[Melbourne-pm] overloading 'print'

Mathew Robertson mathew.robertson at netratings.com.au
Fri Mar 17 00:07:03 PST 2006

>> Does anone know how to overload 'print'?
> The short answer is that you can't.  Print isn't one of Perl's overloadable
> functions.  (The reason is that the syntax is special cased. You cannot make a
> user function with the same prototype.)
ok - I'm guessing this is because print can take a filehandle as the 
first argument ?
> The longer answer is that you can... if you use IO::File and its print method.
> Then you can just subclass IO::File, and mask the print method to do what you need.
> The other non-overridable functions are listed in receipt 12.11 in the Perl
> Cookbook (1st Edition).  Basically, if the keyword function in toke.c returns a
> negative number, then that function can't be overridden.
ok - thats a bit complicated.  Any ideas on the implementation of the 
sub-class of IO::File ?

ASIDE:  The reason for wanting to override 'print' is...  I have built a 
language translation module (Locale::MakePhrase) which works quite well 
- now I am working on simplifying its usage so that it can be used 
within applications more easily. eg:

Currently if I want to print out a string translated (to say Chinese), I 
would code something like:

  use Locale::MakePhrase;
  my $mp = Locale::MakePhrase->new(language => 'zn_ch', ....);
  print $mp->translate("Some text to translate");

thus to use the module within your application, would require the 
application code to modified to support the L::M syntax.  What I would 
like to do is extend L::M to override 'print' so that the code becomes 
much simpler:

  use Locale::MakePhrase qw(print);
  Locale::MakePhrase->new(language  => 'zn_ch',...);
  print "Some text to translate";

Thus with two simple lines at the top of the application, you 
automagically get all of the translation facilities.  If you choose to 
use a different translation tool, you simply change those two lines - 
thus saving you from having to re-code your app for the new API.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.pm.org/pipermail/melbourne-pm/attachments/20060317/a442d5f6/attachment-0001.html

More information about the Melbourne-pm mailing list