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Roman numerals/Encode

From Rosetta Code
Revision as of 11:43, 15 August 2013 by rosettacode>Srborlongan (Bugfix for Java 8 version)
Task
Roman numerals/Encode
You are encouraged to solve this task according to the task description, using any language you may know.

Create a function taking a positive integer as its parameter and returning a string containing the Roman Numeral representation of that integer.

Modern Roman numerals are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero. In Roman numerals 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC. 2008 is written as 2000=MM, 8=VIII; or MMVIII. 1666 uses each Roman symbol in descending order: MDCLXVI.

ActionScript

<lang ActionScript>function arabic2roman(num:Number):String { var lookup:Object = {M:1000, CM:900, D:500, CD:400, C:100, XC:90, L:50, XL:40, X:10, IX:9, V:5, IV:4, I:1}; var roman:String = "", i:String; for (i in lookup) { while (num >= lookup[i]) { roman += i; num -= lookup[i]; } } return roman; } trace("1990 in roman is " + arabic2roman(1990)); trace("2008 in roman is " + arabic2roman(2008)); trace("1666 in roman is " + arabic2roman(1666)); </lang> Output:

1990 in roman is MCMXC
2008 in roman is MMVIII
1666 in roman is MDCLXVI

And the reverse: <lang ActionScript>function roman2arabic(roman:String):Number { var romanArr:Array = roman.toUpperCase().split(); var lookup:Object = {I:1, V:5, X:10, L:50, C:100, D:500, M:1000}; var num:Number = 0, val:Number = 0; while (romanArr.length) { val = lookup[romanArr.shift()]; num += val * (val < lookup[romanArr[0]] ? -1 : 1); } return num; } trace("MCMXC in arabic is " + roman2arabic("MCMXC")); trace("MMVIII in arabic is " + roman2arabic("MMVIII")); trace("MDCLXVI in arabic is " + roman2arabic("MDCLXVI"));</lang> Output:

MCMXC in arabic is 1990
MMVIII in arabic is 2008
MDCLXVI in arabic is 1666

Ada

<lang ada>with Ada.Text_IO; use Ada.Text_IO;

procedure Roman_Numeral_Test is

  function To_Roman (Number : Positive) return String is
     subtype Digit is Integer range 0..9;
     function Roman (Figure : Digit; I, V, X : Character) return String is
     begin
        case Figure is
           when 0 => return "";
           when 1 => return "" & I;
           when 2 => return I & I;
           when 3 => return I & I & I;
           when 4 => return I & V;
           when 5 => return "" & V;
           when 6 => return V & I;
           when 7 => return V & I & I;
           when 8 => return V & I & I & I;
           when 9 => return I & X;
        end case;
     end Roman;
  begin
     pragma Assert (Number >= 1 and Number < 4000);
     return
        Roman (Number / 1000,       'M', ' ', ' ') &
        Roman (Number / 100 mod 10, 'C', 'D', 'M') &
        Roman (Number / 10 mod 10,  'X', 'L', 'C') &
        Roman (Number mod 10,       'I', 'V', 'X');
  end To_Roman;

begin

  Put_Line (To_Roman (1999));
  Put_Line (To_Roman (25));
  Put_Line (To_Roman (944));

end Roman_Numeral_Test;</lang> Output:

MCMXCIX
XXV
CMXLIV

ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8-8d

<lang algol68>[]CHAR roman = "MDCLXVmdclxvi"; # UPPERCASE for thousands # []CHAR adjust roman = "CCXXmmccxxii"; []INT arabic = (1000000, 500000, 100000, 50000, 10000, 5000, 1000, 500, 100, 50, 10, 5, 1); []INT adjust arabic = (100000, 100000, 10000, 10000, 1000, 1000, 100, 100, 10, 10, 1, 1, 0);

PROC arabic to roman = (INT dclxvi)STRING: (

 INT in := dclxvi; # 666 #
 STRING out := "";
 FOR scale TO UPB roman WHILE in /= 0 DO
   INT multiples = in OVER arabic[scale];
   in -:= arabic[scale] * multiples;
   out +:= roman[scale] * multiples;
   IF in >= -adjust arabic[scale] + arabic[scale] THEN
     in -:= -adjust arabic[scale] + arabic[scale];
     out +:=  adjust roman[scale] +  roman[scale]
   FI
 OD;
 out

);

main:(

 []INT test = (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,25,30,40,50,60,69,70,
    80,90,99,100,200,300,400,500,600,666,700,800,900,1000,1009,1444,1666,1945,1997,1999,
    2000,2008,2500,3000,4000,4999,5000,6666,10000,50000,100000,500000,1000000,max int);
 FOR key TO UPB test DO
   INT val = test[key];
   print((val, " - ", arabic to roman(val), new line))
 OD

)</lang> Output (last example is manually wrapped):

         +1 - i
         +2 - ii
         +3 - iii
         +4 - iv
         +5 - v
         +6 - vi
         +7 - vii
         +8 - viii
         +9 - ix
        +10 - x
        +11 - xi
        +12 - xii
        +13 - xiii
        +14 - xiv
        +15 - xv
        +16 - xvi
        +17 - xvii
        +18 - xviii
        +19 - xix
        +20 - xx
        +25 - xxv
        +30 - xxx
        +40 - xl
        +50 - l
        +60 - lx
        +69 - lxix
        +70 - lxx
        +80 - lxxx
        +90 - xc
        +99 - xcix
       +100 - c
       +200 - cc
       +300 - ccc
       +400 - cd
       +500 - d
       +600 - dc
       +666 - dclxvi
       +700 - dcc
       +800 - dccc
       +900 - cm
      +1000 - m
      +1009 - mix
      +1444 - mcdxliv
      +1666 - mdclxvi
      +1945 - mcmxlv
      +1997 - mcmxcvii
      +1999 - mcmxcix
      +2000 - mm
      +2008 - mmviii
      +2500 - mmd
      +3000 - mmm
      +4000 - mV
      +4999 - mVcmxcix
      +5000 - V
      +6666 - Vmdclxvi
     +10000 - X
     +50000 - L
    +100000 - C
    +500000 - D
   +1000000 - M
+2147483647 - MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
              MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMCDLXXXmmmdcxlvii

ALGOL W

Works with: awtoc version any - tested with release Mon Apr 27 14:25:27 NZST 2009

<lang algolw>BEGIN

PROCEDURE ROMAN (INTEGER VALUE NUMBER; STRING(15) RESULT CHARACTERS; INTEGER RESULT LENGTH);

   COMMENT
        Returns the Roman number of an integer between 1 and 3999.
        "MMMDCCCLXXXVIII" (15 characters long) is the longest Roman number under 4000;
   BEGIN
       INTEGER PLACE, POWER;
       PROCEDURE APPEND (STRING(1) VALUE C);
           BEGIN CHARACTERS(LENGTH|1) := C; LENGTH := LENGTH + 1 END;
       PROCEDURE I; APPEND(CASE PLACE OF ("I","X","C","M"));
       PROCEDURE V; APPEND(CASE PLACE OF ("V","L","D"));
       PROCEDURE X; APPEND(CASE PLACE OF ("X","C","M"));
       ASSERT (NUMBER >= 1) AND (NUMBER < 4000);
       CHARACTERS := "               ";  
       LENGTH := 0;
       POWER := 1000;  
       PLACE := 4;
       WHILE PLACE > 0 DO
           BEGIN
               CASE NUMBER DIV POWER + 1 OF BEGIN
                   BEGIN            END;
                   BEGIN I          END;
                   BEGIN I; I       END;
                   BEGIN I; I; I    END;
                   BEGIN I; V       END;
                   BEGIN V          END;
                   BEGIN V; I       END;
                   BEGIN V; I; I    END;
                   BEGIN V; I; I; I END;
                   BEGIN I; X       END
               END;
               NUMBER := NUMBER REM POWER;
               POWER := POWER DIV 10;
               PLACE := PLACE - 1
           END
   END ROMAN;

INTEGER I; STRING(15) S;

ROMAN(1, S, I); WRITE(S, I); ROMAN(3999, S, I); WRITE(S, I); ROMAN(3888, S, I); WRITE(S, I); ROMAN(2009, S, I); WRITE(S, I); ROMAN(405, S, I); WRITE(S, I); END.</lang> Output:

I                           1
MMMCMXCIX                   9
MMMDCCCLXXXVIII            15
MMIX                        4
CDV                         3

AutoHotkey

Translation of: C++

<lang AutoHotkey>MsgBox % stor(444)

stor(value) {

 romans = M,CM,D,CD,C,XC,L,XL,X,IX,V,IV,I
 M := 1000
 CM := 900
 D := 500
 CD := 400
 C := 100
 XC := 90
 L := 50
 XL := 40
 X := 10
 IX := 9
 V := 5
 IV := 4
 I := 1
 Loop, Parse, romans, `,
 {
   While, value >= %A_LoopField%
   {
     result .= A_LoopField
     value := value - (%A_LoopField%)
   }
 }
 Return result . "O" 

}</lang>

AWK

<lang AWK>

  1. syntax: GAWK -f ROMAN_NUMERALS_ENCODE.AWK

BEGIN {

   leng = split("1990 2008 1666",arr," ")
   for (i=1; i<=leng; i++) {
     n = arr[i]
     printf("%s = %s\n",n,dec2roman(n))
   }
   exit(0)

} function dec2roman(number, v,w,x,y,roman1,roman10,roman100,roman1000) {

   number = int(number) # force to integer
   if (number < 1 || number > 3999) { # number is too small | big
     return
   }
   split("I II III IV V VI VII VIII IX",roman1," ")   # 1 2 ... 9
   split("X XX XXX XL L LX LXX LXXX XC",roman10," ")  # 10 20 ... 90
   split("C CC CCC CD D DC DCC DCCC CM",roman100," ") # 100 200 ... 900
   split("M MM MMM",roman1000," ")                    # 1000 2000 3000
   v = (number - (number % 1000)) / 1000
   number = number % 1000
   w = (number - (number % 100)) / 100
   number = number % 100
   x = (number - (number % 10)) / 10
   y = number % 10
   return(roman1000[v] roman100[w] roman10[x] roman1[y])

} </lang>

output:

1990 = MCMXC
2008 = MMVIII
1666 = MDCLXVI

BASIC

Works with: FreeBASIC

<lang freebasic> DIM SHARED arabic(0 TO 12) AS Integer => {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 } DIM SHARED roman(0 TO 12) AS String*2 => {"M", "CM", "D","CD", "C","XC","L","XL","X","IX","V","IV","I"}

FUNCTION toRoman(value AS Integer) AS String

   DIM i 	AS Integer
   DIM result  AS String
   
   FOR i = 0 TO 12
       DO WHILE value >= arabic(i)

result = result + roman(i) value = value - arabic(i) LOOP

   NEXT i
   toRoman = result

END FUNCTION

'Testing PRINT "2009 = "; toRoman(2009) PRINT "1666 = "; toRoman(1666) PRINT "3888 = "; toRoman(3888) </lang>

Output

2009 = MMIX
1666 = MDCLXVI
3888 = MMMDCCCLXXXVIII

ZX Spectrum Basic

<lang zxbasic> 10 DATA 1000,"M",900,"CM"

20 DATA 500,"D",400,"CD"
30 DATA 100,"C",90,"XC"
40 DATA 50,"L",40,"XL"
50 DATA 10,"X",9,"IX"
60 DATA 5,"V",4,"IV",1,"I"
70 INPUT "Enter an arabic number: ";V
80 LET VALUE=V
90 LET V$=""

100 FOR I=0 TO 12 110 READ A,R$ 120 IF V<A THEN GO TO 160 130 LET V$=V$+R$ 140 LET V=V-A 150 GO TO 120 160 NEXT I 170 PRINT VALUE;"=";V$</lang>

BASIC256

Works with: BASIC256

<lang basic256> print 1666+" = "+convert$(1666) print 2008+" = "+convert$(2008) print 1001+" = "+convert$(1001) print 1999+" = "+convert$(1999)

function convert$(value) convert$="" arabic = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 } roman$ = {"M", "CM", "D","CD", "C","XC","L","XL","X","IX","V","IV","I"}

  for i = 0 to 12
          while value >= arabic[i]

convert$ += roman$[i] value = value - arabic[i] end while

   next i

end function </lang> Output:

1666 = MDCLXVI
2008 = MMVIII
1001 = MI
1999 = MCMXCIX

BBC BASIC

<lang bbcbasic> PRINT ;1999, FNroman(1999)

     PRINT ;2012, FNroman(2012)
     PRINT ;1666, FNroman(1666)
     PRINT ;3888, FNroman(3888)
     END
     
     DEF FNroman(n%)
     LOCAL i%, r$, arabic%(), roman$()
     DIM arabic%(12), roman$(12)
     arabic%() = 1,   4,   5,   9,  10,  40,  50,  90, 100, 400, 500, 900,1000
     roman$() = "I","IV", "V","IX", "X","XL", "L","XC", "C","CD", "D","CM", "M"
     FOR i% = 12 TO 0 STEP -1
       WHILE n% >= arabic%(i%)
         r$ += roman$(i%)
         n% -= arabic%(i%)
       ENDWHILE
     NEXT
     = r$</lang>

Output:

1999      MCMXCIX
2012      MMXII
1666      MDCLXVI
3888      MMMDCCCLXXXVIII

Bracmat

<lang bracmat>( ( encode

 =   indian roman cifr tenfoldroman letter tenfold
   .   !arg:#?indian
     & :?roman
     &   whl
       ' ( @(!indian:#%?cifr ?indian)
         & :?tenfoldroman
         &   whl
           ' ( !roman:%?letter ?roman
             &     !tenfoldroman
                   (       (I.X)
                           (V.L)
                           (X.C)
                           (L.D)
                           (C.M)
                       : ? (!letter.?tenfold) ?
                     & !tenfold
                   | "*"
                   )
               : ?tenfoldroman
             )
         & !tenfoldroman:?roman
         & ( !cifr:9&!roman I X:?roman
           |   !cifr:~<4
             &     !roman
                   (!cifr:4&I|)
                   V
               : ?roman
             & !cifr+-5:?cifr
             & ~
           |   whl
             ' ( !cifr+-1:~<0:?cifr
               & !roman I:?roman
               )
           )
         )
     & ( !roman:? "*" ?&~`
       | str$!roman
       )
 )

& 1990 2008 1666 3888 3999 4000:?NS & whl

 ' ( !NS:%?N ?NS
   &   out
     $ ( encode$!N:?K&!N !K
       | str$("Can't convert " !N " to Roman numeral")
       )
   )

);</lang> Output:

