Looping structure

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

Replies are listed 'Best First'.
Re: Looping structure by pg (Canon) on Nov 28, 2003 at 02:33 UTC
The problem is line 17, that "else" at line 17 has nothing to match, all the brackets before that line matched perfectly. Had you well indented your code, you probably figured out this yourself: `if ( exists $list{$location} ) { my $value = $list{$location}; $value++; $list{$location} = $value; } elsif ( $list{$location} eq "" ) { if ( exists $list{Unknown} ) { my $value = $list{Unknown}; $value++; $list{Unknown} = $value; } } else { $list{Unknown} = "1"; } =document else { $list{$location} = "1"; }` [download] How to fix? it really depends on what you want, and I don't want to second guess. By looking at the exsiting code, the logic looks broken. I don't think it will ever run into that elsif branch. If $list{$location} eq "", obviously exists($list{$location}).	[reply] [d/l]
Re: Looping structure by Roger (Parson) on Nov 28, 2003 at 04:29 UTC
Other monks have pointed our your source of error. I just want to say that you are doing a lot of unnecessary work. For example, the code `my $value = $list{$location}; $value++; $list{$location} = $value;` [download] can be written as - `$list{$location}++;` [download] And your entire code block can be simplified to just one line of Perl (assuming your $location is never '0') - `$list{ $location \|\| 'Unknown' }++;` [download]	[reply] [d/l] [select]
Re: Looping structure by The Mad Hatter (Priest) on Nov 28, 2003 at 02:36 UTC
I don't understand how you can't figure out what line the error is on. Read the error, it tells you: `tom@wintermute tom $ perl -c t syntax error at t line 17, near "else" t had compilation errors.` [download] Reformatted code: Read more... (2 kB)	[reply] [d/l] [select]
Re: Looping structure by sunadmn (Curate) on Nov 28, 2003 at 04:10 UTC
It looks like my fellow monks have corrected you, but I would like to offer a helpfull perl hint. When wanting to test a script before running it try this at the command line `perl -cwTM-strict ./yourscript.pl` [download] This will help debug your code without actually running it and possiblyt messing something up. USE PERL	[reply] [d/l]
Re: Looping structure by chanio (Priest) on Nov 28, 2003 at 17:52 UTC
Most programming difficulties might come from having an incomplete knowledge base or not having the right tools to work with. You might need XEmacs that points you all the ({[ pairs for easy visualizing them. There are also other editors that do the same. But XEmacs, once you get used to it looks very much more an expert in perl than oneself :) . By using -w at the starting line: `#!/use/bin/perl -w ##and followed by use strict;` [download] Might help a lot. But remember that you might need to add some more conditionals to your sentences: `if (($location) && exists($list{$location})) { my $value = $list{$location}; $value++; $list{$location} = $value if ($value);` [download] ...for example, just to illustrate the use of verified existing variables. But then, the error messages are very descriptive and easy to track down.	[reply] [d/l] [select]