diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/prime.rb | 47 |
1 files changed, 29 insertions, 18 deletions
diff --git a/lib/prime.rb b/lib/prime.rb index 113af9f702..d2de8dc017 100644 --- a/lib/prime.rb +++ b/lib/prime.rb @@ -174,17 +174,23 @@ class Prime # Re-composes a prime factorization and returns the product. # + # For the decomposition: + # + # [[p_1, e_1], [p_2, e_2], ..., [p_n, e_n]], + # + # it returns: + # + # p_1**e_1 * p_2**e_2 * ... * p_n**e_n. + # # == Parameters - # +pd+:: Array of pairs of integers. The each internal - # pair consists of a prime number -- a prime factor -- - # and a natural number -- an exponent. + # +pd+:: Array of pairs of integers. + # Each pair consists of a prime number -- a prime factor -- + # and a natural number -- its exponent (multiplicity). # # == Example - # For <tt>[[p_1, e_1], [p_2, e_2], ...., [p_n, e_n]]</tt>, it returns: + # Prime.int_from_prime_division([[3, 2], [5, 1]]) #=> 45 + # 3**2 * 5 #=> 45 # - # p_1**e_1 * p_2**e_2 * .... * p_n**e_n. - # - # Prime.int_from_prime_division([[2,2], [3,1]]) #=> 12 def int_from_prime_division(pd) pd.inject(1){|value, (prime, index)| value * prime**index @@ -193,27 +199,32 @@ class Prime # Returns the factorization of +value+. # + # For an arbitrary integer: + # + # p_1**e_1 * p_2**e_2 * ... * p_n**e_n, + # + # prime_division returns an array of pairs of integers: + # + # [[p_1, e_1], [p_2, e_2], ..., [p_n, e_n]]. + # + # Each pair consists of a prime number -- a prime factor -- + # and a natural number -- its exponent (multiplicity). + # # == Parameters # +value+:: An arbitrary integer. # +generator+:: Optional. A pseudo-prime generator. # +generator+.succ must return the next - # pseudo-prime number in the ascending - # order. It must generate all prime numbers, - # but may also generate non prime numbers too. + # pseudo-prime number in ascending order. + # It must generate all prime numbers, + # but may also generate non-prime numbers, too. # # === Exceptions # +ZeroDivisionError+:: when +value+ is zero. # # == Example - # For an arbitrary integer: - # - # n = p_1**e_1 * p_2**e_2 * .... * p_n**e_n, - # - # prime_division(n) returns: - # - # [[p_1, e_1], [p_2, e_2], ...., [p_n, e_n]]. # - # Prime.prime_division(12) #=> [[2,2], [3,1]] + # Prime.prime_division(45) #=> [[3, 2], [5, 1]] + # 3**2 * 5 #=> 45 # def prime_division(value, generator = Prime::Generator23.new) raise ZeroDivisionError if value == 0 |