C++ log1p() function usage and example

C++ Library Function <cmath>

C ++in the log1p() function takes the parameter x and returns x + 1the natural logarithm (logarithm with base e).

This function calculates<cmath>defined in the header file.

log(x+1) = log1p(x)

log1p() prototype [from C ++ 11Standard library begin]

double log1p(double x);
float log1p(float x);
long double log1p(long double x);
double log1p(T x);　//for integer

log1p() function has only one parameter and returns a value of type double, float, or long double.

log1p() parameter

log1p() function uses a single mandatory parameter, ranging from[-1, ∞].

if the value is less than-1, then log1p() returns NaN (Not a Number).

log1p() return value

log1p() function returns1the natural logarithm of the parameter plus the given parameter.

Example1: log1p() function in C ++how it works?

#include <iostream>
#include <cmath>
using namespace std;
int main ()
{
　　　　double x =　21.371, result;
　　　　result = log1p(x);
　　　　cout << "log1p(x) = " << result << endl;
　　　　return 0;
}

When running the program, the output is:

log1p(x) =　3.10777

Example2: integer type log1p() function

#include <iostream>
#include <cmath>
using namespace std;
int main ()
{
　　　　double result =
　　　　int x =　147;
　　　　result = log1p(x);
　　　　cout << "log1p(x) = " << result << endl;
　　　　return 0;
}

When running the program, the output is:

log1p(x) =　4.99721

C++ Library Function <cmath>