C++ Math log1p
The function calculates the natural logarithm of a specified number increased by one.
Suppose a number is 'x':
log1p(x) = log(1+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 : What value are we trying to find the logarithm of?
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 explore a basic scenario where the value of x is above 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 instance, the log1p method calculates the natural logarithm for a value of x that is larger than zero.
Example 2
Let's consider a straightforward example where the value of x equals 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 instance, the log1p method calculates the natural logarithm of x plus one, specifically when x is close to zero.
Example 3
Let's examine a basic scenario where the value of x is negative.
#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 instance, the log1p method calculates the natural logarithm for values of x that are smaller than zero.
Example 4
Let's examine a basic scenario where the value assigned to 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 instance, the log1p function calculates the natural logarithm value when the input value x is -1.
Example 5
Let's examine a basic scenario where the value of x is below -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:
Value of x is : -3
log1p(x) = -nan
In this instance, the log1p method calculates the natural logarithm when x is smaller than -1.
