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Trying to use Perl5 modules

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Richard Hainsworth

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Sep 11, 2006, 12:52:27 AM9/11/06
to perl6...@perl.org
I am trying to find out how to use (in perl6) perl5 modules that contain
subroutines.

Here are two scripts from standard modules. Both work in perl5, but I
cant find a way to use them using pugs (I am using the Debian package
with version 6.2.10-4build1 on GNU/Linux/Ubuntu)

<start of perl5 script - straight out of the Time::gmtime documentation>
use strict;
use Time::gmtime;

my $gm = gmtime();
printf "The day in Greenwich is %s\n",
(qw(Sun Mon Tue Wed Thu Fri Sat Sun))[ $gm->wday() ];
<end of script>

<terminal output, under linux>

$ perl ./p5test.pl
Tue

<start of perl6 script>
use perl5:Time::gmtime;

my $gm = gmtime();
printf "The day in Greenwich is %s\n",
(qw(Sun Mon Tue Wed Thu Fri Sat Sun))[ $gm.wday() ];
# note the change from -> to .
<end of script>

<terminal output>

$ pugs ./p5test.p6
*** No compatible subroutine found: "&gmtime"
at ./p5test.p6 line 6, column 10-18

<second example>

<perl5 script>
use strict;
use Text::Balanced qw(extract_tagged);

my $txt = '<atag>now and then</atag>some text';

my @ret_pars = extract_tagged($txt);

print join("\n",@ret_pars),"\n";
print "$@\n" if $@;
<end script>

<terminal output>
$ perl ./p5test.pl
<atag>now and then</atag>
some text

<atag>
now and then
</atag>

<perl6 script>
use perl5:Text::Balanced qw(extract_tagged);

my $txt = '<atag>now and then</atag>some text';

my @ret_pars = extract_tagged($txt); # this is line 8

print join("\n",@ret_pars),"\n";
#print "$@\n" if $@;
# commented this out as caused a compile error, probably another
# variable should be used for errors.

<terminal output>
$ pugs ./p5test.p6
*** No compatible subroutine found: "&extract_tagged"
at ./p5test.p6 line 5, column 16-36
<terminal output end>

What is going wrong? What have I done wrong? I tried several
alternatives, like putting the & sigil on the function. I just got
different sorts of errors.

Richard


Trey Harris

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Sep 11, 2006, 2:07:26 AM9/11/06
to Richard Hainsworth, perl6...@perl.org
In a message dated Mon, 11 Sep 2006, Richard Hainsworth writes:
> I am trying to find out how to use (in perl6) perl5 modules that contain
> subroutines.

Imports from Perl 5 modules don't currently work.

You can workaround this using .can, see below.

> use perl5:Time::gmtime;
>
> my $gm = gmtime();
> printf "The day in Greenwich is %s\n",
> (qw(Sun Mon Tue Wed Thu Fri Sat Sun))[ $gm.wday() ];
> # note the change from -> to .

use v6-alpha;
use perl5:Time::gmtime;
our &gmtime := Time::gmtime.can('gmtime');

my $gm = gmtime();
say "The day in Greenwich is {(<Sun Mon Tue
Wed Thu Fri Sat Sun>)[ $gm.wday ] }";

There is no printf. You can use a string closure as above, or
say/print with sprintf.

The same goes for your other example:

> use perl5:Text::Balanced qw(extract_tagged);
>
> my $txt = '<atag>now and then</atag>some text';
>
> my @ret_pars = extract_tagged($txt); # this is line 8
>
> print join("\n",@ret_pars),"\n";
> #print "$@\n" if $@;
> # commented this out as caused a compile error, probably another
> # variable should be used for errors.

use perl5:Text::Balanced;
our &extract_tagged := Text::Balanced.can('extract_tagged');

my $txt = '<atag>now and then</atag>some text';

my @ret_pars = extract_tagged($txt); # this is line 8

.say for @ret_pars;
say $! if $!;


$@ is no more, it's $! for all errors whatever their provender. In this
case there's no need for a join, but you could have written it:

say @ret_pars.join("\n");

if you liked.

All that said, there's a problem with Text::Balanced running under pugs;
@ret_pars is reversed from what it should be. I'm not sure what's going
on.

Trey

Richard Hainsworth

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Sep 13, 2006, 11:46:32 AM9/13/06
to Trey Harris, perl6...@perl.org
Where is .can documented?

I saw .can in one of the examples in the pugs distribution, but I didnt
know where it came from, viz., was it related to perl6 or the module
that had been imported.

Not quite sure how the following two statements can be consistent:
'imports from Perl5 modules dont work' and 'there is a workaround with
.can'. From the code examples below, .can seems to be importing the
methods from the modules.

If .can is a universal workaround, then surely a pugs wrapper could be
written for any perl5 module along the lines

use v6-alpha;
use perl5:SomeModule::SomeSubModule;
our &aPublicSub := SomeModule::SomeSubModule.can('aPublicSub');

and so on for all the sub's in the module.

Regards,
Richard

Audrey Tang

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Sep 13, 2006, 12:20:24 PM9/13/06
to Trey Harris, Richard Hainsworth, perl6...@perl.org

在 Sep 11, 2006 2:07 PM 時,Trey Harris 寫到:

> In a message dated Mon, 11 Sep 2006, Richard Hainsworth writes:
>> I am trying to find out how to use (in perl6) perl5 modules that
>> contain subroutines.
>
> Imports from Perl 5 modules don't currently work.

Actually, explicit imports do work (as of a couple weeks ago):

use perl5:Time::gmtime <gmtime>;
say gmtime.wday;

Implicit imports is not yet supported, though...

Audrey

Mark Stosberg

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Sep 16, 2006, 10:57:19 PM9/16/06
to perl6...@perl.org

Thanks for the status update. I've reflected this on the related wiki page:
http://rakudo.org/perl6/index.cgi?using_perl_5_embedding

I welcome other tips about Perl 5 embedding to also appear there!

Mark

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