Java Program to C++?

[TheSkyWookie]

So I'm trying to change this Java program to C++ but have the same result, and compilers haven't been working correctly for me...

Estimate p) p can be computed using the following series:
m(i) = 4(1 - 1 / 3 + 1 / 5 - 1 / 7 + 1 / 9 - 1 / 11 + ... + (((-1)^i + 1) / 2i - 1)))
Write a method that returns m(i) for a given i and write a test program that displays
the following table:

public class Exercise_06_14 {
	/** Main Method */
	public static void main(String[] args) {
		// Display table
		double start = 1;			// Start series
		double end   = 901;		// End series
		System.out.println("\ni           m(i)     ");
		System.out.println("---------------------");
		for (double i = start; i <= end; i += 100) {
			System.out.printf("%-12.0f", i);
			System.out.printf("%-6.4f\n", estimatePI(i));
		}
	}

	/** Method estimatePI */
	public static double estimatePI(double n) {
		double pi = 0;		// Set pi to 0
		for (double i = 1; i <= n; i ++) {
			pi += Math.pow(-1, i +1) / (2 * i - 1);
		}
		pi *= 4;
		return pi;
	}
}

[salem c]

So where is your C++ attempt?

Just rip out all the public static, change the main signature and fix the System.out.println() and you're almost done.

[JLBorges]

#include <iostream>
#include <iomanip>

static double estimatePI( int n ) {

    double piby4 = 0 ;

    // m(i) = 4(1 - 1 / 3 + 1 / 5 - 1 / 7 + 1 / 9 - 1 / 11 + ... + (((-1)^i + 1) / 2i - 1)))
    double num = 1 ;
    double denom = 1 ;

    for( int i = 0 ; i < n ; ++i ) {

        piby4 += num / denom ;
        num = -num ; // alternating +1 -1
        denom += 2 ; // 1, 3, 5, 7 etc.
    }

    return piby4 * 4 ;
}

int main() {

    const int start = 1 ;
    const int end = 901 ;

    std::cout << "\n   i    m(i)     \n-------------\n"
              << std::fixed << std::setprecision(4) ; // 4 digits after the decimal point

    for( int i = start; i <= end; i += 100 )
        std::cout << std::setw(5) << i << std::setw(8) << estimatePI(i) << '\n' ;
}

http://coliru.stacked-crooked.com/a/8646639ff3fd6093

[malibor]

I'm trying to change this Java program to C++ but have the same result.

wait you want C++ program to have different result?

compilers haven't been working correctly for me

please share compiler output errors, and the code which produces these errors.

[salem c]

It's barely worth the effort.

Just some wannabe with "found code" who
a) stumbled on some code to compute PI, but it was written in Java and
b) stumbled into a C++ forum with said code and some bleating to convert it to C++.

[TheSkyWookie]

Hence the reason I'm in the beginner forums...