C++ Math lgamma
The lgamma function computes the logarithm of a gamma function of an argument passed to the function.
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 returns the logarithm of a gamma function of value x.
| Parameter | Return value |
|---|---|
| x= 1 or x=2 | 0 |
| x= ±0 | +∞ |
| x= -ve integer or ±∞ | +∞ |
| x= nan | nan |
Example 1
Let's see the simple example when the value of 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 above example, the value of x is 2. Therefore, the function lgamma returns 0 value.
Example 2
Let's see the simple example when the value of x is 0.
#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 above example, the value of x is zero. Therefore, the function lgamma returns +∞.
Example 3
Let's see the simple example when the value of x is 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 above example, the value of x is a negative integer. Therefore, the function lgamma returns +∞.
Example 4
Let's see the simple example when the value of x is 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 above example, the value of x is nan. Therefore, the function lgamma returns nan.