usr/src/cmd/factor/factor.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*      factor  COMPILE:        cc -O factor.c -s -i -lm -o factor      */
  33 /*
  34  * works up to 14 digit numbers
  35  * running time is proportional to sqrt(n)
  36  * accepts arguments either as input or on command line
  37  * 0 input terminates processing
  38  */
  39
  40 double modf(), sqrt();
  41 double nn, vv;
  42 double huge = 1.0e14;
  43 double sq[] = {
  44         10, 2, 4, 2, 4, 6, 2, 6,
  45          4, 2, 4, 6, 6, 2, 6, 4,
  46          2, 6, 4, 6, 8, 4, 2, 4,
  47          2, 4, 8, 6, 4, 6, 2, 4,
  48          6, 2, 6, 6, 4, 2, 4, 6,
  49          2, 6, 4, 2, 4, 2,10, 2,
  50 };
  51
  52 void try(double);
  53
  54 int
  55 main(int argc, char *argv[])
  56 {
  57         int test = 1;
  58         int ret;
  59         int j;
  60         double junk, temp;
  61         double fr;
  62         double ii;
  63
  64         if(argc > 2){
  65                 printf("Usage: factor number\n");
  66                 exit(1);
  67         }
  68         if(argc == 2){
  69                 ret = sscanf(argv[1], "%lf", &nn);
  70                 test = 0;
  71                 printf("%.0f\n", nn);
  72                 goto start;
  73         }
  74         while(test == 1){
  75                 ret = scanf("%lf", &nn);
  76 start:
  77                 if((ret<1) || (nn == 0.0)){
  78                         exit(0);
  79                 }
  80                 if((nn<0.0) || (nn>huge)){
  81                         printf("Ouch!\n");
  82                         continue;
  83                 }
  84                 fr = modf(nn, &junk);
  85                 if(fr != 0.0){
  86                         printf("Not an integer!\n");
  87                         continue;
  88                 }
  89                 vv = 1. + sqrt(nn);
  90                 try(2.0);
  91                 try(3.0);
  92                 try(5.0);
  93                 try(7.0);
  94                 ii = 1.0;
  95                 while(ii <= vv){
  96                         for(j=0; j<48; j++){
  97                                 ii += sq[j];
  98 retry:
  99                                 modf(nn/ii, &temp);
 100                                 if(nn == temp*ii){
 101                                         printf("     %.0f\n", ii);
 102                                         nn = nn/ii;
 103                                         vv = 1 + sqrt(nn);
 104                                         goto retry;
 105                                 }
 106                         }
 107                 }
 108                 if(nn > 1.0){
 109                         printf("     %.0f\n", nn);
 110                 }
 111                 printf("\n");
 112         }
 113         return (0);
 114 }
 115
 116 void
 117 try(double arg)
 118 {
 119         double temp;
 120 retry:
 121         modf(nn/arg, &temp);
 122         if(nn == temp*arg){
 123                 printf("     %.0f\n", arg);
 124                 nn = nn/arg;
 125                 vv = 1 + sqrt(nn);
 126                 goto retry;
 127         }
 128 }