Re: Constants (was Re: [Nms-cgi-devel] Various Stuff);

[Joseph F. R. <rya...@os...>]

Is this REALLY necessary?  Do we really want to include this in each 
distribution?

Tell me; how many of you use constants for configuration stuff in your own 
Perl code?  It's NEVER done.  The constant pragma isn't even used much, and 
that is in the core.

I think using constants for the config is bad for these reasons:

1.) Clutters the code (see below) - don't forget that we are trying to 
teach good practice
2.) Changes look from MWS - upgraders will get confused
3.) Changes code - anyplace that we used variables in a normal Perl fashion 
would need to be restructured
4.) Less stable - NMS is there partially to teach - what happens when a 
newbie starts changing the code, and can't figure out why he is getting a 
fatal error when he assigns to a variable?  He's going to get discouraged 
and quit.
5.) Unnecessary - The goddamn code works fine now, why do we need to change 
it?  I honestly don't see ANY advantage(s).


At 08:24 AM 1/30/2002 +0000, you wrote:
>On Tue, 29 Jan 2002, Jonathan Stowe wrote:
> >
> > I'm having a little difficulty with the tied scalar part - that would be
> > the best bet though if we could hide the implementation details ...
> >
>
>
>I was having a little moment of brainlessness with this:
>
>#!/usr/bin/perl -w
>
>use strict;
>
>BEGIN
>{
>   @main::config_vars = qw($foo);
>};
>
>
>use vars @main::config_vars;
>
>$foo = 'zub';
>
>
>foreach my $var (@main::config_vars)
>{
>
>   no strict 'refs';
>
>   $main::tmp = eval "$var";
>
>   $var =~ s/\$//g;
>
>   my $obj = tie ${$var}, 'ReadOnly';
>
>   ${$var} = $main::tmp;
>
>   use strict 'refs';
>
>   $obj->readonly(1);
>
>
>}
>
>$foo = 'gab';
>
>
>BEGIN
>{
>
>    package ReadOnly;
>
>    sub TIESCALAR
>    {
>
>      my ( $class ) = @_;
>
>
>      my $gab = {readonly => 0, value => ''};
>
>      return( bless $gab, $class);
>    }
>
>
>    sub STORE
>    {
>       my ( $self, $value  ) = @_;
>
>
>       if ( $self->readonly )
>       {
>         die 'No you dont matey';
>       }
>       else
>       {
>         $self->{value} = $value;
>       }
>    }
>
>    sub FETCH
>    {
>       my ( $self) = @_;
>
>
>       return $self->{value};
>    }
>
>    sub readonly
>    {
>       my ( $self, $readonly ) = @_;
>
>       if ( defined $readonly )
>       {
>          $self->{readonly} = $readonly;
>       }
>
>       return $self->{readonly};
>    }
>
>}
>
>
>Equally shocking as I am sure you will agree.
>
>The XS version is a lot nicer -  shame we can't use that:
>
>#include "EXTERN.h"
>#include "perl.h"
>#include "XSUB.h"
>
>
>MODULE = ReadOnly               PACKAGE = ReadOnly
>
>
>void
>readonly(sv)
>SV *sv
>         PPCODE:
>            SvREADONLY_on(sv);
>
>
>:)
>
>
>I'm sure there is already a module that does this on CPAN, but I've
>reinvented it anyhow (by the time I'd done the above and got a harness
>to test it I'd written a module) ... if anyone is interested it can be
>found in its entirety at:
>
>    <http://petunia.gellyfish.com/modules/ReadOnly-1.2.tar.gz>
>
>Or will be when I get to the office.
>
>/J\
>--
>Jonathan Stowe                      |
><http://www.gellyfish.com>          |      This space for rent
>                                     |
>
>
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