# Prime.include?(1) hangs Ruby scripts and irb

**URL:** <https://www.ruby-forum.com/t/prime-include-1-hangs-ruby-scripts-and-irb/157777>\
**Category:** Ruby\
**Created:** [January 15, 2009, 8:40am UTC](https://www.ruby-forum.com/t/prime-include-1-hangs-ruby-scripts-and-irb/157777 "2009-01-15T08:40:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Frisco\_Del\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/eb9ed0/32.png) [@Frisco\_Del\_R](https://www.ruby-forum.com/u/Frisco_Del_R)\
**Post date:** [January 15, 2009, 8:40am UTC](https://www.ruby-forum.com/t/prime-include-1-hangs-ruby-scripts-and-irb/157777/1 "2009-01-15T08:40:32Z")

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Ruby version 1.8.6  
Mac OS 10.5.2

I would like a Ruby script to do something if a result is a prime  
number, or do something else if the result is not prime. But Ruby is  
hanging on instance\_of\_Prime.includes?(some prime number). For example,  
in irb:

$ irb

> > require ‘mathn’  
> > =\> true
> 
> > foo=Prime.new  
> > =\> #\<Prime:0x32bab8 @primes=[], @seed=1, @counts=[]\>
> 
> > puts foo.include?(2)  
> > true  
> > =\> nil
> 
> > puts foo.include?(1)

Expected:  
false

Got:  
Nothing, and programs won’t exit.

---

<div class="post-metadata">

**Author:** ![Frisco\_Del\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/eb9ed0/32.png) [@Frisco\_Del\_R](https://www.ruby-forum.com/u/Frisco_Del_R)\
**Post date:** [January 15, 2009, 10:20am UTC](https://www.ruby-forum.com/t/prime-include-1-hangs-ruby-scripts-and-irb/157777/2 "2009-01-15T10:20:30Z")

</div>

-------- Original-Nachricht --------

> Datum: Thu, 15 Jan 2009 16:39:03 +0900  
> Von: Frisco Del R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> An: removed\_email\_address@domain.invalid  
> Betreff: Prime.include?(1) hangs Ruby scripts and irb

> =\> true  
> Got:  
> Nothing, and programs won’t exit.

Hi –

I can confirm that behaviour on Ruby 1.8.7 and Ubuntu 8.04.  
I think you should file a bug with the authors of mathn.

Best regards,

Axel