week 162, task 1 in Perl

1 files changed, 46 insertions, 0 deletions

diff --git a/challenge-162/julien-fiegehenn/perl/1.pl b/challenge-162/julien-fiegehenn/perl/1.pl
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+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use feature 'say';
+use List::Util 'sum';
+
+# Write a script to generate the check digit of given ISBN-13 code. Please refer wikipedia for more information.
+
+# Example
+# ISBN-13 check digit for '978-0-306-40615-7' is 7.
+
+# https://en.wikipedia.org/wiki/ISBN#ISBN-13_check_digit_calculation
+
+sub isbn_13 {
+    my $number = shift;
+
+    die 'Input required' unless $number;
+
+    # clean up the number
+    $number =~ s/\D//g;
+
+    # we need to do maths on each digit
+    my @digits = split //, $number;
+
+    # discard the check digit
+    pop @digits if @digits == 13;
+
+    # do we have the right amount of digits?
+    die 'This does not look like an ISBN-13' unless @digits == 12;
+
+    # tripple all the even digits
+    $_ *= 3 for @digits[1, 3, 5, 7, 9, 11];
+
+    # and do the maths
+    return 10 - sum(@digits) % 10;
+}
+
+say isbn_13(shift);
+
+__END__
+use Test::More;
+
+is isbn_13('978-0-306-40615-7'), 7;
+
+done_testing;
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