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/// @example prev_prime.cpp
/// Iterate backwards over primes using primesieve::iterator.
#include <primesieve.hpp>
#include <cstdlib>
#include <iostream>
int main(int argc, char** argv)
{
uint64_t limit = 10000000000ull;
if (argc > 1)
limit = std::atol(argv[1]);
primesieve::iterator it;
it.jump_to(limit);
uint64_t prime = it.prev_prime();
uint64_t sum = 0;
// Backwards iterate over the primes <= 10^9
for (; prime > 0; prime = it.prev_prime())
sum += prime;
std::cout << "Sum of primes <= " << limit << ": " << sum << std::endl;
// Note that since sum is a 64-bit variable the result
// will be incorrect (due to integer overflow) if
// limit > 10^10. However we do allow limits > 10^10
// since this is useful for benchmarking.
if (limit > 10000000000ull)
std::cerr << "Warning: sum is likely incorrect due to 64-bit integer overflow!" << std::endl;
return 0;
}
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