3monkeys

isPrime in One Line of Perl

As a follow up to Finding the first 20 terms in the Fibonacci Series, next in the 3Monkey Golf series — Determining if a number is prime. The following is a fairly simple Perl one liner to do the trick. I’m interested in seeing implementations in other languages. I will be posting follow ups with the best submissions from both Golf challenges at the end of the week.

Perl Code

perl -wle'print(1)if(1xtarget_number)!~/^1?$|^(11+?)\1+$/'

Character count = 36

Golf Rules:

Only pure source characters are counted, that is, in my example the characters “perl -wle’” and trailing “‘” do not count.

For this challenge, the meta variable target_number counts as a single character, butshould be able to be replaced with any reasonable number.

Output must be of the form 0, 1, Y, N, true, false, or some other easily recognizable indication of Yes or No.

Please note that use og characters such as > and < require escaping as & lt; and & gt;
If you have difficulty posting your solution please email me the solution at stacy (at) 3monkeyweb (period) com and I will make sure it gets posted.

Good luck, and until next time.

-3Monkeys

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(4 votes, average: 6.75 out of 10)

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This entry was posted on Tuesday, July 17th, 2007 at 4:45 am and is filed under Fun, Golf, Perl, Programming. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

7 Responses to “isPrime in One Line of Perl”

1. bloid Says:
   July 17th, 2007 at 8:32 am

   The quote at the end of your one line is the wrong type, copy-pasting it doesn’t work (it’s early and it took me a while to spot that)

   And for people who want to see how and why this works, have a look here:

   http://montreal.pm.org/tech/neil_kandalgaonkar.shtml

2. 3Monkeys Says:
   July 17th, 2007 at 3:19 pm

   Finally got the ' correct It should work now as a copy/paste.

3. 3Monkeys Says:
   July 17th, 2007 at 5:20 pm

   @Bloid, I think that’s where I first found this one. I have several of these tucked away for study.

4. Mikhail Sayapin Says:
   July 17th, 2007 at 7:27 pm

   Unfortunately, the code doesn’t work: perl -wle ‘print(1)if(1x(2E+32582657-1))!~/^1?$|^(11+?)\1+$/’ outs nothing. But 2E+32582657-1 IS prime. In fact it’s the largest prime ever found. Well, 2E+32582657-1 is “inf” in Perl, but it’s a fault of Perl, not us fellow programmers. Perl is just not suitable for this kind of tasks. Or prove us it is. Anyway, the idea and syntax are very, very cool. *bows*

5. 3Monkeys Says:
   July 17th, 2007 at 7:52 pm

   @Mikhail, that is why I added the “should be able to be replaced with any reasonable number” caveat in the “rules”. You are correct though about perl being able to handle extremely large numbers. I was hoping for a python shot at it as it should be able to handle it.

6. Mikhail Sayapin Says:
   July 18th, 2007 at 6:18 am

   Well, I see. The same “functionality” Python code is: not re.match(’^1?$|^(11+?)\\1+$’,'1′*target_number) and is 38 chars. Prints “True” if the target_number is prime. However, it doesnt work with long integers and string integers. Definitely good way is to use SciPy library.

7. Daniel Spiewak Says:
   July 18th, 2007 at 5:59 pm

   http://www.dzone.com/links/isprime_in_one_line_of_groovy.html

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