Roman numerals (idea)

Here's code to convert numbers from arabic to roman numerals (up to 5000, I was lazy and ASCII doesn't have those funky characters with bars above them).

The code is, as surprising as it may sound, in Rexx. It was written by me today, in Rexx just for the heck of it. =)

I should have written this in some old IBM mainframe assembler to get the feel of archaicity... =)

/* Ideas from britannica.com - thanks to the wise ones there
   I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000
   This *could* have been implemented more... intelligently, but
   that would certainly have been overkill.
*/
RomanNum: procedure; parse arg number
  /* The Ancient Romans Were Not Y0 Compliant. */
  if number <= 0 then return number          /* No zero, no negative numbers */
  if number % number != 0 then return number /* No decimal numbers */
  if number > 5000 then return number        /* No numbers above 5000 either -
					        limitation of ASCII, mostly */

  number = right(number,4,'0')               /* Pad with zeroes */
  nthousands = value(substr(number,1,1))     /* Split apart per number */
  nhundreds = value(substr(number,2,1))
  ntens = value(substr(number,3,1))
  nones = value(substr(number,4,1))

  select
	  when nones = 1 then cones = 'I'
  	  when nones = 2 then cones = 'II'
	  when nones = 3 then cones = 'III'
	  when nones = 4 then cones = 'IV'
	  when nones = 5 then cones = 'V'
	  when nones = 6 then cones = 'VI'
	  when nones = 7 then cones = 'VII'
	  when nones = 8 then cones = 'VIII'
	  when nones = 9 then cones = 'IX'
	  when nones = 0 then cones = ''
	  end
  
  select
	  when ntens = 1 then ctens = 'X'
  	  when ntens = 2 then ctens = 'XX'
	  when ntens = 3 then ctens = 'XXX'
	  when ntens = 4 then ctens = 'XL'
	  when ntens = 5 then ctens = 'L'
	  when ntens = 6 then ctens = 'LX'
	  when ntens = 7 then ctens = 'LXX'
	  when ntens = 8 then ctens = 'LXXX'
	  when ntens = 9 then ctens = 'XC'
	  when ntens = 0 then ctens = ''
	  end

  select
	  when nhundreds = 1 then chundreds = 'C'
  	  when nhundreds = 2 then chundreds = 'CC'
	  when nhundreds = 3 then chundreds = 'CCC'
	  when nhundreds = 4 then chundreds = 'CD'
	  when nhundreds = 5 then chundreds = 'D'
	  when nhundreds = 6 then chundreds = 'DC'
	  when nhundreds = 7 then chundreds = 'DCC'
	  when nhundreds = 8 then chundreds = 'DCCC'
	  when nhundreds = 9 then chundreds = 'CM' /* M's appended */
	  when nhundreds = 0 then chundreds = ''
	  end

  cthousands = copies('M',nthousands)
  
  result = cthousands || chundreds || ctens || cones
  return result

Tested under Linux with Regina Rexx interpreter.