Module: MissingMath::Integer

Included in:
Integer
Defined in:
lib/missing_math.rb

Overview

Methods that apply to integers

Instance Method Summary collapse

Instance Method Details

#factorial ⇒ Object

Calculates an integer’s factorial



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# File 'lib/missing_math.rb', line 153

def factorial
  throw "Not an Integer" if !self.is_i?
  if self == 0
    1
  else
    self.downto(1).reduce(:*)
  end
end

#factors(include_one = false) ⇒ Object

Returns an array of an integer’s factors

Parameters:

  • boolean —

    include_one Default is to exclude the number 1 from the output; to include set to false



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# File 'lib/missing_math.rb', line 164

def factors(include_one=false)
  throw "Not an Integer" if !self.is_i?
  last = self
  i = include_one ? 1 : 2
  a = []
  while i < last
    if self % i == 0
      last = self / i
      a << i
      a << last
    end
    i += 1
  end
  return a.sort
end

#hexagon ⇒ Object

Returns the hexagonal number



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# File 'lib/missing_math.rb', line 201

def hexagon
  return self * ((2 * self) - 1)
end

#pentagon ⇒ Object

Returns the pentagonal number



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# File 'lib/missing_math.rb', line 196

def pentagon
  return (self * ((3 * self) - 1)) / 2
end

#pentagonal? ⇒ Boolean

Checks if the number is pentagonal. If true, returns the number, otherwise false

Returns:

  • (Boolean) 


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# File 'lib/missing_math.rb', line 217

def pentagonal?
  n = (Math.sqrt((24 * self) + 1) + 1) / 6
  if n.floor == n.ceil
    return n
  else
    return false
  end
end

#prime? ⇒ Boolean

Returns boolean true|false if integer is prime

Returns:

  • (Boolean) 


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# File 'lib/missing_math.rb', line 135

def prime?
  throw "Not an Integer" if !self.is_i?
  begin
    last = Math.sqrt(self).floor
    i = 2
    while i <= last
      if self % i == 0
        return false
      end
      i += 1
    end
    return true
  rescue
    false
  end
end

#prime_factors(force_new = false) ⇒ Object

Returns an array of the integer’s prime factors

Parameters:

  • boolean —

    force_new Force new module variable @esieve generation. Default uses module variable @esieve if it hasn’t been set



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# File 'lib/missing_math.rb', line 182

def prime_factors(force_new=false)
  ceil = (self / 2).ceil
  primes = MissingMath.esieve(ceil, force_new)
  factors = primes.collect { |i| i if self % i == 0 && i <= ceil }
  return factors.compact.uniq
end

#triangle ⇒ Object

Returns the triangle number



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# File 'lib/missing_math.rb', line 191

def triangle
  return (self * (self + 1)) / 2
end

#triangular? ⇒ Boolean

Checks if the number is triangular. If true, returns the number, otherwise false

Returns:

  • (Boolean) 


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# File 'lib/missing_math.rb', line 207

def triangular?
  n = (Math.sqrt((8 * self) + 1) - 1) / 2
  if n.floor == n.ceil
    return n
  else
    return false
  end
end