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https://github.com/niner/Inline-Perl5

Use Perl 5 code in a Raku program
https://github.com/niner/Inline-Perl5

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Use Perl 5 code in a Raku program

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# TITLE



Inline::Perl5



[![Build Status](https://travis-ci.org/niner/Inline-Perl5.svg?branch=master)](https://travis-ci.org/niner/Inline-Perl5)



# SYNOPSIS



```raku

    use DBI:from;



    my $dbh = DBI.connect('dbi:Pg:database=test');

    my $products = $dbh.selectall_arrayref(

    	'select * from products', {Slice => {}}

    );

```



# DESCRIPTION



Module for executing Perl 5 code and accessing Perl 5 modules from Raku.



Supports Perl 5 modules including XS modules. Allows passing integers,

strings, arrays, hashes, code references, file handles and objects between

Perl 5 and Raku. Also supports calling methods on Perl 5 objects from

Raku and calling methods on Raku objects from Perl 5 and subclass

Perl 5 classes in Raku.



Note that installing Inline::Perl5 requires the Perl 5 library to be installed.

See the BUILDING section for more information.



# HOW DO I?



## Load a Perl 5 module



Raku's use statement allows you to load modules from other languages as well.

Inline::Perl5 registers as a handler for the Perl5 language. Rakudo will

automatically load Inline::Perl5 as long as it is installed:



```raku

    use Test::More:from;

```



In Raku the :ver adverb is used for requiring a minimum version of a loaded

module:



```raku

    use Test::More:from:ver<1.001014>;

```



Inline::Perl5's use() method maps to Perl 5's use statement:



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;

    $p5.use('Test::More');

```



To load a Perl 5 module from a specific folder:



```raku

    use lib:from 'lib';

    use MyModule:from;

```



## Load a Perl 5 module and import functions



Just list the functions or groups you want to import



```raku

    use Digest::SHA1:from ;

```



```raku

    use Data::Random:from <:all>;

```



## Call a Perl 5 function



Inline::Perl5 creates wrappers for loaded Perl 5 modules and their functions.

They can be used as if they were Raku modules:



```raku

    use Test::More:from;

    plan tests => 1;

    ok 'yes', 'looks like a Raku function';

```



In this example, the `plan` function exported by `Test::More` is called.



Inline::Perl5's call($name, \*@args) method allows calling arbitrary Perl 5

functions. Use a fully qualified name (like "Test::More::ok") if the function

is not in the "main" namespace.



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;

    $p5.call('print', 'Hello World');

    $p5.use('Test::More');

    $p5.call('Test::More::plan', tests => 1);

```



Please note that since Raku does not have the same concept of "context",

Perl 5 functions are by default called in list context. See "Invoking a

method in scalar context" for how to get around that.



## Create a Perl 5 object / call a Perl 5 package method



Creating Perl 5 objects works just the same as in Perl 5: invoke their

constructor (usually called "new").



```raku

    use Inline::Perl5;

    use Data::Dumper:from;

    my $dumper = Data::Dumper.new;

```



Or using the low level methods:



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;

    $p5.use('Data::Dumper');

    my $dumper = $p5.invoke('Data::Dumper', 'new');

```



Please note that since Raku does not have the same concept of "context",

Perl 5 methods are by default called in list context. See "Invoking a

method in scalar context" for how to get around that.



## Invoke a method on a Perl 5 object



Once you have a Perl 5 object in a variable it will behave just like a Raku

object.  You can call methods on it like on any other object.



```raku

    use IO::Compress::Bzip2:from;

    my $bzip2 = IO::Compress::Bzip2.new('/tmp/foo.bz2');

    $bzip2.print($data);

    $bzip2.close;

```



### Invoking a method in scalar context



Please note that since Raku does not have the same concept of "context",

Perl 5 methods are by default called in list context. If you need to call the

method in scalar context, you can tell it so explicitly, by passing the

`Scalar` type object as first argument:



```raku

    use IO::Compress::Bzip2:from;

    my $bzip2 = IO::Compress::Bzip2.new(Scalar, '/tmp/foo.bz2');

    $bzip2.print(Scalar, $data);

    $bzip2.close(Scalar);

```



This may be neccessary if the Perl 5 method exposes different behavior when

called in list and scalar context. Calling in scalar context may also improve

performance in some cases.



## Access a Perl 5 object's data directly



Most objects in Perl 5 are blessed hash references. Some of them don't even

provide accessor methods but require you to just access the hash fields

directly. This works the same in Raku:



```raku

    use Foo:from;

    my $foo = Foo.new;

    say $foo;

```



## Run arbitrary Perl 5 code



Raku's EVAL function supports multiple languages, just like the "use"

statement. It allows for execution of arbitrary Perl 5 code given as string:



```raku

    EVAL "print 'Hello from Perl 5';", :lang;

```



The low level interface to this functionality is Inline::Perl5's run($str)

method:



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;



    $p5.run(q'

        sub test {

            return 'Hello from Perl 5';

        }

    ');

```



Both "EVAL" and "run" return the value of the last statement in the EVAL'ed

code.



## Call a Raku function from Perl 5



Inline::Perl5 creates a Perl 5 package called "v6". This package contains

a "call" function which allows for calling Raku functions from Perl 5,

same as Inline::Perl5's "call" method. It takes the name of the function

to call and passes on any additional arguments and returns the return value

of the called Perl 5 function.



