/*
* r2fib.c: Compute Fibonacci numbers using a doubly recursive algorithm,
* using the C "unsigned long" data type.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
*/
#include
#include
unsigned long fib(int x)
{
if (x <= 2) {
if (x < 0)
return fib(-x);
return 1;
}
return fib(x - 1) + fib(x - 2);
}
int main(int argc, char *argv[])
{
int i;
int x;
if (argc != 2) {
fprintf(stderr, "%s i\n", argv[0]);
exit(-1);
}
x = atoi(argv[1]);
printf("fib(%d) = %lu\n", x, fib(x));
return 0;
}