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| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | lib/prime.rb | 9 |
2 files changed, 13 insertions, 1 deletions
@@ -1,3 +1,8 @@ +Tue Oct 20 12:17:50 2015 Marc-Andre Lafortune <ruby-core@marc-andre.ca> + + * lib/prime.rb: Optimize Integer#prime? + Patch by Nick Slocum [Bug #10354] + Tue Oct 20 08:12:47 2015 Rei Odaira <Rei.Odaira@gmail.com> * configure.in: pthread_getattr_np is broken on AIX. diff --git a/lib/prime.rb b/lib/prime.rb index c9575f6a2a..d99a51a967 100644 --- a/lib/prime.rb +++ b/lib/prime.rb @@ -31,7 +31,14 @@ class Integer # Returns true if +self+ is a prime number, else returns false. def prime? - Prime.prime?(self) + return self >= 2 if self <= 3 + return false if self % 2 == 0 or self % 3 == 0 + (5..(self**0.5).floor).step(6).each do |i| + if self % i == 0 || self % (i + 2) == 0 + return false + end + end + true end # Iterates the given block over all prime numbers. |