Module: FiveLeaves

Defined in:
lib/five_leaves/maximize.rb,
lib/five_leaves/lazy_enum.rb,
lib/five_leaves/prime_util.rb,
lib/five_leaves/palindromic.rb

Class Method Summary collapse

Class Method Details

.factors(n) ⇒ Object 



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# File 'lib/five_leaves/prime_util.rb', line 21

def self.factors(n)
  [n] + proper_factors(n)
end

.find(init = 0) ⇒ Object 



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# File 'lib/five_leaves/lazy_enum.rb', line 34

def self.find(init=0)
  (init..(1.0/0.0)).find { |x| yield x }
end

.maximize(range = 1..1_000_000) ⇒ Object

find the input in the range which maximizes the result of the block



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# File 'lib/five_leaves/maximize.rb', line 5

def self.maximize(range = 1..1_000_000)
  (range).lazy_map { |x| [yield(x), x] }.max[1]
end

.palindromic?(n) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/five_leaves/palindromic.rb', line 4

def self.palindromic?(n)
  string = n.to_s
  (0..string.size/2).all_match? { |i| string[i] == string[-1-i] }
end

.prime_factors(n) ⇒ Object 



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# File 'lib/five_leaves/prime_util.rb', line 25

def self.prime_factors(n)
  small = small_factors(n)
  (small.map { |f| n / f } + small).uniq.select { |x| x.prime? }
end

.proper_factors(n) ⇒ Object 



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# File 'lib/five_leaves/prime_util.rb', line 16

def self.proper_factors(n)
  sf = small_factors(n)
  (sf.map { |x| n / x } + sf).uniq - [n]
end

.series(init = 0) ⇒ Object 



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# File 'lib/five_leaves/lazy_enum.rb', line 30

def self.series(init=0)
  (init..(1.0/0.0)).lazy_map { |x| yield x }
end

.small_factors(n) ⇒ Object 



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# File 'lib/five_leaves/prime_util.rb', line 12

def self.small_factors(n)
  (Math.sqrt(n).truncate.downto 1).select { |x| x.divides? n }
end