Pos and neg bases

#include <math.h>
#include <stdlib.h>
#include <stdio.h>

#define ipow(n, e) (int)pow(n, e)
#define buf_update(n) printf("buf: %d\n", n)
#define error(msg) fprintf(stderr, "%s", (msg) )


void
_conbase_negbase(int n, int r, int e)
{
    int m;

    /* Find minimum multiplicator of |r^e| that is > |n| */
    for (m = 0; m * abs(ipow(r, e)) < abs(n); ++m) {
        ;
    }

    buf_update(m);

    if (e && n) {
        /* Must not use absolute values here ! */
        _conbase_negbase(n - (m * ipow(r, e)), r, e - 1);
    }

    return;
}

void
_conbase_posbase (int n, int r)
{
    if ( n ) {

        _conbase_posbase(n / r, r);
        buf_update(n % r);

    }
}


void
conbase(int n, int r)
{
    int _exp = -1;
    int _pow;
    int _powpos = 0;
    int _npos = 0;


    if ( r < 0 ) {

        do {

            _pow = ipow(r, ++_exp);
            _powpos = (_pow>=0)?1:0;
            _npos = (n>=0)?1:0;

            if ( abs(_pow) > abs(n) ) {

                if ((!_powpos && !_npos)  || (_powpos && _npos)){
                    break;
                } else if ((_powpos && !_npos) || (!_powpos && _npos) ) {
                    _exp--;
                    break;
                }

            }

        } while (1);

    _conbase_negbase(n, r, _exp);

    }// r < 0
    else if ( r > 1 ) {

    _conbase_posbase(n, r);

    }// r > 1
    else {

    error("conbase: bad base.\n");

    }// r == 0 || r == 1
}

int
main(int argc, char **argv)
{

    printf("<\n");
    conbase(1240, -10);

    printf("<\n");
    conbase(124, -10);

    printf("<\n");
    conbase(-1240, -10);

    printf("<\n");
    conbase(-124, -10);

    printf("<\n");
    conbase(-10, -10);

    /* Positive base */
    printf("<\n");
    conbase(1240, 10);

    printf("<\n");
    conbase(124, 10);

    printf("<\n");
    conbase(10, 10);

    printf("<\n");
    conbase(127, 8);

    printf("<\n");
    conbase(32767, 2);

    printf("<\n");
    conbase(-32768, 2);

    return 0;
}