eulersnumber.cpp

#include <iostream>
#include <string>
#include <cmath>
#include <iomanip>

long double e = 1.0;
long double term = 1.0;
int i = 1;
long double precision = 1.0e-10;
bool flag_found = false;

int main(int argc, char* argv[])
{
    std::cout << "Euler's Number Calculator\n";
    for (int j = 1; j < argc; j++) {
        if (std::string(argv[j]) == "-p") {
            if (j + 1 < argc) {
                int decimal_places = std::stoi(argv[j + 1]);
                precision = std::pow(10.0, -decimal_places);
                flag_found = true;
                std::cout << "Calculating to " << decimal_places << " decimal places.\n";
            }
            else {
                std::cout << "Precision has not been specified correctly.\n";
                return 1;
            }
        }
    }

    if (!flag_found) {
        std::cout << "No precision specified. Calculating to default precision (10 decimal places).\n";
    }

    while (term > precision)
    {
        term = term / i;
        e = e + term;
        i++;
    };

    int output_precision = std::ceil(-std::log10(precision));
    std::cout << std::setprecision(output_precision);

    std::cout << "Computed value of e is: " << e << std::endl;
    std::cout << "Number of iterations: " << i - 1 << std::endl;
    return 0;
}