nth_prime

eve::nth_prime = functor<nth_prime_t>

inlineconstexpr

Header file

#include <eve/module/combinatorial.hpp>

Callable Signatures

namespace eve
{
   constexpr auto nth_prime(unsigned_value auto x) -> decltype(x) noexcept; //1
   template < integral_value T,  floating_scalar_value U>
   constexpr as_wide_as_t<U, T> nth_prime(T x, as<U>)             noexcept; //2
   template < integral_value T,  unsigned_scalar_value U>
   constexpr as_wide_as_t<U, T> nth_prime(T x, as<U>)             noexcept; //2
}

Parameters

• n : unsigned argument. If n is greater than 10'000, behavior is undefined.

Return value

1. The nth prime is returned.
2. Same, but the element type of the result is deduced from U.

Notes

• 2 is the first prime. It is returned for n=0.
• Almost no computations are made, the results are from a lookup table.

External references

• Wikipedia: Prime number

Example

#include <eve/eve.hpp>
#include <eve/module/combinatorial.hpp>
#include <iostream>
 
int main() {
   eve::wide<std::uint32_t> wu([](auto i, auto )->std::uint32_t{ return i;});
   eve::wide n{52u, 53u, 6541u, 6542u, 0u, 1u, 999u, 10000u};
 
   std::cout << "<- wu = " << wu << "\n";
   std::cout << "<- n  = " << n  << "\n";
 
   std::cout << "-> nth_prime(wu)= " << eve::nth_prime(wu) << "\n";
   std::cout << "-> nth_prime(n) = " << eve::nth_prime(n) << "\n";
}