jenglee jenglee - 1 month ago 16
Perl Question

Grep to find item in perl array

Everytime I input something the code always tells me that it exist. But I know some of the inputs do not exist. Can you help we with what is wrong?

#!/usr/bin/perl

@array = <>;
print "Enter the word you what to match\n";
chomp($match = <STDIN>);

if (grep($match, @array)) {
print "found it\n";
}

Answer

The first arg that you give to grep needs to evaluate as true or false to indicate whether there was a match. So it should be:

# note that grep returns a list, so $matched needs to be in brackets to get the 
# actual value, otherwise $matched will just contain the number of matches
if (my ($matched) = grep $_ eq $match, @array) {
    print "found it: $matched\n";
}

If you need to match on a lot of different values, it might also be worth for you to consider putting the array data into a hash, since hashes allow you to do this efficiently without having to iterate through the list.

# convert array to a hash with the array elements as the hash keys and the values are simply 1
my %hash = map {$_ => 1} @array;

# check if the hash contains $match
if (defined $hash{$match}) {
    print "found it\n";
}
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