Trouble with getting a function to calculate and loop correctly in C

Question

I am needing to make a program to take user input of iterations to the formula : PI=4(1/1 -(1/3)+(1/5) ... repeating a number of times. MY problems so far is that it is not taking my input accurately.

Bascially my approach was to try and seperate the numerator and denominator wth x in the denominator and try and get it to add 2 but I haven't even figured out the - + rotation yet since I wanted to make sure what I had was working first.

My first problem was that it was getting random numbers but then I changed the variable type to float and that solved that problem but now everything is straight 0.

int pi_formula(float numerator,int x,int n)
{

    numerator=1.0;
    x=1;
    float fraction= numerator/x;
    float total;
    
    printf("%lf",&fraction);

    for (int i = 1; i <= n; i++) // loop goes for amount of user input times
        
 
        do
    {
        
        fraction; 
        return(total);
        x+= 2;              
     } while (1);
     
      printf("Estimated PI is : %f",&total);



}

When I run this code and the line

printf("%lf",&fraction); 

will return 0.000000.

I can't tell if I even have the loop written properly because I can't seem to get my input to be rcognized.

Here are the prototypes and the main for reference.

int pi_formula(float numerator,int x,int n);


int main ()
{

// Problem 2
    float numerator;
    int x;
    int n;
    printf("ESTIMATE PI\n");
    printf("Enter number of iterations:");
    scanf("%i",&n);
    pi_formula(numerator,x,n);

     




system("pause");
}

I had tried setting up printf calls to check the inputs expecting to see what I input but that also comes up 0.

Answer 1

For starters this function declaration

int pi_formula(float numerator,int x,int n)

does not make sense at least because it has the return type int instead of a floating type and a redundant number of parameters.

The function should be declared at least like

double pi_formula( unsigned int n );

And your function returns nothing though its return type is not void except this while loop

    do
{
    
    fraction; 
    return(total);
    x+= 2;              
 } while (1);

where total has the type float that also does not make sense.

There are other mistakes. For example in this call of printf

printf("Estimated PI is : %f",&total);

you are trying to output a pointer as a floating point number.

The function can be defined the following way

 double pi_formula( unsigned int n )
 {
     double pi = 0.0;

     for ( unsigned int i = 0; i < n; i++ )
     {
         if ( i % 2 == 0 )
         {
             pi += 1.0 / ( 2 * i + 1 );
         }
         else
         {
             pi -= 1.0 / ( 2 * i + 1 );
         }  
     }

     return 4 * pi;
}  

And in main you can write

int main( void )
{
    puts( "ESTIMATE PI" );

    printf( "Enter number of iterations: " );
  
    unsigned int n = 0;

    if ( scanf( "%u", &n ) == 1 )
    {
         printf( "Estimated PI is : %f\n", pi_formula( n ) );
    }
}

Here is all the code combined together

#include <stdio.h>

double pi_formula( unsigned int n )
{
    double pi = 0.0;

    for (unsigned int i = 0; i < n; i++)
    {
        if (i % 2 == 0)
        {
            pi += 1.0 / ( 2 * i + 1 );
        }
        else
        {
            pi -= 1.0 / ( 2 * i + 1 );
        }
    }

    return 4 * pi;
}

int main( void )
{
    puts( "ESTIMATE PI" );

    printf( "Enter number of iterations: " );

    unsigned int n = 0;

    if (scanf( "%u", &n ) == 1)
    {
        printf( "Estimated PI is : %f\n", pi_formula( n ) );
    }
}

The program output is

ESTIMATE PI
Enter number of iterations: 9999
Estimated PI is : 3.141693