grepping arrays

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

Sorry about the two questions in the same day but this is really bugging me. I have a form which I'm using but of course I underestimated the maturity of the people who use it and I got a lot of people tossing in swear words on the sign up form *sigh*.

I tried adding a word filter but when I added it the filter blocked EVERYTHING, even things that weren't in the @ignore didn't go through. Ugh, I am getting frustrated with this one. Why is it blocking things I'm not asking it to?

if(param()){
    my $username  = param('username');
    $username =~ s/\s+\z//;
    my $askname   = param('askname');
    $askname =~ s/\s+\z//;    
    my $update = param('update');   
    
    if($username){
        if($askname){
        
            if(grep($username, @ignore) || grep($askname, @ignore)) {
                print "That didn't quite work";
                exit;
                }
        
            if($update eq "add"){
                if(exists $list{$username}){
                    print "Username already exists in database.\n";
                    }
                else{
                    $list{$username} = $askname;
                    print "Username was added to our system!<p>\n";

                }
            }
            elsif($update eq "rem"){
                if(exists $list{$username}){
                    delete $list{$username};
                    print "Account information was removed from the sy
+stem.\n";
                    }
                else{
                    print "Oops, it doesn't appear that username is in
+ our database.\n";
                }
            }
        }
        else{
            print "For this to work please add your username.\n";
        }
    }else{
        print "Unless your name is null, please go back and fill it in
+.\n";
    }
}

            print end_html();
[download]

Comment on grepping arrays Download Code

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Re: grepping arrays by BrowserUk (Patriarch) on Jun 21, 2003 at 21:42 UTC
Your problem is that you misunderstand the way perlfunc:grep works. As a hint, this line `if(grep($username, @ignore) \|\| grep($askname, @ignore)) {` [download] Should probably look something like this `if(grep( /$username/, @ignore) \|\| grep( /$askname/, @ignore)) {` [download] Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller	[reply] [d/l] [select]
Re: grepping arrays by George_Sherston (Vicar) on Jun 21, 2003 at 21:52 UTC
I think the main thing going wrong is that your first argument needs to be a block of code rather than a scalar. `grep` works by running the block of code for each element in the array and returning the number of times it was true (or, if you did `@output = grep...` it gives you the list of elements from your input array for which it was true... but you don't care about that). So this `if(grep($username =~ m/\b$_\b/, @ignore)) { print "That didn't quite work"; }` [download] ... may do what you want. (the `\b`s are so you only catch whole words). § George Sherston	[reply] [d/l] [select]
Re: grepping arrays by revdiablo (Prior) on Jun 21, 2003 at 22:59 UTC
Your question has been answered directly by the other fine monks, but I thought it would also be useful to point out that this is a common case where a hash is used instead of an array. Hashes make checks for existence much faster than iterating through your array each time (which is what `grep` does). Here's an example of how you could make your array into a hash: `my %ignore; @ignore{ @ignore } = (); # note this is a hash slice. the first @ignor +e # is referring to the hash` [download] And here's how you can check the hash for existence: `if (exists $ignore{$username} or exists $ignore{$askname}) {`	[reply] [d/l] [select]
Re: grepping arrays by grantm (Parson) on Jun 21, 2003 at 23:18 UTC
You might also want to take a look at Regexp::Common::profanity.	[reply]
Re: grepping arrays by Aristotle (Chancellor) on Jun 22, 2003 at 00:15 UTC
What you're missing is that the first parameter to grep is supposed to be an expression or a block of code, whose return value determines success or failure of each match. In your case, that return value is found by evaluating `$username`, which is most likely a true value. So then the grep gives you every single element from `@ignore` because the expression was true for every one of them. What you really meant to do is either a straight comparison: `grep $username eq $_, @ignore` [download] or a pattern match: `grep /$username/, @ignore` [download] Note that the second is still an expression, and gets evaluated with each element in `@ignore` aliased to `$_` in turn. You can just write it in this short form because by default, matches are attempted against `$_` unless otherwise specified. So the second form is exactly equivalent to this: `grep $_ =~ /$username/, @ignore` [download] Makeshifts last the longest.	[reply] [d/l] [select]
Re: grepping arrays by hsweet (Pilgrim) on Jun 21, 2003 at 23:47 UTC
Looks like your substitutions are a bit too broad. You could put a regex into your if for a simple filter. `if (/badword/i){print "You are a naughty person...You should wash your + mouth with soap}` [download] Or you can use substitutions `s/badword1//; s/badword2//; ..etc;` [download] Time flies like an arrow, fruit flies like banannas	[reply] [d/l] [select]
Re: grepping arrays by coldfingertips (Pilgrim) on Jun 21, 2003 at 21:48 UTC
Thank you so much!!	[reply]


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