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/*
* fact.c
*
* Compute factorial of input integer
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
*
* The Initial Developer of the Original Code is
* Michael J. Fromberger.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/* $Id$ */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "mpi.h"
mp_err mp_fact(mp_int *a, mp_int *b);
int main(int argc, char *argv[])
{
mp_int a;
mp_err res;
if(argc < 2) {
fprintf(stderr, "Usage: %s <number>\n", argv[0]);
return 1;
}
mp_init(&a);
mp_read_radix(&a, argv[1], 10);
if((res = mp_fact(&a, &a)) != MP_OKAY) {
fprintf(stderr, "%s: error: %s\n", argv[0],
mp_strerror(res));
mp_clear(&a);
return 1;
}
{
char *buf;
int len;
len = mp_radix_size(&a, 10);
buf = malloc(len);
mp_todecimal(&a, buf);
puts(buf);
free(buf);
}
mp_clear(&a);
return 0;
}
mp_err mp_fact(mp_int *a, mp_int *b)
{
mp_int ix, s;
mp_err res = MP_OKAY;
if(mp_cmp_z(a) < 0)
return MP_UNDEF;
mp_init(&s);
mp_add_d(&s, 1, &s); /* s = 1 */
mp_init(&ix);
mp_add_d(&ix, 1, &ix); /* ix = 1 */
for(/* */; mp_cmp(&ix, a) <= 0; mp_add_d(&ix, 1, &ix)) {
if((res = mp_mul(&s, &ix, &s)) != MP_OKAY)
break;
}
mp_clear(&ix);
/* Copy out results if we got them */
if(res == MP_OKAY)
mp_copy(&s, b);
mp_clear(&s);
return res;
}
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