Sha256: 06810f8242a6d06e2c8d71c0ea837d7aa8dd11c45e464d06001e53b9cae3f3f3
Contents?: true
Size: 528 Bytes
Versions: 12
Compression:
Stored size: 528 Bytes
Contents
# coding: utf-8
class Integer
# Algorithm derived from Formulas for pi(n) and the n-th prime by Sebastian
# Martin Ruiz and Jonathan Sondow [arXiv:math/0210312v2 [math.NT]]
# Returns the number of divisors of self
def τ
n = self
return @nod if defined?(@nod)
square_root = Math.sqrt(n)
@nod = (1..square_root.floor).
map {|i| n.quo(i).to_i - (n - 1).quo(i).to_i }.
reduce(:+) * 2
@nod -= 1 if square_root.integer?
@nod
end
alias :number_of_divisors :τ
alias :d :τ
end
Version data entries
12 entries across 12 versions & 1 rubygems