Challenge 147 task 1

1 files changed, 70 insertions, 0 deletions

diff --git a/challenge-147/jo-37/perl/ch-1.pl b/challenge-147/jo-37/perl/ch-1.pl
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+#!/usr/bin/perl -s
+
+use v5.24;
+use Test2::V0;
+use warnings FATAL => 'all';
+use Math::Prime::Util qw(fromdigits todigits is_prime);
+use Data::Dump qw(dd pp);
+use experimental 'signatures';
+
+our ($tests, $examples, $base);
+$base ||= 10;
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [-base=B] [N]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+-base=B
+    use base B. Default: 10
+
+N
+    check if N is a left-truncatable prime in base B
+
+EOS
+
+
+### Input and Output
+
+say 0 + !!is_truncatable_prime(shift, $base);
+
+
+### Implementation
+
+sub is_truncatable_prime ($p, $b) {
+    my @p = todigits($p, $b);
+    while (@p) {
+        $p = fromdigits([@p], $b);
+        return unless is_prime($p);
+        shift @p;
+    }
+	1;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        ok is_truncatable_prime(9137, 10), 'example';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+        
+        ok !is_truncatable_prime(15, 10), '15';
+        ok  is_truncatable_prime(17, 10), '17';
+        ok !is_truncatable_prime(19, 10), '19';
+	}
+
+    done_testing;
+    exit;
+}