Roman Numeral Program

[faustus at ucbcad.UUCP]

> Do you have a program that either converts numbers to roman numerals
> or (especially!) converts roman numerals to numbers.

Here is one: actually this prints the date in Roman numerals, but
the routine prom() does the real stuff...

	Wayne

/* RCS Info: $Revision: 1.1 $ on $Date: 85/04/18 17:44:51 $
 *           $Source: /cad1/faustus/src/misc/RCS/rdate.c,v $
 * Copyright (c) 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
 *
 * Print the date in roman numerals.
 */

main()
{
	char buf[64], s[3][16], nn[5][16], *prom();
	int q, p[2], n[5];

	pipe(p);
	if(fork() == 0) {
		dup2(p[1], 1);
		execl("/bin/date", "date", 0);
	}
	q = read(p[0], buf, 64);
	buf[q] = '\0';

	sscanf(buf, " %s %s %d %d:%d:%d %s %d ", s[0], s[1], &n[0], &n[1],
		&n[2], &n[3], s[2], &n[4]);
	for(q = 0; q < 5; q++)
		strcpy(nn[q], prom(n[q]));
	printf("%s %s %s %s:%s:%s %s %s\n", s[0], s[1], nn[0], nn[1],
		nn[2], nn[3], s[2], nn[4]);
	exit(0);
}

/* Render number in Roman Numerals. Should be unsigned...  Returns
 * pointer to the rendering. Problems with static data, etc.
 */

char *
prom(num)
	register unsigned int num;
{
	register int pos = 0;
	register int *i, k;
	register char *j;
	static char rbuf[64];	/* Bad assumption? */
	static int ndigits[] = { 1000, 500, 100, 50,  10,   5,   1,  0 } ;
	static char ddigits[] = { 'M', 'D', 'C', 'L', 'X', 'V', 'I', 'Z' } ; 

	if(num == 0)
		return("Z");	/* Well, what do we do? */
	while(num > 0) {
		for((i = ndigits, j = ddigits); *i; (i++, j++)) {
			if(num >= *i) {
				rbuf[pos++] = *j;
				num -= *i;
				break;
			}
			/* If you are on an even index in the array, the
			 * digit to use for filling in (e.g. IX = 9) is
			 * *i / 10, otherwise use *i / 5 (to make sure
			 * that it is a power of 10).
			 */
			k = (!((ndigits - i) % 2) ? (*i / 10) : (*i / 5));
			if(num >= (*i - k)) {
				rbuf[pos++] = *(j + 
					(((ndigits - i) % 2) ? 1 : 2));
				rbuf[pos++] = *j;
				num -= (*i - k);
				break;
			}
		}
	}
	rbuf[pos] = '\0';
	return(rbuf);
}