Largest prime factor: Difference between revisions
→{{header|Raku}}: add example of much faster version using external library
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=={{header|Raku}}==
Note: These are both extreme overkill for the task requirements.
Pure Raku, not particularly fast.▼
Pure Raku. Using [https://modules.raku.org/search/?q=Prime%3A%3AFactor Prime::Factor] from the [https://modules.raku.org/ Raku ecosystem]. Makes it to 2^95 - 1 in 1 second on my system.
<lang perl6>use Prime::Factor;
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for flat 600851475143, (1..∞).map: { 2 +< $_ - 1 } {
say "Largest prime factor of $_: ",
}</lang>
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Largest prime factor of 2475880078570760549798248447: 23140471537
Largest prime factor of 4951760157141521099596496895: 2796203
Largest prime factor of 9903520314283042199192993791: 658812288653553079
Largest prime factor of 19807040628566084398385987583: 165768537521
Largest prime factor of 39614081257132168796771975167: 30327152671</pre>
===Particularly fast===
Using [[:Category:Perl|Perl 5]] [[:Category:ntheory|ntheory]] library via [https://modules.raku.org/search/?q=Inline%3A%3APerl5 Inline::Perl5]. Makes it to about 2^155 - 1 in 1 second on my system. ''Varies from 2^145-1 (lowest seen) to 2^168-1 (highest seen).''
<lang perl6>use Inline::Perl5;
my $p5 = Inline::Perl5.new();
$p5.use: 'ntheory';
my &lpf = $p5.run('sub { ntheory::todigitstring ntheory::vecmax ntheory::factor $_[0] }');
my $start = now;
for flat 600851475143, (1..∞).map: { 2 +< $_ - 1 } {
say "Largest prime factor of $_: ", lpf "$_";
last if now - $start > 1; # quit after one second of total run time
}</lang>
Same output only much longer.
=={{header|Ring}}==
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