C++ std:cout won't print, despite me using std::endl to enter newline and flush

Question

I'm new to C++ (and mainly programming in general).

I'm trying to write a basic program to output the Taylor expansion of x = 1.5 from n = 1 to n = 100. My code is this:

#include <iostream>

int main() {

        double x = 1.5;
        double expx = 1;
        double summand = 1;
        
        for (int n=1; n <100; ++n) {
                summand *= x/n;
                expx += summand;

        }
        return expx

        std::cout << "final expx from n = 1 to 100 is " << expx << std::endl;
}

When I run it, it runs without errors on terminal, but displays no output at all. I'm not quite sure what I'm doing wrong as when I run other code I've written, similar to this, I don't have a problem.

You return from main before outputing to std::cout (note that your example code doesn't even compile) — Pepijn Kramer, Oct 23 '21 at 09:51

score 0 · Answer 1 · answered Oct 23 '21 at 09:54

What you should have done is create an expx() function and output the result of that.

#include <iostream>

double expx()
{
    double x = 1.5;
    double expx = 1.0;
    double summand = 1.0;
        
    for (int n=1; n <100; ++n) 
    {
        summand *= x/n;
        expx += summand;
    }
    return expx;
}

int main() 
{
    double value = expx();
    std::cout << "final expx from n = 1 to 100 is " << value << std::endl;
}

score 0 · Answer 2 · answered Oct 23 '21 at 09:54

0

Anything that you write after a return statement inside a function won't execute. You need to switch the last two lines around, i.e:

std::cout << "final expx from n = 1 to 100 is " << expx << std::endl;
return expx

answered Oct 23 '21 at 09:54

Lior Dahan

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C++ std:cout won't print, despite me using std::endl to enter newline and flush

2 Answers2