calculating e

hello,

I have to calculate the mathetical e.
So I have this :

Code:

 */


#include        <stdio.h>


        int
main ( int argc, char *argv[] )
{
        int n, teller ;
        float  uitkomst=0;
        printf ("Enter n : ");
        scanf ("%d", &n);
        printf( "n is : %d ", n);
        for (teller=1; teller <=n; teller++)
                {
                        uitkomst = 1 / teller;
                        printf (" uitkomst  is : %f \n", uitkomst);
                }
        printf ("e is ongeveer : %f", uitkomst);
return 0 ;
}                               /* ----------  end of function main  ---------- */

But the rule uitkomst = 1/ teller gives as output always zero and not 1/2 , 1/3

What am I doing wrong now.

Roelof

You'll find out the hard way that c really sucks when you try to mix integers and floats.

Try this:

Code:

uitkomst = 1.0 / teller;

That algorithm does not compute e, don't understand why you think it does

I'm hoping he simplified it to demonstrate the issue he was having with mixing floats and ints.

Hello,

I have simplified things because they don't work.

The right formula is : 1 + 1/1 + 1/(1*2) + 1/ (1*2*3) + 1/ (1*2*3...*n)

Roelof

Integer Division
Integer Division and Modulus

Use 1.0 instead of 1 as mentioned in mike65535 post.

Tim S.

Code:

e = d + 1

That's how I calculate e.


Quzah.

This is not the way to calculate e, first of all you will end up with 1/n and you don't need the loop. You must first write a function that calculates the factorial of x " fact(x) " and then change:
uitkomst = 1 / teller;
to:
uitkomst += 1 / fact(teller);

Originally Posted by h_dog

This is not the way to calculate e, first of all you will end up with 1/n and you don't need the loop. You must first write a function that calculates the factorial of x " fact(x) " and then change:
uitkomst = 1 / teller;
to:
uitkomst += 1 / fact(teller);

This is not the most efficient way; using a loop is better.
But, yours is a good and easier to understand way.
But you should use "1.0 /" instead of "1/"

Tim S.

I think you are better off calculating, or more likely, approximating the value of e from the definition of e: lim((1+1/n)^n) where n->infinity. This way you avoid calculating a ton of factorials for no reason. Once you get to a high enough n where you are starting to get the correct value of e, you should experiment with calculating the difference between f(n+1) - f(n) to see if the difference tends to be 0. (where f(n) = (1 + 1/n)^n )

Personally, if I had to compute e, I would do this

Code:

#include <math.h>

int main()
{
    double e = exp(1.0);
}

The precision is naturally limited to the machine precision of a double. But so is any other iterative approach that makes use of a double.

Hello,

Everybody thanks for the help.
I have to use loops because im now reading the chapter about loops.

Roelof