#include <iostream>
#include <fstream>
#include <cstdlib>      // random function rand() and srand()
#include <cmath>        // pow() and sqrt() functions
using namespace std;

float fileout(double resultF4, double resultErr4);

main() {
        double x, func = 0.0, func2 = 0.0, resultF, errorF, resultErr;
        int itry, ntry;
        cout << "Input the number of MC trials" << "\n";
        cin >> ntry;

// seed rand() function with void srand( (unsigned) time((int *)0) ); dependant on time program run

        srand((unsigned)time((long *)0));
        for (itry=0; itry<ntry; itry++) {

// random generate to largest number (2^31 - 1) RAND_MAX

                x = rand()/(float)RAND_MAX;
                func = func + pow(x,2);         // function to be evaluated is parabola of x^2
                func2 = func2 + pow(x,4);
                errorF = sqrt(func - func2);
                resultF = func/ntry;
                resultErr = errorF/ntry;
                fileout(resultF, resultErr);
        }
}

float fileout(double resultF2, double resultErr2)
{
        ofstream out("output.dat");
        if (!out) {
                cout << "Cannot open file." << "\n";
                return 1;
        }

        out << "Function  = " << resultF2 << " " << " Error  = " << resultErr2 << "\n";
        out.close();
}