here is my code for ln(x) but for all 1<=x<2 its output is zero , can anyone please find the mistake in it

Question

#include<iostream>
#include<math.h>
using namespace std;
double ln(double x)
{
double a=1,b,c,i=1,d=0,l=1;
x=x-1;
if(x<=1)
{
c=-x;
while(a/i>0.00000001 || a/i<-0.00000001)
{
a=a*c;
i++;
d=d+a/i;
}
return x*(1+d);
}
if(x>1)
{
while(x>pow(2,l))
l++;
return (l-1)*ln(2)+ln(x/pow(2,l-1));
}
}
int main()
{
int k;
cin>>k;
cout<<ln(k);
}

Answer 1

i think you must first assign value before using it .

Answer 2

what value i must assign ??