1990 MCMXC
2008 MMVIII
1666 MDCLXVI
3888 MMMDCCCLXXXVIII
3999 MMMCMXCIX
Can't convert 4000 to Roman numeral

C

<lang c>#include <stdlib.h>

  1. include <stdio.h>

/*

* Writes the Roman numeral representing n into the buffer s.
* Handles up to n = 3999.
* Since C doesn't have exceptions, n = 0 causes the whole program to exit
* unsuccessfully.
* s should be have room for at least 16 characters, including the trailing
* null.
*/

void roman(char *s, unsigned int n) {

if (n == 0)
{
 fputs(stderr, "Roman numeral for zero requested.");
 exit(EXIT_FAILURE);
}
 #define digit(loop, num, c) \
     loop (n >= num)         \
        {*(s++) = c;         \
         n -= num;}  
 #define digits(loop, num, c1, c2) \
     loop (n >= num)               \
        {*(s++) = c1;              \
         *(s++) = c2;              \
         n -= num;}
 digit  ( while, 1000, 'M'      )
 digits ( if,     900, 'C', 'M' )
 digit  ( if,     500, 'D'      )
 digits ( if,     400, 'C', 'D' )
 digit  ( while,  100, 'C'      )
 digits ( if,      90, 'X', 'C' )
 digit  ( if,      50, 'L'      )
 digits ( if,      40, 'X', 'L' )
 digit  ( while,   10, 'X'      )
 digits ( if,       9, 'I', 'X' )
 digit  ( if,       5, 'V'      )
 digits ( if,       4, 'I', 'V' )
 digit  ( while,    1, 'I'      )
 #undef digit
 #undef digits
 
 *s = 0;}

int main(void) {

char buffer[16];
unsigned int i;
for (i = 1 ; i < 4000 ; ++i)
{
 roman(buffer, i);
 printf("%4u: %s\n", i, buffer);
}
return EXIT_SUCCESS;

}</lang>

An alternative version which builds the string backwards. <lang c>char *ToRoman(int num, char *buf, int buflen) {

  static const char romanDgts[] = "ivxlcdmVXLCDM_";
  char *roman = buf + buflen;
  int  rdix, r, v;
  *--roman = '\0';        /* null terminate return string */
  if (num >= 4000000) {
     printf("Number Too Big.\n");
     return NULL;
     }
  for (rdix = 0; rdix < strlen(romanDgts); rdix += 2) {
     if (num == 0) break;
     v = (num % 10) / 5;
     r = num % 5;
     num = num / 10;
     if (r == 4) {
        if (roman < buf+2) {
           printf("Buffer too small.");
           return NULL;
           }
        *--roman = romanDgts[rdix+1+v];
        *--roman = romanDgts[rdix];
        }
     else {
        if (roman < buf+r+v) {
           printf("Buffer too small.");
           return NULL;
           }
        while(r-- > 0) {
           *--roman = romanDgts[rdix];
           }
        if (v==1) {
           *--roman = romanDgts[rdix+1];
           }
        }
     }
  return roman;

}</lang>

Most straightforward (nothing elegant about it, but it's simple, and can calcuate output length) <lang C>#include <stdio.h>

int to_roman(char *out, int n) {

       int len = 0;
       if (n <= 0) return 0; /* error indication */
  1. define RPUT(c) if (out) out[len] = c; len++
       while(n>= 1000) { n -= 1000;RPUT('M'); };
       if (n >= 900)   { n -= 900; RPUT('C'); RPUT('M'); };
       if (n >= 500)   { n -= 500; RPUT('D'); };
       if (n >= 400)   { n -= 400; RPUT('C'); RPUT('D'); };
       while (n >= 100){ n -= 100; RPUT('C'); };
       if (n >= 90)    { n -= 90;  RPUT('X'); RPUT('C'); };
       if (n >= 50)    { n -= 50;  RPUT('L'); };
       if (n >= 40)    { n -= 40;  RPUT('X'); RPUT('L'); };
       while (n >= 10) { n -= 10;  RPUT('X'); };
       if (n >= 9)     { n -= 9;   RPUT('I'); RPUT('X'); };
       if (n >= 5)     { n -= 5;   RPUT('V'); };
       if (n >= 4)     { n -= 4;   RPUT('I'); RPUT('V'); };
       while (n)       { n--; RPUT('I'); };
       RPUT('\0');
  1. undef RPUT
       return len;

}

int main() {

       char buf[16];
       int d = to_roman(buf, 1666);
       printf("roman for 1666 is %d bytes: %s\n", d, buf);
       d = 68999123;
       printf("%d would have required %d bytes\n", d, to_roman(0, d));
       return 0;

}</lang>Output:

roman for 1666 is 8 bytes: MDCLXVI
68999123 would have required 69006 bytes

C#

<lang csharp>using System; class Program {

   static uint[] nums = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };
   static string[] rum = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
   static string ToRoman(uint number)
   {
       string value = "";
       for (int i = 0; i < nums.Length && number != 0; i++)
       {
           while (number >= nums[i])
           {
               number -= nums[i];
               value += rum[i];
           }
       }
       return value;
   }
   static void Main()
   {
       for (uint number = 1; number <= 1 << 10; number *= 2)
       {
           Console.WriteLine("{0} = {1}", number, ToRoman(number));
       }
   }

}</lang>

Output:

1 = I
2 = II
4 = IV
8 = VIII
16 = XVI
32 = XXXII
64 = LXIV
128 = CXXVIII
256 = CCLVI
512 = DXII
1024 = MXXIV

C++

<lang cpp>#include <iostream>

  1. include <string>

std::string to_roman(int value) {

 struct romandata_t { int value; char const* numeral; };
 static romandata_t const romandata[] =
    { 1000, "M",
       900, "CM",
       500, "D",
       400, "CD",
       100, "C",
        90, "XC",
        50, "L",
        40, "XL",
        10, "X",
         9, "IX",
         5, "V",
         4, "IV",
         1, "I",
         0, NULL }; // end marker
 std::string result;
 for (romandata_t const* current = romandata; current->value > 0; ++current)
 {
   while (value >= current->value)
   {
     result += current->numeral;
     value  -= current->value;
   }
 }
 return result;

}

int main() {

 for (int i = 1; i <= 4000; ++i)
 {
   std::cout << to_roman(i) << std::endl;
 }

}</lang>

COBOL

<lang COBOL> IDENTIFICATION DIVISION. PROGRAM-ID. TOROMAN. DATA DIVISION. working-storage section.

 01 ws-number pic 9(4) value 0.
 01 ws-save-number pic 9(4).
 01 ws-tbl-def.
   03 filler pic x(7) value '1000M  '.
   03 filler pic x(7) value '0900CM '.
   03 filler pic x(7) value '0500D  '.
   03 filler pic x(7) value '0400CD '.
   03 filler pic x(7) value '0100C  '.
   03 filler pic x(7) value '0090XC '.
   03 filler pic x(7) value '0050L  '.
   03 filler pic x(7) value '0040XL '.
   03 filler pic x(7) value '0010X  '.
   03 filler pic x(7) value '0009IX '.
   03 filler pic x(7) value '0005V  '.
   03 filler pic x(7) value '0004IV '.
   03 filler pic x(7) value '0001I  '.
 01  filler redefines ws-tbl-def.
   03 filler occurs 13 times indexed by rx.
     05 ws-tbl-divisor    pic 9(4).
     05 ws-tbl-roman-ch   pic x(1) occurs 3 times indexed by cx.
 01 ocx pic 99.
 01 ws-roman.
   03 ws-roman-ch         pic x(1) occurs 16 times.

PROCEDURE DIVISION.

 accept ws-number
 perform
 until ws-number = 0
   move ws-number to ws-save-number
   if ws-number > 0 and ws-number < 4000
     initialize ws-roman
     move 0 to ocx
     perform varying rx from 1 by +1
     until ws-number = 0
       perform until ws-number < ws-tbl-divisor (rx)
         perform varying cx from 1 by +1 
 		  until ws-tbl-roman-ch (rx, cx) = spaces
           compute ocx = ocx + 1
           move ws-tbl-roman-ch (rx, cx) to ws-roman-ch (ocx)
         end-perform
         compute ws-number = ws-number - ws-tbl-divisor (rx)
       end-perform
     end-perform
     display 'inp=' ws-save-number ' roman=' ws-roman
   else
     display 'inp=' ws-save-number ' invalid'
   end-if
   accept ws-number
 end-perform
 .

</lang>

Output: (input was supplied via STDIN)

inp=0111 roman=CXI             
inp=2234 roman=MMCCXXXIV       
inp=0501 roman=DI              
inp=0010 roman=X               
inp=0040 roman=XL              
inp=0050 roman=L               
inp=0066 roman=LXVI            
inp=0666 roman=DCLXVI          
inp=5666 invalid
inp=3333 roman=MMMCCCXXXIII    
inp=3888 roman=MMMDCCCLXXXVIII 
inp=3999 roman=MMMCMXCIX       
inp=3345 roman=MMMCCCXLV      

CoffeeScript

<lang coffeescript> decimal_to_roman = (n) ->

 # This should work for any positive integer, although it
 # gets a bit preposterous for large numbers.
 if n >= 4000
   thousands = decimal_to_roman n / 1000
   ones = decimal_to_roman n % 1000
   return "M(#{thousands})#{ones}"
   
 s = 
 translate_each = (min, roman) ->
   while n >= min
     n -= min
     s += roman
 translate_each 1000, "M"
 translate_each  900, "CM"
 translate_each  500, "D"
 translate_each  400, "CD"
 translate_each  100, "C"
 translate_each   90, "XC"
 translate_each   50, "L"
 translate_each   40, "XL"
 translate_each   10, "X"
 translate_each    9, "IX"
 translate_each    5, "V"
 translate_each    4, "IV"
 translate_each    1, "I"
 s
 

tests =

 IV: 4
 XLII: 42
 MCMXC: 1990
 MMVIII: 2008
 MDCLXVI: 1666
 'M(IV)': 4000
 'M(VI)IX': 6009
 'M(M(CXXIII)CDLVI)DCCLXXXIX': 123456789
 'M(MMMV)I': 3005001

for expected, decimal of tests

 roman = decimal_to_roman(decimal)
 if roman == expected
   console.log "#{decimal} = #{roman}"
 else
   console.log "error for #{decimal}: #{roman} is wrong"

</lang>

Common Lisp

<lang lisp>(defun roman-numeral (n)

 (format nil "~@R" n))</lang>

Clojure

The easiest way is to use the built-in cl-format function <lang Clojure> (def arabic->roman

 (partial clojure.pprint/cl-format nil "~@R"))

(arabic->roman 147)

"CXXIII"

(arabic->roman 99)

"XCIX"

</lang>

Alternatively

<lang Clojure> (def arabic-roman-map

    {1 "I", 5 "V", 
     10 "X", 50 "L", 
     100 "C", 500 "D", 
     1000 "M", 
     4 "IV", 9 "IX", 
     40 "XL", 90 "XC", 
     400 "CD", 900 "CM" })

(def arabic-roman-map-sorted-keys

    (sort (keys arabic-roman-map)))

(defn find-value-in-coll

 [coll k]
 (let [aval (find coll k)]
 (if (nil? aval) "" (val aval))))

(defn to-roman

 [result n]
 (let
     [closest-key-for-n (last (filter #(> n %) arabic-roman-map-sorted-keys))
      roman-value-for-n (find-value-in-coll arabic-roman-map n)
      roman-value-for-closet-to-n (find-value-in-coll arabic-roman-map

closest-key-for-n)]

      (if (or (<= n 0)(contains? arabic-roman-map n))

(conj result roman-value-for-n) (recur (conj result roman-value-for-closet-to-n) (- n closest-key-for-n)))))

Usage: >(to-roman [] 1999) result: ["M" "CM" "XC" "IX"]

</lang>


An alternate implementation:

<lang Clojure> (defn a2r

 [a]
 (let [rv [1000 500 100 50 10 5 1]
       rm (zipmap rv "MDCLXVI")
       dv (->> rv (take-nth 2) next (#(interleave % %)))]
   (loop [a a rv rv dv dv r nil]
     (if (<= a 0)
       r
       (let [v (first rv)
             d (or (first dv) 0)
             l (- v d)]
         (cond
           (= a v) (str r (rm v))
           (= a l) (str r (rm d) (rm v))
           (and (> a v) (> a l)) (recur (- a v) rv dv (str r (rm v)))
           (and (< a v) (< a l)) (recur a (rest rv) (rest dv) r)
           :else (recur (- a l) (rest rv) (rest dv) (str r (rm d) (rm v)))))))))

</lang>

Usage:

<lang Clojure> (a2r 1666) "MDCLXVI"

(map a2r [1000 1 389 45]) ("M" "I" "CCCLXXXIX" "XLV") </lang>

D

<lang d>string toRoman(int n) pure nothrow in {

   assert(n < 5000);

} body {

   static immutable weights = [1000, 900, 500, 400, 100, 90,
                               50, 40, 10, 9, 5, 4, 1];
   static immutable symbols = ["M","CM","D","CD","C","XC","L",
                               "XL","X","IX","V","IV","I"];
   string roman;
   foreach (i, w; weights) {
       while (n >= w) {
           roman ~= symbols[i];
           n -= w;
       }
       if (n == 0)
           break;
   }
   return roman;

} unittest {

   assert(toRoman(455)  == "CDLV");
   assert(toRoman(3456) == "MMMCDLVI");
   assert(toRoman(2488) == "MMCDLXXXVIII");

}

void main() {}</lang>

Delphi

Translation of: DWScript

<lang delphi>program RomanNumeralsEncode;

{$APPTYPE CONSOLE}

function IntegerToRoman(aValue: Integer): string; var

 i: Integer;

const

 WEIGHTS: array[0..12] of Integer = (1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1);
 SYMBOLS: array[0..12] of string = ('M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I');

begin

 for i := Low(WEIGHTS) to High(WEIGHTS) do
 begin
   while aValue >= WEIGHTS[i] do
   begin
     Result := Result + SYMBOLS[i];
     aValue := aValue - WEIGHTS[i];
   end;
   if aValue = 0 then
     Break;
 end;

end;

begin

 Writeln(IntegerToRoman(1990)); // MCMXC
 Writeln(IntegerToRoman(2008)); // MMVIII
 Writeln(IntegerToRoman(1666)); // MDCLXVI

end.</lang>

DWScript

Translation of: D

<lang delphi>const weights = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]; const symbols = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];

function toRoman(n : Integer) : String; var

  i, w : Integer;

begin

  for i := 0 to weights.High do begin
     w := weights[i];
     while n >= w do begin
        Result += symbols[i];
        n -= w;
     end;
     if n = 0 then Break;
  end;

end;

PrintLn(toRoman(455)); PrintLn(toRoman(3456)); PrintLn(toRoman(2488));</lang>

Emacs Lisp

<lang lisp> (defun ar2ro (AN)

 "translate from arabic number AN to roman number,
  ar2ro(1666) returns (M D C L X V I)"
 (cond
  ((>= AN 1000) (cons 'M (ar2ro (- AN 1000))))
  ((>= AN 900) (cons 'C (cons 'M (ar2ro (-AN 900)))))
  ((>= AN 500) (cons 'D (ar2ro (- AN 500))))
  ((>= AN 400) (cons 'C (cons 'D (ar2ro (- AN 400)))))
  ((>= AN 100) (cons 'C (ar2ro (- AN 100))))
  ((>= AN 90) (cons 'X (cons 'C (ar2ro (- AN 90)))))
  ((>= AN 50) (cons 'L (ar2ro (- AN 50))))
  ((>= AN 40) (cons 'X (cons 'L (ar2ro (- AN 40)))))
  ((>= AN 10) (cons 'X (ar2ro (- AN 10))))
  ((>= AN 5) (cons 'V (ar2ro (- AN 5))))
  ((>= AN 4) (cons 'I (cons 'V (ar2ro (- AN 4)))))
  ((>= AN 1) (cons 'I (ar2ro (- AN 1))))
  ((= AN 0) nil)))

</lang>

Erlang

Translation of: OCaml

<lang erlang>-module(roman). -export([to_roman/1]).

to_roman(0) -> []; to_roman(X) when X >= 1000 -> [$M | to_roman(X - 1000)]; to_roman(X) when X >= 100 ->

   digit(X div 100, $C, $D, $M) ++ to_roman(X rem 100);

to_roman(X) when X >= 10 ->

   digit(X div 10, $X, $L, $C) ++ to_roman(X rem 10);

to_roman(X) when X >= 1 -> digit(X, $I, $V, $X).

digit(1, X, _, _) -> [X]; digit(2, X, _, _) -> [X, X]; digit(3, X, _, _) -> [X, X, X]; digit(4, X, Y, _) -> [X, Y]; digit(5, _, Y, _) -> [Y]; digit(6, X, Y, _) -> [Y, X]; digit(7, X, Y, _) -> [Y, X, X]; digit(8, X, Y, _) -> [Y, X, X, X]; digit(9, X, _, Z) -> [X, Z].</lang>

sample:

1> c(roman).            
{ok,roman}
2> roman:to_roman(1999).
"MCMXCIX"
3> roman:to_roman(25).  
"XXV"
4> roman:to_roman(944).
"CMXLIV"

Alternative: <lang erlang> -module( roman_numerals ).

-export( [encode_from_integer/1]).

-record( encode_acc, {n, romans=""} ).

encode_from_integer( N ) when N > 0 ->

       #encode_acc{romans=Romans} = lists:foldl( fun encode_from_integer/2, #encode_acc{n=N}, map() ),
       Romans.


encode_from_integer( _Map, #encode_acc{n=0}=Acc ) -> Acc; encode_from_integer( {_Roman, Value}, #encode_acc{n=N}=Acc ) when N < Value -> Acc; encode_from_integer( {Roman, Value}, #encode_acc{n=N, romans=Romans} ) ->

       Times = N div Value,
       New_roman = lists:flatten( lists:duplicate(Times, Roman) ),
       #encode_acc{n=N - (Times * Value), romans=Romans ++ New_roman}.

map() -> [{"M",1000}, {"CM",900}, {"D",500}, {"CD",400}, {"C",100}, {"XC",90}, {"L",50}, {"XL",40}, {"X",10}, {"IX",9}, {"V",5}, {"IV",4}, {"I\ ",1}]. </lang>

Output:
36> roman_numerals:encode_from_integer( 1990 ).
"MCMXC"
37> roman_numerals:encode_from_integer( 2008 ).
"MMVIII"
38> roman_numerals:encode_from_integer( 1666 ).
"MDCLXVI"

Euphoria

Translation of: BASIC

<lang Euphoria>constant arabic = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 } constant roman = {"M", "CM", "D","CD", "C","XC","L","XL","X","IX","V","IV","I"}

function toRoman(integer val)

   sequence result
   result = ""
   for i = 1 to 13 do
       while val >= arabic[i] do
           result &= roman[i]
           val -= arabic[i]
       end while
   end for
   return result

end function

printf(1,"%d = %s\n",{2009,toRoman(2009)}) printf(1,"%d = %s\n",{1666,toRoman(1666)}) printf(1,"%d = %s\n",{3888,toRoman(3888)})</lang>

Output:

2009 = MMIX
1666 = MDCLXVI
3888 = MMMDCCCLXXXVIII


Excel

Excel can encode numbers in Roman forms in 5 successively concise forms. These can be indicated from 0 to 4. Type in a cell: <lang Excel> =ROMAN(2013,0) </lang>

It becomes: <lang> MMXIII </lang>

F#

<lang fsharp>let digit x y z = function

   1 -> x
 | 2 -> x + x
 | 3 -> x + x + x
 | 4 -> x + y
 | 5 -> y
 | 6 -> y + x
 | 7 -> y + x + x
 | 8 -> y + x + x + x
 | 9 -> x + z
 | _ -> failwith "invalid call to digit"

let rec to_roman acc = function

   | x when x >= 1000 -> to_roman (acc + "M") (x - 1000)
   | x when x >= 100 -> to_roman (acc + digit "C" "D" "M" (x / 100)) (x % 100)
   | x when x >= 10 -> to_roman (acc + digit "X" "L" "C" (x / 10)) (x % 10)
   | x when x > 0 -> acc + digit "I" "V" "X" x
   | 0 -> acc
   | _ -> failwith "invalid call to_roman (negative input)"

let roman n = to_roman "" n

[<EntryPoint>] let main args =

   [1990; 2008; 1666]
   |> List.map (fun n -> roman n)
   |> List.iter (printfn "%s")
   0</lang>

Output

MCMXC
MMVIII
MDCLXVI

Factor

A roman numeral library ships with Factor. <lang factor>USE: roman ( scratchpad ) 3333 >roman . "mmmcccxxxiii"</lang>

Parts of the implementation:

<lang factor>CONSTANT: roman-digits

   { "m" "cm" "d" "cd" "c" "xc" "l" "xl" "x" "ix" "v" "iv" "i" }

CONSTANT: roman-values

   { 1000 900 500 400 100 90 50 40 10 9 5 4 1 }

ERROR: roman-range-error n ;

roman-range-check ( n -- n )
   dup 1 10000 between? [ roman-range-error ] unless ;
>roman ( n -- str )
   roman-range-check
   roman-values roman-digits [
       [ /mod swap ] dip <repetition> concat
   ] 2map "" concat-as nip ;</lang>

FALSE

<lang false>^$." " [$999>][1000- "M"]#

$899> [ 900-"CM"]?
$499> [ 500- "D"]?
$399> [ 400-"CD"]?

[$ 99>][ 100- "C"]#

$ 89> [  90-"XC"]?
$ 49> [  50- "L"]?
$ 39> [  40-"XL"]?

[$ 9>][ 10- "X"]#

$  8> [   9-"IX"]?
$  4> [   5- "V"]?
$  3> [   4-"IV"]?

[$ ][ 1- "I"]#%</lang>

Fan

<lang Fan>**

    • converts a number to its roman numeral representation

class RomanNumerals {

 private Str digit(Str x, Str y, Str z, Int i)
 {
   switch (i)
   {
     case 1: return x
     case 2: return x+x
     case 3: return x+x+x
     case 4: return x+y
     case 5: return y
     case 6: return y+x
     case 7: return y+x+x
     case 8: return y+x+x+x
     case 9: return x+z
   }
   return ""
 }
 Str toRoman(Int i)
 {
   if (i>=1000) { return "M" + toRoman(i-1000) }
   if (i>=100) { return digit("C", "D", "M", i/100) + toRoman(i%100) }
   if (i>=10) { return digit("X", "L", "C", i/10) + toRoman(i%10) }
   if (i>=1) { return digit("I", "V", "X", i) }
   return ""
 }
 Void main()
 {
   2000.times |i| { echo("$i = ${toRoman(i)}") }
 }

}</lang>

Forth

<lang forth>: vector create ( n -- ) 0 do , loop does> ( n -- ) swap cells + @ execute ; \ these are ( numerals -- numerals )

,I dup c@ C, ;  : ,V dup 1 + c@ C, ;  : ,X dup 2 + c@ C, ;

\ these are ( numerals -- )

noname ,I ,X drop ; :noname ,V ,I ,I ,I drop ; :noname ,V ,I ,I drop ;
noname ,V ,I drop ; :noname ,V drop ; :noname ,I ,V drop ;
noname ,I ,I ,I drop ; :noname ,I ,I drop ; :noname ,I drop ;

' drop ( 0 : no output ) 10 vector ,digit

roman-rec ( numerals n -- ) 10 /mod dup if >r over 2 + r> recurse else drop then ,digit ;
roman ( n -- c-addr u )
 dup 0 4000 within 0= abort" EX LIMITO!" 
 HERE SWAP  s" IVXLCDM" drop swap roman-rec  HERE OVER - ;

1999 roman type \ MCMXCIX

 25 roman type     \ XXV
944 roman type     \ CMXLIV</lang>

Alternative implementation <lang forth>create romans 0 , 1 , 5 , 21 , 9 , 2 , 6 , 22 , 86 , 13 ,

 does> swap cells + @ ;
roman-digit ( a1 n1 a2 n2 -- a3)
 drop >r romans
 begin dup while tuck 4 mod 1- chars r@ + c@ over c! char+ swap 4 / repeat
 r> drop drop
(split) swap >r /mod r> swap ;
>roman ( n1 a -- a n2)
 tuck 1000 (split) s" M  " roman-digit 100 (split) s" CDM" roman-digit
 10 (split) s" XLC" roman-digit 1 (split) s" IVX" roman-digit nip over -

create (roman) 16 chars allot

1999 (roman) >roman type cr</lang>

Fortran

Works with: Fortran version 90 and later

<lang fortran>program roman_numerals

 implicit none
 write (*, '(a)') roman (2009)
 write (*, '(a)') roman (1666)
 write (*, '(a)') roman (3888)

contains

function roman (n) result (r)

 implicit none
 integer, intent (in) :: n
 integer, parameter   :: d_max = 13
 integer              :: d
 integer              :: m
 integer              :: m_div
 character (32)       :: r
 integer,        dimension (d_max), parameter :: d_dec = &
   & (/1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1/)
 character (32), dimension (d_max), parameter :: d_rom = &
   & (/'M ', 'CM', 'D ', 'CD', 'C ', 'XC', 'L ', 'XL', 'X ', 'IX', 'V ', 'IV', 'I '/)
 r = 
 m = n
 do d = 1, d_max
   m_div = m / d_dec (d)
   r = trim (r) // repeat (trim (d_rom (d)), m_div)
   m = m - d_dec (d) * m_div
 end do

end function roman

end program roman_numerals</lang>

Output:

 MMIX
 MDCLXVI
 MMMDCCCLXXXVIII

Go

For fluff, the unicode overbar is recognized as a factor of 1000, as described in WP.

If you see boxes in the code below, those are supposed to be the Unicode combining overline (U+0305) and look like IVXLCDM. Or, if you see overstruck combinations of letters, that's a different font rendering problem. (If you need roman numerals > 3999 reliably, it might best to stick to chiseling them in stone...) <lang go>package main

import "fmt"

var (

   m0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
   m1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
   m2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
   m3 = []string{"", "M", "MM", "MMM", "I̅V̅",
       "V̅", "V̅I̅", "V̅I̅I̅", "V̅I̅I̅I̅", "I̅X̅"}
   m4 = []string{"", "X̅", "X̅X̅", "X̅X̅X̅", "X̅L̅",
       "L̅", "L̅X̅", "L̅X̅X̅", "L̅X̅X̅X̅", "X̅C̅"}
   m5 = []string{"", "C̅", "C̅C̅", "C̅C̅C̅", "C̅D̅",
       "D̅", "D̅C̅", "D̅C̅C̅", "D̅C̅C̅C̅", "C̅M̅"}
   m6 = []string{"", "M̅", "M̅M̅", "M̅M̅M̅"}

)

func formatRoman(n int) (string, bool) {

   if n < 1 || n >= 4e6 {
       return "", false
   }
   // this is efficient in Go.  the seven operands are evaluated,
   // then a single allocation is made of the exact size needed for the result.
   return m6[n/1e6] + m5[n%1e6/1e5] + m4[n%1e5/1e4] + m3[n%1e4/1e3] +
       m2[n%1e3/1e2] + m1[n%100/10] + m0[n%10],
       true

}

func main() {

   // show three numbers mentioned in task descriptions
   for _, n := range []int{1990, 2008, 1666} {
       r, ok := formatRoman(n)
       if ok {
           fmt.Println(n, "==", r)
       } else {
           fmt.Println(n, "not representable")
       }
   }

}</lang> Output:

1990 == MCMXC
2008 == MMVIII
1666 == MDCLXVI

Groovy

<lang groovy>symbols = [ 1:'I', 4:'IV', 5:'V', 9:'IX', 10:'X', 40:'XL', 50:'L', 90:'XC', 100:'C', 400:'CD', 500:'D', 900:'CM', 1000:'M' ]

def roman(arabic) {

   def result = ""
   symbols.keySet().sort().reverse().each { 
       while (arabic >= it) {
           arabic-=it
           result+=symbols[it]
       }
   }
   return result

} assert roman(1) == 'I' assert roman(2) == 'II' assert roman(4) == 'IV' assert roman(8) == 'VIII' assert roman(16) == 'XVI' assert roman(32) == 'XXXII' assert roman(25) == 'XXV' assert roman(64) == 'LXIV' assert roman(128) == 'CXXVIII' assert roman(256) == 'CCLVI' assert roman(512) == 'DXII' assert roman(954) == 'CMLIV' assert roman(1024) == 'MXXIV' assert roman(1666) == 'MDCLXVI' assert roman(1990) == 'MCMXC' assert roman(2008) == 'MMVIII'</lang>

Haskell

With an explicit decimal digit representation list:

<lang haskell>digit x y z k =

 [[x],[x,x],[x,x,x],[x,y],[y],[y,x],[y,x,x],[y,x,x,x],[x,z]] !! 
 (fromInteger k - 1)

toRoman :: Integer -> String toRoman 0 = "" toRoman x | x < 0 = error "Negative roman numeral" toRoman x | x >= 1000 = 'M' : toRoman (x - 1000) toRoman x | x >= 100 = digit 'C' 'D' 'M' q ++ toRoman r where

 (q,r) = x `divMod` 100

toRoman x | x >= 10 = digit 'X' 'L' 'C' q ++ toRoman r where

 (q,r) = x `divMod` 10

toRoman x = digit 'I' 'V' 'X' x</lang>

Output:

<lang haskell>*Main> map toRoman [1999,25,944] ["MCMXCIX","XXV","CMXLIV"]</lang>

HicEst

<lang hicest>CHARACTER Roman*20

CALL RomanNumeral(1990, Roman) ! MCMXC CALL RomanNumeral(2008, Roman) ! MMVIII CALL RomanNumeral(1666, Roman) ! MDCLXVI

END

SUBROUTINE RomanNumeral( arabic, roman)

 CHARACTER roman
 DIMENSION ddec(13)
 DATA      ddec/1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1/
 roman = ' '
 todo = arabic
 DO d = 1, 13
   DO rep = 1, todo / ddec(d)
     roman = TRIM(roman) // TRIM(CHAR(d, 13, "M  CM D  CD C  XC L  XL X  OX V  IV I  "))
     todo = todo - ddec(d)
   ENDDO
 ENDDO

END</lang>

Icon and Unicon

<lang Icon>link numbers # commas, roman

procedure main(arglist) every x := !arglist do

  write(commas(x), " -> ",roman(x)|"*** can't convert to Roman numerals ***")

end</lang>

numbers.icn provides roman as seen below and is based upon a James Gimple SNOBOL4 function.

