diff options
Diffstat (limited to 'src/libs/libgroff/prime.cpp')
-rw-r--r-- | src/libs/libgroff/prime.cpp | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/src/libs/libgroff/prime.cpp b/src/libs/libgroff/prime.cpp new file mode 100644 index 00000000..f0b1eadc --- /dev/null +++ b/src/libs/libgroff/prime.cpp @@ -0,0 +1,26 @@ +#include <math.h> + +int is_prime(unsigned n) +{ + if (n <= 3) + return 1; + if (!(n & 1)) + return 0; + if (n % 3 == 0) + return 0; + unsigned lim = unsigned(sqrt((double)n)); + unsigned d = 5; + for (;;) { + if (d > lim) + break; + if (n % d == 0) + return 0; + d += 2; + if (d > lim) + break; + if (n % d == 0) + return 0; + d += 4; + } + return 1; +} |