C++ frexp() function usage and example

C++ Library Function <cmath>

C ++The frexp(x, exp) function in the returns the mantissa and exponent of a floating-point number.

The binary significant bits are a floating-point number, whose absolute value (mantissa) is in the interval [0.5,1]. The integer exponent is2.

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

Mathematically

x = Binary significand　*　2exponent

where the exponent is stored at the location pointed to by exp, and the binary significant bits are the value returned by frexp().

frexp() prototype [from C ++ 11Standard start]

double frexp(double x, int*　exp);
float frexp(float x, int*　exp);
long double frexp(long double x, int*　exp);
double frexp(T x, int*　exp);　//for integer

frexp() function has two parameters and returns a binary significant value of double, float, or long double type.

frexp() parameters

• x -the value to be decomposed.

• exp -a pointer to an integer to store the exponent value.

frexp() return value

frexp() function returns the mantissa, whose absolute value is in the range [0.5,1]. If x is zero, both the significand and the exponent are zero.

Example1: frexp() function in C ++How does it work?

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
	double x =　6.81, significand;
	int　*exp;
	significand = frexp(x, exp);
	cout << x << " = " << significand << ""　*　2^" <<　*exp << endl;
	return 0;
}

When the program is run, the output is:

6.81　= 0.85125　*　2^3

Example2: frexp() function with integer type

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
	double significand;
	int　*exp, x =　25;
	significand = frexp(x, exp);
	cout << x << " = " << significand << ""　*　2^" <<　*exp << endl;
	return 0;
}

When the program is run, the output is:

25　= 0.78125　*　2^5

　 C++ Library Function <cmath>