The set of all prime numbers.
Example
Prime.each(100) do |prime| p prime #=> 2, 3, 5, 7, 11, ...., 97 end
Prime is Enumerable:
Prime.first 5 # => [2, 3, 5, 7, 11]
Retrieving the instance
Prime.new is obsolete. Now Prime has the default
instance and you can access it as Prime.instance.
For convenience, each instance method of Prime.instance can be
accessed as a class method of Prime.
e.g.
Prime.instance.prime?(2) #=> true Prime.prime?(2) #=> true
Generators
A “generator” provides an implementation of enumerating pseudo-prime numbers and it remembers the position of enumeration and upper bound. Furthermore, it is a external iterator of prime enumeration which is compatible to an Enumerator.
Prime::PseudoPrimeGenerator is the base class for
generators. There are few implementations of generator.
-
Prime::EratosthenesGenerator -
Uses eratosthenes's sieve.
-
Prime::TrialDivisionGenerator -
Uses the trial division method.
-
Prime::Generator23 -
Generates all positive integers which is not divided by 2 nor 3. This sequence is very bad as a pseudo-prime sequence. But this is faster and uses much less memory than other generators. So, it is suitable for factorizing an integer which is not large but has many prime factors. e.g. for #prime? .