RE: Finding if a module is already 'require'd

[NYIMI Jose (BMB)]

> -----Original Message-----
> From: Janek Schleicher [mailto:[EMAIL PROTECTED]] 
> Sent: Monday, September 30, 2002 10:05 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Finding if a module is already 'require'd
> 
> 
> Ramprasad A Padmanabhan wrote at Mon, 30 Sep 2002 09:36:50 +0200:
> 
> > How do I find in a function if a particular module is already loaded
> > 
> > for eg,
> > 
> > sub mysub {
> >     my @vars = @_;
> >     require Data::Dumper unless ( already_required('Data::Dumper'));
> >     print Data::Dumper::Dumper(\@vars);
> > }
> > 
> > I want help writing the function already_required()
> 
> You don't need it.
> From perldoc -f require:
> 
>                Otherwise, demands that a library file be included
>                if it hasn't already been included.  The file is
>                included via the do-FILE mechanism, which is
>                essentially just a variety of "eval".  Has
>                semantics similar to the following subroutine:
> 
> So a required module is only loaded when it hadn't been loaded yet.

As from which version of Perl this functionality has been included.
I'm asking this because, I have seen in the DBI code (DBI.pm file)
That the author is checking if a DBD::* module has been already installed (loaded) ...

Here an extract of DBI.pm file :


sub install_driver {            # croaks on failure
    my $class = shift;
    my($driver, $attr) = @_;
    my $drh;

    $driver ||= $ENV{DBI_DRIVER} || '';

    # allow driver to be specified as a 'dbi:driver:' string
    $driver = $1 if $driver =~ s/^DBI:(.*?)://i;

    Carp::croak("usage: $class->install_driver(\$driver [, \%attr])")
                unless ($driver and @_<=3);

    # already installed
    return $drh if $drh = $DBI::installed_drh{$driver};

[snip]


José.


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