Re: [MacPerl] new: Mac::FileSpec::Unixish in CPAN

[aml@world.std.com (Andrew M. Langmead)]

sean_mis@mail.misinc.net wrote:
> 
> >> I've just sent to CPAN a new module, Mac::FileSpec::Unixish.  It
> >> should be in <http://www.perl.com/CPAN/authors/id/S/SB/SBURKE/>; if
> >
> >If you are going to create a module that does Unix<->Macintosh
> >filesystem mapping, why not override open(), opendir(), etc. to
> >translate them transparently?
> 
> How would one override the filetest operators (functions?) like -s $foo?
> BTW, I've never overridden any core functions, or used overload.pm, but
> looking at overload.pm, it doesn't list the filetesters as things you can

Your right. I don't see a way to override the filetest
operators. Either I havn't looked in the right place, or that really
stinks.

The overload.pm module is not for redefining the standard perl
functions, its for C++ like overloaded operators. For example, if you
have a class and you want someone to be able to add two objects
together and come up with another object as the result.

$blue = new Color 'blue';
$red = new Color 'red';

$purple = $blue + $red;

The recipe for overriding built in functions is buried in the perlsub
documentation file. For overriding the built in functions, you simply
define a similarly named function in your module, and put it into your
@EXPORT_OK list. (Putting it in @EXPORT being considered rather
antisocial.)

@EXPORT_OK = qw(&open &opendir &stat);


sub open (*;$){
  my($fh,$unixname) = @_;
  my $nativname;
  if(defined $unixname) {
    $nativname = nativize($unixname);
  }
  else {
    # handle single arg open(filename) correctly
    # since the filehandle has to be an identifer, it contains no
    # path separators.
    $nativname = (*{$fh} =~ /::(\w+)$/);
  }
  CORE::open($fh,$nativname);
}


When open() is exported it replaces the built in function in the
module that imported it.


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