Name
frexp, frexpf, frexpl - convert floating-point number to fractional and integral componentsLibrary
Math library ( libm ", " -lm )Synopsis
#include <math.h> double frexp(double " x ", int * exp );
float frexpf(float " x ", int * exp );
long double frexpl(long double " x ", int * exp );
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
frexpf() frexpl()
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Description
These functions are used to split the number x into a normalized fraction and an exponent which is stored inexp
. Return Value
These functions return the normalized fraction. If the argument x is not zero, the normalized fraction is x times a power of two, and its absolute value is always in the range 1/2 (inclusive) to 1 (exclusive), that is, [0.5,1).If x is zero, then the normalized fraction is zero and zero is stored in exp
.
If x is a NaN, a NaN is returned, and the value of *exp is unspecified.
If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned, and the value of *exp is unspecified.
Errors
No errors occur.Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
Standards
C11, POSIX.1-2008.History
C99, POSIX.1-2001.The variant returning double also conforms to SVr4, 4.3BSD, C89.
Examples
The program below produces results such as the following:"$" " ./a.out 2560" frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560 "$" " ./a.out -4" frexp(-4, &e) = -0.5: -0.5 * 2^3 = -4
Program Source
#include <float.h> #include <math.h> #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { double x, r; int exp; x = strtod(argv[1], NULL); r = frexp(x, &exp); printf("frexp(%g, &e) = %g: %g * %d^%d = %g\en", x, r, r, FLT_RADIX, exp, x); exit(EXIT_SUCCESS); }