<lang Icon>procedure roman(n) #: convert integer to Roman numeral

  local arabic, result
  static equiv
  initial equiv := ["","I","II","III","IV","V","VI","VII","VIII","IX"]
  integer(n) > 0 | fail
  result := ""
  every arabic := !n do
     result := map(result,"IVXLCDM","XLCDM**") || equiv[arabic + 1]
  if find("*",result) then fail else return result

end</lang>

Sample output:

#roman.exe  3 4 8 49 2010 1666 3000 3999 4000 

3 -> III
4 -> IV
8 -> VIII
49 -> XLIX
2,010 -> MMX
1,666 -> MDCLXVI
3,999 -> MMMCMXCIX
4,000 -> *** can't convert to Roman numerals ***

Io

Translation of: C#

<lang Io>Roman := Object clone do (

   nums := list(1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1)
   rum := list("M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I")
   
   numeral := method(number,
       result := ""
       for(i, 0, nums size,
           if(number == 0, break)
           while(number >= nums at(i),
               number = number - nums at(i)
               result = result .. rum at(i)
           )
       )
       return result
   )

)

Roman numeral(1666) println</lang>

J

rfd obtains Roman numerals from decimals.

<lang j>R1000=. ;L:1 ,{ <@(<;._1);._2]0 :0

 C CC CCC CD D DC DCC DCCC CM
 X XX XXX XL L LX LXX LXXX XC
 I II III IV V VI VII VIII IX

)

rfd=: ('M' $~ <.@%&1000) , R1000 {::~ 1000&|</lang>

Explanation: R1000's definition contains rows representing each of 10 different digits in the 100s, 10s and 1s column (the first entry in each row is blank -- each entry is preceded by a space). R1000 itself represents the first 1000 roman numerals (the cartesian product of these three rows of roman numeral "digits" which is constructed so that they are in numeric order. And the first entry -- zero -- is just blank). To convert a number to its roman numeral representation, we will separate the number into the integer part after dividing by 1000 (that's the number of 'M's we need) and the remainder after dividing by 1000 (which will be an index into R1000).

For example:<lang j> rfd 1234 MCCXXXIV

  rfd 567

DLXVII

  rfd 89

LXXXIX</lang>

Derived from the J Wiki. Further examples of use will be found there.

Java

Translation of: Ada

The conversion function throws an IllegalArgumentException for non-positive numbers, since Java does not have unsigned primitives.

Works with: Java version 1.5+

<lang java5>public class RN {

   enum Numeral {
       I(1), IV(4), V(5), IX(9), X(10), XL(40), L(50), XC(90), C(100), CD(400), D(500), CM(900), M(1000);
       int weight;
       Numeral(int weight) {
           this.weight = weight;
       }
   };
   public static String roman(long n) {
       
       if( n <= 0) {
           throw new IllegalArgumentException();
       }
       
       StringBuilder buf = new StringBuilder();
       final Numeral[] values = Numeral.values();
       for (int i = values.length - 1; i >= 0; i--) {
           while (n >= values[i].weight) {
               buf.append(values[i]);
               n -= values[i].weight;
           }
       }
       return buf.toString();
   }
   public static void test(long n) {
       System.out.println(n + " = " + roman(n));
   }
   public static void main(String[] args) {
       test(1999);
       test(25);
       test(944);
       test(0);
   }

}</lang> Output:

1999 = MCMXCIX
25 = XXV
944 = CMXLIV
Exception in thread "main" java.lang.IllegalArgumentException
	at RN.roman(RN.java:15)
	at RN.test(RN.java:31)
	at RN.main(RN.java:38)
Works with: Java version 1.8+

<lang java5>import java.util.Set; import java.util.EnumSet; import java.util.Collections; import java.util.stream.Collectors; import java.util.stream.LongStream;

public interface RomanNumerals {

 public enum Numeral {
   M(1000), CM(900), D(500), CD(400), C(100), XC(90), L(50), XL(40), X(10), IX(9), V(5), IV(4), I(1);
   public final long weight;
   private static final Set<Numeral> SET = Collections.unmodifiableSet(EnumSet.allOf(Numeral.class));
   private Numeral(long weight) {
     this.weight = weight;
   }
   public static Numeral getLargest(long weight) {
     return SET.stream()
       .filter(numeral -> weight >= numeral.weight)
       .findFirst()
       .orElse(I)
     ;
   }
 };
 public static String encode(long n) {
   return LongStream.iterate(n, l -> l - Numeral.getLargest(l).weight)
     .limit(Numeral.values().length)
     .filter(l -> l > 0)
     .mapToObj(Numeral::getLargest)
     .map(String::valueOf)
     .collect(Collectors.joining())
   ;
 }
 public static long decode(String roman) {
   long result =  new StringBuilder(roman.toUpperCase()).reverse().chars()
     .mapToObj(c -> Character.toString((char) c))
     .map(numeral -> Enum.valueOf(Numeral.class, numeral))
     .mapToLong(numeral -> numeral.weight)
     .reduce(0, (a, b) -> a + (a <= b ? b : -b))
   ;
   if (roman.charAt(0) == roman.charAt(1)) {
     result += 2 * Enum.valueOf(Numeral.class, roman.substring(0, 1)).weight;
   }
   return result;
 }
 public static void test(long n) {
   System.out.println(n + " = " + encode(n));
   System.out.println(encode(n) + " = " + decode(encode(n)));
 }
 public static void main(String[] args) {
   LongStream.of(1999, 25, 944).forEach(RomanNumerals::test);
 }

}</lang> Output:

1999 = MCMXCIX
MCMXCIX = 1999
25 = XXV
XXV = 25
944 = CMXLIV
CMXLIV = 944

JavaScript

Translation of: Tcl

<lang javascript>var roman = {

   map: [
       1000, 'M', 900, 'CM', 500, 'D', 400, 'CD', 100, 'C', 90, 'XC',
       50, 'L', 40, 'XL', 10, 'X', 9, 'IX', 5, 'V', 4, 'IV', 1, 'I',
   ],
   int_to_roman: function(n) {
       var value = ;
       for (var idx = 0; n > 0 && idx < this.map.length; idx += 2) {
           while (n >= this.map[idx]) {
               value += this.map[idx + 1];
               n -= this.map[idx];
           }
       }
       return value;
   }

}

roman.int_to_roman(1999); // "MCMXCIX"</lang>

LaTeX

The macro \Roman is defined for uppercase roman numeral, accepting as argument a name of an existing counter.

<lang latex>\documentclass{article} \begin{document} \newcounter{currentyear}\setcounter{currentyear}{\year} Anno Domini \Roman{currentyear} \end{document}</lang>

Liberty BASIC

<lang lb>

   dim arabic( 12)
   for i =0 to 12
       read k
       arabic( i) =k
   next i
   data 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1
   dim roman$( 12)
   for i =0 to 12
       read k$
       roman$( i) =k$
   next i
   data "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"
   print 2009, toRoman$( 2009)
   print 1666, toRoman$( 1666)
   print 3888, toRoman$( 3888)
   end

function toRoman$( value)

   i       =0
   result$ =""
   for i = 0 to 12
       while value >=arabic( i)
           result$ = result$ + roman$( i)
           value   = value   - arabic( i)
       wend
   next i
   toRoman$ =result$ 

end function </lang>

2009          MMIX
1666          MDCLXVI
3888          MMMDCCCLXXXVIII


<lang logo>make "roman.rules [

 [1000 M] [900 CM] [500 D] [400 CD]
 [ 100 C] [ 90 XC] [ 50 L] [ 40 XL]
 [  10 X] [  9 IX] [  5 V] [  4 IV]
 [   1 I]

]

to roman :n [:rules :roman.rules] [:acc "||]

 if empty? :rules [output :acc]
 if :n < first first :rules [output (roman :n bf :rules :acc)]
 output (roman :n - first first :rules  :rules  word :acc last first :rules)

end</lang>

Works with: UCB Logo

<lang logo>make "patterns [[?] [? ?] [? ? ?] [? ?2] [?2] [?2 ?] [?2 ? ?] [?2 ? ? ?] [? ?3]]

to digit :d :numerals

 if :d = 0 [output "||]
 output apply (sentence "\( "word (item :d :patterns) "\)) :numerals

end to digits :n :numerals

 output word ifelse :n < 10 ["||] [digits int :n/10 bf bf :numerals] ~
             digit modulo :n 10 :numerals

end to roman :n

 if or :n < 0 :n >= 4000 [output [EX MODVS!]]
 output digits :n [I V X L C D M]

end

print roman 1999  ; MCMXCIX print roman 25  ; XXV print roman 944  ; CMXLIV</lang>

LotusScript

<lang lss> Function toRoman(value) As String Dim arabic(12) As Integer Dim roman(12) As String

arabic(0) = 1000 arabic(1) = 900 arabic(2) = 500 arabic(3) = 400 arabic(4) = 100 arabic(5) = 90 arabic(6) = 50 arabic(7) = 40 arabic(8) = 10 arabic(9) = 9 arabic(10) = 5 arabic(11) = 4 arabic(12) = 1

roman(0) = "M" roman(1) = "CM" roman(2) = "D" roman(3) = "CD" roman(4) = "C" roman(5) = "XC" roman(6) = "L" roman(7) = "XL" roman(8) = "X" roman(9) = "IX" roman(10) = "V" roman(11) = "IV" roman(12) = "I"

Dim i As Integer, result As String

For i = 0 To 12 Do While value >= arabic(i) result = result + roman(i) value = value - arabic(i) Loop Next i

toRoman = result End Function

</lang>

Lua

<lang lua>romans = { {1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"}, {100, "C"}, {90, "XC"}, {50, "L"}, {40, "XL"}, {10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"} }

k = io.read() + 0 for _, v in ipairs(romans) do --note that this is -not- ipairs.

 val, let = unpack(v)
 while k >= val do
   k = k - val

io.write(let)

 end

end print()</lang>

M4

<lang M4>define(`roman',`ifelse(eval($1>=1000),1,`M`'roman(eval($1-1000))', `ifelse(eval($1>=900),1,`CM`'roman(eval($1-900))', `ifelse(eval($1>=500),1,`D`'roman(eval($1-500))', `ifelse(eval($1>=100),1,`C`'roman(eval($1-100))', `ifelse(eval($1>=90),1,`XC`'roman(eval($1-90))', `ifelse(eval($1>=50),1,`L`'roman(eval($1-50))', `ifelse(eval($1>=40),1,`XL`'roman(eval($1-40))', `ifelse(eval($1>=10),1,`X`'roman(eval($1-10))', `ifelse(eval($1>=9),1,`IX`'roman(eval($1-9))', `ifelse(eval($1>=5),1,`V`'roman(eval($1-5))', `ifelse(eval($1>=4),1,`IV`'roman(eval($1-4))', `ifelse(eval($1>=1),1,`I`'roman(eval($1-1))' )')')')')')')')')')')')')dnl dnl roman(3675)</lang>

Output:

MMMDCLXXV

Mathematica

Define a custom function that works on positive numbers (RomanForm[0] will not be evaluated): <lang Mathematica>RomanForm[i_Integer?Positive] :=

Module[{num = i, string = "", value, letters, digits}, 
 digits = {{1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"}, {100, 
    "C"}, {90, "XC"}, {50, "L"}, {40, "XL"}, {10, "X"}, {9, 
    "IX"}, {5, "V"}, {4, "IV"}, {1, "I"}};
 While[num > 0, {value, letters} = 
   Which @@ Flatten[{num >= #1, ##} & /@ digits, 1];
  num -= value;
  string = string <> letters;];
 string]</lang>

Examples: <lang Mathematica>RomanForm[4] RomanForm[99] RomanForm[1337] RomanForm[1666] RomanForm[6889]</lang> gives back: <lang Mathematica>IV XCIX MCCCXXXVII MDCLXVI MMMMMMDCCCLXXXIX</lang>

Mercury

The non-ceremonial work in this program starts at the function to_roman/1. Unusually for Mercury the function is semi-deterministic. This is because some of the helper functions it calls are also semi-deterministic and the determinism subsystem propagates the status upward. (There are ways to stop it from doing this, but it would distract from the actual Roman numeral conversion process so the semi-determinism has been left in.)

to_roman/1 is just a string of chained function calls. The number is passed in as a string (and the main/2 predicate ensures that it is *only* digits!) is converted into a list of characters. This list is then reversed and the Roman numeral version is built from it. This resulting character list is then converted back into a string and returned.

build_roman/1 takes the lead character off the list (reversed numerals) and then recursively calls itself. It uses the promote/2 predicate to multiply the ensuing Roman numerals (if any) by an order of magnitude and converts the single remaining digit to the appropriate list of Roman numerals. To clarify, if it's passed the number "123" (encoded by this point as ['3', '2', '1']) the following transpires:

  • The '3' is removed and build_roman/1 is now called with ['2', '1'].
    • The '2' is removed and the function is recursively called with ['1'].
      • The '1' is removed and the function is recursively called with [] (the empty list)..
        • The function returns [].
      • The [] has its (non-existent) digits promoted and then gets ['I'] appended (1 converts to ['I'] via digit_to_roman/1).
    • The ['I'] has its (single) digit promoted and is converted to ['X'] and then gets ['I','I'] appended from the 2's conversion. The resulting list is now ['X','I','I'] (or 12).
  • The ['X','I','I'] has all of its digits promoted, yielding ['C','X','X'] before getting ['I','I','I'] appended. The resulting list is now ['C','X','X','I','I','I'] which is converted into the string "CXXIII" back up in to_roman/1.

