Type:
Class

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Prime.new is obsolete.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? .

upper_bound
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::PseudoPrimeGenerator

upper_bound() Instance Public methods

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succ
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::PseudoPrimeGenerator

succ() Instance Public methods returns the next pseudo-prime number, and move

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rewind
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::EratosthenesGenerator

rewind() Instance Public methods

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next
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::OldCompatibility

next() Instance Public methods Alias for:

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new
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::TrialDivisionGenerator

new() Class Public methods

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succ
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::OldCompatibility

succ() Instance Public methods Returns the next prime number and forwards internal

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succ
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::Generator23

succ() Instance Public methods Also aliased as:

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with_object
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::PseudoPrimeGenerator

with_object(obj) Instance Public methods see Enumerator#with_object

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primes
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::TrialDivision

primes() Instance Public methods Alias for:

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next
  • References/Ruby on Rails/Ruby/Classes/Prime/Prime::TrialDivisionGenerator

next() Instance Public methods Alias for:

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