# FREXP

Section: POSIX Programmer's Manual (3P)

Updated: 2003

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## PROLOG

This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
## NAME

frexp, frexpf, frexpl - extract mantissa and exponent from a double
precision number
## SYNOPSIS

**#include <math.h>
**

**
double frexp(double** *num***, int ****exp***);
**

float frexpf(float *num***, int ****exp***);
**

long double frexpl(long double *num***, int ****exp***);
**

## DESCRIPTION

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*.

## RETURN VALUE

For finite arguments, these functions shall return the value *x*,
such that *x* has a magnitude in the interval
[0.5,1) or 0, and *num* equals *x* times 2 raised to the power
**exp*.

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.

## ERRORS

No errors are defined.

*The following sections are informative.*

## EXAMPLES

None.

## APPLICATION USAGE

None.

## RATIONALE

None.

## FUTURE DIRECTIONS

None.

## SEE ALSO

*isnan*(), *ldexp*(), *modf*(), the
Base Definitions volume of IEEE Std 1003.1-2001, *<math.h>*

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .