Go Premium for a chance to win a PS4. Enter to Win


perl, check if data exists in array

Posted on 2010-11-17
Medium Priority
Last Modified: 2012-06-21
@coins = ("Quarter","Dime","Nickel");
my $money = "Dime";

How do I check if Dime is one of the value in the array?  Would be nice if i don't have to loop through it.
Question by:rgbcof

Accepted Solution

whosbetterthanme earned 500 total points
ID: 34159681

@coins = ("Quarter","Dime","Nickel");
my $money = "Dimes";

if (grep(/$money/,@coins)) {
print "Yep, it's there\n";

Author Closing Comment

ID: 34159727
That works.  
LVL 85

Expert Comment

ID: 34161953
perldoc -q "How can I tell whether a certain element is contained in a list or array"
Found in pods/perlfaq4.pod
       How can I tell whether a certain element is contained in a list or

       (portions of this answer contributed by Anno Siegel)

       Hearing the word "in" is an indication that you probably should have
       used a hash, not a list or array, to store your data.  Hashes are
       designed to answer this question quickly and efficiently.  Arrays

       That being said, there are several ways to approach this.  If you are
       going to make this query many times over arbitrary string values, the
       fastest way is probably to invert the original array and maintain a
       going to make this query many times over arbitrary string values, the
       fastest way is probably to invert the original array and maintain a
       hash whose keys are the first array's values.

               @blues = qw/azure cerulean teal turquoise lapis-lazuli/;
               %is_blue = ();
               for (@blues) { $is_blue{$_} = 1 }

       Now you can check whether $is_blue{$some_color}.  It might have been a
       good idea to keep the blues all in a hash in the first place.

       If the values are all small integers, you could use a simple indexed
       array.  This kind of an array will take up less space:

               @primes = (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31);
               @is_tiny_prime = ();
               for (@primes) { $is_tiny_prime[$_] = 1 }
               # or simply  @istiny_prime[@primes] = (1) x @primes;

       Now you check whether $is_tiny_prime[$some_number].

       If the values in question are integers instead of strings, you can save
       quite a lot of space by using bit strings instead:

               @articles = ( 1..10, 150..2000, 2017 );
               undef $read;
               for (@articles) { vec($read,$_,1) = 1 }

       Now check whether "vec($read,$n,1)" is true for some $n.

       These methods guarantee fast individual tests but require a re-
       organization of the original list or array.  They only pay off if you
       have to test multiple values against the same array.

       If you are testing only once, the standard module "List::Util" exports
       the function "first" for this purpose.  It works by stopping once it
       finds the element. It's written in C for speed, and its Perl equivalent
       looks like this subroutine:

               sub first (&@) {
                       my $code = shift;
                       foreach (@_) {
                               return $_ if &{$code}();

       If speed is of little concern, the common idiom uses grep in scalar
       context (which returns the number of items that passed its condition)
       to traverse the entire list. This does have the benefit of telling you
       how many matches it found, though.

               my $is_there = grep $_ eq $whatever, @array;

       If you want to actually extract the matching elements, simply use grep
       in list context.

               my @matches = grep $_ eq $whatever, @array

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

On Microsoft Windows, if  when you click or type the name of a .pl file, you get an error "is not recognized as an internal or external command, operable program or batch file", then this means you do not have the .pl file extension associated with …
Many time we need to work with multiple files all together. If its windows system then we can use some GUI based editor to accomplish our task. But what if you are on putty or have only CLI(Command Line Interface) as an option to  edit your files. I…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Six Sigma Control Plans

963 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question