get prime factorization

primes.c

/* primes.c
 * prints prime factorization of number
 * `make primes`
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static const char *supers[] = {
	"\u2070",
	"\u00b9",
	"\u00b2",
	"\u00b3",
	"\u2074",
	"\u2075",
	"\u2076",
	"\u2077",
	"\u2078",
	"\u2079"
};

const char *ltosup (long n) {
	static char buf[64];
	int i = sizeof(buf)-1;

	buf[i] = '\0';
	for (; n != 0; n /= 10) {
		int size = strlen (supers [n % 10]);
		i -= size;
		strncpy(&buf[i], supers[n % 10], size);
	}

	return &buf[i];
}

void print_primes (long n) {
	long f = 2;
	long p;
	ldiv_t d;

	printf ("1 \u00d7");
	while (f*f <= n) {
		p = 0;
		while ((d = ldiv(n, f)).rem == 0) {
			++p;
			n = d.quot;
		}
		if (p > 0)
			printf (" %ld%s \u00d7", f, ltosup(p));
		if (f == 2)
			++f;
		else f += 2;
	}

	if (n > 1)
		printf (" %ld%s\n", n, supers[1]);
	else
		printf ("\b\b  \n");
}

int main(int argc, char *argv[]) {
	if (argc != 2) {
		printf("usage: %s [n]\n", argv[0]);
		exit(1);
	}

	print_primes (atol(argv[1]));
}

optimizations in second revision