Fibonacci.cpp

#include <iostream>
#include <cstdint>

using Int = std::uintmax_t;
using Float = long double;

constexpr Float getPhi()
{
  Float Phi = 1;
  for(Int i = 0; i < 0xffff; ++i)
    Phi = 1/Phi + 1;
  return Phi;
}

constexpr Float Phi = getPhi();

Int getNextInt(Int num)
{ return (Float(num)*Phi) + Float(0.5); }

Int getLastInt(Int num)
{ return (Float(num)/Phi) + Float(0.5); }

int main(int argc, char** argv)
{
  while(1)
  {
    std::cout << "Enter Number: ";
    std::string inputStr;
    std::getline(std::cin, inputStr);
    const Int input = std::stoll(inputStr);
    std::cout
      << getLastInt(getLastInt(input)) << ' '
      << getLastInt(input) << " ["
      << input << "] "
      << getNextInt(input) << ' '
      << getNextInt(getNextInt(input)) << "\n\n";
  }
}