cmd/factor/factor.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
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 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*  factor  COMPILE:    cc -O factor.c -s -i -lm -o factor  */
/*
 * works up to 14 digit numbers
 * running time is proportional to sqrt(n)
 * accepts arguments either as input or on command line
 * 0 input terminates processing
 */

double modf(), sqrt();
double nn, vv;
double huge = 1.0e14;
double sq[] = {
    10, 2, 4, 2, 4, 6, 2, 6,
     4, 2, 4, 6, 6, 2, 6, 4,
     2, 6, 4, 6, 8, 4, 2, 4,
     2, 4, 8, 6, 4, 6, 2, 4,
     6, 2, 6, 6, 4, 2, 4, 6,
     2, 6, 4, 2, 4, 2,10, 2,
};

void try(double);

int
main(int argc, char *argv[])
{
    int test = 1;
    int ret;
    int j;
    double junk, temp;
    double fr;
    double ii;

    if(argc > 2){
        printf("Usage: factor number\n");
        exit(1);
    }
    if(argc == 2){
        ret = sscanf(argv[1], "%lf", &nn);
        test = 0;
        printf("%.0f\n", nn);
        goto start;
    }
    while(test == 1){
        ret = scanf("%lf", &nn);
start:
        if((ret<1) || (nn == 0.0)){
            exit(0);
        }
        if((nn<0.0) || (nn>huge)){
            printf("Ouch!\n");
            continue;
        }
        fr = modf(nn, &junk);
        if(fr != 0.0){
            printf("Not an integer!\n");
            continue;
        }
        vv = 1. + sqrt(nn);
        try(2.0);
        try(3.0);
        try(5.0);
        try(7.0);
        ii = 1.0;
        while(ii <= vv){
            for(j=0; j<48; j++){
                ii += sq[j];
retry:
                modf(nn/ii, &temp);
                if(nn == temp*ii){
                    printf("     %.0f\n", ii);
                    nn = nn/ii;
                    vv = 1 + sqrt(nn);
                    goto retry;
                }
            }
        }
        if(nn > 1.0){
            printf("     %.0f\n", nn);
        }
        printf("\n");
    }
    return (0);
}

void
try(double arg)
{
    double temp;
retry:
    modf(nn/arg, &temp);
    if(nn == temp*arg){
        printf("     %.0f\n", arg);
        nn = nn/arg;
        vv = 1 + sqrt(nn);
        goto retry;
    }
}