It is possible for this to be implemented differently even keeping the same algorithm. For example the map module from the standard library could be used for looking up conversions and promotions instead of having digit_to_roman/1 and promote. This would require, however, either passing around the conversion tables constantly (bulking up the parameter lists of all functions and predicates) or creating said conversion tables each time at point of use (slowing down the implementation greatly).

Now the semi-determinism of the functions involved is a little bit of a problem. In the main/2 predicate you can see one means of dealing with it. main/2 *must* be deterministic (or cc_multi, but this is equivalent for this discussion). There can be *no* failure in a called function or predicate … unless that failure is explicitly handled somehow. In this implementation the failure is handled in the foldl/4's provided higher-order predicate lambda. The call to to_roman/1 is called within a conditional and both the success (true) and failure (false) branches are handled. This makes the passed-in predicate lambda deterministic, even though the implementation functions and predicates are semi-deterministic.

But why are they semi-deterministic? Well, this has to do with the type system. It doesn't permit sub-typing, so when the type of a predicate is, say pred(char, char) (as is the case for promote/2), the underlying implementation *must* handle *all* values that a type char could possibly hold. It is trivial to see that our code does not. This means that, in theory, it is possible that promote/2 (or digit_to_roman/1) could be passed a value which cannot be processed, thus triggering a false result, and thus being semi-deterministic.

roman.m

<lang Mercury>

- module roman.
- interface.
- import_module io.
- pred main(io::di, io::uo) is det.
- implementation.
- import_module char, int, list, string.

main(!IO) :-

   command_line_arguments(Args, !IO),
   filter(is_all_digits, Args, CleanArgs),
   foldl((pred(Arg::in, !.IO::di, !:IO::uo) is det :-
              ( Roman = to_roman(Arg) ->
                    format("%s => %s", [s(Arg), s(Roman)], !IO), nl(!IO)
              ;     format("%s cannot be converted.", [s(Arg)], !IO), nl(!IO) )
         ), CleanArgs, !IO).
- func to_roman(string::in) = (string::out) is semidet.

to_roman(Number) = from_char_list(build_roman(reverse(to_char_list(Number)))).

- func build_roman(list(char)) = list(char).
- mode build_roman(in) = out is semidet.

build_roman([]) = []. build_roman([D|R]) = Roman :-

   map(promote, build_roman(R), Interim),
   Roman = Interim ++ digit_to_roman(D).
- func digit_to_roman(char) = list(char).
- mode digit_to_roman(in) = out is semidet.

digit_to_roman('0') = []. digit_to_roman('1') = ['I']. digit_to_roman('2') = ['I','I']. digit_to_roman('3') = ['I','I','I']. digit_to_roman('4') = ['I','V']. digit_to_roman('5') = ['V']. digit_to_roman('6') = ['V','I']. digit_to_roman('7') = ['V','I','I']. digit_to_roman('8') = ['V','I','I','I']. digit_to_roman('9') = ['I','X'].

- pred promote(char::in, char::out) is semidet.

promote('I', 'X'). promote('V', 'L'). promote('X', 'C'). promote('L', 'D'). promote('C', 'M').

- end_module roman.

</lang>

Usage and output

$ mmc roman && ./roman 1 8 27 64 125 216 343 512 729 1000 1331 1728 2197 2744 3375
1 => I
8 => VIII
27 => XXVII
64 => LXIV
125 => CXXV
216 => CCXVI
343 => CCCXLIII
512 => DXII
729 => DCCXXIX
1000 => M
1331 => MCCCXXXI
1728 => MDCCXXVIII
2197 => MMCXCVII
2744 => MMDCCXLIV
3375 => MMMCCCLXXV

roman2.m

Another implementation using an algorithm inspired by the Erlang implementation could look like this:

<lang Mercury>

- module roman2.
- interface.
- import_module io.
- pred main(io::di, io::uo) is det.
- implementation.
- import_module char, int, list, string.

main(!IO) :-

   command_line_arguments(Args, !IO),
   filter_map(to_int, Args, CleanArgs),
   foldl((pred(Arg::in, !.IO::di, !:IO::uo) is det :-
              ( Roman = to_roman(Arg) ->
                    format("%i => %s", 
                           [i(Arg), s(from_char_list(Roman))], !IO), 
                    nl(!IO)
              ;     format("%i cannot be converted.", [i(Arg)], !IO), nl(!IO) )
         ), CleanArgs, !IO).
- func to_roman(int) = list(char).
- mode to_roman(in) = out is semidet.

to_roman(N) = ( N >= 1000 ->

                   ['M'] ++ to_roman(N - 1000)
             ;( N >= 100 -> 
                    digit(N / 100, 'C', 'D', 'M') ++ to_roman(N rem 100)
              ;( N >= 10 ->
                     digit(N / 10, 'X', 'L', 'C') ++ to_roman(N rem 10)
               ;( N >= 1 ->
                      digit(N, 'I', 'V', 'X')
                ; [] ) ) ) ).
- func digit(int, char, char, char) = list(char).
- mode digit(in, in, in, in) = out is semidet.

digit(1, X, _, _) = [X]. digit(2, X, _, _) = [X, X]. digit(3, X, _, _) = [X, X, X]. digit(4, X, Y, _) = [X, Y]. digit(5, _, Y, _) = [Y]. digit(6, X, Y, _) = [Y, X]. digit(7, X, Y, _) = [Y, X, X]. digit(8, X, Y, _) = [Y, X, X, X]. digit(9, X, _, Z) = [X, Z].

- end_module roman2.

</lang>

This implementation calculates the value of the thousands, then the hundreds, then the tens, then the ones. In each case it uses the digit/4 function and some tricks with unification to build the appropriate list of characters for the digit and multiplier being targeted.

Its output is identical to that of the previous version.

MUMPS

<lang MUMPS>TOROMAN(INPUT)

;Converts INPUT into a Roman numeral. INPUT must be an integer between 1 and 3999
;OUTPUT is the string to return
;I is a loop variable
;CURRVAL is the current value in the loop
QUIT:($FIND(INPUT,".")>1)!(INPUT<=0)!(INPUT>3999) "Invalid input"
NEW OUTPUT,I,CURRVAL
SET OUTPUT="",CURRVAL=INPUT
SET:$DATA(ROMANNUM)=0 ROMANNUM="I^IV^V^IX^X^XL^L^XC^C^CD^D^CM^M"
SET:$DATA(ROMANVAL)=0 ROMANVAL="1^4^5^9^10^40^50^90^100^400^500^900^1000"
FOR I=$LENGTH(ROMANVAL,"^"):-1:1 DO
.FOR  Q:CURRVAL<$PIECE(ROMANVAL,"^",I)  SET OUTPUT=OUTPUT_$PIECE(ROMANNUM,"^",I),CURRVAL=CURRVAL-$PIECE(ROMANVAL,"^",I)
KILL I,CURRVAL
QUIT OUTPUT</lang>

Output:

USER>W $$ROMAN^ROSETTA(1666)
MDCLXVI
USER>W $$TOROMAN^ROSETTA(2010)
MMX
USER>W $$TOROMAN^ROSETTA(949)
CMXLIX
USER>W $$TOROMAN^ROSETTA(949.24)
Invalid input
USER>W $$TOROMAN^ROSETTA(-949)
Invalid input

Objeck

Translation of: C sharp

<lang objeck> bundle Default {

 class Roman {
   nums: static : Int[];
   rum : static : String[];
 
   function : Init() ~ Nil {
     nums := [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1];
     rum := ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"];
   }
   function : native : ToRoman(number : Int) ~ String {
     result := "";
     for(i :=0; i < nums->Size(); i += 1;) {
       while(number >= nums[i]) {
         result->Append(rum[i]);
         number -= nums[i];
       };
     };
     return result;
   }
   function : Main(args : String[]) ~ Nil {
     Init();
     ToRoman(1999)->PrintLine();
     ToRoman(25)->PrintLine();
     ToRoman(944)->PrintLine();
   }
 }

} </lang>

OCaml

With an explicit decimal digit representation list:

<lang ocaml>let digit x y z = function

   1 -> [x]
 | 2 -> [x;x]
 | 3 -> [x;x;x]
 | 4 -> [x;y]
 | 5 -> [y]
 | 6 -> [y;x]
 | 7 -> [y;x;x]
 | 8 -> [y;x;x;x]
 | 9 -> [x;z]

let rec to_roman x =

 if x = 0 then []
 else if x < 0 then
   invalid_arg "Negative roman numeral"
 else if x >= 1000 then
   'M' :: to_roman (x - 1000)
 else if x >= 100 then
   digit 'C' 'D' 'M' (x / 100) @ to_roman (x mod 100)
 else if x >= 10 then
   digit 'X' 'L' 'C' (x / 10) @ to_roman (x mod 10)
 else
   digit 'I' 'V' 'X' x</lang>

Output:

# to_roman 1999;;
- : char list = ['M'; 'C'; 'M'; 'X'; 'C'; 'I'; 'X']
# to_roman 25;;
- : char list = ['X'; 'X'; 'V']
# to_roman 944;;
- : char list = ['C'; 'M'; 'X'; 'L'; 'I'; 'V']

OpenEdge/Progress

<lang progress>FUNCTION encodeRoman RETURNS CHAR (

  i_i AS INT

):

  DEF VAR cresult   AS CHAR.
  DEF VAR croman    AS CHAR EXTENT 7 INIT [  "M", "D", "C", "L", "X", "V", "I" ].
  DEF VAR idecimal  AS INT  EXTENT 7 INIT [ 1000, 500, 100,  50,  10,   5,   1 ].
  DEF VAR ipos      AS INT  INIT 1.
  
  DO WHILE i_i > 0:
     IF i_i - idecimal[ ipos ] >= 0 THEN
        ASSIGN
           cresult  =  cresult + croman[ ipos ]
           i_i      =  i_i - idecimal[ ipos ]
           .
     ELSE IF ipos < EXTENT( croman ) - 1 AND i_i - ( idecimal[ ipos ] - idecimal[ ipos + 2 ] ) >= 0 THEN
        ASSIGN
           cresult  =  cresult + croman[ ipos + 2 ] + croman[ ipos ]
           i_i      =  i_i - ( idecimal[ ipos ] - idecimal[ ipos + 2 ] )
           ipos     =  ipos + 1
           .
     ELSE
        ipos = ipos + 1.
  END.
  RETURN cresult.

END FUNCTION. /* encodeRoman */

MESSAGE

  1990 encodeRoman( 1990 ) SKIP
  2008 encodeRoman( 2008 ) SKIP
  2000 encodeRoman( 2000 ) SKIP
  1666 encodeRoman( 1666 ) SKIP

VIEW-AS ALERT-BOX. </lang> Output:

---------------------------
Message (Press HELP to view stack trace)
---------------------------
1990 MCMXC 
2008 MMVIII 
2000 MM 
1666 MDCLXVI 
---------------------------
OK   Help   
---------------------------

Oz

Translation of: Haskell

<lang oz>declare

 fun {Digit X Y Z K}
    unit([X] [X X] [X X X] [X Y] [Y] [Y X] [Y X X] [Y X X X] [X Z])
    .K
 end
 fun {ToRoman X}
    if     X == 0    then ""
    elseif X < 0     then raise toRoman(negativeInput X) end
    elseif X >= 1000 then "M"#{ToRoman X-1000}
    elseif X >= 100  then {Digit &C &D &M  X div 100}#{ToRoman X mod 100}
    elseif X >= 10   then {Digit &X &L &C  X div 10}#{ToRoman X mod 10}
    else                  {Digit &I &V &X  X}
    end
 end

in

 {ForAll {Map [1999 25 944] ToRoman} System.showInfo}</lang>

PARI/GP

Old-style Roman numerals <lang parigp>oldRoman(n)={

 while(n>999999,
   n-=1000000;
   print1("((((I))))")
 );
 if(n>499999,
   n-=500000;
   print1("I))))")
 );
 while(n>99999,
   n-=100000;
   print1("(((I)))")
 );
 if(n>49999,
   n-=50000;
   print1("I)))")
 );
 while(n>9999,
   n-=10000;
   print1("((I))")
 );
 if(n>4999,
   n-=5000;
   print1("I))")
 );
 while(n>999,
   n-=1000;
   print1("(I)")
 );
 if(n>499,
   n-=500;
   print1("I)")
 );
 while(n>99,
   n-=100;
   print1("C")
 );
 if(n>49,
   n-=50;
   print1("L");
 );
 while(n>9,
   n-=10;
   print1("X")
 );
 if(n>4,
   n-=5;
   print1("V");
 );
 while(n,
   n--;
   print1("I")
 );
 print()

};</lang>

This simple version of medieval Roman numerals does not handle large numbers. <lang parigp>medievalRoman(n)={

 while(n>999,
   n-=1000;
   print1("M")
 );
 if(n>899,
   n-=900;
   print1("CM")
 );
 if(n>499,
   n-=500;
   print1("D")
 );
 if(n>399,
   n-=400;
   print1("CD")
 );
 while(n>99,
   n-=100;
   print1("C")
 );
 if(n>89,
   n-=90;
   print1("XC")
 );
 if(n>49,
   n-=50;
   print1("L")
 );
 if(n>39,
   n-=40;
   print1("XL")
 );
 while(n>9,
   n-=10;
   print1("X")
 );
 if(n>8,
   n-=9;
   print1("IX")
 );
 if(n>4,
   n-=5;
   print1("V")
 );
 if(n>3,
   n-=4;
   print1("IV")
 );
 while(n,
   n--;
   print1("I")
 );
 print()

};</lang>

Pascal

See Delphi

Perl

Works with: Romana::Perligata

Perligata outputs numbers in Arabic, but the verb come ("beautify") may be used to convert numbers to proper Roman numerals:

<lang perl>per quisque in I tum C conscribementum sic

       hoc tum duos multiplicamentum comementum egresso scribe.

cis</lang>

Ported version of Perl6

<lang perl>use v5.12; use Sub::SmartMatch; use SmartMatch::Sugar qw(any); use List::MoreUtils qw( natatime );

my %symbols = (

   1 => "I", 5 => "V", 10 => "X", 50 => "L", 100 => "C",
   500 => "D", 1_000 => "M"

