Re: FW: Error in Sect. 7 on using a variable as a variable name

Nobody screamed (or even whimpered) so patch committed.  Thanks for point
out the bug, Eric.

-R

At Sat, 19 Jul 2003 23:12:51 -0700,
Robert Spier wrote:
> 
> 
> Eric is correct, the FAQ is wrong.
> 
> The simplest patch is probably:
> 
> --- perlfaq7.pod        31 Jan 2003 17:38:14 -0000      1.14
> +++ perlfaq7.pod        20 Jul 2003 06:09:30 -0000
> @@ -809,5 +809,5 @@
>  use your own hash or a real reference instead.
>  
> -    $fred    = 23;
> +    $USER_VARS{"fred"} = 23;
>      $varname = "fred";
>      $USER_VARS{$varname}++;  # not $$varname++
> 
> 
> 
> 
> 
> === Forwarded Message:
> 
> Date: Fri, 11 Jul 2003 09:40:56 -0500
> From: Eric Pement <[email protected]>
> Subject: Error in Sect. 7 on using a variable as a variable name
> To: [email protected]
> 
> To whom it may concern:
> 
> In trying to learn about references, I believe I've found an error in
> the Perl FAQ, section 7 ("General Perl Language Issues"), under the
> question, "How can I use a variable as a variable name?" The problem
> exists in the documentation for Perl 5.6 and Perl 5.8. I tried
> emailing this message to "[email protected]" and got
> no response. Now that I've got a newer email address, perhaps I can
> get a reply.
> 
> The FAQ currently reads in part:
> 
>    By using symbolic references, you are just using the package's
>    symbol-table hash (like %main::) instead of a user-defined hash.
>    The solution is to use your own hash or a real reference instead.
> 
>        $fred    = 23;
>        $varname = "fred";
>        $USER_VARS{$varname}++;  # not $$varname++
> 
> This solution does not work and does not provide "24" as the FAQ
> authors seem to have intended. This can be demonstrated like so:
> 
>     #!/usr/bin/perl
>     use strict;
>     my ($fred, $varname, %USER_VARS);
>     $fred    = 23;
>     $varname = "fred";
>     $USER_VARS{$varname}++;
>     print "Value is: $USER_VARS{$varname}\n";
> 
> The output is "Value is: 1". So how should this be corrected? Here's
> a replacement I suggest for the FAQ. It returns "24", as expected:
> 
>     $USER_VARS{fred} = 23;
>     $varname         = "fred";
>     $USER_VARS{$varname}++;  # not $$varname++
> 
> Finally, the FAQ says another solution is to use a real reference
> instead. Perhaps you could tell new perl users how this is done:
> 
>     $fred       = 23;
>     $varname    = \$fred;
>     $$varname++; 
> 
> Thanks in advance for your time.
> 
> 
> -- 
> Eric Pement - [email protected]
> Education Technical Services, MBI
> 
> === End of Forwarded Message