg3)
end
function(1, 2, 3) { |x| print "hello #{x}\n" }
Passing a Perl Block to such a function is just like passing a Perl Block to
any other function:
iter(\&my_block)->function($arg1, $arg2, $arg3);
Ruby also allows you to pass "real" compiled blocks around. The next section
talks about that.
=head2 Perl Subs as Proc Objects
Like Perl, Ruby allows variables to contain subroutine references. They're
called C<Proc>s in Ruby, and they're very similar to compiled blocks. You
created them by calling C<Proc.new { }>, which returns an object with a
C<call> method. A Proc is not allowed to call C<yield>.
Perl subroutines are very similar to Ruby's Proc: they can't call C<yield>
(Perl doesn't have it) and they are closures (which makes them suitable for
calling from Ruby).
If you pass a code ref as a parameter to a Ruby function or method, it will be
converted to a Proc object, callable from Ruby:
use Inline Ruby;
ine(\&my_iter);
__END__
__Ruby__
def ine(beckand)
beckand.call("I'm at your")
end
Inline::Ruby ships with this sample script:
use Inline Ruby => 'require "tk"';
# Create a button widget that prints 'hello', and pack it.
TkButton->new(undef,{text=>'hello',command=>sub{print"hello\n"}})->pack;
# Create a button widget that exits the process, and pack it.
TkButton->new(undef,{text=>'quit',command=>'exit'})->pack;
# Run Tk's mainloop
Tk->mainloop;
This example pops up a windows with two buttons in it: "hello", and "quit".
Clicking "hello" prints "hello\n" to your console, and "quit" does the
expected.
=head2 Exceptions
Exceptions are an important part of Ruby. Any function can throw an exception
at any time. If you don't catch an exception, Ruby will immediately exit the
process (even if you're inside Inline::Ruby).
To avoid this rather unpleasant exit, Inline::Ruby always wraps every call to
the Ruby interpreter with a C<rescue> block (Ruby's equivalent of Perl's block
C<eval>). When an exception occurs, Inline::Ruby creates a wrapper exception
object and generates a Perl exception.
use Inline Ruby;
print divby0(10);
__END__
__Ruby__
def divby0(n)
n/0
end
This throws a ZeroDivisionError in Ruby. Because it wasn't caught in Ruby, it
gets caught by Inline::Ruby's internals, which generate a Perl exception. But
Perl didn't trap the error either... so the process exits:
ttul:~/dev/cpan/Inline-Ruby$ perl -Mblib t.pl
Using /home/nwatkiss/dev/cpan/Inline-Ruby/blib
#<ZeroDivisionError: divided by 0>
ttul:~/dev/cpan/Inline-Ruby$
The exception is actually an object, so you can call these methods on it:
=over 4
=item 1
type
What type of Exception was it? Returns the class of the Ruby exception
("ZeroDivisionError" in this case).
=item 2
message
Returns the error message thrown by the code ("divided by 0" in this case).
=item 3
inspect
Returns this: sprintf("#<%s: %s>", $@->type, $@->message)
=item 4
backtrace
Prints the backtrace as far as Ruby is concerned. This does not include any
Perl calls that may exists between consecutive entries.
=back
If you "stringify" the exception ("$@"), it returns $@->inspect plus a
newline.
=head2 Perl Exceptions Inside Callbacks
What happens when a callback C<die>s? This generates a Perl exception
which is caught by Inline::Ruby. It throws a new exception to Ruby:
PerlException. The description is whatever is contained in C<"$@">. The new
Ruby exception might be caught inside the Ruby code, or it might percolate
back to Inline::Ruby, where it will be wrapped back into C<$@> and thrown as a
Perl Exception again.
use Inline Ruby;
sub callback { die "died!" }
iter(\&callback)->func;
__END__
__Ruby__
def func
yield [1, 2, 3]
end
This example prints the following:
ttul:~/dev/cpan/Inline-Ruby$ perl -Mblib t.pl
Using /home/nwatkiss/dev/cpan/Inline-Ruby/blib
#<PerlException: (in cleanup) died! at t.pl line 3.>
So the Perl exception was wrapped in a Ruby exception (PerlException), and
then re-wrapped into an Inline::Ruby::Exception object, which was printed out
when Perl exited.
This exception could have been caught in two places:
=over 4
=item 1
Catching Perl Exceptions in Ruby
Here's an example of catching a Perl exception from Ruby:
use Inline Ruby;
sub callback { die "died!" }
iter(\&callback)->func;
__END__
__Ruby__
def func
begin
yield [1, 2, 3]
rescue PerlException => e
print "Got an exception: " + e + "\n"
end
end
Resulting in this output:
ttul:~/dev/cpan/Inline-Ruby$ perl -Mblib t.pl
Using /home/nwatkiss/dev/cpan/Inline-Ruby/blib
Got an exception: (in cleanup) died! at t.pl line 3.
=item 2
Catching exceptions in Perl
Here's a familiar example of catching exceptions in Perl:
use Inline Ruby;
sub callback { die "died!" }
eval {
iter(\&callback)->func;
};
print "Got an exception: $@" if $@;
__END__
__Ruby__
def func
yield [1, 2, 3]
end
Which prints:
ttul:~/dev/cpan/Inline-Ruby$ perl -Mblib t.pl
Using /home/nwatkiss/dev/cpan/Inline-Ruby/blib
Got an exception: #<PerlException: (in cleanup) died! at t.pl line 3.>
=back
=head1 Supported Data Types
Inline::Ruby seamlessly converts between most types of Perl and Ruby data
types.
