/* ** PRIMES: Simple prime number functions ** Copyright (C) 2002 Michael W. Shaffer ** ** 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 (see the file COPYING). If not, write to: ** ** The Free Software Foundation, Inc. ** 59 Temple Place, Suite 330, ** Boston, MA 02111-1307 USA */ #include unsigned long find_prime (unsigned long max) { unsigned long i = 0; unsigned long f = 0; unsigned long prime = 1; for (i = max ; i > 1 ; i--) { if ((i % 2) == 0) goto NOTPRIME; for (f = 2 ; f <= ((unsigned long) floor (sqrt (i))) ; f++) { if ((i % f) == 0) goto NOTPRIME; } prime = i; goto EXIT; NOTPRIME: continue; } EXIT: return prime; }