1 2/* An example that finds all primes between 2 and limit. */ 3 4define 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 29print "\ntyping 'twins (10)' will print all twin primes less than 10.\n" 30 31define 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} 41