From: "Yugui (Yuki Sonoda)" <yugui@...>
Date: 2009-03-04T17:15:45+09:00
Subject: [ruby-core:22661] Re: [Bug #1243] 1 is prime

On 3/4/09 1:40 AM, Dave B wrote:
> +    value = -value if value < 0  <--- NOT required ?
> +    return false if value < 2
> 
> I think your negative guard is not required?

For a arbitrary positive prime number p, -p is a prime element in the
ring of integers. On the other hand, it is sure that just saying "prime
numbers" means positive ones.

(http://en.wikipedia.org/wiki/Prime_number)
> Without further specification, however, �prime number� always means a
positive integer prime

I am at a loss whether -2.prime? should return true or false?  Which is
more useful for Rubyists?

-- 
Yugui <yugui@yugui.jp>
http://yugui.jp