=head2 Supported Perl Data Types
The following data types may be passed from Perl into Ruby. Any unrecognized
type is replaced with C<undef> during translation.
=over 4
=item 1
Integer
Converted to Ruby "Fixnum" object.
=item 2
Floating Point
Convert to Ruby "Float" object.
=item 3
String
Converted to Ruby "String" object.
=item 4
Array Reference
Converted to Ruby "Array" object (elements recursively converted).
=item 5
Hash Reference
Converted to Ruby "Hash" object (elements recursively converted).
=item 6
Code Reference
Converted to Ruby "Proc" object.
=item 7
Undef (and all others)
Converted to Ruby NilClass object (known as nil).
=back
=head2 Supported Ruby Data Types
The following Ruby types map be either returned from a Ruby method or function
to Perl, or may be passed as arguments to a Perl callback. Unrecognized types
are replaced with C<nil> and translated to C<undef>.
=over 4
=item 1
Object
Ruby objects are wrapped in instances of the C<Inline::Ruby::Object> class.
This allows Perl to call methods on the object as usual.
=item 2
Fixnum
Converted to a Perl integer scalar.
=item 3
Float
Converted to a Perl floating point scalar.
=item 4
String
Converted to a Perl string.
=item 5
Array
Converted to a Perl array reference (elements recursively converted).
=item 6
Hash
Converted to a Perl hash reference (elements recursively converted).
=item 7
True
Converted to a scalar containing 1.
=item 8
False, Nil, and anything else
Converted to C<undef>.
=back
=head1 Low-Level Inline::Ruby
Unlike most other Inline languages, you can C<use Inline::Ruby> independently
of Inline:
use Inline::Ruby qw(rb_eval);
rb_eval('print "hello from Ruby!\n"');
By default, Inline::Ruby doesn't export anything. You can request any or all
of the following functions:
=over 4
=item rb_eval()
Takes one string argument, a Ruby expression, and returns the result of
evaluating it. For example:
$sum = rb_eval("3 + 4");
=item rb_call_function()
Takes the following arguments:
=over 4
=item 1
$func
The name of the Ruby function to call.
=item 2
@_
Optional arguments to the Ruby function.
=back
For example:
rb_eval <<END;
def func(a, b, c)
p [a, b, c]
end
END
rb_call_function("func", 1, "2", [3, 4])
=item rb_call_class_method()
Takes the following arguments:
=over 4
=item 1
$class
The class containing the class method.
=item 2
$method
The name of the method to call.
=item 3
@_
Optional arguments to the class method.
=back
For example:
print Dumper rb_call_class_method("Class", "methods");
=item rb_new_object()
Takes the following arguments:
=over 4
=item 1
$class
A class into which to bless the Perl object.
=item 2
$ruby_class
The ruby class to create an instance of.
=item 3
@_
Optional arguments to the object's constructor.
=back
For example:
rb_eval <<END;
class Cls
def initialize(a, b)
print "Creating new Cls: #{a} #{b}\n"
end
end
END
my $o = rb_new_object("main::Cls", "Cls", 1, 2);
=item rb_call_instance_method()
Takes the following arguments:
=over 4
=item 1
$instance
An instance of Inline::Ruby::Object or a derived class.
=item 2
$method
The name of the method to run on the object.
=item 3
@_
Optional arguments to the method.
=back
For example:
my $o = rb_new_object("Inline::Ruby::Object", "Object")
my $ans = rb_call_instance_method($o, "methods");
=item rb_iter()
Sets up a Ruby method for calling in iterator context.
Takes the following arguments:
=over 4
=item 1
$obj
An object upon which the method will be called. This object is stored inside
the returned object, so that when you call a method on it, it is retrieved at
that point.
If you pass 'undef' as the C<$obj>, the calling methods on the returned object
will invoke the global Ruby function of the same name with the iterator block.
=item 2
$iterator
A reference to a Perl subroutine which will be passed as an iterator to the
Ruby method.
=back
For example:
my $obj = rb_new_obj("Something");
my $ready = rb_iter($obj, sub { ... });
# call Something#some_method with an iterator
$ready->some_method;
# call Something#some_method without an iterator
$obj->some_method;
=item rb_bind_class()
Currently undocumented.
=item rb_bind_func()
Currently undocumented.
=back
=head1 METHODS FOR INTERNAL USE
=head2 build
=head2 config_var
=head2 dl_load_flags
=head2 info
=head2 load
=head2 register
=head2 validate
=head1 SUPPORTED PLATFORMS
Inline::Ruby has so far been tested on Linux only.
Perl versions tested: 5.005_03, 5.6.0, and 5.6.1. It will probably work with
5.7.x as well.
Ruby versions tested: 1.6.[3-6].
The next release will focus on increasing the number of supported platforms. I
suspect that any platform where Perl and Ruby both compile will be easy to
support.
=head1 SEE ALSO
For information about using C<Inline>, see L<Inline>.
For information about other Inline languages, see L<Inline-Support>.
Inline::Ruby's mailing list is inline@perl.org
To subscribe, send email to inline-subscribe@perl.org
=head1 BUGS AND DEFICIENCIES
None so far.
There are bound to be some bugs lurking about. Feel free to email bug reports
to inline@perl.org.
They're mite evan bee spelyng mystaikz.
=head1 AUTHOR
Maintainer: Shlomi Fish, L<http://www.shlomifish.org> .
Neil Watkiss <NEILW@cpan.org>
=head1 COPYRIGHT
Copyright (c) 2002, Neil Watkiss.
All Rights Reserved. This module is free software. It may be used,
redistributed and/or modified under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html.