Class: Arrabiata

Inherits:
Object
  • Object
show all
Defined in:
lib/arrabiata.rb

Defined Under Namespace

Classes: ArrabiataError, NoZeroInRomanNumbers, UnknownRomanNumberError

Constant Summary collapse

CONVERSION = 
{
  "M" => 1000,
  "D" => 500,
  "C" => 100,
  "L" => 50,
  "X" => 10,
  "V" => 5,
  "I" => 1
}

Class Method Summary collapse

Class Method Details

.to_arabian(str) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/arrabiata.rb', line 34

def self.to_arabian(str)
  raise ArgumentError, "first argument is not a String" if !str.is_a?(String)

  result = 0

  str.scan(/\w/).each do |char|
    raise UnknownRomanNumberError, "'#{char}' is not defined in roman numbers" if !CONVERSION[char]
    result = result + CONVERSION[char]
  end

  result
end

.to_roman(n) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/arrabiata.rb', line 16

def self.to_roman(n)
  raise ArgumentError, "first argument is not a Fixnum" if !n.is_a?(Fixnum)
  raise NoZeroInRomanNumbers, "roman numeral system doesn't include 0" if n == 0

  result = ""

  # NOTE: this version doesn't yet respects the subtractive principle
  CONVERSION.sort_by { |d| d.last }.reverse.each do |k|
    x = n / k.last
    if x != 0
      result << k.first * x
      n = n - x * k.last
    end
  end

  result
end