C ++的大价值

Question

I'm doing a fibonacci and I want to save all the numbers in a .txt, i have done the code but when the cicles gets big values the program express it as an exponential, and then gets bigger as .INF. How I can save the entry number?

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main()  {

    ofstream File;
    File.open("fibo.txt");

    double val0 = 0, val1 = 1, i = 0, n, out;
    cout << "Enter n of Fibonacci(n): ";
    cin >> n;

    while (i < n)   {
        if (n == 0) {
            File << i << "- " << 0 << endl;
            i++;
        }
        else    {
            out = val0 + val1;
            val0 = val1;
            val1 = out;
            i++;
            File << i << "- " << val0 << endl;
            }
        }
        File.close();
        return 0;
    }

Answer 1

You can use boost::multiprecision , it's very intuitive and easy to use. Your code can be modified by changing (only) a couple of lines:

#include <boost/multiprecision/cpp_int.hpp> // need this

#include <iostream>
#include <fstream>
#include <string>

using namespace std;
using namespace boost::multiprecision;

int main()
{

    ofstream File;
    File.open("fibo.txt");

    cpp_int val0 = 0, val1 = 1, out; // arbitrary precision integers
    int i = 0, n;
    cout << "Enter n of Fibonacci(n): ";
    cin >> n;

    while (i < n)   {
        if (n == 0) {
            File << i << "- " << 0 << endl;
            i++;
        }
        else    {
            out = val0 + val1;
            val0 = val1;
            val1 = out;
            i++;
            File << i << "- " << val0 << endl;
        }
    }
    File.close();
    return 0;
}