/* rom2arab.c

   David S McMeans   Not copyrighted April 1993
   [[Email Removed]]

Roman2Arabic()
Converts a Roman number to its Arabic equivalent.

Call

int Roman2Arabic( str )
char *str;           roman number to be converted

Returns

INT         

Description

Roman2Arabic() does no error checking.  Invalid Roman numerals are ignored.

Notes

Roman2Arabic_() does rudimentary error checking.  If the Roman number is
receives is invalid, it returns 0.

This information was compiled from a discussion in comp.lang.pascal around
March 1993.  Acknowledgements go to Bengt Oehman ([[Email Removed]]), and to
David Conrad ([[Email Removed]]).

*/


#include "tailor.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>


/*
 *    PUBLIC DECLARATIONS
 */

typedef enum bool {FALSE, TRUE} Boolean;
typedef enum ret_t {ERROR=-1, SUCCESS} ReturnType;

extern  int Roman2Arabic    OF(( char * ));
extern  int Roman2Arabic_   OF(( char * ));

/*
 *    PRIVATE DECLARATIONS
 */

static  int           roman_val    OF(( char ));
static  Boolean       is_a_five    OF(( char ));

/* The following routine was provided by Dave Conrad */

int Roman2Arabic( str )
char *str;
{
  int len, i, r, r_ahead, arab;

  arab = 0;
  len = strlen( str );
  for (i=0; i < len-1; i++)
  {
    r = roman_val( str[ i ] );
    r_ahead = roman_val( str[ i+1 ] );
    if (r < r_ahead)
      arab -= r;
    else
      arab += r;
  }
  arab += roman_val( str[ len-1 ] );

  return arab;
}

/* The following routine was provided by Bengt Oehman */

int Roman2Arabic_( str )
char *str;
{
  int pos;
  int value, curval, highestprev;

  highestprev = curval = value = 0;
 
  for (pos=strlen( str )-1; pos>-1; pos--)
  {
    if ((curval = roman_val( str[ pos ] ))==0)  /* invalid char in str */
      return 0;
   
    if (curval >= highestprev)
    {
      value += curval;
      highestprev = curval;
    }
    else /* numeral precedes one larger */
    {
      if (is_a_five( str[ pos ] ))  /* five may not precede anything larger */
        return 0;

      if (highestprev / curval > 10) /* XM  IC  XD ... */
        return 0;

      value -= curval;
    }
  }
  return value;
}

static int roman_val( n )
char n;
{
  switch( toupper( n ) )
  {
    case 'I':
      return 1;
    case 'V':
      return 5;
    case 'X':
      return 10;
    case 'L':
      return 50;
    case 'C':
      return 100;
    case 'D':
      return 500;
    case 'M':
      return 1000;
    default:
      return 0;
  }
}

static Boolean is_a_five( n )
char n;
{
  char c=toupper( n );

  return (c=='V' || c=='L' || c=='D');
}

/* end rom2arab.c */