FREXP(3) Library Functions Manual FREXP(3)

frexp frexpf frexpl — extract significand and exponent from a double precision number

#include <math.h>

double frexp(double num, int *exp);
float frexpf(float num, int *exp);
long double frexpl(long double num, int *exp);

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

These functions shall break a floating-point number num into a normalized fraction and an integral power of 2. The integer exponent shall be stored in the int object pointed to by exp; if the integer exponent is outside the range of int, the results are unspecified.

For finite arguments, these functions shall return the value x, such that x has a magnitude in the interval [½,1) or 0, and num equals x times 2 raised to the power * exp.

When the radix of the argument is a power of 2, the returned value shall be exact and shall be independent of the current rounding direction mode.

If num is NaN, a NaN shall be returned, and the value of * exp is unspecified.

If num is ±0, ±0 shall be returned, and the value of * exp shall be 0.

If num is ±Inf, num shall be returned, and the value of * exp is unspecified.

No errors are defined.

None.

None.

None.

None.

isnan(3), ldexp(3), modf(3)

XBD <math.h>

First released in Issue 1. Derived from Issue 1 of the SVID.

The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

The () and () functions are added for alignment with the ISO/IEC 9899:1999 (“ISO C99”) standard.

The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 (“ISO C99”) standard.

IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 (“ISO C99”) standard are marked.

Austin Group Defect 1302 is applied, aligning these functions with the ISO/IEC 9899:2018 standard.

Austin Group Defect 1753 is applied, changing the NAME section.

June 14, 2024 posix.fail