<h2>Overview</h2>

The `log1p()`﻿ function in C++ is defined in the `<cmath>` header file. `log1p()` takes an argument `x` of type double as input and returns the natural logarithm of `1+x`.The returned value is equivalent to the following in mathematical notation:

$log_{e}$(x+1)

The function is defined in the C++ `<cmath>` header file as:

```C++
double log1p (double x);
```

Below is an example of how ﻿to use the `log1p()` function:




#include <iostream>
#include <cmath>
using namespace std;

int main() {
  // your code goes here
  double x = 0.2;
  cout<<"The natural logarithm for "<<1+x<<" is ";
  cout<<log1p(x)<<endl;
  return 0;
}

Now, let's perform the same calculations using ﻿the `log(x+1)` function to compare the return values of the two functions. The following code demonstrates that both methods give us similar results:


#include <iostream>
#include <cmath>
using namespace std;

int main() {
  // your code goes here
  double x = 0.2;
  cout<<"The natural logarithm for "<<1+x<<" is ";
  cout<<log(x+1)<<endl;
  return 0;
}

<h2>Examples</h2>

﻿﻿It is important to note the following pointers on what kind﻿s of input parameters the `log1p()` function ﻿allows:

1. If we pass the parameter 0, the return value will also be 0. 

2. If we pass parameter -1, the return value will be $\infty$.

3. When passing a parameter below -1, the return value is NaN ( Not a Number)

4. Only values greater than -1 produce a legitimate result.

The following code demonstrates these input values and their return values:

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  // your code goes here
  cout<<"The natural logarithm for x=0 is: ";
  cout<<log1p(0)<<endl;
  cout<<"The natural logarithm for x>0 is: ";
  cout<<log1p(1)<<endl;
  cout<<"The natural logarithm for x=-1 is: ";
  cout<<log1p(-1)<<endl;
  cout<<"The natural logarithm for 0<x<-1 is: ";
  cout<<log1p(-0.2)<<endl;
  return 0;
}

What is log1p in C++?

The log1p() function in C++ returns the natural logarithm of 1+x and handles x as a double. Values below -1 result in NaN.