Data commit

Task/Unprimeable-numbers/Perl/unprimeable-numbers.pl

@@ -0,0 +1,30 @@
+use strict;
+use warnings;
+use feature 'say';
+use ntheory 'is_prime';
+use enum qw(False True);
+
+sub comma { reverse ((reverse shift) =~ s/(.{3})/$1,/gr) =~ s/^,//r }
+
+sub is_unprimeable {
+    my($n) = @_;
+    return False if is_prime($n);
+    my $chrs = length $n;
+    for my $place (0..$chrs-1) {
+        my $pow = 10**($chrs - $place - 1);
+        my $this = substr($n, $place, 1) * $pow;
+        map { return False if $this != $_ and is_prime($n - $this + $_ * $pow) } 0..9;
+     }
+     True
+}
+
+my($n, @ups);
+do { push @ups, $n if is_unprimeable(++$n); } until @ups == 600;
+say "First 35 unprimeables:\n" . join ' ', @ups[0..34];
+printf "\n600th unprimeable: %s\n", comma $ups[599];
+
+map {
+    my $x = $_;
+    while ($x += 10) { last if is_unprimeable($x) }
+    say "First unprimeable that ends with $_: " . sprintf "%9s", comma $x;
+} 0..9;