Module: Boqwij::IntegerExtensions

Defined in:
lib/boqwij/integer_extensions.rb

Overview

A set of extensions to the Integer class.

Instance Method Summary collapse

Instance Method Details

#delimit(delimiter = ",") ⇒ Object

Add a delimiter to every three digits of a long integer. The default delimiter is a comma.



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# File 'lib/boqwij/integer_extensions.rb', line 35

def delimit(delimiter = ",")
	self.to_s.gsub(/(\d)(?=(\d\d\d)+(?!\d))/, "\\1#{delimiter}")
rescue
	self.to_s
end

#even? ⇒ Boolean

Test if integer is even.

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 10

def even?
  !self.odd?
end

#factorial ⇒ Object

Get the factorial of given number. (e.g., 6.factorial # => 720)



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# File 'lib/boqwij/integer_extensions.rb', line 43

def factorial
  return nil if self < 1
  n = self
  count = n
  fact = 1
  count.times do
    fact = fact * n
    n -= 1
  end
  fact
end

#fibonacci ⇒ Object

Get the fibonacci number associated with a particular integer. (e.g., 6.fibonacci # => 8; 10.fibonacci # => 55)



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# File 'lib/boqwij/integer_extensions.rb', line 57

def fibonacci
  return nil if self < 1
  current, successor = 0, 1
	self.times { |i| current, successor = successor, current + successor}
	current
end

#is_divisible_by?(factor) ⇒ Boolean

Test if a number is divisible by a given factor. (e.g., 18.is_divisible_by?(3) #=> true)

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 115

def is_divisible_by?(factor)
  self%factor == 0
end

#is_fibonacci? ⇒ Boolean

Checks to see if integer is contained in the fibonacci sequence. (e.g, 12.is_fibonacci? # => false; 55.is_fibonacci? # => true)

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 66

def is_fibonacci?
  return true if self == 1
  a, b = Math.sqrt((5*(self**2))+4), Math.sqrt((5*(self**2))-4)
  return true if (a.to_i == a and b.to_i != b) or (a.to_i != a && b.to_i == b)
  return false
end

#is_palindrome? ⇒ Boolean

Test to see if a given number is a palindrome. (e.g., 1001.is_palindrome? # => true; 4654.is_palindrome? # => false)

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 121

def is_palindrome?
  return false if self < 0
  @original = self.to_s
  @backwards = @original.reverse
  @original.to_i == @backwards.to_i
end

#is_permutation_of?(x) ⇒ Boolean

Compares two integers to see if they are permutations of each other. (e.g, 314159.is_permutation_of?(431951) # => true)

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 130

def is_permutation_of?(x)
  return true if self == x
  primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
  s, s_total, x_total = self, 1, 1
  while s > 0
    s_total *= primes[s % 10]
    s /= 10
  end
  while x > 0
    x_total *= primes[x % 10]
    x /= 10
  end
  s_total == x_total
end

#is_prime? ⇒ Boolean

Test to see if a given number is prime. (e.g., 2.is_prime? # => true; 104743.is_prime? # => true; e.g., 4.is_prime? # => false; 104742.is_prime? # => false)

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 76

def is_prime?
  if    self == 1     then return false
  elsif self < 4      then return true
  elsif self % 2 == 0 then return false
  elsif self < 9      then return true
  elsif self % 3 == 0 then return false
  else
    5.step(Math.sqrt(self).to_i, 2) do |x|
      return false if self % x == 0
    end
  end
  return true
end

#length ⇒ Object

Find the length of an integer.



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# File 'lib/boqwij/integer_extensions.rb', line 25

def length
  n, count = self, 1
  while n > 9
    n /= 10
    count += 1
  end
  count
end

#neg? ⇒ Boolean

Test if integer is negative.

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 15

def neg?
  self < 0
end

#odd? ⇒ Boolean

Test if integer is odd.

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 5

def odd?
  self%2 != 0
end

#pos? ⇒ Boolean

Test if integer is positive.

Returns:

  • (Boolean) 


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# File 'lib/boqwij/integer_extensions.rb', line 20

def pos?
  self > 0
end

#prime_factors ⇒ Object

Get an array of prime factors for any integer. (e.g., 30.prime_factors # => [2,3,5])



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# File 'lib/boqwij/integer_extensions.rb', line 92

def prime_factors
  return [self] if self.is_prime?
  current, to_factor, factors, max = 2, self, [], 0
  while to_factor % current == 0
    factors << current
    to_factor /= current
  end
  current += 1
  max = Math.sqrt(to_factor).to_i + 1
  while to_factor >= max
    if to_factor % current == 0
      factors << current
      to_factor /= current
    else
      current += 2
    end
  end
  factors << to_factor if to_factor > 1
  factors
end