);

my @subtractors = (

       1_000, 100,  500, 100,  100, 10,  50, 10,  10, 1,  5, 1,  1, 0

);

multi roman => [0], sub { }; multi roman => any, sub {

   my $n = shift;
   my $iter = natatime 2, @subtractors;
   while( my ($cut, $minus) = $iter->() ) {
       $n >= $cut
           and return $symbols{$cut} . roman($n - $cut);
       $n >= $cut - $minus
           and return $symbols{$minus} . roman($n + $minus);
   }

};</lang>

Sample usage

<lang perl>say roman($_) for 1..2_012;</lang>

Perl 6

<lang perl6>my %symbols =

   1 => "I", 5 => "V", 10 => "X", 50 => "L", 100 => "C",
   500 => "D", 1_000 => "M";

my @subtractors =

   1_000, 100,  500, 100,  100, 10,  50, 10,  10, 1,  5, 1,  1, 0;

multi sub roman (0) { } multi sub roman (Int $n) {

   for @subtractors -> $cut, $minus {
       $n >= $cut
           and return %symbols{$cut} ~ roman($n - $cut);
       $n >= $cut - $minus
           and return %symbols{$minus} ~ roman($n + $minus);
    }

}</lang>

Sample usage

<lang perl6>for 1 .. 2_010 -> $x {

   say roman($x);

}</lang>

PHP

Works with: PHP version 4+ tested in 5.2.12

<lang php> /**

* int2roman
* Convert any positive value of a 32-bit signed integer to its modern roman 
* numeral representation. Numerals within parentheses are multiplied by 
* 1000. ie. M == 1 000, (M) == 1 000 000, ((M)) == 1 000 000 000
* 
* @param number - an integer between 1 and 2147483647
* @return roman numeral representation of number
*/

function int2roman($number) { if (!is_int($number) || $number < 1) return false; // ignore negative numbers and zero

$integers = array(900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1); $numerals = array('CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I'); $major = intval($number / 1000) * 1000; $minor = $number - $major; $numeral = $leastSig = ;

for ($i = 0; $i < sizeof($integers); $i++) { while ($minor >= $integers[$i]) { $leastSig .= $numerals[$i]; $minor -= $integers[$i]; } }

if ($number >= 1000 && $number < 40000) { if ($major >= 10000) { $numeral .= '('; while ($major >= 10000) { $numeral .= 'X'; $major -= 10000; } $numeral .= ')'; } if ($major == 9000) { $numeral .= 'M(X)'; return $numeral . $leastSig; } if ($major == 4000) { $numeral .= 'M(V)'; return $numeral . $leastSig; } if ($major >= 5000) { $numeral .= '(V)'; $major -= 5000; } while ($major >= 1000) { $numeral .= 'M'; $major -= 1000; } }

if ($number >= 40000) { $major = $major/1000; $numeral .= '(' . int2roman($major) . ')'; }

return $numeral . $leastSig; } </lang>

PicoLisp

<lang PicoLisp>(de roman (N)

  (pack
     (make
        (mapc
           '((C D)
              (while (>= N D)
                 (dec 'N D)
                 (link C) ) )
           '(M CM D CD C XC L XL X IX V IV I)
           (1000 900 500 400 100 90 50 40 10 9 5 4 1) ) ) ) )</lang>

Output:

: (roman 1009)
-> "MIX"

: (roman 1666)
-> "MDCLXVI"

Pike

<lang pike>import String; int main(){

  write(int2roman(2009) + "\n");
  write(int2roman(1666) + "\n");
  write(int2roman(1337) + "\n");

}</lang>

Plain TeX

TeX has its own way to convert a number into roman numeral, but it produces lowercase letters; the following macro (and usage example), produce uppercase roman numeral.

<lang tex>\def\upperroman#1{\uppercase\expandafter{\romannumeral#1}} Anno Domini \upperroman{\year} \bye</lang>

PL/I

<lang PL/I> /* From Wiki Fortran */ roman: procedure (n) returns(character (32) varying);

  declare n fixed binary nonassignable;
  declare (d, m) fixed binary;
  declare (r, m_div) character (32) varying;
  declare d_dec(13) fixed binary static initial
     (1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1);
  declare d_rom(13) character (2) varying static initial
     ('M', 'CM', 'D', 'CD', 'C', 'XC', 'L',
      'XL', 'X', 'IX', 'V', 'IV', 'I');
  r = ;
  m = n;
  do d = 1 to 13;
     m_div = m / d_dec (d);
     r = r || copy (d_rom (d), m_div);
     m = m - d_dec (d) * m_div;
  end;
  return (r);

end roman; </lang> Results:

   11                   XI 
   1990                 MCMXC 
   2008                 MMVIII 
   1666                 MDCLXVI 
   1999                 MCMXCIX 

PL/SQL

<lang PL/SQL>

/*****************************************************************

* $Author: Atanas Kebedjiev $
*****************************************************************
* Encoding an Arabic numeral to a Roman in the range 1..3999 is much simpler as Oracle provides the conversion formats.
* Please see also the SQL solution for the same task.
*/

DECLARE FUNCTION rencode(an IN NUMBER) RETURN VARCHAR2 IS

  rs VARCHAR2(20);

BEGIN SELECT to_char(to_char(to_date(an,'YYYY'), 'RRRR'), 'RN') INTO rs FROM dual; RETURN rs; END;

BEGIN

   DBMS_OUTPUT.PUT_LINE ('2012 = ' || rencode('2012'));     -- MMXII
   DBMS_OUTPUT.PUT_LINE ('1951 = ' || rencode('1951'));     -- MCMLI
   DBMS_OUTPUT.PUT_LINE ('1987 = ' || rencode('1987'));     -- MCMLXXXVII
   DBMS_OUTPUT.PUT_LINE ('1666 = ' || rencode('1666'));     -- MDCLXVI
   DBMS_OUTPUT.PUT_LINE ('1999 = ' || rencode('1999'));     -- MCMXCIX

END; </lang>

PowerBASIC

Translation of: BASIC
Works with: PB/Win version 8+
Works with: PB/CC version 5

<lang powerbasic>FUNCTION toRoman(value AS INTEGER) AS STRING

   DIM arabic(0 TO 12) AS INTEGER
   DIM roman(0 TO 12) AS STRING
   ARRAY ASSIGN arabic() = 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1
   ARRAY ASSIGN roman() = "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"
   DIM i AS INTEGER
   DIM result AS STRING
   FOR i = 0 TO 12
       DO WHILE value >= arabic(i)
           result = result & roman(i)
           value = value - arabic(i)
       LOOP
   NEXT i
   toRoman = result

END FUNCTION

FUNCTION PBMAIN

   'Testing
   ? "2009 = " & toRoman(2009)
   ? "1666 = " & toRoman(1666)
   ? "3888 = " & toRoman(3888)

END FUNCTION</lang>

Prolog

Works with SWI-Prolog and library clpfd.
Library clpfd assures that the program works in both managements : Roman towards Arabic and Arabic towards Roman. <lang Prolog>:- use_module(library(clpfd)).

roman :- LA = [ _ , 2010, _, 1449, _], LR = ['MDCCLXXXIX', _ , 'CX', _, 'MDCLXVI'], maplist(roman, LA, LR), maplist(my_print,LA, LR).


roman(A, R) :- A #> 0, roman(A, [u, t, h, th], LR, []), label([A]), parse_Roman(CR, LR, []), atom_chars(R, CR).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % using DCG

roman(0, []) --> [].

roman(N, [H | T]) --> {N1 #= N / 10, N2 #= N mod 10}, roman(N1, T), unity(N2, H).

unity(1, u) --> ['I']. unity(1, t) --> ['X']. unity(1, h) --> ['C']. unity(1, th)--> ['M'].

unity(4, u) --> ['IV']. unity(4, t) --> ['XL']. unity(4, h) --> ['CD']. unity(4, th)--> ['MMMM'].

unity(5, u) --> ['V']. unity(5, t) --> ['L']. unity(5, h) --> ['D']. unity(5, th)--> ['MMMMM'].

unity(9, u) --> ['IX']. unity(9, t) --> ['XC']. unity(9, h) --> ['CM']. unity(9, th)--> ['MMMMMMMMM'].

unity(0, _) --> [].


unity(V, U)--> {V #> 5, V1 #= V - 5}, unity(5, U), unity(V1, U).

unity(V, U) --> {V #> 1, V #< 4, V1 #= V-1}, unity(1, U), unity(V1, U).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Extraction of roman "lexeme" parse_Roman(['C','M'|T]) --> ['CM'], parse_Roman(T).

parse_Roman(['C','D'|T]) --> ['CD'], parse_Roman(T).

parse_Roman(['X','C'| T]) --> ['XC'], parse_Roman(T).


parse_Roman(['X','L'| T]) --> ['XL'], parse_Roman(T).


parse_Roman(['I','X'| T]) --> ['IX'], parse_Roman(T).


parse_Roman(['I','V'| T]) --> ['IV'], parse_Roman(T).

parse_Roman([H | T]) --> [H], parse_Roman(T).


parse_Roman([]) --> [].

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% my_print(A, R) :- format('~w in roman is ~w~n', [A, R]). </lang> Output :

 ?- roman.
1789 in roman is MDCCLXXXIX
2010 in roman is MMX
110 in roman is CX
1449 in roman is MCDXLIX
1666 in roman is MDCLXVI
true .

Protium

Roman numbers are built in to Protium as a particular form of national number. However, for the sake of the task the _RO opcode has been defined. <lang html><@ DEFUDOLITLIT>_RO|__Transformer|<@ DEFKEYPAR>__NationalNumericID|2</@><@ LETRESCS%NNMPAR>...|1</@></@>

<@ ENU$$DLSTLITLIT>1990,2008,1,2,64,124,1666,10001|,| <@ SAYELTLST>...</@> is <@ SAY_ROELTLSTLIT>...|RomanLowerUnicode</@> <@ SAY_ROELTLSTLIT>...|RomanUpperUnicode</@> <@ SAY_ROELTLSTLIT>...|RomanASCII</@> </@></lang>

Same code in padded-out, variable-length English dialect <lang html><# DEFINE USERDEFINEDOPCODE LITERAL LITERAL>_RO|__Transformer|<# DEFINE KEYWORD PARAMETER>__NationalNumericID|2</#><# LET RESULT CAST NATIONALNUMBER PARAMETER>...|1</#></#>

<# ENUMERATION LAMBDASPECIFIEDDELMITER LIST LITERAL LITERAL>1990,2008,1,2,64,124,1666,10001|,| <# SAY ELEMENT LIST>...</#> is <# SAY _RO ELEMENT LIST LITERAL>...|RomanLowerUnicode</#> <# SAY _RO ELEMENT LIST LITERAL>...|RomanUpperUnicode</#> <# SAY _RO ELEMENT LIST LITERAL>...|RomanASCII</#> </#></lang>

Output. Notice here the three different ways of representing the results. For reasons for notational differences, see wp:Roman_numerals#Alternate_forms

1990 is ⅿⅽⅿⅹⅽ ⅯⅭⅯⅩⅭ MCMXC
2008 is ⅿⅿⅷ ⅯⅯⅧ MMVIII
1 is ⅰ Ⅰ I
2 is ⅱ Ⅱ II
64 is ⅼⅹⅳ ⅬⅩⅣ LXIV
124 is ⅽⅹⅹⅳ ⅭⅩⅩⅣ CXXIV
1666 is ⅿⅾⅽⅼⅹⅵ ⅯⅮⅭⅬⅩⅥ MDCLXVI
10001 is ⅿⅿⅿⅿⅿⅿⅿⅿⅿⅿⅰ ↂⅠ MMMMMMMMMMI

PureBasic

<lang PureBasic>#SymbolCount = 12 ;0 based count DataSection

 denominations:
 Data.s "M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I" ;0-12
 
 denomValues:
 Data.i  1000,900,500,400,100,90,50,40,10,9,5,4,1 ;values in decending sequential order

EndDataSection

-setup

Structure romanNumeral

 symbol.s 
 value.i

EndStructure

Global Dim refRomanNum.romanNumeral(#SymbolCount)

Restore denominations For i = 0 To #SymbolCount

 Read.s refRomanNum(i)\symbol

Next

Restore denomValues For i = 0 To #SymbolCount

 Read refRomanNum(i)\value

Next

Procedure.s decRoman(n)

 ;converts a decimal number to a roman numeral
 Protected roman$, i
 
 For i = 0 To #SymbolCount
   Repeat
     If n >= refRomanNum(i)\value
       roman$ + refRomanNum(i)\symbol
       n - refRomanNum(i)\value
     Else
       Break
     EndIf
   ForEver
 Next
 ProcedureReturn roman$

EndProcedure

If OpenConsole()

 PrintN(decRoman(1999)) ;MCMXCIX
 PrintN(decRoman(1666)) ;MDCLXVI
 PrintN(decRoman(25))   ;XXV
 PrintN(decRoman(954))  ;CMLIV
 Print(#CRLF$ + #CRLF$ + "Press ENTER to exit")
 Input()
 CloseConsole()

EndIf</lang>

Python

<lang python>roman = "MDCLXVmdclxvi"; # UPPERCASE for thousands # adjust_roman = "CCXXmmccxxii"; arabic = (1000000, 500000, 100000, 50000, 10000, 5000, 1000, 500, 100, 50, 10, 5, 1); adjust_arabic = (100000, 100000, 10000, 10000, 1000, 1000, 100, 100, 10, 10, 1, 1, 0);

def arabic_to_roman(dclxvi):

 org = dclxvi; # 666 #
 out = "";
 for scale,arabic_scale  in enumerate(arabic): 
   if org == 0: break
   multiples = org / arabic_scale;
   org -= arabic_scale * multiples;
   out += roman[scale] * multiples;
   if org >= -adjust_arabic[scale] + arabic_scale: 
     org -= -adjust_arabic[scale] + arabic_scale;
     out +=  adjust_roman[scale] +  roman[scale]
 return out

if __name__ == "__main__":

 test = (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,25,30,40,50,60,69,70,
    80,90,99,100,200,300,400,500,600,666,700,800,900,1000,1009,1444,1666,1945,1997,1999,
    2000,2008,2500,3000,4000,4999,5000,6666,10000,50000,100000,500000,1000000);
 for val in test: 
   print '%d - %s'%(val, arabic_to_roman(val))</lang>

