Use of next unless and subs

Win has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

I have some code as follows.


      opendir(DIR_C,"$input_directory") or die $!;
      while(my $job_C=readdir(DIR_C)){   
                
        next unless   $job_C =~ /$tag\.txt$/;
         
        my $job_out;
        my $job_new_name; 
        my $job_out_complete;
        my $job_out_complete_B;
        
        
        
        if ($job_C =~ /(.{36})\.txt$/)
          {           
           Check_file_name_conditions ($job_C, $node);                
+     
           next unless ($do_I_pick_up_request == 'Y' && $When_process_
+request== 'Now');
[download]

I have a couple of questions relating to this:

Is the last next unless statement used correctly? I want it to go to the next iteration in the while loop.

Am I right in assuming that $do_I_pick_up_request and $When_process_request will have been picked up when returned from the Check_file_name_conditions sub using return ($do_I_pick_up_request, $When_process_request)?

Comment on Use of next unless and subs Select or Download Code

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Re: Use of next unless and subs by davido (Cardinal) on Jan 31, 2007 at 18:18 UTC
if(){} statements aren't considered loop blocks, and `next` isn't affected by your being within an if(){} statement. It will still jump to the next loop iteration. However, it may simply be less ambiguous to code readers / maintainers if you explicitly specify where to `next` to, using a label on your while loop: `LOOP_NAME: while( ... ) { .... next LOOP_NAME unless .....; }` [download] Dave	[reply] [d/l] [select]
Re: Use of next unless and subs by educated_foo (Vicar) on Jan 31, 2007 at 18:15 UTC
That seems to be correct use of `next`. However, `$do_I_pick_up_request == 'Y'` is actually testing whether `$do_I_pick_up_request` equals zero, so you probably want `eq`.	[reply]
Re: Use of next unless and subs by Herkum (Parson) on Jan 31, 2007 at 18:25 UTC
Sometimes I look at your posts and wonder, do you even try and test your code? You have been here 3 years, you have to have learned something! Make a simple example like this. `#!/usr/bin/perl -w use strict; for my $no (1..10) { print "No. $no \n"; next unless $no < 5; print "\t is less than 5\n"; }` [download] You would have an answer more quickly than the time you spent writing your post.	[reply] [d/l]
Re: Use of next unless and subs by shmem (Chancellor) on Jan 31, 2007 at 18:20 UTC
Is the last next unless statement used correctly? I want it to go to the next iteration in the while loop. Syntactically, yes. Am I right in assuming that $do_I_pick_up_request and $When_process_request will have been picked up when returned from the Check_file_name_conditions sub using return ($do_I_pick_up_request, $When_process_request)? You need the following for that: `my ($do_I_pick_up_request, $When_process_request) = Check_file_name_co +nditions ($job_C, $node);` [download] For your variable checking, use 'eq'. '==' is for numeric comparison. --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l]
Re: Use of next unless and subs by chakram88 (Pilgrim) on Jan 31, 2007 at 18:28 UTC
Am I reading you correctly that in your code you have a subroutine `Check_file_name_conditions` which returns the two values `$do_I_pick_up_request, $When_process_request`? If that's the case, when you call the subroutine you'll want to capture those return values into a var in your current scope to use them. `my ($do, $when) = Check_file_name_conditions($job_C, $node); next unless ($do eq 'Y' && $when eq 'Now');` [download]	[reply] [d/l] [select]