Question

How to turn this file into a main.cpp, a header which contains the function declaration, and a implementation fiel containing the function definition ?
#include<iostream>
#include<string>
#include<iomanip>
using namespace std;

#define NUM 1
#define MULT 4

void getPi(int iter);

int main()
{

   int it;

   cout << "Enter the number of iterations needed to find PI: ";
   cin >> it;

   while (it < 1) {
       cout << "Error!!! Iteration input should be positive." << endl;
       cout << "Enter the number of iterations needed to find PI: ";
       cin >> it;
   }

   getPi(it);
    return 0;
}

void getPi(int iter) {
   double j = 1, k = 1;
   for (int i = 1; i <= iter; i++) {
       if (i == 1) {
           cout << fixed << setprecision(5);
           cout << "Iterations: " << i << " Pi is approximated to be " << (j*MULT) << endl;
           j = 1;
           k += 2;
       }
       else {
           if (i % 2 == 0) {
               cout << fixed << setprecision(5);
               cout << "Iterations: " << i << " Pi is approximated to be " << ((j - (NUM / k))*MULT) << endl;
               j = (j - (NUM / k));
               k += 2;
           }
           else {
               cout << fixed << setprecision(5);
               cout << "Iterations: " << i << " Pi is approximated to be " << ((j + (NUM / k))*MULT) << endl;
               j = (j + (NUM / k));
               k += 2;
           }
       }
      
   }
}

Answer 1

so we are creating our own header file to complete your objective the main.cpp file contains the main function.

I have created a header file with headerfilename.h extension that contains the function declaration.

The definition of the function is declared in headerfilename.cpp file.

main.cpp

#include <iostream>

#include "exampleheader.h" //the header file included that is created manually is shown below.

using namespace std;
int main()
{

int it;

cout << "Enter the number of iterations needed to find PI: ";
cin >> it;

while (it < 1) {
cout << "Error!!! Iteration input should be positive." << endl;
cout << "Enter the number of iterations needed to find PI: ";
cin >> it;
}

getPi(it);
return 0;
}

exampleheader.h

#ifndef EXAMPLEHEADER_H //this is to define our header file
#define EXAMPLEHEADER_H

void getPi(int x);

#endif

exampleheader.cpp // definition of our function

#include <iostream>
#include<string>
#include<iomanip>
#include "exampleheader.h"
#define NUM 1
#define MULT 4

int i,j,k;
void getPi(int iter) {
double j = 1, k = 1;
for (int i = 1; i <= iter; i++) {
if (i == 1) {
std::cout << std::fixed << std::setprecision(5);
std::cout << "Iterations: " << i << " Pi is approximated to be " << (j*MULT) << std::endl;
j = 1;
k += 2;
}
else {
if (i % 2 == 0) {
std::cout << std::fixed << std::setprecision(5);
std::cout << "Iterations: " << i << " Pi is approximated to be " << ((j - (NUM / k))*MULT) << std::endl;
j = (j - (NUM / k));
k += 2;
}
else {
std::cout << std::fixed << std::setprecision(5);
std::cout << "Iterations: " << i << " Pi is approximated to be " << ((j + (NUM / k))*MULT) << std::endl;
j = (j + (NUM / k));
k += 2;
}
}
  
}
}

## any queries feel free to comment