An alternative which uses the divmod() function<lang python>romanDgts= 'ivxlcdmVXLCDM_'

def ToRoman(num):

  namoR = 
  if num >=4000000:
     print 'Too Big -'
     return '-----'
  for rdix in range(0, len(romanDgts), 2):
     if num==0: break
     num,r = divmod(num,10)
     v,r = divmod(r, 5)
     if r==4:
        namoR += romanDgts[rdix+1+v] + romanDgts[rdix]
     else:
        namoR += r*romanDgts[rdix] + (romanDgts[rdix+1] if(v==1) else )
  return namoR[-1::-1]</lang>

It is more Pythonic to use zip to iterate over two lists together: <lang python>anums = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1] rnums = "M CM D CD C XC L XL X IX V IV I".split()

def to_roman(x):

   ret = []
   for a,r in zip(anums, rnums):
       n,x = divmod(x,a)
       ret.append(r*n)
   return .join(ret)
       

if __name__ == "__main__":

   test = (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,25,30,40,
           50,60,69,70,80,90,99,100,200,300,400,500,600,666,700,800,900,
           1000,1009,1444,1666,1945,1997,1999,2000,2008,2010,2011,2500,
           3000,3999)
   
   for val in test:
       print '%d - %s'%(val, to_roman(val))

</lang>

R

R has a built-in function, as.roman, for conversion to Roman numerals. The implementation details are found in utils:::.numeric2roman (see previous link), and utils:::.roman2numeric, for conversion back to Arabic decimals. <lang R>as.roman(1666) # MDCLXVI</lang> Since the object as.roman creates is just an integer vector with a class, you can do arithmetic with Roman numerals: <lang R>as.roman(1666) + 334 # MM</lang>

Racket

Straight recursion: <lang Racket>#lang racket (define (encode/roman number)

 (cond ((>= number 1000) (string-append "M" (encode/roman (- number 1000))))
       ((>= number 900) (string-append "CM" (encode/roman (- number 900))))
       ((>= number 500) (string-append "D" (encode/roman (- number 500))))
       ((>= number 400) (string-append "CD" (encode/roman (- number 400))))
       ((>= number 100) (string-append "C" (encode/roman (- number 100))))
       ((>= number 90) (string-append "XC" (encode/roman (- number 90))))
       ((>= number 50) (string-append "L" (encode/roman (- number 50))))
       ((>= number 40) (string-append "XL" (encode/roman (- number 40))))
       ((>= number 10) (string-append "X" (encode/roman (- number 10))))
       ((>= number 5) (string-append "V" (encode/roman (- number 5))))
       ((>= number 4) (string-append "IV" (encode/roman (- number 4))))
       ((>= number 1) (string-append "I" (encode/roman (- number 1))))
       (else "")))</lang>

Using for/fold and quotient/remainder to remove repetition: <lang Racket>#lang racket (define (number->list n)

 (for/fold ([result null])
   ([decimal '(1000 900 500 400 100 90 50 40 10 5 4  1)]
    [roman   '(M    CM  D   CD  C   XC L  XL X  V IV I)])
   #:break (= n 0)
   (let-values ([(q r) (quotient/remainder n decimal)])
     (set! n r)
     (append result (make-list q roman)))))

(define (encode/roman number)

 (string-join (map symbol->string (number->list number)) "")) 

(for ([n '(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 25 30 40

          50 60 69 70 80 90 99 100 200 300 400 500 600 666 700 800 900 
          1000 1009 1444 1666 1945 1997 1999 2000 2008 2010 2011 2500 
          3000 3999)])
 (printf "~a ~a\n" n (encode/roman n)))</lang>

Retro

This is a port of the Forth code; but returns a string rather than displaying the roman numerals. It only handles numbers between 1 and 3999.

<lang Retro>

vector ( ...n"- )
 here [ &, times ] dip : .data ` swap ` + ` @ ` do ` ; ;
.I dup @ ^buffer'add ;
.V dup 1 + @ ^buffer'add ;
.X dup 2 + @ ^buffer'add ;

[ .I .X drop ] [ .V .I .I .I drop ] [ .V .I .I drop ] [ .V .I drop ] [ .V drop ] [ .I .V drop ] [ .I .I .I drop ] [ .I .I drop ] [ .I drop ] &drop 10 vector .digit

record ( an- )
 10 /mod dup [ [ over 2 + ] dip record ] &drop if .digit ;
toRoman ( n-a )
 here ^buffer'set
 dup 1 3999 within 0 =
 [ "EX LIMITO!\n" ] [ "IVXLCDM" swap record here ] if ;

</lang>

REXX

version 1

<lang rexx>roman: procedure arg number

/* handle only 1 to 3999, else return ? */ if number >= 4000 | number <= 0 then return "?"

romans = " M CM D CD C XC L XL X IX V IV I" arabic = "1000 900 500 400 100 90 50 40 10 9 5 4 1"

result = "" do i = 1 to words(romans)

 do while number >= word(arabic,i)
   result = result || word(romans,i)
   number = number - word(arabic,i)
 end

end return result</lang>

version 2

This version of a REXX program allows almost any non-negative (whole) decimal number.

Most people think that the Romans had no word for "zero".   The Roman numeral system has no need for a
zero placeholder, so there was no name for it (just as we have no name for a "¶" in the middle of our numbers ---
as we don't have that possibility).   However, the Romans did have a name for zero (or nothing).
In fact the Romans had several names for zero (see the REXX code), as does modern English.   In American English, many words can be used:
zero, nothing, naught, bupkis, zilch, goose-egg, nebbish, squat, nil, crapola, what-Patty-shot-at, nineteen (only in cribbage), love (in tennis), etc.

Also, this REXX version supports large numbers (with parentheses and deep parentheses).
(This code was ripped out of a general routine that also supported versions for Attic, ancient Roman, and modern Roman numerals.)
The code is bulkier than most at it deals with any non-negative decimal number, and more boilerplate code is(was) present to handle the above versions. <lang rexx>/*REXX program converts (Arabic) decimal numbers (≥0) ──► Roman numerals*/ numeric digits 10000 /*could be higher if wanted*/ parse arg nums

if nums= then do /*not specified? Gen some.*/

                        do j=0  by 11  to 111
                        nums=nums j
                        end   /*j*/
               nums=nums 49
                        do k=88  by 100  to 1200
                        nums=nums k
                        end   /*k*/
               nums=nums 1000 2000 3000 4000 5000 6000
                        do m=88  by 200  to 1200
                        nums=nums m
                        end   /*m*/
               nums=nums 1304 1405 1506 1607 1708 1809 1910 2011
                        do p=4  to 50       /*there is no limit to this*/
                        nums=nums 10**p
                        end   /*p*/
               end                          /*end generation of numbers*/
     do i=1  for words(nums);   x=word(nums,i)
     say right(x,55) dec2rom(x)
     end   /*i*/

exit /*stick a fork in it, we're done.*/ /*───────────────────────────DEC2ROM subroutine─────────────────────────*/ dec2rom: procedure; parse arg n,# /*get number, assign # to a null. */ n=space(translate(n,,','),0) /*remove any commas from number. */ nulla='ZEPHIRUM NULLAE NULLA NIHIL' /*Roman words for nothing or none.*/ if n==0 then return word(nulla,1) /*return a Roman word for zero. */ maxnp=(length(n)-1)%3 /*find max(+1) # of parens to use.*/ highPos=(maxnp+1)*3 /*highest position of number. */ nn=reverse(right(n,highPos,0)) /*digits for Arabic───►Roman conv.*/ nine=9 four=4; do j=highPos to 1 by -3

        _=substr(nn,j,1);    select
                             when _==nine   then hx='CM'
                             when _>=   5   then hx='D'copies("C",_-5)
                             when _==four   then hx='CD'
                             otherwise           hx=copies('C',_)
                             end
        _=substr(nn,j-1,1);  select
                             when _==nine   then tx='XC'
                             when _>=   5   then tx='L'copies("X",_-5)
                             when _==four   then tx='XL'
                             otherwise           tx=copies('X',_)
                             end
        _=substr(nn,j-2,1);  select
                             when _==nine   then ux='IX'
                             when _>=   5   then ux='V'copies("I",_-5)
                             when _==four   then ux='IV'
                             otherwise           ux=copies('I',_)
                             end
        xx=hx || tx || ux
        if xx\== then #=# ||copies('(',(j-1)%3)xx ||copies(')',(j-1)%3)
        end   /*j*/

if pos('(I',#)\==0 then do i=1 for 4 /*special case: M,MM,MMM,MMMM.*/

                       if i==4  then _ = '(IV)'
                                else _ = '('copies("I",i)')'
                       if pos(_,#)\==0 then #=changestr(_,#,copies('M',i))
                       end   /*i*/

return #</lang> Some older REXXes don't have a changestr bif, so one is included here ──► CHANGESTR.REX.

output when using the default input (within the REXX program):

                                                      0 ZEPHIRUM
                                                     11 XI
                                                     22 XXII
                                                     33 XXXIII
                                                     44 XLIV
                                                     55 LV
                                                     66 LXVI
                                                     77 LXXVII
                                                     88 LXXXVIII
                                                     99 XCIX
                                                    110 CX
                                                     49 XLIX
                                                     88 LXXXVIII
                                                    188 CLXXXVIII
                                                    288 CCLXXXVIII
                                                    388 CCCLXXXVIII
                                                    488 CDLXXXVIII
                                                    588 DLXXXVIII
                                                    688 DCLXXXVIII
                                                    788 DCCLXXXVIII
                                                    888 DCCCLXXXVIII
                                                    988 CMLXXXVIII
                                                   1088 MLXXXVIII
                                                   1188 MCLXXXVIII
                                                   1000 M
                                                   2000 MM
                                                   3000 MMM
                                                   4000 MMMM
                                                   5000 (V)
                                                   6000 (VI)
                                                     88 LXXXVIII
                                                    288 CCLXXXVIII
                                                    488 CDLXXXVIII
                                                    688 DCLXXXVIII
                                                    888 DCCCLXXXVIII
                                                   1088 MLXXXVIII
                                                   1304 MCCCIV
                                                   1405 MCDV
                                                   1506 MDVI
                                                   1607 MDCVII
                                                   1708 MDCCVIII
                                                   1809 MDCCCIX
                                                   1910 MCMX
                                                   2011 MMXI
                                                  10000 (X)
                                                 100000 (C)
                                                1000000 (M)
                                               10000000 ((X))
                                              100000000 ((C))
                                             1000000000 ((M))
                                            10000000000 (((X)))
                                           100000000000 (((C)))
                                          1000000000000 (((M)))
                                         10000000000000 ((((X))))
                                        100000000000000 ((((C))))
                                       1000000000000000 ((((M))))
                                      10000000000000000 (((((X)))))
                                     100000000000000000 (((((C)))))
                                    1000000000000000000 (((((M)))))
                                   10000000000000000000 ((((((X))))))
                                  100000000000000000000 ((((((C))))))
                                 1000000000000000000000 ((((((M))))))
                                10000000000000000000000 (((((((X)))))))
                               100000000000000000000000 (((((((C)))))))
                              1000000000000000000000000 (((((((M)))))))
                             10000000000000000000000000 ((((((((X))))))))
                            100000000000000000000000000 ((((((((C))))))))
                           1000000000000000000000000000 ((((((((M))))))))
                          10000000000000000000000000000 (((((((((X)))))))))
                         100000000000000000000000000000 (((((((((C)))))))))
                        1000000000000000000000000000000 (((((((((M)))))))))
                       10000000000000000000000000000000 ((((((((((X))))))))))
                      100000000000000000000000000000000 ((((((((((C))))))))))
                     1000000000000000000000000000000000 ((((((((((M))))))))))
                    10000000000000000000000000000000000 (((((((((((X)))))))))))
                   100000000000000000000000000000000000 (((((((((((C)))))))))))
                  1000000000000000000000000000000000000 (((((((((((M)))))))))))
                 10000000000000000000000000000000000000 ((((((((((((X))))))))))))
                100000000000000000000000000000000000000 ((((((((((((C))))))))))))
               1000000000000000000000000000000000000000 ((((((((((((M))))))))))))
              10000000000000000000000000000000000000000 (((((((((((((X)))))))))))))
             100000000000000000000000000000000000000000 (((((((((((((C)))))))))))))
            1000000000000000000000000000000000000000000 (((((((((((((M)))))))))))))
           10000000000000000000000000000000000000000000 ((((((((((((((X))))))))))))))
          100000000000000000000000000000000000000000000 ((((((((((((((C))))))))))))))
         1000000000000000000000000000000000000000000000 ((((((((((((((M))))))))))))))
        10000000000000000000000000000000000000000000000 (((((((((((((((X)))))))))))))))
       100000000000000000000000000000000000000000000000 (((((((((((((((C)))))))))))))))
      1000000000000000000000000000000000000000000000000 (((((((((((((((M)))))))))))))))
     10000000000000000000000000000000000000000000000000 ((((((((((((((((X))))))))))))))))
    100000000000000000000000000000000000000000000000000 ((((((((((((((((C))))))))))))))))

Ruby

Roman numeral generation was used as an example for demonstrating Test Driven Development in Ruby. The solution came to be: <lang ruby>Symbols = { 1=>'I', 5=>'V', 10=>'X', 50=>'L', 100=>'C', 500=>'D', 1000=>'M' } Subtractors = [ [1000, 100], [500, 100], [100, 10], [50, 10], [10, 1], [5, 1], [1, 0] ]

def roman(num)

 return Symbols[num]  if Symbols.has_key?(num)
 Subtractors.each do |cutPoint, subtractor| 
   return roman(cutPoint) + roman(num - cutPoint)      if num >  cutPoint
   return roman(subtractor) + roman(num + subtractor)  if num >= cutPoint - subtractor and num < cutPoint
 end

end

[1990, 2008, 1666].each do |i|

 puts "%4d => %s" % [i, roman(i)]

end</lang>

Output:
1990 => MCMXC
2008 => MMVIII
1666 => MDCLXVI

Run BASIC

<lang runbasic>[loop] input "Input value:";val$ print roman$(val$) goto [loop]

' ------------------------------ ' Roman numerals ' ------------------------------ FUNCTION roman$(val$) a2r$ = "M:1000,CM:900,D:500,CD:400,C:100,XC:90,L:50,XL:40,X:10,IX:9,V:5,IV:4,I:1" v = val(val$) for i = 1 to 13

 r$  = word$(a2r$,i,",")
 a   = val(word$(r$,2,":"))
 while v >= a 
   roman$ = roman$ + word$(r$,1,":")
   v      = v - a
 wend

next i END FUNCTION</lang>

Scala

Works with: Scala version 2.8

<lang scala>val romanDigits = Map(

 1 -> "I", 5 -> "V", 
 10 -> "X", 50 -> "L", 
 100 -> "C", 500 -> "D", 
 1000 -> "M", 
 4 -> "IV", 9 -> "IX", 
 40 -> "XL", 90 -> "XC", 
 400 -> "CD", 900 -> "CM")

val romanDigitsKeys = romanDigits.keysIterator.toList sortBy (x => -x) def toRoman(n: Int): String = romanDigitsKeys find (_ >= n) match {

 case Some(key) => romanDigits(key) + toRoman(n - key)
 case None => ""

}</lang>

Sample:

scala> List(1990, 2008, 1666) map toRoman
res55: List[String] = List(MCMXC, MMVIII, MDCLXVI)

Scala Using foldLeft

<lang Scala>def toRoman( v:Int ) : String = {

 val romanNumerals = List(1000->"M",900->"CM",500->"D",400->"CD",100->"C",90->"XC",
                          50->"L",40->"XL",10->"X",9->"IX",5->"V",4->"IV",1->"I")	
                           
 var n = v                          
 romanNumerals.foldLeft(""){(s,t) => {val c = n/t._1; n = n-t._1*c;  s + (t._2 * c) } }

}

// A small test def test( arabic:Int ) = println( arabic + " => " + toRoman( arabic ) )

test(1990) test(2008) test(1666)</lang>

Output:
1990 => MCMXC
2008 => MMVIII
1666 => MDCLXVI

Scheme

This uses format directives supported in Chez Scheme since v6.9b; YMMV.

