Can someone help me understand how to perform this expression using C++ skills?

Question

I have tried to perform this arithmetic expression from command line but it doesn't give me valid output. How do I perform the expression in the below code using the simplest skills of C++?

#include <iostream>
using namespace std;

int main()
{
    cout << " 4 * (1.0 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11) = ";
    return 0;
}

You've attached no picture and this question is of super low quality. Post whaty ou've tried — Halfpint, Jan 16 '17 at 18:30
why are you wrapping it in a string? of course it wont output anything — Halfpint, Jan 16 '17 at 18:31
Most likely you are doing integer division. In C++ `4/5 != .8` — NathanOliver, Jan 16 '17 at 18:32
I'm not criticizing your work, im pointing out that you have wrapped your equation in a string, therefore it will print a string. — Halfpint, Jan 16 '17 at 18:33
The is site where we help each other; not tear each other down — DMicheal, Jan 16 '17 at 18:33
Right...instead of helping you I will now choose to ignore you given that you are getting offended by me pointing out that you are not printing out a calculation...you're printing a STRING. Don't ask questions if A) You can't accept help without getting advice from people who have more knowledge in the subject area B) Write low quality questions. — Halfpint, Jan 16 '17 at 18:34
Can you lead me to some sources for this? Sorry that I got defensive — DMicheal, Jan 16 '17 at 18:36
Francois posted an answer below which answers this. Good luck — Halfpint, Jan 16 '17 at 18:36
@DMicheal If you are new to C++ programming: [read a good book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) about it. — Algirdas Preidžius, Jan 16 '17 at 18:46
I getting a jump start on the new language so I can be prepared for college course tomorrow. Thanks for the advice!!!!!!!!!! — DMicheal, Jan 16 '17 at 18:53

François Andrieux · Answer 1 · 2017-01-16T18:40:55.063

The first problem is that you are not actually preforming any calculations, you are only printing the literal equation as a string of characters. The second issue you will face is that 1/3 is integer 1 divided by integer 3. Integer division does not account for decimals. Add a decimal point to convert an integral literal to a double.

#include <iostream>
using namespace std;

int main()
{
    // Prints the equation
    cout << " 4 * (1.0 - 1./3 + 1./5 - 1./7 + 1./9 - 1./11) = ";

    // Prints the result of the equation
    cout << 4 * (1.0 - 1./3 + 1./5 - 1./7 + 1./9 - 1./11);

    return 0;
}

score 3 · Answer 2 · answered Jan 16 '17 at 18:36

Calculation of PI is best performed using floating point data type such as double:

#include <iostream>
#include <cstdlib>
int main(void)
{
  double pi = 4.0 * (1.0 - 1.0/3.0 + 1.0/5.0 - 1.0/7.0 + 1.0/9.0 - 1.0/11.0);
  std:: cout << "PI: " << pi << "\n";
  return EXIT_SUCCESS;
}

In short, the cout facility does not evaluate text strings, it only outputs them.

Can someone help me understand how to perform this expression using C++ skills?

2 Answers2