1: 2: /* An example that finds all primes between 2 and limit. */ 3: 4: define primes (limit) { 5: auto num, p, root, i 6: 7: prime[1] = 2; 8: prime[2] = 3; 9: num = 2; 10: scale = 0; 11: 12: for ( p=5; p <= limit; p += 2) { 13: root = sqrt(p); 14: isprime = 1; 15: for ( i = 1; i < num && prime[i] <= root; i++ ) { 16: if ( p % prime[i] == 0 ) { 17: isprime = 0; 18: break; 19: } 20: } 21: if (isprime) { 22: num += 1; 23: prime [num] = p; 24: } 25: } 26: } 27: 28: 29: print "\ntyping 'twins (10)' will print all twin primes less than 10.\n" 30: 31: define twins (limit) { 32: auto i; 33: 34: i = primes(limit+2); 35: 36: for (i=1; prime[i] > 0; i++) { 37: if ((prime[i]+2) == prime[i+1]) \ 38: print "twins are ", prime[i], " and ", prime[i+1], "\n" 39: } 40: } |