Module: RomanNumeral

Defined in:
lib/fast_roman.rb,
lib/slow_roman.rb,
lib/roman_numeral.rb

Constant Summary collapse

ROMANS = 
(1...4000).reduce([nil],&->(a,i){a<<slow_i_to_roman(i).to_sym})
INTS = 
ROMANS.each_with_index.reduce({},&->(h,p){h[p[0]]=p[1];h})
DIGIT_TO_I = 
I_TO_DIGIT.invert
I_TO_DIGIT = 
{
  1 => :I,
  2 => :II,
  3 => :III,
  4 => :IV,
  5 => :V,
  6 => :VI,
  7 => :VII,
  8 => :VIII,
  9 => :IX,
  10 => :X,
  20 => :XX,
  30 => :XXX,
  40 => :XL,
  50 => :L,
  60 => :LX,
  70 => :LXX,
  80 => :LXXX,
  90 => :XC,
  100 => :C,
  200 => :CC,
  300 => :CCC,
  400 => :CD,
  500 => :D,
  600 => :DC,
  700 => :DCC,
  800 => :DCCC,
  900 => :CM,
  1000 => :M,
  2000 => :MM,
  3000 => :MMM
}

Class Method Summary collapse

Class Method Details

.high_digit_value(i) ⇒ Object 



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# File 'lib/roman_numeral.rb', line 36

def self.high_digit_value i
  return nil unless -1 < i
  return [0, 0] if 0 == i
  shift = 0
  v = i
  while v > 9
    v = v/10
    shift += 1
  end
  while shift > 0
    v *= 10
    shift -= 1
  end
  [v, i - v]
end

.i_to_roman(i) ⇒ Object Also known as: slow_i_to_roman 



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# File 'lib/fast_roman.rb', line 8

def self.i_to_roman i
  sym = ROMANS[i.to_i]
  return nil unless sym
  sym.to_s
end

.next_roman_digit(r) ⇒ Object 



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# File 'lib/slow_roman.rb', line 17

def self.next_roman_digit r
  result = next_roman_digit_of_size r, 4
  return result if result
  result = next_roman_digit_of_size r, 3
  return result if result
  result = next_roman_digit_of_size r, 2
  return result if result
  next_roman_digit_of_size r, 1
end

.next_roman_digit_of_size(r, size) ⇒ Object 



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# File 'lib/slow_roman.rb', line 7

def self.next_roman_digit_of_size r, size
  len = r.length
  rn = r.slice(0, size)
  v = DIGIT_TO_I[rn.to_sym]
  return nil unless v
  tail = r.slice(size, len - size)
  tail = nil if '' == tail
  [v, tail]
end

.roman_to_i(r) ⇒ Object Also known as: slow_roman_to_i 



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# File 'lib/fast_roman.rb', line 14

def self.roman_to_i r
  r = r.to_s.to_sym unless Symbol == r.class
  INTS[r]
end