frexp(), frexpf(), frexpl() — Extract mantissa and exponent of the floating-point value

Standards

Standards / Extensions	C or C++	Dependencies
ISO C POSIX.1 XPG4 XPG4.2 ISO/ANSI C++ C99 Single UNIX Specification, Version 3 C++ TR1 C99	both

Format

#include <math.h>

double frexp(double x, int *expptr);
float frexp(float x, int *expptr);               /* C++ only */
long double frexp(long double x, int *expptr);   /* C++ only */
float frexpf(float x, int *expptr);
long double frexpl(long double x, int *expptr);

General description

Breaks down the floating-point value x into a component m for the normalized fraction component and another term n for the exponent, such that the absolute value of m is greater than or equal to 0.5 and less than 1.0 or equal to 0, and x = m * 2ⁿ. The function stores the integer exponent n at the location to which expptr points.

Note: These functions work in both IEEE Binary Floating-Point and hexadecimal floating-point formats. See IEEE binary floating-point for more information about IEEE Binary Floating-Point.

Restriction: The frexpf() and frexpl() functions do not support the _FP_MODE_VARIABLE feature test macro.

Returned value

Returns the normalized fraction m. If x is 0, the function returns 0 for both the fraction and exponent. The fraction has the same sign as the argument x. The result of the function cannot have a range error.

Example

CELEBF41

⁄* CELEBF41                                      

   This example decomposes the floating-point value of x, 16.4, into its        
   normalized fraction 0.5125, and its exponent 5.                              
   It stores the mantissa in y and the exponent in n.                           

 *⁄                                                                             
                                                                                
#include <math.h>                                                               
#include <stdio.h>                                                              
                                                                                
int main(void)                                                                  
{                                                                               
   double x, m;                                                                 
   int n;                                                                       
                                                                                
   x = 16.4;                                                                    
   m = frexp(x, &n);                                                            
                                                                                
   printf("The fraction is %lf and the exponent is %d\n", m, n);                
}

Output

The mantissa is 0.512500 and the exponent is 5