Merge pull request #65 from stclib/dev43

Dev43

1 files changed, 58 insertions, 0 deletions

diff --git a/misc/examples/bitsets/prime.c b/misc/examples/bitsets/prime.c
new file mode 100644
index 00000000..7e5a2b3f
--- /dev/null
+++ b/misc/examples/bitsets/prime.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <math.h>
+#include <time.h>
+#include <stc/cbits.h>
+#include <stc/algorithm.h>
+
+typedef long long llong;
+
+cbits sieveOfEratosthenes(llong n)
+{
+    cbits bits = cbits_with_size(n/2 + 1, true);
+    llong q = (llong)sqrt((double) n) + 1;
+    for (llong i = 3; i < q; i += 2) {
+        llong j = i;
+        for (; j < n; j += 2) {
+            if (cbits_test(&bits, j>>1)) {
+                i = j;
+                break;
+            }
+        }
+        for (llong j = i*i; j < n; j += i*2)
+            cbits_reset(&bits, j>>1);
+    }
+    return bits;
+}
+
+int main(void)
+{
+    llong n = 100000000;
+    printf("Computing prime numbers up to %lld\n", n);
+
+    clock_t t = clock();
+    cbits primes = sieveOfEratosthenes(n + 1);
+
+    llong np = cbits_count(&primes);
+    t = clock() - t;
+
+    printf("Number of primes: %lld, time: %f\n\n", np, (double)t/CLOCKS_PER_SEC);
+
+    puts("Show all the primes in the range [2, 1000):");
+    printf("2");
+    c_forrange (i, 3, 1000, 2)
+        if (cbits_test(&primes, i>>1)) printf(" %lld", i);
+    puts("\n");
+
+    puts("Show the last 50 primes using a temporary crange generator:");
+    crange range = crange_init(n - 1, 0, -2);
+
+    c_forfilter (i, crange, range,
+        cbits_test(&primes, *i.ref/2) &&
+        c_flt_take(i, 50)
+    ){
+        printf("%lld ", *i.ref);
+        if (c_flt_getcount(i) % 10 == 0) puts("");
+    }
+
+    cbits_drop(&primes);
+}