frexp
Gets the mantissa and exponent of a floating-point number.
double frexp( double x, int *expptr ); float frexp( float x, int * expptr ); // C++ only long double frexp( long double x, int * expptr ); // C++ only
Parameters
- x
- Floating-point value.
- expptr
- Pointer to stored integer exponent.
Return Value
frexp returns the mantissa. If x is 0, the function returns 0 for both the mantissa and the exponent. There is no error return.
Remarks
The frexp function breaks down the floating-point value (x) into a mantissa (m) and an exponent (n), such that the absolute value of m is greater than or equal to 0.5 and less than 1.0, and x = m*2n. The integer exponent n is stored at the location pointed to by expptr.
C++ allows overloading, so you can call overloads of frexp. In a C program, frexp always takes a double and an int and returns a double.
Requirements
| Function | Required header | Compatibility |
|---|---|---|
| frexp | <math.h> | ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
All versions of the C run-time libraries.
Example
// crt_frexp.c
/* This program calculates frexp( 16.4, &n )
* then displays y and n.
*/
#include <math.h>
#include <stdio.h>
int main( void )
{
double x, y;
int n;
x = 16.4;
y = frexp( x, &n );
printf( "frexp( %f, &n ) = %f, n = %d\n", x, y, n );
}
Output
frexp( 16.400000, &n ) = 0.512500, n = 5
See Also
Floating-Point Support Routines | ldexp | modf | Run-Time Routines and .NET Framework Equivalents