<lang scheme>(define (to-roman n)

 (format "~@r" n))</lang>

Seed7

The following program writes the numbers between 1 and 3999 as roman numerals. The wrinum.s7i library contains the function str(ROMAN,), which writes a roman numeral to a string.

<lang seed7>$ include "seed7_05.s7i";

 include "stdio.s7i";
 include "wrinum.s7i";

const proc: main is func

 local
   var integer: number is 0;
 begin
   for number range 1 to 3999 do
     writeln(str(ROMAN, number));
   end for;
 end func;</lang>

Original source [1].

Smalltalk

Works with: Smalltalk/X

in ST/X, integers already know how to print themself as roman number: <lang smalltalk>2013 printRomanOn:Stdout naive:false</lang>

outputs:

MMXIII

the implementation is: <lang smalltalk> printRomanOn:aStream naive:naive

   "print the receiver as roman number to the argument, aStream.
    The naive argument controls if the conversion is
    correct (i.e. subtracting prefix notation for 4,9,40,90, etc.),
    or naive (i.e. print 4 as IIII and 9 as VIIII); also called simple.
    The naive version is often used for page numbers in documents."
   |restValue spec|
   restValue := self.
   restValue > 0 ifFalse:[self error:'negative roman'].
   naive ifTrue:[
       spec := #(
               " value string repeat "
                  1000 'M'    true
                   500 'D'    false
                   100 'C'    true
                    50 'L'    false
                    10 'X'    true
                     5 'V'    false
                     1 'I'    true
                ).
   ] ifFalse:[
       spec := #(
               " value string repeat "
                  1000 'M'    true
                   900 'CM'   false
                   500 'D'    false
                   400 'CD'   false
                   100 'C'    true
                    90 'XC'   false
                    50 'L'    false
                    40 'XL'   false
                    10 'X'    true
                     9 'IX'   false
                     5 'V'    false
                     4 'IV'   false
                     1 'I'    true
                ).
   ].
   spec
       inGroupsOf:3
       do:[:rValue :rString :repeatFlag |
           [
               (restValue >= rValue) ifTrue:[
                   aStream nextPutAll:rString.
                   restValue := restValue - rValue.
               ].
           ] doWhile:[ repeatFlag and:[ restValue >= rValue] ].
       ].

</lang>

Tcl

<lang tcl>proc to_roman {i} {

   set map {1000 M 900 CM 500 D 400 CD 100 C 90 XC 50 L 40 XL 10 X 9 IX 5 V 4 IV 1 I}
   foreach {value roman} $map {
       while {$i >= $value} {
           append res $roman
           incr i -$value
       }
   }
   return $res

}</lang>

SQL

<lang SQL> -- -- This only works under Oracle and has the limitation of 1 to 3999 --- Higher numbers in the Middle Ages were represented by "superscores" on top of the numeral to multiply by 1000 --- Vertical bars to the sides multiply by 100. So |M| means 100,000 -- When the query is run, user provides the Arabic numerals for the ar_year -- A.Kebedjiev --

SELECT to_char(to_char(to_date(&ar_year,'YYYY'), 'RRRR'), 'RN') AS roman_year FROM DUAL;

-- or you can type in the year directly

SELECT to_char(to_char(to_date(1666,'YYYY'), 'RRRR'), 'RN') AS roman_year FROM DUAL;

ROMAN_YEAR MDCLXVI

</lang>

SNOBOL4

Adapted from Catspaw SNOBOL Tutorial, Chapter 6

<lang snobol4>

  • ROMAN(N) - Convert integer N to Roman numeral form.
  • N must be positive and less than 4000.
  • An asterisk appears in the result if N >= 4000.
  • The function fails if N is not an integer.

DEFINE('ROMAN(N)UNITS')  :(ROMAN_END)

  • Get rightmost digit to UNITS and remove it from N.
  • Return null result if argument is null.

ROMAN N RPOS(1) LEN(1) . UNITS = :F(RETURN)

  • Search for digit, replace with its Roman form.
  • Return failing if not a digit.

'0,1I,2II,3III,4IV,5V,6VI,7VII,8VIII,9IX,' UNITS + BREAK(',') . UNITS :F(FRETURN)

  • Convert rest of N and multiply by 10. Propagate a
  • failure return from recursive call back to caller.

ROMAN = REPLACE(ROMAN(N), 'IVXLCDM', 'XLCDM**') + UNITS :S(RETURN) F(FRETURN) ROMAN_END

  • Testing

OUTPUT = "1999 = " ROMAN(1999) OUTPUT = " 24 = " ROMAN(24) OUTPUT = " 944 = " ROMAN(944)

END</lang> Outputs:

1999 = MCMXCIX
  24 = XXIV
 944 = CMXLIV

Here's a non-recursive version, and a Roman-to-Arabic converter to boot.

<lang SNOBOL4>* # Arabic to Roman

       define('roman(n)s,ch,val,str') :(roman_end)

roman roman = ge(n,4000) n :s(return)

       s = 'M1000 CM900 D500 CD400 C100 XC90 L50 XL40 X10 IX9 V5 IV4 I1 '

rom1 s span(&ucase) . ch break(' ') . val span(' ') = :f(rom2)

       str = str dupl(ch,(n / val))
       n = remdr(n,val) :(rom1)

rom2 roman = str :(return) roman_end

  • # Roman to Arabic
       define('arabic(n)s,ch,val,sum,x') :(arabic_end)

arabic s = 'M1000 D500 C100 L50 X10 V5 I1 '

       n = reverse(n)

arab1 n len(1) . ch = :f(arab2)

       s ch break(' ') . val
       val = lt(val,x) (-1 * val)
       sum = sum + val; x = val :(arab1)

arab2 arabic = sum :(return) arabic_end

  • # Test and display
       tstr = '2010 1999 1492 1066 476 '

tloop tstr break(' ') . year span(' ') = :f(out)

       r = roman(year)
       rstr = rstr year '=' r ' ' 
       astr = astr r '=' arabic(r) ' ' :(tloop)

out output = rstr; output = astr end</lang>

Output:

2010=MMX 1999=MCMXCIX 1492=MCDXCII 1066=MLXVI 476=CDLXXVI
MMX=2010 MCMXCIX=1999 MCDXCII=1492 MLXVI=1066 CDLXXVI=476

TI-83 BASIC

<lang ti83b>PROGRAM:DEC2ROM

"="→Str1
Lbl ST
ClrHome
Disp "NUMBER TO"
Disp "CONVERT:"
Input A
If fPart(A) or A≠abs(A)
Then
Goto PI
End
A→B
While B≥1000
Str1+"M"→Str1
B-1000→B
End
If B≥900
Then
Str1+"CM"→Str1
B-900→B
End
If B≥500
Then
Str1+"D"→Str1
B-500→B
End
If B≥400
Then
Str1+"CD"?Str1
B-400→B
End
While B≥100
Str1+"C"→Str1
B-100→B
End
If B≥90
Then
Str1+"XC"→Str1
B-90→B
End
If B≥50
Then
Str1+"L"→Str1
B-50→B
End
If B≥40
Then
Str1+"XL"→Str1
B-40→B
End
While B≥10
Str1+"X"→Str1
B-10→B
End
If B≥9
Then
Str1+"IX"→Str1
B-9→B
End
If B≥5
Then
Str1+"V"→Str1
B-5→B
End
If B≥4
Then
Str1+"IV"→Str1
B-4→B
End
While B>0
Str1+"I"→Str1
B-1→B
End
ClrHome
Disp A
Disp Str1
Stop
Lbl PI
ClrHome
Disp "THE NUMBER MUST"
Disp "BE A POSITIVE"
Disp "INTEGER."
Pause
Goto ST

</lang>


TUSCRIPT

<lang tuscript> $$ MODE TUSCRIPT LOOP arab_number="1990'2008'1666" roman_number = ENCODE (arab_number,ROMAN) PRINT "Arabic number ",arab_number, " equals ", roman_number ENDLOOP </lang> Output:

Arabic number 1990 equals MCMXC
Arabic number 2008 equals MMVIII
Arabic number 1666 equals MDCLXVI 

Ursala

The algorithm is to implement the subtractive principle by string substitution only after constucting the numeral from successive remainders. The order among the substitutions matters. For example, occurrences of DCCCC must be replaced by CM before any occurrences of CCCC are replaced by CD. The substitution operator (%=) is helpful here. <lang Ursala>#import nat

roman =

-+

  'IIII'%='IV'+ 'VIIII'%='IX'+ 'XXXX'%='XL'+ 'LXXXX'%='XC'+ 'CCCC'%='CD'+ 'DCCCC'%='CM',
  ~&plrDlSPSL/'MDCLXVI'+ iota*+ +^|(^|C/~&,\/division)@rlX=>~&iNC <1000,500,100,50,10,5>+-</lang>

This test program applies the function to each member of a list of numbers. <lang Ursala>#show+

test = roman* <1990,2008,1,2,64,124,1666,10001></lang> output:

MCMXC
MMVIII
I
II
LXIV
CXXIV
MDCLXVI
MMMMMMMMMMI

Vedit macro language

<lang vedit>// Main program for testing the function // do {

   #1 = Get_Num("Number to convert: ", STATLINE)
   Call("NUM_TO_ROMAN")
   Num_Type(#1, NOCR) Message(" = ") Reg_Type(1) Type_Newline

} while (Reg_Size(1)) Return

// Convert numeric value into Roman number // #1 = number to convert; on return: T-reg(1) = Roman number //

NUM_TO_ROMAN:
   Reg_Empty(1)                        // @1 = Results (Roman number)
   if (#1 < 1) { Return }              // non-positive numbers return empty string

   Buf_Switch(Buf_Free)
   Ins_Text("M1000,CM900,D500,CD400,C100,XC90,L50,XL40,X10,IX9,V5,IV4,I1")

   BOF
   #2 = #1
   Repeat(ALL) {
       Search("|A|[|A]", ADVANCE+ERRBREAK)         // get next item from conversion list
       Reg_Copy_Block(20, CP-Chars_Matched, CP)    // @20 = Letter(s) to be inserted
       #11 = Num_Eval()                            // #11 = magnitude (1000...1)
       while (#2 >= #11) {
           Reg_Set(1, @20, APPEND)
           #2 -= #11
       }
   }
   Buf_Quit(OK)

Return</lang>

Output:

    4 = IV
   12 = XII
 1666 = MDCLXVI
 1990 = MCMXC
 2011 = MMXI

Visual Basic

Translation of: BASIC

<lang vb>Function toRoman(value) As String

   Dim arabic As Variant
   Dim roman As Variant
   arabic = Array(1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1)
   roman = Array("M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I")
   Dim i As Integer, result As String
   For i = 0 To 12
       Do While value >= arabic(i)
           result = result + roman(i)
           value = value - arabic(i)
       Loop
   Next i
   toRoman = result

End Function

Sub Main()

   MsgBox toRoman(Val(InputBox("Number, please")))

End Sub</lang>

XSLT

<lang xslt> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

   <xsl:template match="/data/number">
       <xsl:call-template name="for">
              <xsl:with-param name="stop">13</xsl:with-param>
       	<xsl:with-param name="value"><xsl:value-of select="@value"></xsl:value-of></xsl:with-param>
       </xsl:call-template>
   </xsl:template>
   
   <xsl:template name="for">
     <xsl:param name="start">1</xsl:param>
     <xsl:param name="stop">1</xsl:param>
     <xsl:param name="step">1</xsl:param>
     <xsl:param name="value">1</xsl:param>
     <xsl:text/>
     <xsl:choose>
     <xsl:when test="($value > /data/roman

/numeral[@pos=$start]/@value or $value = /data/roman /numeral[@pos=$start]/@value) ">

         <xsl:value-of select="/data/roman

/numeral[@pos=$start]/@letter"/>

         <xsl:call-template name="for">
         <xsl:with-param name="stop">
           <xsl:value-of select="$stop"/>
         </xsl:with-param>
         <xsl:with-param name="start">
           <xsl:value-of select="$start"/>
         </xsl:with-param>
         <xsl:with-param name="value">
         	<xsl:value-of select="$value - /data/roman/numeral[@pos=$start]/@value"/>
         </xsl:with-param>
       </xsl:call-template>
     </xsl:when>
     <xsl:otherwise>
       <xsl:if test="$start < $stop">
       <xsl:call-template name="for">
         <xsl:with-param name="stop">
           <xsl:value-of select="$stop"/>
         </xsl:with-param>
         <xsl:with-param name="start">
           <xsl:value-of select="$start + $step"/>
         </xsl:with-param>
         <xsl:with-param name="value">
         	<xsl:value-of select="$value"/>
         </xsl:with-param>
       </xsl:call-template>
       </xsl:if>
     </xsl:otherwise>
     </xsl:choose>
   </xsl:template>

</xsl:stylesheet> </lang>

Zsh

Based on the python solution. <lang zsh>function printroman () {

 local -a conv
 local number=$1 div rom num out
 conv=(I 1 IV 4 V 5 IX 9 X 10 XL 40 L 50 XC 90 C 100 CD 400 D 500 CM 900 M 1000)
 for num rom in ${(Oa)conv}; do
   (( div = number / num, number = number % num ))
   while (( div-- > 0 )); do
     out+=$rom
   done
 done
 echo $out

}</lang>

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