Find square root of given floating point number

[WishonTD]

Hi. I'm obviously new to C++. I thank you in advance for your help. I know this is a very simple program but I can't figure out what I'm doing wrong. A user will input a number in order to find the square root of the floating point number. I have to keep track of the iterations and print out the square root and the number of iterations it took. I'm also trying to implement a pass by reference. Could someone please point me in the right direction?

  
#include <iostream>
#include <cmath>
#include <iostream>

using namespace std;


int main ( )

{
float A, X;

cout << "Let's compute the square root of any number you choose!" << endl;
cout << "Make sure the number you choose is a positive number!" << endl;

        cout << "Enter your number: " << endl;
        cin >> A;
        while (A <= 0)
        {
                cout << "Invalid Input, must be greater than 0" << endl;
                cout << "Enter your number: " << endl;
                cin >> A;
        }

const double EPSILON = 1e-10;
double xnew = A;
double xold;
double sqrt(A, int& iter);

        iter = 0;
        while (fabs(xnew - xold) > EPSILON && iter < 100);
                {
                        ++iter;
                        xold = xnew;
                        xnew = (xold + A / xold) / 2;
                }

return xnew

cout << endl << "The sqare root is: ";
cout << fixed << showpoint << setprecision << xnew << endl;
cout << endl << "It took " << iter << " times." << endl;

}

[soranz]

line 39 should be at line 44 and end with ';'

[squished18]

In order to implement pass by reference you need to declare a function. For example,

void square_root(float &find_root)
{
...
}

Put your algorithm to find the square root inside this function (lines 26 to 37).

[48T7M4Gy]

#include <iostream>
#include <cmath>
#include <stdio.h>      /* printf */

using namespace std;

const double EPSILON = 1e-6;
void squareroot(double, int& );

int main ( )

{
    double A;
    int cycles = 0;

    cout << "Let's compute the square root of any number you choose!" << endl;
    cout << "Make sure the number you choose is a positive number!" << endl;

    cout << "Enter your number: ";
    cin >> A;

    double answer = squareroot(A, cycles);

    cout << endl << "It took " << cycles << " times." << endl;

    return 0;
}

double squareroot(double A, int &c)
{
    // put you code here including that c = iter or just change 'iter' to 'c' everywhere.

    return xnew;
}

[WishonTD]

Thanks kemort. The comment you have for line 31, was that referring to my code for the lines that I had at 27 - 39? If so, I received the errors below. If not, then I used the wrong part of my code. :(

wishonp2x.cpp: In function ‘int main()’:
wishonp2x.cpp:23:32: error: void value not ignored as it ought to be
wishonp2x.cpp: In function ‘double sqrt(double, int&)’:
wishonp2x.cpp:30:29: error: new declaration ‘double sqrt(double, int&)’
wishonp2x.cpp:9:6: error: ambiguates old declaration ‘void sqrt(double, int&)’

[WishonTD]

Thank you soranz and squished18!

[WishonTD]

I've changed my code and the first part of Main runs (data input and data validation) but I can't get what I thought was the function to run. I understand the concept of passing by reference...I just can't completely understand the logic yet.

// This program will compute the square root of a given floating point number.


using namespace std;


void sqrt(double, int&);

int main ( )

{
double A;
int cycles = 0;

cout << "Let's compute the square root of any number you choose!" << en$
cout << "Make sure the number you choose is a positive number!" << endl;
cout << "Enter your number: " << endl;

cin >> A;
while (A <= 0)
{
cout << "Invalid Input, must be greater than 0" << endl;
cout << "Enter your number: " << endl;
cin >> A;

return A;
}




{
const double EPSILON = 1e-10;
double sqrt(double A, int &c);
double xnew = A;
double xold;

int c = 0;
while (fabs(xnew - xold) > EPSILON && c < 100);
{
++c;
xold = xnew;
xnew = (xold + A / xold) / 2.0;
}


cout << endl << "The sqare root is: ";
cout << fixed << showpoint << setprecision << xnew << endl;
cout << endl << "It took " << c << " times." << endl;

return xnew;
}
}

[48T7M4Gy]

Wishon, the layout of your code needs to be very similar to mine. You have two SEPARATE functions - main() and squareroot(....)

Show us the code that produced the errors and please use the code tags. You also need to tidy up your formatting - proper indents, remove unnecessary blank lines etc. at the moment it's far too messy.

Line 8 in my code replace void with double.

[WishonTD]

#include <iostream>
#include <cmath>
#include <stdio.h>


using namespace std;

const double EPSILON = 1e-6;
double sqrt(double, int& );

int main()

{
        double A;
        int cycles = 0;

        cout << "Let's compute the square root of any number  you choose!" << e$
        cout << "Make sure the nmber you choose is a positive number!" << endl;

        cout << "Enter your number: ";
        cin >> A;

        double answer = sqrt(A, cycles);

        cout << endl << "It took " << cycles << " times. " << endl;

        return 0;
}

double sqrt(double A, int &c)

{
double xnew = A;
double xold;

        c = 0;
        while (fabs(xnew - xold) > EPSILON && c < 100);
                {
                        ++c;
                        xold = xnew;
                        xnew = (xold + A / xold) / 2;
                }

return xnew;

}

[WishonTD]

Hi kemort. After I compile the code and run it, I enter the number I wish to find a square root for and then nothing. I don't think it's caught in an infinite loop but I don't know. I enter '8' below and it ends line and I can enter another number or anything. Any ideas? I appreciate your help!

Let's compute the square root of any number you choose!
Make sure the nmber you choose is a positive number!
Enter your number: 8

[48T7M4Gy]

what are you doing with "<< e$" at the end of line 17?

[WishonTD]

that's just an "endl;" truncated....the code says endl;....not e$

[48T7M4Gy]

what are you doing with a ';' in the wrong place somewhere between lines 30 an 46 inclusive. Look VERY carefully, line by line, and you'll see why you have an infinite loop.

[WishonTD]

Got it. Thank you kemort! Thanks everyone.

const double EPSILON = 1e-10;
double sqrt(double, int & );

int main()
{
        double A;
        int cycles = 0;

        cout << "Let's compute the square root of any number you choose!" << endl;
        cout << "Make sure the nmber you choose is a positive number!" << endl;

        cout << "Enter your number: ";
        cin >> A;

        while (A <= 0)
        {
        cout << "Invalid input.  Your number must be greater than zero." << endl;
        cout << "Enter your number: ";
        cin >> A;
        }

        double answer = sqrt(A, cycles);

        cout << endl << "The sqare root of " << A << " is " << answer << "." << endl;
        cout << endl << "It took " << cycles << " cycles. " << endl;

        return 0;
}

double sqrt(double A, int &cycles)

{

double xnew = A;
double xold;
cycles = 0;
while (fabs(xnew - xold) > EPSILON && cycles < 100)
        {
        ++cycles;
        xold = xnew;
        xnew = (xold + A / xold) / 2;
        }
        return xnew;
}

[48T7M4Gy]

Looks like you got there W. Dont forget the #include etc

Cheers

[WishonTD]

oh yeah...I forgot to paste those. haha. It took a bit but it finally compiled. I had to do some research about the errors I was getting and things finally fell into place. But I appreciate your input and direction. It helped tremendously.

cheers from the U.S.A.!