Simple (probably)

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

Hello, I am merely trying to get the number of times a character labeled as $search appears in a series of different hash values.
Instead, I get the number of values which contain at least one $search.
I.E, PERL stops searching once it has found at least one instance of the $search inside the hash value. How can I cound the total amount of $search strings found in every hash key?

    while (my ($key,$value) = each(%no)) {
      if ($value =~/$search/gi) {
      $contains++;
    }
  }
[download]

Each hash value is a long sequence of about 300 characters. If I search for a common letter, I will get $contains to equal to number of hash sequences instead of the true number of characters in the collection of values. Thanks!

Comment on Simple (probably) Download Code

Replies are listed 'Best First'.
Re: Simple (probably) by ikegami (Patriarch) on Dec 13, 2009 at 04:49 UTC
For each hash element, you execute `if ($value =~ /$search/gi) { $contains++; }` [download] `$contains++` isn't in any kind of loop, so it gets executed at most once. So let's add the loop we need: `while ($value =~ /$search/gi) { $contains++; }` [download] This is equivalent, yet simpler and faster: `++contains while $value =~ /$search/gi;` [download] And this is faster yet (assuming `$search` contains no captures): `$contains += () = /$search/gi;` [download] By the way, using `m//g` in scalar context outside of `while` condition is a bug.* This includes using it as an `if` condition. * — Yes, this is a generalisation, but it's accurate for those don't know what makes the statement incomplete.	[reply] [d/l] [select]
Re^2: Simple (probably) by MaroonBalloon (Acolyte) on Dec 13, 2009 at 05:21 UTC
I appreciate your explanations. Very succinct teacher. Kind of unrelated, but what are captures? & What do you mean that m//g is a bug? I am quite a newbie...Thanks! -Eric	[reply]
Re^3: Simple (probably) by ikegami (Patriarch) on Dec 13, 2009 at 05:37 UTC
what are captures? The parens in `if ('foo 123 bar' =~ /(\d+)/) { print("$1\n"); }` [download] `123` [download] What do you mean that m//g is a bug? `for (1..2) { if ('ab' =~ /a/g) { print("match\n"); } else { print("no match\n"); } }` [download] `match no match` [download] `for (1..2) { if ('ab' =~ /a/) { print("match\n"); } else { print("no match\n"); } }` [download] `match match` [download]	[reply] [d/l] [select]
Re: Simple (probably) by FalseVinylShrub (Chaplain) on Dec 13, 2009 at 04:44 UTC
Hi How about this: `while (my ($key,$value) = each(%no)) { $contains++ while $value =~ /$search/gi; }` [download] There's probably a better way, but that seems to work. HTH, FalseVinylShrub Disclaimer: Please review and test code, and use at your own risk... If I answer a question, I would like to hear if and how you solved your problem.	[reply] [d/l]
Re^2: Simple (probably) by MaroonBalloon (Acolyte) on Dec 13, 2009 at 05:18 UTC
Brilliant! Thank you. It worked straight off. I hadn't realized that IF wasn't executing what I needed and that I required "while"	[reply]