Bug #7395
closedNegative numbers can't be primes by definition
Description
from github:
https://github.com/ruby/ruby/pull/187
By definition, a prime number can be a positive integer greater than 1.
Files
Updated by usa (Usaku NAKAMURA) almost 12 years ago
- Status changed from Open to Assigned
Updated by ko1 (Koichi Sasada) over 11 years ago
- Subject changed from Negative numbers can't be primes by definition to Negative numbers can't be primes by definition
- Target version changed from 2.0.0 to 2.1.0
Updated by hsbt (Hiroshi SHIBATA) almost 11 years ago
- Target version changed from 2.1.0 to 2.2.0
Updated by ayumin (Ayumu AIZAWA) over 10 years ago
- Status changed from Assigned to Closed
- % Done changed from 0 to 100
Applied in changeset r45878.
- lib/prime.rb (Prime#prime?): negative numbers can't be primes
by definition. reported by Ivan Kataitsev. [Bug #7395] - test/test_prime.rb: add test.
Updated by hsbt (Hiroshi SHIBATA) over 10 years ago
ayumin
this issue seems incompatible changes. it should be add NEWS.
Updated by mame (Yusuke Endoh) over 10 years ago
- Status changed from Closed to Assigned
Read the rdoc carefully:
Returns true if +self+ is a prime number, false for a composite.
By definition, a composite number can be also a positive integer greater than 1.
http://mathworld.wolfram.com/CompositeNumber.html
Thus,
1.prime? #=> false
0.prime? #=> false
(-1).prime? #=> false
looks all buggy (or undefined behavior) to me.
If we can change the spec, it would be good to raise an exception, return nil, or at least update the rdoc.
Anyway, the maintainer (Yugui) should treat this, I think.
--
Yusuke Endoh mame@tsg.ne.jp
Updated by ayumin (Ayumu AIZAWA) over 10 years ago
Endo-san
Your opinion seems right.
IMHO, I think Rdoc should be updated.
This method should evaluate the number is prime number or not.
It should not refer the number is composite number or not.
We may have to confirm Yugui's intention anyway.
Luckily I'm going to meet her on Wed, so I will ask her about this issue.
Shibata-san
I will add information to NEWS, once change was accepted by Yugui.
Updated by ayumin (Ayumu AIZAWA) over 10 years ago
- Status changed from Assigned to Closed