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;



    our sub foo($str) {

        say "Raku says hello to $str";

    };



    $p5.run(q:to/PERL5/);

        v6::call("foo", "Perl 5");

    PERL5

```



## Invoke a method on a Raku object from Perl 5



Raku objects passed to Perl 5 functions will behave just like any other

objects in Perl 5, so you can invoke methods using the -> operator.



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;



    $p5.run(q'

        sub test {

            my ($raku) = @_;

            $raku->hello;

        }

    ');



    class Foo {

        method hello {

            say "Hello Raku";

        }

    }



    $p5.call('test', Foo.new);

```



## Run arbitrary Raku code from Perl 5



The "run" function in the automatically created "v6" package can be used to

execute arbitrary Raku code from Perl 5. It returns the value of the last

evaluated expression in the executed code.



```raku

    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;



    $p5.run(q:to/PERL5/);

        v6::run("say foo");

    PERL5

```



## Inherit from a Perl 5 class



Inline::Perl5 creates a corresponding Raku class for each Perl 5 module

loaded via the use Foo:from or $p5.use('Foo')

mechanisms.



You can subclass these automatically created classes as if they were original

Raku classes:



```raku

    use Data::Dumper:from;

    class MyDumper is Data::Dumper {

        has $.bar;

        method foo { say "foo!"; }

    }

    my $dumper = MyDumper.new([1], bar => 1);

    say $dumper.Dump();

    say $dumper.foo;

    say $dumper.bar;

```



You can override methods and the overridden methods will be called even by the

Perl 5 methods in your base class. However, it is not yet possible to directly

write to the Perl 5 object's data, i.e. $self->{foo} = 1;. Read

access however is possible, i.e. my $foo = self;.



When use cannot be used to load the Perl 5 module, the

Inline::Perl5::Perl5Parent role allows can be used for subclassing.

Pass the Perl 5 package's name as parameter to the role. Pass the Inline::Perl5

object as named parameter to your classes constructor when creating objects.



```raku

    $p5.run(q:heredoc/PERL5/);



    package Foo;



    sub test {

        my ($self) = @_;



        return $self->bar;

    }



    PERL5



    class Bar does Inline::Perl5::Perl5Parent['Foo'] {

        method bar {

            return "Raku";

        }

    }



    use Inline::Perl5;

    my $p5 = Inline::Perl5.new;

    say Bar.new(perl5 => $p5).test;

```



## Pass a scalar reference to Perl 5 code



Simply pass a [`Capture`](https://docs.raku.org/type/Capture) object containing

the object you want to pass as a reference:



```raku

    $p5obj.takes-a-scalar-ref-to-str: \("the string");

```



`HASH` and `ARRAY` references are made automatically if the Raku objects

are [containerized](https://perl6advent.wordpress.com/2017/12/02/):



```raku

    $p5obj.takes-an-array:      [];

    $p5obj.takes-an-array-ref: $[];

```



`CODE` objects are passed by reference automatically:



```raku

    $p5obj.takes-a-coderef: *.so;

```



`Regex` objects are passed by reference automatically:



```raku

    $p5obj.takes-a-regex: /foo/;

```



## Catch exceptions thrown by Perl 5 code



Perl 5's exceptions (die) are translated to X::AdHoc exceptions in Raku and

can be caught like any other Raku exceptions:



```raku

    {

        EVAL "die 'a Perl 5 exception!';", :lang;

        CATCH {

            when X::AdHoc {

                say "Caught a Perl 5 exception: $_";

            }

        }

    }

```



## Catch exceptions thrown by Raku code in Perl 5



Raku's exceptions (die) are translated to Perl 5 exceptions and

can be caught like any other Perl 5 exceptions:



```raku

    EVAL q:to:PERL5, :lang;

        use 5.10.0;

        eval {

            v6::run('die("test");');

        };

        say $@;

    PERL5

```



## Mix Perl 5 and Raku code in the same file



Inline::Perl5 creates a virtual module called "v6-inline". By saying

"use v6-inline;" in a Perl 5 module, you can declare that the rest of the file

is written in Raku:



```perl

    package Some::Perl5::Module;



    use v6-inline;



    has $.name;



    sub greet {

        say "Hello $.name";

    }

```



Note that this Perl 5 module obviously will only work when Inline::Perl5 is

loaded, i.e. in a Raku program or if you are using Inline::Perl6 in Perl 5.

This functionality is aimed at supporting Perl 5 frameworks (think Catalyst

or DBIx::Class or Dancer or ...) that automatically load modules and of course

expect these modules to be written in Perl 5.



# BUILDING



The oldest rakudo version supported is 2019.03.1.

The oldest perl version supported is 5.20.0.



You will need a perl 5 built with the -fPIC option (position independent

code). Most distributions build their Perl 5 that way. When you use perlbrew,

you have to build it as:



    perlbrew install perl-stable -Duseshrplib



(or, if you want to use more than one Inline::Perl5 interpeter safely, for

instance from within Raku threads, add the `-Dusemultiplicity` option as well)



If you use plenv:



    plenv install 5.24.0 -Duseshrplib



If you use the perl that comes with a Linux distribution, you may need to

install a separate package containing the perl library. Consult the table below

or the distribution documentation for details.



| Distribution             | Package name |

| -------------------------|--------------|

| Fedora/Red Hat/CentOs    | perl-libs    |

| Debian/Ubuntu/Linux Mint | libperl-dev  |

| openSUSE                 | perl         |

| Arch Linux/Manjaro       | perl         |



Build Inline::Perl5 with



    raku configure.pl6

    make



and test with



    make test



and install with



    make install



# AUTHOR



Stefan Seifert