C++ Math lgamma

The lgamma function calculates the natural logarithm of the gamma function for a given input argument.

Suppose a number is x :

Syntax

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

Parameter

x : It is a floating point value.

Return value

It provides the natural logarithm of the gamma function applied to the input value x.

Example 1

Let's examine a basic scenario where the value assigned to x is 2.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     int x=2;
     cout<<"Value of x is : "<<x<<'\n';
     cout<<"lgamma(x) :"<<lgamma(x);
     return 0;
}

Output:

Value of x is : 2
lgamma(x) :0

In the aforementioned scenario, when the variable x is set to 2, the lgamma function will yield a result of 0.

Example 2

Let's consider a basic scenario where the value assigned to x is zero.

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

Output:

Value of x is : 0
lgamma(x) : inf

In the previous example, when x equals zero, the lgamma function will output positive infinity.

Example 3

Let's consider a basic scenario where the value of x represents a negative integer.

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     int x= -5;
     cout<<"Value of x is : "<<x<<'\n';
     cout<<"lgamma(x) : "<<lgamma(x);
     return 0;
}

Output:

Value of x is : -5
lgamma(x) : inf

In the aforementioned scenario, x represents a negative integer. Consequently, the lgamma function yields positive infinity.

Example 4

Let's consider a basic scenario where the value assigned to x is not a number (NaN).

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
     float x=sqrt(-6);
     cout<<"Value of x is : "<<x<<'\n';
     cout<<"lgamma(x) :"<<lgamma(x);
     return 0;
}

Output:

Value of x is : -nan
lgamma(x) :-nan

In the previously mentioned scenario, the value of x equals NaN. As a result, the lgamma function will yield NaN.