C++ Math log1p()

The function computes the natural logarithm of a given number plus one.

Suppose a number is 'x':

Syntax

float log1p(float x);
double log1p(double x);
long double log1p(long double x);
double log1p(integral x);

Note: The return_type can be float, double or long double.

Parameter

x: The value of which logarithm is to be calculated.

Return value

Parameter	Return value
x>0	Positive
x=0	zero
0>x> -1	Negative
x= -1	-infinity
x<-1	Not a Number(nan)

Example 1

Let's see a simple example when the value of x is greater than zero.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     int x=10;
     std::cout << "Value of x is : " <<x <<std::endl;
     cout<<"log1p(x) = "<<log1p(x);
     return 0;
}

Output:

Value of x is : 10
log1p(x) = 2.3979

In this example, log1p() function computes the logarithm value when x is greater than zero.

Example 2

Let's see a simple example when the value of x is zero

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     int x=0;
     std::cout << "Value of x is : " <<x <<std::endl;
     cout<<"log1p(x) = "<<log1p(x);
     return 0;
}

Output:

Value of x is : 0
log1p(x) = 0

In this example, log1p() function computes the logarithm value when the value of x is zero.

Example 3

Let's see a simple example when the value of x is less than zero.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     float x= -0.5;
     std::cout << "Value of x is : " <<x <<std::endl;
     cout<<"log1p(x) = "<<log1p(x);
     return 0;
}

Output:

Value of x is : -0.5
log1p(x) = -0.693147

In this example, log1p() function computes the logarithm value when the value of x is less than zero.

Example 4

Let's see the simple example when the value of x is -1.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     int x= -1;
     std::cout << "Value of x is : " <<x <<std::endl;
     cout<<"log1p(x) = "<<log1p(x);
     return 0;
}

Output:

Value of x is : -1
log1p(x) = -inf

In this example, log1p() function computes the logarithm value when the value of x is -1.

Example 5

Let's see the simple example when the value of x is less than -1.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
    int x= -3;
    std::cout << "Value of x is : " <<x <<std::endl;
    cout<<"log1p(x) = "<<log1p(x);
    return 0;
}

Output: