libcxx/test/libcxx-03/containers/unord/next_prime.pass.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// REQUIRES: long_tests

// Not a portable test

// <__hash_table>

// size_t __next_prime(size_t n);

// If n == 0, return 0, else return the lowest prime greater than or equal to n

#include <__cxx03/__hash_table>
#include <cassert>
#include <cstddef>

#include "test_macros.h"

bool is_prime(std::size_t n) {
  switch (n) {
  case 0:
  case 1:
    return false;
  }
  for (std::size_t i = 2; i * i <= n; ++i) {
    if (n % i == 0)
      return false;
  }
  return true;
}

int main(int, char**) {
  assert(std::__next_prime(0) == 0);
  for (std::size_t n = 1; n <= 100000; ++n) {
    std::size_t p = std::__next_prime(n);
    assert(p >= n);
    for (std::size_t i = n; i < p; ++i)
      assert(!is_prime(i));
    assert(is_prime(p));
  }

  return 0;
}