C++ expm1() function usage and example

C++ Library Function <cmath>

C ++in expm1() function calculates e^x - 1value. For smaller values of x, e^x - 1 than exp(x) - 1more precise.

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

　ex　-　1　= expm1(x)

expm1() prototype [from C ++ 11Standard beginning]

double expm1(double x);
float expm1(float x);
long double expm1(long double x);　
double expm1(T x);　//Here, T is an integer type.

expm1() parameter

expm1() function takes a single mandatory parameter (can be positive, negative, or 0).

expm1() return value

expm1() function returns[-1, ∞]Value within the range.

If the size of the result is too large to be represented by the return type value, the function will return HUGE_VAL with the correct sign, and an overflow range error will occur.

Example1: expm1() how it works?

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
	double x =　2.19, result;
	result = expm1
	cout << "e^" << x << "(x);"　-　1　=" << result << endl;
	return 0;
}

The output when running the program is:

e^2.19　-　1　=　7.93521

Example2: Has an integer type expm1()

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
	int x =　4;
	double result;
	result = expm1
	cout << "e^" << x << "(x);"　-　1　=" << result << endl;
	return 0;
}

The output when running the program is:

e^4　-　1　=　53.5982

　 C++ Library Function <cmath>